Dynamic magnetic information storage or retrieval – Head mounting – Disk record
Reexamination Certificate
2001-11-28
2003-04-08
Cao, Allen (Department: 2652)
Dynamic magnetic information storage or retrieval
Head mounting
Disk record
C360S097020
Reexamination Certificate
active
06545842
ABSTRACT:
FIELD OF THE INVENTION
This application relates to magnetic disc drives and more particularly to the incorporation of drag reduction features within the disc drive to reduce vibrations on the actuator assembly and read/write heads caused by air turbulence and drag loads on the actuator assembly.
BACKGROUND OF THE INVENTION
Disc drives are data storage devices that store digital data in magnetic form on a rotating storage medium on a disc. Modern disc drives comprise one or more rigid discs that are coated with a magnetizable medium and are mounted on the hub of a spindle motor for rotation at a constant high speed. Information is stored on the discs in a plurality of concentric circular tracks typically by an array of transducers (“heads”) mounted to a radial actuator for movement of the heads relative to the discs. Each of the concentric tracks is generally divided into a plurality of separately addressable data sectors. The read/write transducer, e.g. a magnetoresistive read/write head, is used to transfer data between a desired track and an external environment. During a write operation, data is written onto the disc track and during a read operation the head senses the data previously written on the disc track and transfers the information to the external environment. Critical to both of these operations is the accurate locating of the head over the center of the desired track.
The heads are mounted via flexures or suspensions at the ends of a plurality of actuator arms that project radially outward from the actuator body. The actuator body pivots about a shaft mounted to the disc drive housing at a position closely adjacent the outer extreme of the discs. The pivot shaft is parallel with the axis of rotation of the spindle motor and the discs, so that the heads move in a plane parallel with the surfaces of the discs. Alternatively, linear actuators may be used in place of rotary actuators to move the heads in a linear direction along a radial line of the discs. Regardless of whether a rotary or a linear actuator mechanism is utilized, the heads are typically mounted on a slider (e.g., a ceramic block) having a specially etched air bearing surface that forms an air cushion or “bearing” as the disc rotates beneath the slider. The hydrodynamic lifting force provided by the air bearing surface counters an opposing preload force supplied by the suspension and causes the slider to lift off and “fly” a very small distance above the surface of the disc. Although the fly height of the slider is only a fraction of a micron, this thin film of air between the slider and the disc prevents damage to the fragile magnetic coating on the surface of the disc.
The current generation of disc drives rotates faster and writes data on data tracks that are more closely spaced together than on prior disc drives. Thus, it has become more difficult on these current disc drives to maintain the read/write head centered over a particular disc track as the disc is spinning. Any error in the position of the head relative to the desired track can lead to improper read or write operations and ultimately to data loss.
The ability to maintain the proper head position is made even more difficult by the aerodynamic conditions within the disc drive. As noted above, air within the disc drive is pulled along with the spinning discs to form the cushion or “bearing” that allows the head to fly at a very low altitude over the disc surface. This airflow is often quite turbulent, particularly where the discs rotate at a relatively high rate of speed, and the impact of the turbulent airflow on the actuator arm and suspension causes the suspension (and thus the head) to vibrate in a random manner.
In an effort to reduce the turbulent nature of the airflow within a disc drive, some drive manufacturers have added one or more air dams to the disc drive as shown in U.S. Pat. No. 6,097,568, entitled “Air Dams Positioned Between Spinning Disks for Reducing the Vibration in a Data Storage Device.” Such air dams include an arm positioned in the airspace between two adjacent discs to provide an obstruction to the airflow, thereby reducing the energy of the airflow so that the actuator arm/suspension experiences a less turbulent flow. However, it has been found that the presence of such air dams within the enclosed disc drive can often create turbulence as the airflow passes over the air dam. Specifically, as most air dams have a rectangular cross section, it is known that flow separation can occur as the airflow passes over the fingers of the air dam, thereby creating a low pressure area and turbulent eddies immediately downstream of the air dam. These turbulent eddies propagate throughout the drive and ultimately impact the actuator arm/suspension to cause undesired vibrations in the read/write head. Furthermore, it has been observed that the presence of conventional air dams immediately upstream of the actuator assembly can create sufficient additional turbulence that the power requirement of the disc drive (i.e., the power requirement of the spindle motor) is actually increased due to increased “skin friction drag” between the airflow and the surfaces of the disc.
As an alternative to air dams, manufacturers may choose to add structures such as shrouds to closely surround the rotating discs and thereby direct or channel the air within the disc drive in a controlled manner. One such shroud is shown in U.S. Pat. No. 5,696,649, entitled “Elastic Insert Shroud to Provide Maximum Effective Shrouding Shock Mitigation and Filtering in High Speed Disk Drives.”
A further alternative is to streamline the leading edge of the actuator arm/suspension to reduce the impact of the turbulent flow on the actuator arm. Such a design is shown in U.S. Pat. No. 5,999,372, entitled “Actuator Arm with Streamlined Leading Edge to Reduce Air Turbulence,” which patent is assigned to the assignee of the present application. This patent describes streamlining the leading edges of the actuator arm/suspension as a way to reduce turbulence within the disc drive, thereby reducing the “skin friction drag” on the discs and the power requirement of the spindle motor. That is, this patent describes the creation of a more laminar flow within the disc drive. However, laminar flow is more likely than a turbulent flow to become separated from an object (such as an actuator arm) as the airflow passes over and around the object. Such flow separation leads to relatively high levels of “pressure drag” which is caused by areas of low pressure behind the object, as noted above.
Thus, prior art attempts to reduce airflow induced vibrations on the actuator arm/suspension have concentrated on adding additional structure to reduce the amount of turbulent airflow within the disc drive. However, while the use of air dams, shrouds and tapered actuator arms/suspensions may create a more laminar flow between the discs, relatively large levels of pressure drag may still be experienced by the actuator arms/suspensions as the airflow separates from these structures.
Accordingly, there is a need for reducing the level of airflow induced vibrations experienced by the actuator arm/suspension of a disc drive. The present invention provides a solution to this and other problems, and offers other advantages over the prior art.
SUMMARY OF THE INVENTION
The present invention relates to a disc drive having surface features that reduce the drag forces experienced by the actuator assembly during operation of the disc drive, thereby reducing read/write errors due to drag-induced vibrations on the heads of the disc drive.
In accordance with one embodiment of the present invention, a disc drive includes a disc mounted for rotation on a spindle motor, and an actuator assembly for moving a head above the surface of the disc. The actuator assembly includes an actuator arm and a suspension, wherein the suspension includes a load beam connected at one end to a distal end of the actuator arm and at an opposite end to the head. The actuator assembly includes a plurality of surface features formed on a
Boutaghou Zine Eddine
Himes Adam Karl
Mangold Markus Erwin
Rao Ram Mohan
Ryun Scott Edward
Cao Allen
Seagate Technology LLC
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