Dynamic magnetic information storage or retrieval – Automatic control of a recorder mechanism – Controlling the head
Reexamination Certificate
1998-06-30
2001-02-13
Kim, W. Chris (Department: 2753)
Dynamic magnetic information storage or retrieval
Automatic control of a recorder mechanism
Controlling the head
C360S069000
Reexamination Certificate
active
06188540
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
Embodiments of this invention relate generally to disk drives of the type generally used for storing digital data, and in particular to methods and devices for parking the heads used in a disk drive at a constant velocity, and disk drive systems incorporating the same.
2. Description of Related Art
Modern computers require media in which digital data can be quickly stored and retrieved. Magnetizable (hard) layers on disks have proven to be a reliable media for fast and accurate data storage and retrieval. Disk drives that store and retrieve data from hard disks have thus become popular components of computer systems.
FIG. 1
illustrates a conventional disk drive system that could be used to implement embodiments of the present invention.
FIG. 1
shows a disk drive system
2
comprising a disk drive microprocessor
4
, control logic
6
, voice coil motor driver
8
, voice coil motor
10
, head assembly
12
, read/write heads
14
, hard disks
16
, spindle motor
18
, and spindle motor drivers
20
. In operation, a computer
22
communicates through controller
24
with the disk drive microprocessor
4
. In response to commands from the controller
24
, the disk drive microprocessor
4
, by means of control logic
6
, activates voice coil motor driver
8
. The voice coil motor driver
8
energizes the voice coil motor
10
to position the head assembly
12
and read/write heads
14
over specific track locations on the hard disks
16
, which are rotating at a substantially constant velocity under the impetus of the spindle motor
18
and spindle motor drivers
20
. Once the read/write heads
14
have stabilized over the appropriate tracks, the read/write heads
14
can read data from, or write data to, the hard disks
16
.
Those skilled in the art will recognize that the disk drive system
2
of
FIG. 1
is not intended to limit embodiments of the present invention. Indeed, those skilled in the art will recognize that alternative hardware configurations may be used without departing from the scope of the present invention.
In typical disk drive systems, the hard disks rotate at high velocities and read/write heads are positioned over the hard disks with very little air gap separation. In this configuration, read/write head contact with the hard disks (a head crash) can be catastrophic. Data can be permanently lost, or the read/write heads or hard disks can be damaged such that the entire disk drive system no longer functions. Therefore, modern disk drive systems avoid head contact with the hard disks as much as possible. To minimize read/write head contact with the hard disks, many disk drives park their read/write heads when the disk drive system is powered down so that the read/write heads rest over a parking zone (an area on the hard disks where no data is stored, typically the innermost central region of the disks) instead of an area used for storing data. The use of a parking zone minimizes wear on the recording area of the disks and thus increases the reliability of the disk drive system and the integrity of the stored data. Head parking circuitry activates when the disk drive system is being powered down or when the hard disks temporarily stop spinning. Such circuitry energizes the voice coil motor and moves the read/write heads to the parked position on the hard disks.
FIG. 2
illustrates a conventional head positioning system that includes a head parking system. Under normal operating conditions where data is being written to or read from the hard disks, a voice coil motor driver
8
, consisting of a first driver
8
a
and a second driver
8
b
, produces a current flow through a voice coil motor
10
. This current flow magnetizes a voice coil
10
a
, and causes the voice coil
10
a
to push or pull on a fixed permanent magnet
10
b
surrounding the voice coil
10
a
. These forces of repulsion or attraction cause the voice coil
10
a
to move in relation to the fixed permanent magnet
10
b
. Because the voice coil
10
a
is fixedly attached to the read/write heads
14
through the head assembly
12
, movement of the voice coil
10
a
results in movement of the read/write heads
14
in relation to the hard disks
16
.
Activation of the parking circuitry is triggered by the application of a park voltage source
26
to the voice coil motor
10
through a park voltage resistive network
28
. The park voltage source
26
is typically generated by stored energy in the spindle motor
18
or a storage capacitor
18
a
When the park voltage source
26
is applied, a constant current is sourced through the voice coil motor
10
, which magnetizes the voice coil
10
a
and results in movement of the voice coil
10
a
and fixedly attached read/write heads
14
towards the park position.
However, the constant current provided by the park voltage source
26
causes the read/write heads
14
to accelerate towards the park position, creating high gravitational forces and mechanical stress on the head assembly
12
. Acceleration of the head assembly
12
and gravitational forces can be minimized if the read/write heads
14
are parked at a constant velocity. Constant velocity parking will drastically reduce the chance of head slap (heads slapping on the disc) and resultant media defects.
One proposed way of parking read/write heads at a constant velocity is disclosed in the Carobolante patent (U.S. Pat. No. 5,566,369), incorporated herein by reference, which uses a feedback loop comprised of an active component (op amp) and resistors to maintain a constant voltage across the voice coil. In Carobolante, knowledge of the resistive component of the voice coil is necessary to select proper resistor values.
SUMMARY OF THE DISCLOSURE
Therefore, it is an object of embodiments of the invention to provide a system, method, or device for parking the read/write heads in a disk drive system at a constant velocity.
It is a further object of preferred embodiments of the invention to provide a system, method, or device for parking the read/write heads in a disk drive system at a constant velocity, wherein the system, method, or device is adjustable so that the optimum park velocity can be selected.
It is a further object of preferred embodiments of the invention to provide a system, method, or device for parking the read/write heads in a disk drive system at a constant velocity which avoids the use of active feedback and the necessity of knowing the resistivity of the voice coil.
These and other objects are accomplished according to a system for moving a plurality of heads in a disk drive, wherein the system is comprised of (1) hard disks, (2) a plurality of heads for reading from or writing to the hard disks, (3) a voice coil motor for moving the plurality of heads, (4) a voice coil motor driver for energizing the voice coil motor and moving the heads during normal read/write operations, (5) a voltage clamp device for regulating the voltage across the voice coil motor and moving the heads with constant velocity during head parking, and (6) a park voltage source for energizing the voltage clamp device through a park voltage resistive network during head parking. The voltage clamp device is further comprised of (1) a first transistor for providing a constant voltage at the output of the voltage clamp device, (2) a switch for providing current to the first transistor, and (3) a voltage divider for dividing down the input voltage to the voltage clamp device and turning on the first transistor.
These and other objects, features, and advantages of embodiments of the invention will be apparent to those skilled in the art from the following detailed description of embodiments of the invention, when read with the drawings and appended claims.
REFERENCES:
patent: 3705333 (1972-12-01), Galetto et al.
patent: 4306117 (1981-12-01), Jacobson
patent: 4831469 (1989-05-01), Hanson et al.
patent: 5455496 (1995-10-01), Williams et al.
patent: 5566369 (1996-10-01), Carobolante
patent: 5838515 (1998-11-01), Mortazavi et al.
Chia Kok Hoe
Gan Kah Liang
Lum Chee Wai
Quak Beng Wee
Kim W. Chris
Merchant & Gould P.C.
Seagate Technology LLC
Wong K.
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