Dynamic magnetic information storage or retrieval – Head mounting – Disk record
Reexamination Certificate
1996-03-25
2002-06-25
Tupper, Robert S. (Department: 2652)
Dynamic magnetic information storage or retrieval
Head mounting
Disk record
C360S246200, C360S246300, C360S246400, C360S246500
Reexamination Certificate
active
06411470
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to disk drives that store and retrieve information on a spinning, rigid magnetic recording disk.
BACKGROUND OF THE INVENTION
Conventional hard disk drive systems spin at least one disk containing a thin magnetic media layer or layers in which a head of the system stores data for later retrieval. The head includes an inductive transducer which converts electrical signals from read/write electronics, usually associated with a computer, to magnetic fields which in turn create magnetic patterns in the media during information storage. During reading the transducer converts those magnetic patterns to electrical signals. Alternatively, the written signals may be read with a magnetoresistive sensor included in the head, which senses a change in current or voltage due to the effect of the magnetic patterns on the resistance of the sensor.
The head also includes an aerodynamic slider which is designed to interact with an air layer that accompanies the moving disk to cause a slight separation of the disk and the head, the essentially stationary head “flying” over the spinning disk. Though this separation serves the purpose of avoiding wear of the head and the disk, it also reduces resolution of signal communication between the transducer and the media. To increase data storage density, the air separation between the transducer and the media has generally decreased over many years of development in the magnetic storage industry. However, a smaller separation generally increases the probability of impact between the head and the disk during operation of the disk drive system, often resulting in destruction of the disk drive and loss of stored information. Perhaps the most destructive type of impact can occur due to dynamic instabilities of the head, which cause a corner of the head to impact the disk, focusing the energy transfer of the impact in the relatively small region of contact between the corner and the disk.
Instead of completely separating from the disk, U.S. Pat. No. 4,901,185, to Kubo et al. discloses a slider designed to operate with a leading edge lifted by the air layer that accompanies the spinning disk while a trailing edge contacts the disk, the slider holding a magnetic read/write transducer that is designed for vertically magnetized recording. To avoid destructive wear and to minimize variations in the head-disk separation the head is mounted on the trailing edge of the tail dragging slider so that a constant separation between the head and the disk is maintained.
In U.S. Pat. No. 4,819,091, Brezoczky et al. propose a magnetic recording head comprised of a slider composed of a single crystal material, onto which a magnetic read/write transducer is appended. During operation of the disk drive system the rubbing between the disk and the slider produces an electrical attractive force maintaining contact between the slider and the disk. To avoid destructive wear of the head it is important that the slider be so much more thermally conductive than the much larger disk that the slider is maintained at a lower temperature than the disk during operation of the system. It is also important for the Brezoczky invention to maintain an orientation of the slider relative to the spinning disk that avoids flying and other problems.
An object of the present invention was to provide a hard disk drive recording system which affords substantially continuous operational contact between the head and disk without damaging the head or the disk. More specific objects included the intuitively contradictory goals of minimizing dynamic instabilities of the transducer that would otherwise cause damage or interfere with the reading and writing of data, providing flexibility for transducer conformance to the rapidly spinning, rigid disk surface and providing rapid accessibility of the transducer to various points on the disk surface for data storage and retrieval.
SUMMARY OF THE INVENTION
The above objects have been achieved in a hard disk drive system employing an elongated flexible beam to hold a transducer in sliding contact with a hard magnetic disk during writing and reading, the flexure beam extending lengthwise over the disk substantially along the direction that the transducer slides on the disk. This orientation aligns the most rigid dimension of the beam with the direction of relative motion during contact between the disk and the transducer, thereby reducing deleterious vibrations that may otherwise be induced by friction between the disk and transducer. Due to the alignment between the rapidly spinning disk and the direction of the beam most resistant to mechanical forces, the flexure and transducer can be made smaller and lighter.
The flexure size reduction affords increased flexibility in a direction normal to the disk surface, while the weight reduction provides lower inertial resistance to disk surface variations, both of which help to decrease wear and avoid catastrophic impacts between the head and the disk. The decreased mass and increased flexibility also allow for a reduction in the load applied to hold the transducer to the disk, which along with the decreased mass and increased flexibility affords a reduction in area of contact between the transducer and the disk without a destructive increase in pressure therebetween, while a smaller area of contact reduces the aerodynamic lift of the transducer from the disk, affording a further reduction in applied load. The small transducer contact area also minimizes frictional forces that cause vibrations and power loss, the reduction of friction also allowing a skew to occur between the flexure axis and the motion of the disk at the contact area without inducing excessive lateral vibrations. A magnetic poletip or pair of magnetic poletips separated by an amagnetic gap borders the disk in the contact area of the transducer, reducing spacing between the transducer and the information storage medium of the disk.
The disk can be rotated with the flexure beam oriented along the direction of sliding in either a forward or a reverse mode. In the forward mode a localized portion of the disk contacting the transducer moves generally from an end of the beam adjacent to the actuator to an end of the beam adjacent to the transducer, while in the reverse mode such a portion of the disk moves generally from the transducer end to the mounting end of the beam. One difference between spinning the disk in these two modes is the amount of vertical force between the transducer and the disk due to the friction between the transducer and the disk, as translated by the moment arm of the flexure beam. Spinning the disk in the reverse mode generally creates additional loading between the transducer and the disk, as the beam is usually mounted in a plane outside the disk surfaces, allowing a lower static load to be applied to the beam, although this force is minimized by the extremely low beam angle and flexibility. The ability to operate in either the forward or reverse mode has an added benefit during start up of the system, when bi-directional motion may be employed during motor seeking and for loosening the slider from the disk, an operation which commonly causes conventional aerodynamic sliders, which are not designed for sliding in either direction, to dig into the disk.
In a preferred embodiment a gimbal is interposed between the slider and the flexure beam, providing the slider with additional flexibility to react to disk surface anomalies by pitching and rolling. This improved conformance between the disk and the slider decreases wear to the head and the disk in addition to increasing the tendency of the transducer to remain in contact with the disk. A microscopic slider having three hard disk-contacting projections or pads, at least one of which contains a pole structure of the transducer, is attached to the gimbal. Having a pole structure encased in a disk-contacting pad offers a durable reduction in spacing between the pole structure and the media, while the pads hold the body of the slider sufficiently
Hamilton Harold J.
Martin Timothy W.
Censtor Corporation
Lauer Mark
Tupper Robert S.
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