Patent Publication Number: US-2006007599-A1

Title: System, method, and apparatus for high performance, four-piece suspension with extended hinge plate

Description:
BACKGROUND OF THE INVENTION  
      1. Technical Field  
      The present invention relates in general to an improved suspension for a disk drive and, in particular, to an improved system, method, and apparatus for improving the performance of a four-piece suspension using a separate, extended hinge plate.  
      2. Description of the Related Art  
      Data access and storage systems generally comprise one or more storage devices that store data on magnetic or optical storage media. For example, a magnetic storage device is known as a direct access storage device (DASD) or a hard disk drive (HDD) and includes one or more disks and a disk controller to manage local operations concerning the disks. The hard disks themselves are usually made of aluminum alloy or a mixture of glass and ceramic, and are covered with a magnetic coating. Typically, one to five disks are stacked vertically on a common spindle that is turned by a disk drive motor at several thousand revolutions per minute (rpm). Hard disk drives have several different typical standard sizes or formats, including server, desktop, mobile (2.5 and 1.8 inches) and microdrive.  
      A typical HDD also uses an actuator assembly to move magnetic read/write heads to the desired location on the rotating disk so as to write information to or read data from that location. Within most HDDs, the magnetic read/write head is mounted on a slider. A slider generally serves to mechanically support the head and any electrical connections between the head and the rest of the disk drive system. The slider is aerodynamically shaped to glide over moving air in order to maintain a uniform distance from the surface of the rotating disk, thereby preventing the head from undesirably contacting the disk.  
      A slider is typically formed with an aerodynamic pattern of protrusions on its air bearing surface (ABS) that enables the slider to fly at a constant height close to the disk during operation of the disk drive. A slider is associated with each side of each disk and flies just over the disk&#39;s surface. Each slider is mounted on a suspension, such as an integrated lead suspension (ILS), to form a head gimbal assembly (HGA). The HGA is then attached to a semi-rigid actuator arm that supports the entire head flying unit. Several semi-rigid arms may be combined to form a single movable unit having either a linear bearing or a rotary pivotal bearing system.  
      A typical four-piece ILS  11  is shown in  FIG. 1 . ILS  11  includes a flexure  13 , a slider  16 , a load beam  17 , a hinge plate  19 , and a mount plate  21 . In this design, the flexure  13  is routed completely outside of the hinge area  19  (e.g., off to one lateral side) of the suspension. With an external routing path before and after the hinge area, the ILS flexure at the hinge area is asymmetric and creates an inherent mass imbalance. Imbalances cause unwanted slider off-track motion for vibration modes in the bending direction under excitations, such as shock and windage. Thus, an improved ILS flexure design that overcomes these problems would be desirable. The most direct way to improve this asymmetric flexure routing is to change the routing of the flexure to a centralized routing through the center of the hinge area. Such a centralized routing can eliminate much of the mass imbalance produced by the flexure going outside of the hinge springs of the HGA.  
      Referring now to  FIGS. 2 and 3 , for a HGA design  11  that requires ILS flexures  13  to go through the center of the two hinge springs  2 A via the opening in the hinge plate  2 B, the flexure  13  undergoes a change in elevation  15  or height as they extend along the length of the HGA between locations  13 A and  13 B on the flexure  13 . The reason for the change in elevation  15  is that at location  13 A, the flexure  13  is welded on the surface of the load beam  3 . This load beam surface is at the same level as the top surface of the mount plate  4 . The flexure then goes between the center of the two hinge springs  2 A of the hinge plate  2 . It is then welded on top of the hinge plate  2  at flexure location  13 B. The top surface of the hinge plate is higher than the top surface of the load beam by the thickness of the hinge plate, which is typically about 0.025 mm to 0.050 mm.  
      The change in elevation  15  is an undesirable bend in the structure of the flexure  13  that is required to go from a relative height of the load beam  3  to that of the hinge plate  2  on the mount plate  4 . Such a bend puts a mechanical moment in the flexure  13 , which can twist the HGA at the hinge springs  2 A. This twist can increase the off-track motion of the slider under excitation, such as windage or any other external vibration in the file. It can be detrimental to the performance of the device.  
     SUMMARY OF THE INVENTION  
      One embodiment of a system, method, and apparatus for improving the performance of a four-piece suspension having a separate, extended hinge plate is disclosed. The present invention comprises an ILS flexure that is centrally-routed through the hinge area of the suspension and, in one version, is completely symmetrical. This design eliminates many of previously described problems associated with the prior art, including much of the unwanted off-track motion of the slider for bending modes. By extending the hinge plate from the base of the load beam to the base of the flexure legs, any height mismatch for the flexure is completely eliminated. The ILS flexure, hinge plate, and load beam may be welded together to provide a stiff structure for high torsional frequencies. Flexure torsional mode frequency is further increased by welding the flexure to the hinge plate and load beam at two locations closer to the dimple formed at the distal end of the suspension.  
      The foregoing and other objects and advantages of the present invention will be apparent to those skilled in the art, in view of the following detailed description of the present invention, taken in conjunction with the appended claims and the accompanying drawings. For example, other types of suspensions (e.g., wireless suspensions, CIS, etc.) that employ a four-piece construction also benefit from the present invention.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      So that the manner in which the features and advantages of the invention, as well as others which will become apparent are attained and can be understood in more detail, more particular description of the invention briefly summarized above may be had by reference to the embodiment thereof which is illustrated in the appended drawings, which drawings form a part of this specification. It is to be noted, however, that the drawings illustrate only an embodiment of the invention and therefore are not to be considered limiting of its scope as the invention may admit to other equally effective embodiments.  
       FIG. 1  is an isometric view of a conventional four-piece suspension;  
       FIG. 2  is an isometric view of a conventional suspension requiring a change in the elevation of the flexure;  
       FIG. 3  is an isometric view of a hinge plate for the conventional suspension of  FIG. 2 ;  
       FIG. 4  is an isometric view of one embodiment of a suspension constructed in accordance with the present invention;  
       FIG. 5  is a sectional side view of the suspension of  FIG. 4  and is constructed in accordance with the present invention;  
       FIG. 6  is an isometric view of a hinge plate for the suspension of  FIG. 4  and is constructed in accordance with the present invention; and  
       FIG. 7  is a schematic plan view of a disk drive that utilizes the suspension of  FIG. 4  and is constructed in accordance with the present invention.  
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      Referring now to  FIG. 7 , a schematic drawing of one embodiment of an information storage system comprising a magnetic hard disk file or drive  111  for a computer system is shown. Drive  111  has an outer housing or base  113  containing at least one magnetic disk  115 . Disk  115  is rotated by a spindle motor assembly having a central drive hub  117 . An actuator  121  comprises a plurality of parallel actuator arms  125  (one shown) in the form of a comb that is pivotally mounted to base  113  about a pivot assembly  123 . A controller  119  is also mounted to base  113  for selectively moving the comb of arms  125  relative to disk  115 .  
      In the embodiment shown, each arm  125  has extending from it at least one of the suspensions  127 . A magnetic read/write transducer or head is mounted on a slider  129  and secured to the flexure that is flexibly mounted to each suspension  127 . The read/write heads magnetically read data from and/or magnetically write data to disk  115 . The level of integration called the head gimbal assembly is head and the slider  129 , which are mounted on suspension  127 . The slider  129  is usually bonded to the end of suspension  127 . The head is typically pico size (approximately 1250×1000×300 microns) and formed from ceramic or intermetallic materials. The head also may be femto size (approximately 850×700×230 microns), Pemto size (approximately 1250×700×230 microns), or even smaller in size. The head is pre-loaded against the surface of disk  115  (e.g., in the range two to ten grams) by suspension  127 .  
      The hinge of the suspension  127  has a spring-like quality which biases or urges the air bearing surface of the slider  129  against the disk  115  to enable the creation of the air bearing film between the slider  129  and disk surface. A voice coil  133  housed within a conventional voice coil motor magnet assembly  134  (top pole not shown) is also mounted to arms  125  opposite the head gimbal assemblies. Movement of the actuator  121  (indicated by arrow  135 ) by controller  119  moves the head gimbal assemblies radially across tracks on the disk  115  until the heads settle on their respective target tracks. The head gimbal assemblies operate in a conventional manner and always move in unison with one another, unless drive  111  uses multiple independent actuators (not shown) wherein the arms can move independently of one another.  
      Referring now to  FIGS. 4-6 , one embodiment of a suspension  127  constructed in accordance with the present invention is shown. The suspension  127  comprises four primary components, including a mount plate  151 , a hinge plate  153 , a flexure  155 , and a load beam  157 . The arm  125  to which suspension  127  is mounted defines a longitudinal direction that extends radially relative to the axis of the pivot  123 , and a lateral direction that is transverse to the longitudinal direction.  
      The mount plate  151  is mounted to the arm  125  and extends in the longitudinal direction to define a first plane. The hinge plate  153  is mounted to the mount plate  151  and also extends in the longitudinal direction. As shown in  FIG. 6 , the planar hinge plate  153  has an extension  156  that protrudes from its symmetric hinge springs  154 . The extension  156  is part of the hinge springs  154  and provides a mounting location for the load beam  157 . The load beam  157  is mounted to the hinge plate  153  and extends in the longitudinal direction to define a second plane. The first and second planes may be co-planar (as shown in  FIG. 5 ), or they may intersect each other at an offset angle  161  whose apex is located in the hinge region provided by hinge plate  153 .  
      The flexure  155  is mounted to the load beam  157  and extends in the longitudinal direction. The read/write transducer  129  is mounted to the flexure  155  for reading data from and writing data to the magnetic media  115 . The flexure defines and extends in a configuration that is parallel to the first and second planes. Thus, the flexure  155  may lie in a single plane (e.g., from flexure area  155 A to  155 B in  FIG. 4 ), or may incorporate the offset angle  161  ( FIG. 5 ) to remain parallel to the first and second planes.  
      However, flexure  155  has no distortions that form mechanical moments therein. The plane defined by the flexure  155  extends from the mount plate  151  to the read/write transducer  129  to reduce undesirable off-track motion of the read/write transducer  129  relative to media tracks on the magnetic media  105 . Furthermore, the flexure  155  may extend symmetrically down a lateral center of the hinge plate  153  and the load beam  157  to the read/write transducer  129 .  
      The present invention has several advantages, including the ability to eliminate many of the problems associated with the prior art, such as the unwanted off-track motion of the slider for bending modes. Height mismatch for the flexure is eliminated by extending the hinge plate from the base of the load beam to the base of the flexure legs. The welded ILS flexure, hinge plate, and load beam provide a stiff structure for high torsional frequencies.  
      While the invention has been shown or described in only some of its forms, it should be apparent to those skilled in the art that it is not so limited, but is susceptible to various changes without departing from the scope of the invention. For example, other types of suspensions (e.g., wireless suspensions, CIS, etc.) that employ a four-piece construction also benefit from the present invention.