Dynamic magnetic information storage or retrieval – Automatic control of a recorder mechanism – Controlling the head
Reexamination Certificate
1999-05-05
2003-08-12
Hudspeth, David (Department: 2651)
Dynamic magnetic information storage or retrieval
Automatic control of a recorder mechanism
Controlling the head
Reexamination Certificate
active
06606216
ABSTRACT:
FIELD OF THE INVENTION
The invention relates generally to magnetic disk drive storage systems and, more specifically, to a method and an apparatus for using separate servo and data read elements to allow for more efficient positioning of a transducer.
BACKGROUND OF THE INVENTION
A magnetic disk drive system is a digital data storage device that stores digital information within concentric tracks on a storage disk (or platter). The storage disk is coated with a magnetic material that is capable of changing its magnetic orientation in response to an applied magnetic field. During operation of a disk drive, the disk is rotated about a central axis at a substantially constant rate. To write data to or read data from the disk, a magnetic transducer is positioned above a desired track of the disk while the disk is spinning.
Writing is performed by delivering a write signal having a variable current to a transducer while the transducer is held close to the rotating disk over the desired track. The write signal creates a variable magnetic field at a gap portion of the transducer that induces magnetic polarity transitions into the desired track. The magnetic polarity transitions are representative of the data being stored.
Reading is performed by sensing magnetic polarity transitions previously written on tracks of the rotating disk with the transducer. As the disk spins below the transducer, the magnetic polarity transitions on the track present a varying magnetic field to the transducer. The transducer converts the magnetic signal into an analog read signal which is amplified in a preamplifier, whereafter the signal is delivered to a read channel for appropriate processing. The read channel converts the analog read signal into a properly timed digital signal that, after additional processing, can be recognized by a host computer system external to the drive.
The transducer contains a read element and a write element to respectively perform the functions of writing to and reading from the disk. Some transducers contain dual-purpose elements which can both write to and read from the disk, but modern transducers separate the read element from the write element for reasons explained below.
Portions of a standard disk drive, generally designated
100
, are illustrated in
FIGS. 1A and 1B
, where
FIG. 1A
is a top view of the disk drive
100
and
FIG. 1B
is a sectional side view thereof The disk drive comprises disks
104
that are rotated by a spin motor (not shown). The spin motor is mounted to a base plate (not shown). Data is stored on magnetic material which coats the two surfaces
108
of the disk
104
. An actuator arm assembly
112
is also mounted to the base plate.
The actuator arm assembly
112
includes a transducer
116
mounted to an actuator arm
124
. The actuator arm
124
rotates about a bearing assembly
128
. The actuator arm assembly
112
cooperates with a voice-coil motor (VCM)
132
which moves the transducer
116
relative to the disk
104
. The spin motor and voice-coil motor
132
are coupled to a number of electronic circuits mounted to a printed circuit board (not shown) which control their operation. A number of wires
136
, among other things, are used to couple the transducer
116
to the read channel (not shown in FIG.
1
A). These wires are routed from circuitry within the drive, across the actuator arm assembly
112
and to the transducer
116
. An analog read signal and an analog write signal are transported by these wires
136
. The analog read signal is amplified by a preamplifier
140
before it is further processed by other circuitry (not shown) into a digital representation of the data stored on the disk
104
. The preamplifier
140
is typically located on the actuator arm assembly
112
and positioned as close to the transducer
116
as practical so that noise may be reduced. After the preamplifier
140
, the amplified analog read signal is passed to other circuitry which may include a read channel chip, a microprocessor-based controller and a random access memory (RAM) device, among other things.
As shown in
FIG. 1B
, each of the plurality of disks
104
has two sides, with magnetic material
108
on each of those sides. Two actuator arm assemblies
112
are provided for each disk
104
. To position the transducer
116
, the VCM
132
moves all actuator arms
124
in unison relative to their respective disks
104
. The VCM
132
makes position adjustments to the pivotally connected actuator arms
124
so that a particular transducer is centered over a data track
144
(see FIG.
1
A). As is well understood in the art, movement of each actuator arm
124
can be independently optimized for imperfections in the arcuate geometry of each data track
144
on the actuator arm's corresponding magnetic surface
108
.
Referring to
FIG. 1A
, data is stored on the disk
104
within a number of concentric data tracks
144
(or cylinders). Each data track
144
is divided into a plurality of sectors, and each sector is further divided into a data region
148
and a servo region (or servo sector)
152
.
Servo sectors
152
are used to, among other things, provide transducer position information so that the transducer
116
can be accurately positioned by the actuator arm
124
over the data track
144
, such that user data can be properly written onto and read from the disk
104
. The data regions
148
are where non-servo related data (i.e., user data) is stored and retrieved. Such data, upon proper conditions, may be overwritten. Because servo sectors are embedded into each data track
144
on each disk
104
between adjacent data regions
148
, the type of servo-scheme shown in
FIG. 1A
is known by those skilled in the art as an embedded servo scheme (or sectored servo scheme).
A more detailed view of a transducer, generally designated
116
, used for reading and writing magnetic polarity transitions to a magnetic media (not shown) is illustrated in FIG.
2
. Referring to the figure, portions of the transducer
116
which face the magnetic media are shown. The part of the transducer
116
shown in this view is commonly called the air bearing surface. The transducer
116
includes a write element
200
, write gap
204
, first shield
208
, second shield
212
, read gap
216
, and magnetoresistive (MR) read element
220
. Unlike some early inductive transducers, the depicted transducer
116
has separate read and write elements. Magnetoresistive (MR) strips are commonly used in read elements because they change resistance when exposed to a magnetic field, and this change in resistance is relatively easy to sense. It should be noted that the read element
220
is used for reading both servo and data regions. It is further noted that the write element
200
typically has a width
224
which is greater than a width
228
of the MR read element
220
. For example, the width
224
of the write element
200
might be twice the width
228
of the read element
220
. The reason for this width variance is explained below.
As part of the writing process, a variable current is used to induce magnetic flux across the write gap
204
between the write element
200
and the first shield
208
. The write element
200
and first shield
208
act as poles for an electromagnet which induces magnetic flux across the write gap
204
. The direction of the variable current defines the direction in which the magnetic flux will be oriented across the write gap
204
. In some simple recording systems, flux polarized in one direction across the write gap
204
will record a binary “one” on the magnetic media while flux polarized in the opposite direction will record a binary “zero.” In most recording systems, a change in the direction that the flux travels across the gap
204
is interpreted as a “one” while the lack of a change is interpreted as a “zero.” As the magnetic material on the disk surface
108
(shown in
FIG. 1A
) travels under the transducer
116
in the direction shown by arrow
232
, a series of digital “ones” and “zeros” can be written within the data track
Dovek Moris M.
Liikanen Bruce A.
Purkett John C.
Hansra Tejpal S.
Hudspeth David
Maxtor Corporation
Slavitt Mitchell
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