Geometrical instruments – Gauge – Collocating
Reexamination Certificate
1999-06-04
2001-10-16
Fulton, Christopher W. (Department: 2859)
Geometrical instruments
Gauge
Collocating
C033S551000, C414S935000
Reexamination Certificate
active
06301797
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to rotating disk technology, particularly to disk drive apparatus employed as a memory device and, more specificaly, to a technique for determining computer hard disk alignment and alignment shifts and for providing compensation.
2. Description of the Related Art
In the state of the art of digital data storage, hard disks form the basis for main memory in most computer systems. Hard disk drives provide rapid access to a very large number of data records. Magnetic storage hard disk drives are faster than floppy disk, magnetic tape, and optical disk drives, and cost less than equivalent capacity semiconductor memory. Fundamentals of magnetic recording and disk drives can be found in
The Complete Handbook of Magnetic Recording
by Finn Jorgensen, copyright 1988 (3rd Edition, TAB BOOK Inc., Blue Ridge Summit, Pa.)
FIG. 1
(Prior Art) illustrates the fundamental components of a computer memory, hard disk apparatus (generally referred to simply as the “hard drive”), head-disk assembly
101
. A stack
103
of individual disks
103
a
, each having magnetic recording surface layers (on both sides of the disk), rotates (arrow
105
) at a constant speed (e.g., approximately 5400 RPM) on a hub
106
suitably mounted on a base plate
108
. Mounted in a head stack assembly
111
, load beams
107
extend magnetic transducers (“heads”)
109
which are selectively positioned with respect to each disk's recording surface in order to read and write digital data on the disks
103
a
(see also FIG.
2
). A coil
113
on the head stack assembly
111
interacts with a magnetic drive subassembly
117
to swing the head stack assembly via a rotary shaft, or pivot bearing,
115
reversibly driven about the shaft axis, selectively moving the heads
109
from the inner diameter data tracks to the outer diameter data tracks of the recording surfaces. Appropriate electronics (not shown) are provided for controlling positioning and performing read/write functions via the heads
109
. (See also
FIG. 2
regarding disk formatting). The head stack assembly
111
in combination with the magnetic drive subassembly
117
and pivot bearing
115
is referred to as the “actuator assembly.” In the state of the art, the typical read/write head may have physical dimensions of approximately 0.080-inch by 0.00125-inch; the height of the head above the disk surface may be on the order of approximately 0.75-micro-inch. Because of its shape, the head stack assembly main body part which encompasses the rotary shaft
115
is referred to as an “E-block.” A unitary E-block assembly for use in a disk drive is disclosed in U.S. Pat. No. 5,095,396 (Putnam et al., assigned to the common assignee of the present invention.)
FIG. 2
(Prior Art) illustrates the fundamental constructs (dimensions exaggerated) involved in recording data on a magnetic disk
203
. Physically, a hard drive disk comprises an aluminum substrate platter having a series of thin film layers thereon used in the data recording process and an outer, protective lubricant layer open to the environment (see e.g., U.S. Pat. No. Re. 32,464 (Aine) and its related patents). The disk
203
is formatted by dividing it into sectors
212
by a number of radially-extending spokes
214
placed at regular angular intervals about the disk. The spokes
214
are areas on the disk containing tracking servo bursts and sector identification information. The sectors
212
are areas on the disk containing data blocks
216
, each block having a fixed amount of data, for example 512-bytes. The data blocks
216
occupy circular tracks
218
. The tracks
218
are grouped into bands
220
; all of the tracks
218
in a given band
220
contain the same number of radially aligned data blocks
216
. The section of a band
220
where a set of radially aligned data blocks
16
is recorded is called a block frame
222
. The number of block frames
222
per band increases with band
220
radius. The beginning and end of a block frame
222
are defined by a timing system in a disk controller (not shown). The number of bands
220
is maximized if each band has exactly one more block frame
222
than its inwardly adjacent band. In that case, the number of bands
220
is simply the difference between the number of block frames
222
in the outermost band and the number of block frames in the innermost band. The spokes
214
are numbered, e.g., zero to seven, in the direction opposite to disk rotation. The sectors
212
are also numbered, each sector being numbered the same as the immediately preceding spoke
214
. The block frames
222
in each band
220
are numbered starting from zero; block frame zero in each band is adjacent to spoke zero. In order to maximize storage capacity of the disk
210
, the data blocks
216
along the innermost track
218
of each band
220
are recorded as close as possible to a predetermined maximum linear bit density. As a result, the data rate in megabytes per second in each band increases with radius. The number of tracks
218
is predetermined for a given disk, normally spaced as close as possible to maximize storage density. In the state of the art, typical track density is approximately fifteen thousand (15,000) TPI; a typical data bit density is approximately two-hundred twenty thousand (220,000) BPI; average access time to find any particular data stream is approximately five-to nine milliseconds, holding several gigabytes of information.
The location of any recorded programs and data is stored in a directory area on a disk and informs the disk operating system about the exact sector and track number where the recorded data are to be found. Servo burst signals recorded in the spokes
214
provide positioning information; generally, amplitude and phase of servo-signals provide correction signals to the motor drive electronics associated with the actuator assembly. As known in the art, the design of servo-follower mechanisms, associated electronics, and optimized servo-tracking algorithms requires an analysis of the specific disk drive design implementation. While servo-tracking algorithms can provide for track following where small distortions are involved (e.g., ±100-microinch), inherent limitations in servo-tracking algorithms limits the tracking correction which is available for gross track shifts such as might occur if the head-to-track alignment is skewed, such as by a shock event. With the recognition of the advanced state of the art of such servo technology, a further detailed description is not necessary to an understanding of the present invention for a person skilled in the art.
As should now be recognized, considering the speed of the disk, the size of the heads, the complex data formatting on the disk, servo-follower limitations, and the high track and bit densities, for reliable read/write functionality it is critical that head-to-track alignment be precise.
Disk drive durability has to be maintained under sometimes severe environmental conditions, particularly during computer assembly and in the actual use of portable computers. One of the parameters that affect drive durability is shock, used to describe impact loading of drives. Shock is characterized by its magnitude in G-forces and shock duration. In disk drive technology, withstanding a shock implies that the head-media interface reliability is not compromised due to violent dynamic response of drive components following the shock event. To improve drive insensitivity to both computer assembly process, transportation, in-use handling conditions, and any other environmental situation in which a shock might be imparted to a unit, drive manufacturers are forced to design systems able to withstand higher G-forces over shorter durations; an exemplary shock load specification goal is for a disk drive to withstand a shock of 1000-G's at 1-millisecond without affecting performance.
One of the primary drive failure modes caused by a shock event is referred to as “disk shift” or “disk slippage.
Kuo David Shiao-Min
Sundaram Ramesh
Wang Li-Ping
Yao Wei
Fulton Christopher W.
LaRiviere Grubman & Payne, LLP
Seagate Technology LLC
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