Patent Document

CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application claims priority from provisional application number 60/124,552, filed Mar. 16, 1999 for “Side-Arm Microactuator” by James Morgan Murphy. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to a suspension-level microactuator having an improved stroke length. More particularly, it relates to a microactuator located between a suspension and an actuator arm in a disc drive system having piezoelectric elements to selectively move a transducing head radially with respect to a rotatable disc. 
     Disc drive systems include disc drive suspensions for supporting transducing heads over information tracks of a rotatable disc. Typically, suspensions include a load beam having a mounting region on a proximal end, a flexure on a distal end, a relatively rigid region adjacent to the flexure, and a spring region between the mounting region and the rigid region. An air bearing slider which holds the transducing head is mounted to the flexure. The mounting region is typically attached to a base plate for mounting the load beam to an actuator arm. A motor which is controlled by a servo control system rotates the actuator arm to position the transducing head over the desired information tracks on the disc. This type of suspension is used with both magnetic and non-magnetic discs. 
     The density of concentric data tracks on magnetic discs continues to increase (i.e., the size of data tracks and radial spacing between data tracks are decreasing), requiring more precise radial positioning of the head. Conventionally, head positioning is accomplished by operating an actuator arm with a large-scale actuation motor, such as a voice coil motor, to radially position a head on a slider at the end of the actuator arm. The large-scale motor lacks sufficient resolution to effectively accommodate high track-density discs. Thus, a high resolution head positioning mechanism, or microactuator, is necessary to accommodate the more densely spaced tracks. 
     One promising design for high resolution head positioning involves employing a high resolution microactuator in addition to the conventional low resolution actuator motor, thereby effecting head positioning through dual-stage actuation. Various microactuator designs have been considered to accomplish high resolution head positioning. These designs, however, all had shortcomings that limited the effectiveness of the microactuator. Many designs increased the complexity of designing and assembling the existing components of the disc drive, while other designs were unable to achieve the force and bandwidth necessary to accommodate rapid track access. Therefore, the prior designs did not present ideal microactuator solutions. More recent microactuator designs employ electroactive elements to effect movement of the suspension with respect to the actuator arm. This technique has proven effective but suffers from a small range of motion. 
     The positioning of a transducing head through dual-stage actuation using electroactive elements has been disclosed in prior patent applications. One such application is U.S. patent application Ser. No. 09/311,086 filed May 13, 1999 by Budde et al. entitled “PIEZOELECTRIC MICROACTUATOR SUSPENSION ASSEMBLY WITH IMPROVED STROKE LENGTH,” which is assigned to Seagate Technology, Inc., the assignee of the present application and is hereby incorporated by reference. There remains a need in the art, however, for an electroactive element microactuator design that provides efficient high resolution head positioning in a dual-stage actuation system and allows for a greater range of motion than current designs. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention is a microactuator for selectively altering a position of a transducing head carried by a slider in a disc drive system with respect to a track of a rotatable disc having a plurality of concentric tracks. The microactuator includes an actuator arm for attachment to a suspension. The suspension supports the slider over the rotatable disc. The microactuator includes a first electroactive element and a first bearn attached between the actuator arm and the suspension. The first electroactive element is deformable in response to an electrical control signal applied thereto. The first bean is flexible to permit movement of the head suspension with respect to the actuator arm. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is perspective view of a disc drive system including an actuation system for positioning a slider over tracks of a disc. 
     FIG. 2A is an exploded perspective view of a microactuation system for use in a dual-stage disc drive actuation system for high resolution positioning of a slider according to the present invention. 
     FIG. 2B is a top view of the microactuation system shown in FIG.  2 A. 
     FIG. 3 is a top view of a microactuation system for use in a dual-stage disc drive actuation system for high resolution positioning of a slider according to a first embodiment of the present invention. 
     FIG. 4 is a bottom view of a microactuation system for use in a dual-stage disc drive actuation system for high resolution positioning of a slider according to a second embodiment of the present invention. 
     FIG. 5 is a top view of a microactuation system for use in a dual-stage disc drive actuation system for high resolution positioning of a slider according to a third embodiment of the present invention. 
     FIG. 6 is a top view of a microactuation system for use in a dual-stage disc drive actuation system for high resolution positioning of a slider according to a fourth embodiment of the present invention. 
     FIG. 7A is a top view of a microactuation system for use in a dual-stage disc drive actuation system for high resolution positioning of a slider according to a fifth embodiment of the present invention. 
     FIG. 7B is a top view of a leverage mechanism used in connection with the microactuation system shown in FIG.  7 A. 
     FIG. 8 is a top view of a piezoelectric support structure according to the present invention. 
     FIG. 9 is a top view of a microactuation system for use in dual-stage disc drive actuation system for high resolution positioning of a slider according a sixth embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 shows a top view of a disc drive actuation system  10 , as known in the prior art, for positioning a transducing head (not shown) over a track of a magnetic disc. The actuation system  10  includes, as shown from left to right in FIG. 1, a voice coil motor (VCM)  12 , an actuator arm  14 , a suspension  16 , a flexure  18 , and a slider  20 . The slider  20  is connected to the distal end of the suspension  16  by the flexure  18 . The suspension  16  is connected to the actuator arm  14  which is coupled to the VCM  12 . 
     As shown on the right side of FIG. 1, the disc drive assembly includes a disc  22  having a multiplicity of tracks  24  which rotate about an axis  26 . During operation of the disc drive assembly, the rotation of the disc  22  generates air movement which is encountered by the slider  20 . This air movement acts to keep the slider  20  aloft a small distance above the surface of the disc  22  allowing the slider  20  to “fly” above the surface of the disc  22 . Any wear associated with physical contact between the slider  20  and the disc  22  is thus minimized. 
     The flexure  18  provides a spring connection between the slider  20  and the suspension  16 . Flexure  18  is configured such that is allows the slider  20  to move in pitch and roll directions to compensate for fluctuations in the spinning surface of the disc  22 . Many different types of flexures  18 , also known as gimbals, are known to provide the spring connection allowing for pitch and roll movement of the slider  20  and can be used with the present invention. 
     The VCM  12  is selectively operated to move the actuator arm  14  around an axis  28  thereby moving the suspension  16  and positioning the transducing head (not shown) carried by the slider  20  between tracks  24  of disc  22 . Proper positioning of the transducing head (not shown) is necessary for reading and writing of data on the concentric tracks  24  of the disc  22 . For a disc  22  having a high density, however, the VCM  12  lacks sufficient resolution and frequency response to position the transducing head (not shown) on the slider  20  over a selected track  24  of the disc  22 . Therefore, a higher resolution microactuation system is used. 
     FIG. 2A is an exploded perspective view, and FIG. 2B is a top view, of a microactuation system  30  for use in a dual-stage disc drive actuation system for high resolution positioning of a transducing head (not shown) according to the present invention. FIGS. 2A and 2B illustrate a generic embodiment of the present invention wherein the specific structures for allowing pivotal or rotational movement of the suspension  16  with respect to the actuator arm  14  are not shown. The specific structures employed will be disclosed at a later point in the specification. Absent these pivotal or rotational structures, the device shown will not function effectively. FIGS. 2A and 2B are intended to illustrate the general technique employed by the present invention to improve performance of the dual-stage disc drive actuation system. 
     As shown from top to bottom in FIG. 2A, the microactuation system  30  includes two piezoelectric elements  32   a  and  32   b , the actuator arm  14 , a load beam  34 , and a base plate  36 . The actuator arm  14  has an arm tip  37 , having a hole running generally through its center, located at its distal end. The base plate  36  has a swage boss  39  that acts to couple the load beam  34  to the arm tip  37  of the actuator arm  14 . The swage boss  39  is inserted through a hole in the load beam  34  and into the opening in the arm tip  37 . The base plate  36  is then swaged to the actuator arm  14 . As shown in FIG. 2A, the load beam  34  is attached to a bottom surface of the arm tip  37  by the base plate  36 . Generally, a second load beam  34  is attached to a top surface of the arm tip  37  by a second base plate  36 . The two piezoelectric elements  32   a ,  32   b  are attached to the load beam  34  and actuator arm  14  as explained in greater detail below. The two piezoelectric elements  32   a ,  32   b , the load beam  34 , and the base plate  36  are all components of the suspension  16  as illustrated in FIG.  1 . 
     As shown in FIGS. 2A and 2B, moving from left to right, or from a proximal end to a distal end, the load beam  34  includes a mounting region  38 , two pre-load bend legs  40   a ,  40   b , and a head suspension  42 . The head suspension  42  is flexibly coupled to the mounting region  38  by the two pre-load bend legs  40   a  and  40   b . As best shown in FIG. 2B, the piezoelectric elements  32   a ,  32   b  connect at a first end to the mounting steps  41   a ,  41   b  on the actuator arm  14  and, at a second end, to the mounting region  38  of the load beam  34 . 
     In a first preferred embodiment, the piezoelectric elements  32   a ,  32   b  are disposed orthogonally with respect to the actuator arm  14  and the mounting region  38 , as illustrated in FIG.  2 A. In other words, the piezoelectric elements  32   a ,  32   b  are disposed such that their width dimension lies in a plane normal to the general plane of the load beam  34 . In a second preferred embodiment, the piezoelectric elements  32   a ,  32   b  are disposed in generally the same plane as the actuator arm  14  and the mounting region  38 . In other words, the piezoelectric elements  32   a ,  32   b  are disposed such that their width dimension lies in a plane parallel to the general plane of the load beam  34 . 
     In the first preferred embodiment, the piezoelectric elements  32   a ,  32   b  are mounted on a first end to an outside surface of the mounting tabs  43   a ,  43   b  located on the mounting region  38  and, on a second end, to the mounting steps  41   a ,  41   b  of the actuator arm  14 . The orthogonal configuration, shown in FIG. 2A, offers several advantages. It allows thicker or multilayer piezoelectric elements  32   a ,  32   b  to be used because the available space is not restricted by the presence of the disc  22 . This provides for a greater stroke length of the piezoelectric elements  32   a ,  32   b . Also, in a disc drive system having multiple suspensions  16  disposed one on top of another, this configuration facilitates using the piezoelectric elements  32   a ,  32   b  to drive two suspensions  16  at the same time. In FIGS. 3-9, the piezoelectric elements  32  are thicker or multilayer elements shown in the orthogonal configuration. It is important to note, however, that in each of these figures the piezoelectric elements  32  could be mounted in the parallel configuration discussed above. 
     The head suspension  42 , which is located on the right side of FIG. 2B, includes two edge rails  44   a ,  44   b . The edge rails  44   a ,  44   b  are located on transversely opposite sides of the head suspension  42  and provide stiffness to that element. The pre-load bend legs  40   a ,  40   b , shown near the center of FIG. 2B, surround a cutout window  46 . The mounting region  38  of the load beam  34  is mounted to a top surface of the base plate  36  by welds  48 . The base plate  36  is attached to the actuator arm  14  (shown in FIG. 2A) as discussed above. The two pre-load bend legs  40   a ,  40   b  flexibly couple the head suspension  42  to the mounting region  38 . The two pre-load bend legs  40   a ,  40   b  accept a pre-load when the load beam  34  is placed into its intended operating position. This pre-load force tends to bias the head suspension  42  toward the disc  22 . The head suspension  42  of the load beam  34  provides a relatively stiff element for mounting the flexure  18  and the slider  20  (as shown in FIG.  2 A), which in turn carries the transducing head (not shown). 
     As shown in FIGS. 2A and 2B, the piezoelectric elements  32   a ,  32   b  are mounted using adhesive to the mounting tabs  43   a ,  43   b  of the mounting region  38  at one end and to the mounting steps  41   a ,  41   b  of the actuator arm  14  at the other end. Only a small portion of each end of the piezoelectric elements  32   a ,  32   b  is attached to the mounting region  38  and the actuator arm  14 . The remainder of the lengths of the piezoelectric elements  32   a ,  32   b  remain unattached. The piezoelectric elements  32   a ,  32   b , in a longitudinal direction, are disposed generally parallel to a longitudinal axis of the load beam  34 . The piezoelectric elements  32   a ,  32   b  are generally configured such that they have a length exceeding a length of the mounting region  38  in a longitudinal direction. This configuration allows substantially longer piezoelectric elements  32   a ,  32   b  to be used. The piezoelectric elements  32   a ,  32   b  are longitudinally deformable (in the direction of the arrows shown in FIG. 2B) in response to a voltage applied across the elements. In other words, an applied voltage across the piezoelectric elements  32   a ,  32   b  causes the elements to expand or contract in a longitudinal direction. The voltage is applied using methods generally known to those of ordinary skill in the art such that an electric field is generated causing activation of the piezoelectric elements  32   a ,  32   b . The piezoelectric elements  32   a ,  32   b  may be poled such that a positive voltage may cause either expansion or contraction. 
     In the present invention, the piezoelectric elements  32   a ,  32   b  are poled oppositely such that application of a positive voltage causes expansion of one element and contraction of the other element. Expansion and contraction of the piezoelectric elements  32   a ,  32   b  generates a torque in the head suspension  42 , which tends to cause rotational motion of the head suspension  42  with respect to the mounting region  38 . In the embodiment shown in FIG.  2 A and FIG. 2B, however, rotational movement of the head suspension  42  will be minimal as the structural components allowing motion are not present. 
     An important aspect of the present invention is the use of the configuration in FIG.  2 A and FIG. 2B for mounting the piezoelectric elements  32   a ,  32   b  to the load beam  34  and the actuator arm  14 . The illustrated mounting technique allows for greater length piezoelectric elements  32   a ,  32   b  to be used. The amount of expansion or contraction along a longitudinal axis of the piezoelectric elements  32   a ,  32   b  is directly proportional to the lengths of those elements. Therefore, the piezoelectric elements  32   a ,  32   b , which have a greater length than those previously employed in the prior art, allow for a greater range of motion of the head suspension  42  and the transducing head (not shown). 
     In the preferred embodiments, the piezoelectric elements  32   a ,  32   b  are constructed from a piezoelectric material. Piezoelectric materials are polable materials generally known in the art. In this first embodiment, the same polarity and magnitude of voltage is applied to each of the piezoelectric elements  32   a ,  32   b . The amount of motion of the transducing head carried by the slider  20  is controlled by the magnitude and polarity of the voltage applied to the piezoelectric elements  32   a ,  32   b  of a specified length. Other similar materials could be used and would function in a similar manner as piezoelectric elements  32   a ,  32   b . For example, any one of electroactive ceramics, electroactive polymers, and electrostrictive ceramic materials (collectively, electroactive materials or electroactive elements) could be used as piezoelectric elements  32   a ,  32   b  (as shown in FIG.  2 A and FIG.  2 B). It is also important to note that the present invention allows for the width&#39;s of the piezoelectric elements  32   a ,  32   b  to be varied. A wider width element, which may also be accomplished by employing multiple layers of elements, provides improved performance in many circumstances. 
     FIG. 3 shows a top view of a microactuation system  50  for use in a dual-stage disc drive actuation system for high resolution positioning of a transducing head (not shown) according to a first embodiment of the present invention. For purposes of illustration, the arm tip  37  of the actuator arm  14  has been omitted from FIG.  3 . As shown from left to right in FIG. 3, the microactuation system  50  includes an actuator arm  14 , two piezoelectric elements  32   a ,  32   b , a base plate  36 , and a load beam  34 . The mounting region  38  of the load beam  34  is mounted to the base plate  36 , and the two piezoelectric elements  32   a ,  32   b  are attached to the actuator arm  14  and the load beam  34  in a configuration normal to the plane of the load beam  34 . The base plate  36  is commonly about the same general size as the mounting region  38 , but it is shown larger in several of the figures for ease of illustration. The microactuation system  50  is located near the center of the disc drive actuation system  10 , as shown in FIG. 1, and incorporates the actuator arm  14  and the suspension  16  shown in FIG.  1 . 
     As shown in FIG. 3, moving from left to right, or from a proximal end to a distal end of the microactuation system  50 , the actuator arm  14  includes steps  52   a  and  52   b  disposed symmetrically about and transverse to a longitudinal centerline of the actuator arm  14 . The steps  52   a ,  52   b  are cut into each side of the actuator arm  14  and act to provide a mounting location for one end of the piezoelectric elements  32   a ,  32   b . The load beam  34  includes a mounting region  38 , a longitudinal microactuation beam  54 , two microactuation hinges  56   a ,  56   b , and a head suspension  42 . The head suspension  42  is flexibly coupled to the mounting region  38  by the two microactuation hinges  56   a ,  56   b  and the longitudinal microactuation beam  54 . 
     As best shown in FIG. 3, the two microactuation hinges  56   a ,  56   b  are disposed between the mounting region  38  and the head suspension  42  such that they are perpendicular to a longitudinal centerline of the load beam  34 . The perpendicular configuration of the hinges  56   a ,  56   b  is intended to be exemplary only. The hinges  56   a ,  56   b  could be disposed at any of a numerous variety of angles. The longitudinal microactuation beam  54  shares a common longitudinal centerline with the head suspension  42 . The longitudinal microactuation beam  54  could also be disposed at other angles with respect to the longitudinal centerline of the load beam  34 . The microactuation hinges  56   a ,  56   b  and the longitudinal microactuation beam  54  flexibly couple the head suspension  42  to the mounting region  38 . These components form the pivotal or rotational region of the load beam  34 . These components bias the head suspension  42  to a position in the same plane as, and sharing a centerline with, the mounting region  38  while allowing movement with respect thereto upon application of a force having an appropriate magnitude and direction. 
     As shown in FIG. 3, the mounting region  38  of the load beam  34  is mounted to a top surface of the base plate  36  by welds  48 . The base plate  36  is attached, commonly by a swage technique as described above, to the actuator arm  14 . The head suspension  42  of the load beam  34  carries the flexure  18  and the slider  20  at a distal end (as shown in FIGS.  2 A and  2 B). The slider  20  carries the transducing head (not shown) for transducing data with the disc  22 . 
     At a proximal end, near the center of the load beam  34  as shown in FIG. 3, the head suspension  42  has two pre-load bend legs  40   a ,  40   b  surrounding a cutout window  46 . Located between the two pre-load bend legs  40   a ,  40   b  at the proximal end of the head suspension  42 , and the slider  20 , at the distal end of the head suspension  42 , are two edge rails  44   a ,  44   b . The edge rails  44   a ,  44   b  are located on transversely opposite sides of the head suspension  42  and provide stiffness to its central region. At a far left end, as shown in FIG. 3, the head suspension  42  has two piezoelectric mounting tabs  60   a ,  60   b  standing laterally outward from a longitudinal centerline of the head suspension  42  and a hinge mounting arm  62  extending toward the mounting region  38 . The two microactuation hinges  56   a ,  56   b  and the longitudinal microactuation beam  54  attach to the hinge mounting arm  62  of the head suspension  42 . As discussed in greater detail above, the mounting tabs  60   a ,  60   b , in a preferred embodiment, are bent orthogonal to the general plane of the load beam  34 . 
     The piezoelectric elements  32   a ,  32   b  are mounted using adhesive to the steps  52   a ,  52   b , in the actuator arm  14  at one end and to the piezoelectric mounting tabs  60   a ,  60   b , respectively, of the head suspension  42  at the other end. Only a small portion of each end of the piezoelectric elements  32   a ,  32   b  is attached to the actuator arm  14  and the head suspension  46 . The remainder of the lengths of the piezoelectric elements  32   a ,  32   b  remain unattached. The piezoelectric elements  32   a ,  32   b  are disposed generally parallel to the longitudinal microactuation beam  54  and extend along the lateral edges of the mounting region  38  of the load beam  34 . The piezoelectric elements  32   a ,  32   b  are configured such that they have a length exceeding the longitudinal length of the mounting region  38 . This configuration allows substantially longer elements to be used, which, as discussed earlier, allows for a greater range of motion. The piezoelectric elements  32   a ,  32   b  are deformable longitudinally (in the direction of the arrows shown in FIG. 3) in response to an applied voltage across the elements. The voltage is applied by methods known to those of skill in the art such that an electric field is generated causing activation of the piezoelectric elements  32   a ,  32   b . The piezoelectric elements  32   a ,  32   b  may be poled such that a positive voltage may cause either expansion or contraction. 
     In this particular embodiment, the piezoelectric elements  32   a ,  32   b  are poled oppositely such that application of a positive voltage causes expansion of one element and contraction of the other element. Expansion and contraction of the piezoelectric elements  32   a ,  32   b  generates a torque in the head suspension  42  thereby causing deformation of the microactuation hinges  56   a ,  56   b  and the longitudinal microactuation beam  54  and causing rotation of the head suspension  42  about a virtual pivot VP. The amount of torque generated in the head suspension  42  is determined by the force applied by the piezoelectric elements  32   a ,  32   b  multiplied by the longitudinal distance between the point of application of the force (mounting tabs  60   a ,  60   b ) and a virtual pivot VP. Rotation of the head suspension  42  about the virtual pivot VP causes motion of the slider  20  carrying the transducing head radially with respect to the disc  22 . Thus, a controlled voltage applied to the piezoelectric elements  32   a ,  32   b  may be utilized to effect high resolution positioning of a transducing head carried by the slider  20  radially with respect to the disc  22 . The amount of displacement is directly proportional to the length of the piezoelectric elements  32   a ,  32   b  employed. 
     Although the microactuation system  50  is shown in FIG. 3 as having two piezoelectric elements  32   a ,  32   b , it could also be constructed using only one piezoelectric element  32 . The use of only one piezoelectric element  32  results in both cost and space savings. Using only one piezoelectric element  32  requires that the single piezoelectric element  32  be able to produce the torque, previously produced by two elements, necessary for causing rotation of the head suspension  42 . Also, the use of a single piezoelectric element  32  results in an asymmetric configuration. If necessary, this asymmetric configuration may be compensated for by changing the dimensions of the microactuation hinges  56   a ,  56   b . One of the microactuation hinges  56   a ,  56   b  could be made shorter or wider than the other to decrease its compliance and thus the amount of deformation it experiences. Alternatively, one of the two pre-load bend legs  40   a ,  40   b  on the head suspension  42  could be made wider than the other. Either of these methods could be used to add symmetrical stiffness to the load beam  34 . 
     FIG. 4 is a bottom view of a microactuation system  70  used in a dual-stage disc drive actuation system for high resolution positioning of a transducing head (not shown) according to a second embodiment of the present invention. In this second embodiment, the microactuation system  70  includes, as shown from left to right, an actuator arm  14 , a piezoelectric element  32 , a base plate  36 , and a load beam  34 . The load beam  34  is attached to a top or bottom surface of the base plate  36  by welds  48 . The base plate  36  is attached to the actuator arm  14 , commonly by a swage process. The piezoelectric element  32  is attached to a surface of the actuator arm  14  and the base plate  36 , in an orthogonal configuration, as explained in further detail below. The microactuation system  70  includes the actuator arm  14  and the suspension  16 , as shown in FIG.  1 . 
     As shown in FIG. 4, near the left side, the actuator arm  14  includes a step  71  cut into a lateral surface to provide a mounting point for one end of the piezoelectric element  32 . As shown in FIG. 4, moving from left to right, or from a proximal end to a distal end, the base plate  36  includes a longitudinal microactuation hinge  72  and a head suspension mount  74 . The longitudinal microactuation hinge  72  flexibly couples the head suspension mount  74  to the remainder of the base plate  36  and acts as the pivot structure. In a preferred embodiment, the longitudinal microactuation hinge  72  is disposed generally parallel to a longitudinal centerline of the head mounting region  38  and is disposed lateral to the longitudinal centerline in the direction toward the piezoelectric element  32 . The longitudinal microactuation hinge, however, could effectively be placed at any point between the mounting region  38  and the head suspension mount  74 . The length and width of the longitudinal microactuation hinge  72  can be varied to change the flexibility of the element. For instance, making the longitudinal microactuation hinge  72  shorter or wider will decrease its flexibility. The longitudinal microactuation hinge  72  biases the head suspension  42  to a position having a common centerline with the mounting region  38  while allowing motion of the head suspension  42  with respect to the mounting region  38  by application of a force having an appropriate magnitude and direction. 
     The load beam  34  is coupled to the head suspension mount  74 . The load beam  34  includes two pre-load bend legs  40   a ,  40   b , surrounding a cut-out window  46 , and a head suspension  42 . The head suspension  42  of the load beam  34  carries the flexure  18  and the slider  20  (as shown in FIGS.  2 A and  2 B). The slider  20  carries the transducing head (not shown) for transducing data with a disc  22 . Located between the pre-load bend legs  40   a ,  40   b , at the proximal end of the load beam  34 , and the slider  20 , at the distal end of the head suspension  42 , are two edge rails  44   a ,  44   b . The edge rails  44   a ,  44   b  are located on transversely opposite sides of the head suspension  42  and provide stiffness to its central region. 
     As shown in FIG. 4, the piezoelectric element  32  is mounted, generally using adhesive, to the step  71  of the actuator arm  14  and the mounting tab  76  located on the head suspension mount  74 . As discussed above, the mounting tab  76  may extend directly outward from the suspension mount  74  or may be bent orthogonal to the plane of the suspension mount  74 . The piezoelectric element  32  is disposed near a lateral edge of the actuator arm  14  and the load beam  34 . As shown from left to right in FIG. 4, a first end of the piezoelectric element  32  is connected to the step  72  of the actuator arm  14 , and a second end is connected to the mounting tab  76  located on the head suspension mount  74 . As is also apparent from FIG. 4, the piezoelectric element  32  has a length that exceeds the length of the mounting region  38 . 
     Like the piezoelectric elements  32   a ,  32   b  in the first embodiment of the present invention, the piezoelectric element  32  in the second embodiment of the present invention is deformable longitudinally in response to an applied voltage. The deformation occurs in the direction of the arrow located on the piezoelectric element  32 , in FIG.  4 . Expansion and contraction, in a longitudinal direction (as shown by the arrow in FIG.  4 ), of the piezoelectric element  32  generates a torque in the head suspension  42  which causes deformation of the longitudinal microactuation hinge  72  and causes rotation of the head suspension  42  about a virtual pivot VP. The amount of torque generated in the head suspension  42  is determined by the amount of force applied by the piezoelectric element  32  multiplied by the lateral distance between the point of application of the force and the virtual pivot VP. As shown in FIG. 4, the longitudinal microactuation hinge  72  is disposed lateral to a longitudinal centerline of the mounting region  38  toward the piezoelectric element  32 . This causes the point of rotation about the virtual pivot VP to be closer to the point of application of the force generated by the piezoelectric element  32 , which increases the amount of displacement of the head suspension  42 . 
     Rotation of the head suspension  42  about the virtual pivot VP causes motion of the slider  20  carrying the transducing head radially with respect to the disc  22 . Thus, during operation of the microactuation system  70 , a control voltage is applied to the piezoelectric element  32  to effect high resolution positioning of the transducing head with respect to tracks  24  of the disc  22 . The amount of displacement is directly proportional to the magnitude of voltage applied and the length of the piezoelectric element  32  employed. 
     The microactuation system  70 , shown in FIG. 4, is similar to the microactuation system  30 , shown in FIG.  2 A and FIG. 2B, except that the hinge in FIG. 4 is part of the base plate  36  as opposed to the load beam  34 . Although the microactuation system  70 , shown in FIG. 4, uses only one piezoelectric element  32 , it would be possible to mount a second piezoelectric element between the actuator arm  14  and the head suspension mount  74  on the opposite side. As discussed above, the use of two piezoelectric elements would increase the amount of torque generated and would minimize the problems associated with an asymmetric configuration. 
     FIG. 5 is a top view of a microactuation system  80  for use in a dual-stage disc drive actuation system for high resolution positioning of a transducing head (not shown) according to a third embodiment of the present invention. For purposes of illustration, the arm tip  37  of the actuator arm  14  has been omitted from FIG.  5 . As shown from left to right in FIG. 5, the microactuation system  80  includes an actuator arm  14 , a piezoelectric element  32 , a base plate  36 , and a load beam  34 . A mounting region  38  of the load beam  34  is attached to a top or bottom surface of the base plate  36  by welds  48 , which is attached to the actuator arm  14 . The piezoelectric element  32  is attached between two portions of the actuator arm  14 , as explained in greater detail below, normal to the plane of the load beam  34 . 
     As shown from left to right in FIG. 5, the actuator arm  14  includes a body  82 , a longitudinal microactuation hinge  84 , and a mounting arm  86 . In a preferred embodiment, the longitudinal microactuation hinge  84  is disposed substantially along a centerline of the actuator arm  14  and flexibly couples the body  82  to the mounting arm  86 . In other embodiments, however, the longitudinal microactuation hinge  84  could be placed lateral to the longitudinal centerline of the actuator arm  14 . As the longitudinal microactuation hinge  84  moves closer to the piezoelectric element  32 , it results in a greater amount of stroke. The body  82  of the actuator arm  14  has a step  88  cut into one side for attachment of one end of the piezoelectric element  32 . The mounting arm  86  of the actuator arm  14  is L-shaped and includes a mounting tab  90  for securing a second end of the piezoelectric element  32 . The mounting tab  90  is generally disposed near the farthest distal portion of the mounting arm  86  to maximize the effective length of the piezoelectric element  32 . Again, the mounting tab  90 , in a first preferred embodiment, is configured orthogonal to the plane of the load beam  34  and, in a second preferred embodiment, is configured parallel to the plane of the load beam  34 . 
     As shown in FIG. 5, load beam  34  is essentially identical to those shown and described with reference to FIG. 2B above. The major distinction between microactuation system  80 , shown in FIG.  5  and microactuation systems  50  and  70 , shown in FIGS. 3 and 4, is that in the microactuation system  80 , the hinge is part of the actuator arm  14 . The piezoelectric element  32  is mounted, at one end, to the step  88  on the body  82  of the actuator arm  14  and at the other end to the mounting tab  90  on the mounting arm  86 . As illustrated in FIG. 5, the piezoelectric element  32  has a length greater than the mounting region  38  of the load beam  34 . 
     When the microactuation system  80  is in use, the piezoelectric element  32  may be activated to effect positioning of a transducing head on the slider  20  relative to the disc  22 . The piezoelectric element  32  is constructed from the same material as that of the previously described embodiments. When a positive voltage is applied to the piezoelectric element  32 , it expands (in the direction of the arrow shown in FIG. 5) and imparts a torque on the mounting arm  86  of the actuator arm  14  causing a rotation of the mounting arm  86 , and thus the head suspension  42  of the load beam  34 , about a virtual pivot VP. This rotation of the head suspension  42  causes movement of the slider  20  with respect to the disc  22 . 
     The amount of torque experienced by the mounting arm  86  of the actuator arm  14  is determined by the magnitude of the force applied by the piezoelectric element  32  multiplied by the longitudinal distance between the point of attachment on the mounting arm  86  (shown as mounting tab  90  in FIG. 5) and the virtual pivot VP. When a negative voltage is applied to piezoelectric element  32 , it contracts causing rotation of the head suspension  42  about the virtual pivot VP in an opposite direction. The polarity and magnitude of voltage applied to the piezoelectric element  32  controls the direction and amount of displacement of the transducing head (not shown) on the slider  20 . 
     Like the microactuation system  70 , shown in FIG. 4, the microactuation system  80 , shown in FIG. 5, may also employ a second piezoelectric element. The second piezoelectric element would be mounted on an opposite side of the actuator arm  14  between the body  82  and the mounting arm  86 . A second piezoelectric element would allow more torque to be generated and would result in a symmetric configuration. 
     FIG. 6 is a top view of a microactuation system  100  for use in a dual stage disc drive actuation system for high resolution positioning of a transducing head (not shown) according to a fourth embodiment of the present invention. For purposes of illustration, the arm tip  37  of the actuator arm  14  has been omitted from FIG.  6 . As shown from left to right in FIG. 6, the microactuation system  100  includes an actuator arm  14 , two piezoelectric elements  32   a ,  32   b , a base plate  36 , and a load beam  34 . A mounting region  38  of the load beam  34  is attached to a top or bottom surface of the base plate  36  by welds  48 , which is attached to the actuator arm  14 . The piezoelectric elements  32   a ,  32   b  are attached between the actuator arm  14  and the load beam  34 , as explained in greater detail below, orthogonal to the plane of the load beam  34 . 
     As shown in FIG. 6, the actuator arm  14  includes two steps  102   a ,  102   b  for attachment of a first end of the piezoelectric elements  32   a ,  32   b . As shown from left to right in FIG. 6, the load beam  34  includes a mounting region  38 , a hinge region  104 , and a head suspension  42 . The head suspension  42  is flexibly coupled to the mounting region  38  by the hinge region  104 . The hinge region  104  may be constructed in any of a variety of configurations known to those of ordinary skill in the art. The hinge region  104 , illustrated in FIG. 6, shows one possible configuration for this element. 
     As shown near the middle of FIG. 6, the hinge region  104  includes a body  106  and a mounting-arm  108 . The body  106  of the hinge region  104  includes five microactuation beams  110   a ,  110   b ,  10   c ,  110   d ,  110   e  (moving in a counterclockwise direction around the mounting arm  108 ). The specific dimensions of the microactuation beams  110   a ,  110   b ,  110   c ,  10   d ,  110   e  may be manipulated depending on the level of flexibility desired between the head suspension  42  and the mounting region  38 . In the embodiment disclosed in FIG. 6, the microactuation beams  110   a ,  110   b ,  110   c ,  110   d ,  110   e  are disposed in a semicircle about the mounting arm  108 , spaced at approximately forty-five degree intervals. The microactuation beams  110   a ,  110   b ,  110   c ,  110   d ,  110   e  bias the head suspension  42  to a position having a common centerline with the mounting region  38 , while allowing motion of the head suspension  42  with respect to the mounting region  38  upon application of a force having an appropriate magnitude and direction. The mounting arm  108  includes mounting tabs  112   a ,  112   b , which provide a mounting surface for the piezoelectric elements  32   a ,  32   b , respectively. Again, the mounting tabs  112   a ,  112   b , in a first preferred embodiment, are disposed orthogonal to the general plane of the load beam  34  and, in a second preferred embodiment, are disposed parallel to the general plane of the load beam  34 . 
     The piezoelectric elements  32   a ,  32   b  are mounted, generally using an adhesive, at a first end to the steps  102   a ,  102   b  of the actuator arm  14  and at a second end to the mounting tabs  112   a ,  112   b  of the mounting arm  108  of the hinge region  104 . As shown in FIG. 6, the piezoelectric elements  32   a ,  32   b  have a length that exceeds the length of the mounting region  38 , and are disposed on each lateral side of the mounting region  38 . The piezoelectric elements  32   a ,  32   b  are disposed substantially parallel to a longitudinal centerline of the mounting region  38 . As shown in FIG. 6, the head suspension  42  has generally the same configuration as that disclosed in FIG.  2 B. 
     When the microactuation system  100  is in use, the piezoelectric elements  32   a ,  32   b  may be activated to effect positioning of a transducing head on the slider  20  relative to the disc  22 , in the same manner as described with respect to the previous embodiments. The piezoelectric elements  32   a ,  32   b  are constructed from the same material as that of the previously described embodiments. When a voltage is applied to the piezoelectric elements  32   a ,  32   b , they expand longitudinally (in the direction of the arrows shown in FIG. 6) and impart a torque on the hinge region  104  of the load beam  34  causing deflection of the microactuation beams  110   a ,  110   b ,  110   c ,  110   d ,  110   e , and rotation of a mounting arm  108  with respect to the body  106  of the hinge region  104 . This rotation, in turn, causes rotation of the head suspension  42  of the load beam  34  about a virtual pivot VP. This rotation of the head suspension  42  causes movement of the slider  20  with respect to the disc  22 . The amount of torque experienced by the mounting arm  108  is determined by the magnitude of force applied by the piezoelectric elements  32   a ,  32   b  multiplied by the longitudinal distance between the point of attachment on the mounting arm  108  and the virtual pivot VP. 
     When the microactuation system  100  is placed in its intended operating position, a pre-load is applied to the head suspension  42  and is transmitted from the two pre-load bend legs  40   a ,  40   b  to the mounting arm and through the microactuation beams  110   a ,  110   b ,  110   c ,  110   d ,  110   e , to the mounting region  38 . 
     As shown in FIG. 6, the microactuation system  100  includes two piezoelectric elements  32   a ,  32   b . It is also possible for the microactuation system  100  to employ only one piezoelectric element to effect displacement of the transducing head. In a configuration employing only one piezoelectric element, the device will be asymmetric with respect to a longitudinal axis. Various features of the load beam  34  may be modified to enhance symmetrical stiffness. For example, one of the two pre-load bend legs  40   a ,  40   b  could be widened to enhance stiffness, or one of the microactuation beams  110   a ,  110   b ,  110   c ,  110   d ,  110   e  could be modified to enhance symmetrical stiffness. Increasing the length of one of the microactuation beams  110   a ,  110   b ,  110   c ,  110   d ,  110   e  will increase its compliance in the general plane of the load beam  34  and decreasing the length will have an opposite effect. Also, the placement of the welds  48 , bonding the mounting region  38  to the base plate  36 , could be altered. 
     FIG. 7A is a top view of microactuation system  120  for use in a dual-stage disc drive actuation system for high resolution positioning of a transducing head (not shown) according a fifth embodiment of the present invention. For purposes of illustration, the arm tip  37  of the actuator arm  14  has been omitted from FIG.  7 A. As shown for left to right in FIG. 7A, the microactuation system  120  includes an actuator arm  14 , two piezoelectric elements  32   a ,  32   b , a base plate  36 , and load beam  34 . The load beam  34  is attached to a top or bottom surface of the base plate  36  by welds  48 , which is attached to the actuator arm  14 . The piezoelectric elements  32   a ,  32   b , are attached between a portion of the actuator arm  14  and a portion of the load beam  34 , as explained in greater below, in a configuration generally orthogonal to the load beam  34 . 
     As shown from left to right in FIG. 7A, the actuator arm  14  includes two steps  122   a ,  122   b  for attachment of a first end of the piezoelectric elements  32   a ,  32   b . As shown from left to right in FIG. 7A, the load beam  34  includes a mounting region  38 , two microactuation hinges  124   a ,  124   b , a longitudinal microactuation beam  126 , and a head suspension  42 . The longitudinal microactuation beam  126  and the microactuation hinges  124   a ,  124   b  flexibly couple the mounting region  38  to the head suspension  42 . In the preferred embodiment, the microactuation hinges  124   a ,  124   b  are disposed at an angle of approximately forty-five degrees from a longitudinal centerline of the head suspension  42 . This angle, however, could be varied to alter the performance characteristics. The microactuation hinges  124   a ,  124   b  are generally formed from the same sheet as the head suspension  42 . The microactuation hinges  124   a ,  124   b  are formed by bending an amount of material normal to the head suspension  42 . The structural configuration of the microactuation hinges  124   a ,  124   b  normal to the head suspension  42  provides maximum stiffness of the head suspension in the dimension perpendicular to the plane of the head suspension  42  and disc  22 , while minimizing stiffness in the plane of the head suspension  42 . The lengths and widths of the microactuation hinges  124   a ,  124   b  and the longitudinal microactuation beam  126  may be varied to change the stiffness of the coupling between the mounting region  38  and the head suspension  42 . 
     The head suspension  42  of the load beam  34  carries the flexure  18  and the slider  20  (as shown in FIGS.  2 A and  2 B). The slider  20  carries a transducing head (not shown) for writing data to and reading data from the disc  22 . Near the center of the load beam  34 , as shown in FIG. 7A, the head suspension  42  has two pre-load bend legs  40   a ,  40   b  surrounding cutout window  46 . Located between the pre-load bend legs  40   a ,  40   b , at the proximal end of the head suspension  42 , and the slider  20 , at the distal end of the head suspension  42 , are two edge rails  44   a ,  44   b . The edge rails  44   a ,  44   b  are located on transversely opposite sides of the head suspension  42  and provide stiffness to its central region. 
     As shown in FIG. 7A, the piezoelectric element  32   a ,  32   b  are mounted, generally using adhesive, to the steps  122   a ,  122   b  of the actuator arm and the mounting tabs  128   a ,  128   b  located on the head suspension  42 . The mounting tabs  128   a ,  128   b  may be disposed, depending upon the desired configuration of the piezoelectric elements, either parallel to or orthogonal to the general plane of the load beam  34 . The piezoelectric element  32   a ,  32   b , are disposed near a lateral edge of the actuator arm  14  and the load beam  34 . As shown from left to right in FIG. 7A, a first end of the piezoelectric element  32   a  is connected to the step  122   a  and the actuator arm  14  and a second end is connected to the mounting tab  128   a  located on the head suspension  42 . As also shown in FIG. 7A, a first end of the piezoelectric element  32   b , is connected to the step  122   b  of the actuator arm  14 , and the second end is connected to the mounting tab  128   b  located on the head suspension  42 . As is also apparent from FIG. 7A, the piezoelectric elements  32   a ,  32   b  have lengths that exceed the length of the mounting region  38 . 
     When the microactuation system  120  is in use, the piezoelectric elements  32   a ,  32   b  may be activated to effect positioning of a transducing head on a slider  20  relate to the disc  22 . The piezoelectric elements  32   a ,  32   b  are constructed from the same material of the previous described embodiments. When a voltage is applied to the piezoelectric elements  32   a ,  32   b , they expand or contract (in the direction of the arrows shown in FIG. 7A) causing deformation of the microactuation hinges  124   a ,  124   b  and the longitudinal microactuation beam  126 . This deformation causes rotation of the head suspension  42  about a virtual pivot VP. This rotation of the head suspension  42  causes movement of the slider  20  with respect to the disc  22 . The amount of torque experienced by the head suspension  42  is determined by the magnitude of the force applied by the piezoelectric elements  32   a ,  32   b  multiplied by the longitudinal distance between the point of attachment on the mounting tabs  128   a ,  128   b  and the virtual pivot VP. Although the microactuation system  120 , shown in FIG. 7A, uses two piezoelectric elements  32   a ,  32   b  it is possible to use only one piezoelectric element  32 . 
     FIG. 7B shows a top view of a leverage mechanism  130  according to the present invention. The leverage mechanism  130  may be used in combination with the microactuation system  120  shown in FIG.  7 A. The leverage mechanism  130 , explained in greater detail below, acts to move the line of action of the piezoelectric elements  32   a ,  32   b  closer to the virtual pivot VP, thereby increasing the leverage ratio and increasing the motion of the slider  20 . As shown from left to right in FIG. 7B, the leverage mechanism  130  includes a stator  132 , a longitudinal microactuation beam  134 , and a rotor  136 . The longitudinal microactuation beam  134  acts to flexibly couple the rotor  136  to the stator  132 . In operation, the leverage mechanism  130  is placed on top of the microactuation system  120  shown in FIG.  7 A. The stator  132  of the leverage mechanism  130  is fixed to the mounting region  38  of the load beam  34  by welds  138 . The rotor  136  of the leverage mechanism  130  is fixed to the head suspension  42  by welds  138 . 
     During operation of the microactuation system  120 , including the leverage mechanism  130 , the force applied by the piezoelectric elements  32   a ,  32   b  is transferred through the rotor  136  to the longitudinal microactuation beam  134 . Using the leverage mechanism  130 , the line of action of piezoelectric elements  32   a ,  32   b  is moved closer to the virtual pivot VP and thus the amount of motion of the head suspension  42  is increased. Increasing the motion of the head suspension  42  results in increased displacement of the head carried by the slider  20 . 
     FIG. 8 shows a top view of a microactuation system  140  including supports  142   a ,  142   b . Again, for purposes of illustration, the arm tip  37  of the actuator arm  14  has been omitted from FIG.  8 . The supports  142   a ,  142   b  extend outward from the mounting region  38  and extend under piezoelectric elements  32   a ,  32   b . The supports  142   a ,  142   b  support the weight of the piezoelectric elements  32   a ,  32   b  but are not fixedly coupled thereto. The supports  142   a ,  142   b  act to increase the stiffness of the microactuation structure which helps to optimize the pivot function. 
     FIG. 9 shows a top view of microactuation system  150  for use in a dual-stage disc drive actuation system for high resolution positioning of a transducing head (not shown) according to a sixth embodiment of the present invention. Again, for purposes of illustration, the arm tip  37  of the actuator arm  14  has been omitted. FIG. 9 illustrates a generic embodiment of the present invention wherein the specific structures for allowing pivotal or rotational movement of the head suspension  42  with respect to the actuator arm  14  are not shown. The significance of the microactuation system  150 , shown in FIG. 9, is the illustration of an alternative method for attaching the piezoelectric elements  32   a ,  32   b . As in the previous embodiments, the piezoelectric elements  32   a ,  32   b  are disposed, in a first preferred embodiment, in a plane orthogonal to the load beam  34  and, in a second preferred embodiment, in a plane parallel to the load beam  34 . 
     In the microactuation system  150 , as shown in FIG. 9, piezoelectric elements  32   a ,  32   b  are attached between the mounting region  38  and the head suspension  42 . In this embodiment the piezoelectric elements  32   a ,  32   b  are disposed substantially parallel to a lateral edge of the mounting region  38  and have a length exceeding the length of the: mounting region  38 . The configuration of the piezoelectric elements  32   a ,  32   b , shown in the microactuation system  150  of FIG. 9, could be applied to any of the microactuation system  50  shown in FIG. 3, microactuation system  70  shown in FIG. 4, the microactuation system  80  shown in FIG. 5, the microactuation system  100  shown in FIG. 6, the microactuation system  120  shown in FIG. 7A, or the microactuation system  140  shown in FIG.  8 . 
     While the preferred embodiment of the present invention has been described in detail, it should be apparent that many modifications and variations to it are possible, all of which fall within the true spirit and scope of the present invention. For example, while the present invention is described as reading and writing data from rotating magnetic disc, the present invention is not intended to be limited in this respect. The transducing head in the recording surface may utilize magnetic, optical, or other data storage techniques to store data. Also, the various embodiments disclosed show various pivot structures in the load beam  34 . It is important to note, however, that a multitude of alternative pivot structures could also be employed with the techniques of the present invention. The invention is not intended to be limited to the structures disclosed in the various preferred embodiments. 
     Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.

Technology Category: g