Dynamic magnetic information storage or retrieval – Automatic control of a recorder mechanism – Controlling the head
Reexamination Certificate
1996-02-05
2001-05-29
Sniezek, Andrew L. (Department: 2651)
Dynamic magnetic information storage or retrieval
Automatic control of a recorder mechanism
Controlling the head
C360S078040
Reexamination Certificate
active
06239935
ABSTRACT:
FIELD OF THE INVENTION
The present invention is directed to disk drives. More particularly, the present invention provides an architecture for implementing contact start and stop operations (CSS) in a high data density disk drive product utilizing a magnetoresistive head and a zone texture media.
BACKGROUND OF THE INVENTION
Disk drives are commonly used in workstations, personal computers, laptops and other computer systems to store large amounts of data in a form that can be made readily available to a user. In general, a disk drive comprises a magnetic disk that is rotated by a spindle motor. The surface of the disk is divided into a series of data tracks. The data tracks are spaced radially from one another across a band having an inner diameter and an outer diameter.
Each of the data tracks extends generally circumferentially around the disk and can store data in the form of magnetic transitions within the radial extent of the track on the disk surface. An interactive element, such as a magnetic transducer, is used to sense the magnetic transitions to read data, or to transmit an electric signal that causes a magnetic transition on the disk surface, to write data. The magnetic transducer includes a read/write gap that contains the active elements of the transducer at a position suitable for interaction with the magnetic surface of the disk. The radial dimension of the gap fits within the radial extent of the data track containing the transitions so that only transitions of the single track are transduced by the interactive element when the interactive element is properly centered over the respective data track.
The magnetic transducer is mounted by a head structure to a rotary actuator arm and is selectively positioned by the actuator arm over a preselected data track of the disk to either read data from or write data to the preselected data track of the disk, as the disk rotates below the transducer. The actuator arm is, in turn, mounted to a voice coil motor that can be controlled to move the actuator arm across the disk surface.
A servo system is typically used to control the position of the actuator arm to insure that the head is properly centered over the magnetic transitions during either a read or write operation. In a known servo system, servo position information is recorded on the disk surface between written data blocks, and periodically read by the head for use in a closed loop control of the voice coil motor to position the actuator arm. Such a servo arrangement is referred to as an embedded servo system.
In modern disk drive architectures utilizing an embedded servo, each data track is divided into a number of data sectors for storing fixed sized data blocks, one per sector. Associated with the data sectors are a series of servo sectors, generally equally spaced around the circumference of the data track. The servo sectors can be arranged between data sectors or arranged independently of the data sectors such that the servo sectors split data fields of the data sectors.
Each servo sector contains magnetic transitions that are arranged relative to a track centerline such that signals derived from the transitions can be used to determine head position. For example, the servo information can comprise two separate bursts of magnetic transitions, one recorded on one side of the track centerline and the other recorded on the opposite side of the track centerline. Whenever a head is over a servo sector, the head reads each of the servo bursts and the signals resulting from the transduction of the bursts are transmitted to, e.g., a microprocessor within the disk drive for processing.
When the head is properly positioned over a track centerline, the head will straddle the two bursts, and the strength of the combined signals transduced from the burst on one side of the track centerline will equal the strength of the combined signals transduced from the burst on the other side of the track centerline. The microprocessor can be used to subtract one burst value from the other each time a servo sector is read by the head. When the result is zero, the microprocessor will know that the two signals are equal, indicating that the head is properly positioned.
If the result is other than zero, then one signal is stronger than the other, indicating that the head is displaced from the track centerline and overlying one of the bursts more than the other. The magnitude and sign of the subtraction result can be used by the microprocessor to determine the direction and distance the head is displaced from the track centerline, and generate a control signal to move the actuator back towards the centerline.
Each servo sector also contains encoded information to uniquely identify the specific track location of the head. For example, each track can be assigned a unique number, which is encoded using a Gray code and recorded in each servo sector of the track. The Gray code information is used in conjunction with the servo bursts to control movement of the actuator arm when the arm is moving the head in a seek operation from a current track to a destination track containing a data field to be read or written.
The head structure also includes a slider having an air bearing surface that causes the transducer to fly above the data tracks of the disk surface due to fluid currents caused by rotation of the disk. Thus, the transducer does not physically contact the disk surface during normal operation of the disk drive to minimize wear at both the head and disk surface. The amount of distance that the transducer flies above the disk surface is referred to as the “fly height.” By maintaining the fly height of the head at an even level regardless of the radial position of the head, it is ensured that the interaction of the head and magnetic charge stored on the media will be consistent across the disk.
It is expected that users of disk drives will place ever greater demands on disk drive manufacturers with regard to the amount of data that can be stored in and rapidly retrieved from disk drive products. Modern software programs include graphics and other data structures that dramatically increase the amount of data that need to be stored. In addition, the rapid growth in the use of servers on computer networks requires large storage capabilities to accommodate the data needs of a large number of users on the network who utilize the servers.
Accordingly, recent disk drive research and development efforts have focused on the need to continually improve, among other things, the magnetic media used in the disks so as to substantially increase the storage capacity of each new disk drive design to levels sufficient to accommodate the ever greater demands for storage capacity placed on disk drive products by users. The trend in media design is to develop magnetic materials capable of storing magnetic transitions at ever greater densities, both radially and circumferentially, to achieve a total data storage capacity that is greater than heretofore available.
As noted above, due to operation of the air bearing surface, the transducer does not physically contact the disk surface during normal read and write operation of the disk drive. However, it is generally an objective to achieve an overall fly height that brings the read/write gap of the transducer as close to the disk surface as possible. The closer the active read/write gap of the transducer is brought to the surface of the disk, the stronger the electric signal generated by the transducer due to a magnetic transition on the disk surface which represents data. It is generally advantageous to develop as strong a data signal as possible, to insure reliable electrical performance of the disk drive.
Continuing advances in disk drive design that permit lower fly heights make it feasible to further increase the density of magnetic transitions since the smaller transitions that result from greater densities, as measured by the radial and circumferential extent of each transition, can be adequately sensed by the low flying head. A consequence of the increasin
Merchant & Gould P.C.
Seagate Technolgy LLC
Sniezek Andrew L.
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