Dynamic magnetic information storage or retrieval – Automatic control of a recorder mechanism
Reexamination Certificate
2000-11-20
2004-05-11
Hudspeth, David (Department: 2651)
Dynamic magnetic information storage or retrieval
Automatic control of a recorder mechanism
C360S073030, C360S075000, C360S097020
Reexamination Certificate
active
06735035
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and apparatus for enabling cold temperature performance of a disk.
2. Background of the Invention
There are environmental conditions where applying power and attempting to spin up a magnetic disk drive storage device can lead to extensive and often irreversible damage and data loss. Among such detrimental environmental conditions is cold temperatures. Manufacturers often warn users of computer systems, particularly personal computers and laptop computers, to avoid turning on “cold” or “frozen” systems until the unit has warmed up to a “safe” temperature. Unfortunately, such warnings are often unheeded, or completely ignored, by users. Thus, it is imperative to protect such computer systems from damage and/or data loss resulting from such ill-advised attempts at turning on “cold” or “frozen” systems before the unit has been sufficiently warmed up.
Direct access storage devices, or hard drives, are widely used in modern computers. Disk drive units, often incorporating stacked, commonly rotated rigid magnetic disks for example, are used for storage of data in magnetic form on the disk surfaces. Data may be recorded in radially spaced data information tracked arrays on the surfaces of the disks. Transducer heads driven in a path towards and away from the drive axis write data to the disks and read data from the disks.
FIG. 2
shows an example of a data storage disk file
100
that includes a magnetic disk drive unit
102
and interface control unit
114
. Magnetic disk drive unit
102
includes at least one disk
116
having at least one magnetic surface
118
which may be contained within a disk drive enclosure
122
. The disk
116
may be mounted for rotation on and by integrated spindle motor assembly
126
. Information on each magnetic disk surface
118
may be read from or written to the disk surface
118
by a corresponding transducer head assembly
128
which may be movable in a path having a radial component across the rotating disk surface
118
. Each transducer head assembly
128
may be carried by a suspension arm assembly
130
. The suspension arm assemblies
130
are bundled together for simultaneous pivotal movement by actuator coil motor
132
cooperating with an internal magnet and core assembly. Drive signals applied to the actuator coil motor
132
cause the suspension arm assemblies
130
to move in unison to position the transducer head assemblies
128
in correspondence with information storage tracks on the disk surfaces
118
on which information may be written or read.
In particular, disk drive unit
102
has two major mechanical mechanisms that may be affected by cold temperatures. The first mechanism is actuator coil motor
132
, where read/write heads are disposed, and the second mechanism is spindle motor assembly
126
. The problem that cold weather poses to the spindle motor assembly
126
is that, since a torque constant increases as the temperature thereof decreases, grease in the bearings thereof becomes more viscous thereby affecting the performance and ability to move or spin the disk drive.
Current solutions for operation of disk drive unit
102
in cold temperatures include attaching a resistive heater to the top cover
122
of the disk drive unit
102
, wherein the heater may be a resistive wire encapsulated in captan sheet. A thermistor, or equivalent temperature sensor, may then attached to the disk drive unit
102
or adjacent thereto to thereby measure ambient temperature. During system power up, the temperature of the disk drive unit
102
is measured before spin-up of the actuator coil motor
132
or spindle motor assembly
126
. If the measured temperature is below a predetermined minimum threshold temperature, current (either DC, AC or pulsed current) may be applied to the heater, and the temperature may be measured once more. The steps described above are repeated as necessary until the measured temperature equals or exceeds the minimum threshold temperature. Then the heater may be turned off, and power may be applied to the disk drive unit
102
. The actuator coil motor
132
and spindle motor assembly
126
, while spinning and read/write accessing, should then provide sufficient heat dissipation to self-heat the disk drive. However, if the temperature of the disk drive unit
102
drops below a set-limit (i.e., 10° C. below the minimum threshold temperature for example), then the heater may once again be turned on until temperature of the disk drive unit
102
equals or exceeds the minimum threshold temperature. This method requires a significant amount of power to completely heat up the entire disk drive unit
102
prior to spin up of both the actuator coil motor
132
and the spindle motor assembly
126
.
Thus, it is essential to overcome the problems posed by cold weather environments on the normal operation of hard disk drives, which until present has been done by merely avoiding turning on “cold” or “frozen” systems until the unit has warmed up to a “safe” temperature. Since such warnings are often unheeded, or completely ignored, by users, it is imperative to protect such computer systems from damage and/or data loss resulting from such ill-advised attempts at turning on “cold” or “frozen” systems before the unit has been sufficiently warmed up.
SUMMARY OF THE INVENTION
It is, therefore, a principle of object of this invention to provide a method and apparatus for enabling cold temperature performance of a disk.
It is another object of the invention to provide a method and apparatus for enabling cold temperature performance of a disk that solves the above-mentioned problems.
These and other objects of the present invention are accomplished by the method and apparatus for enabling cold temperature performance of a disk disclosed herein.
In view of the fact that spindle torque requirements increase as a temperature thereof decreases, the present invention overcomes the higher torque required due to the increased viscosity of the grease by localizing the heating to the spindle motor assembly. Thus, the viscosity of the grease is reduced, and therefore the present invention enables self-heating by the disk drive during and after spin-up of the spindle motor assembly.
According to a first example embodiment of the present invention a small current (DC, AC or pulsed current) may be applied to one or more windings of a stator of a disk drive unit. Due to the electrical resistance within the windings, heat may be dissipated in the spindle motor assembly, and the dissipated heat may be conducted into the bearing and bearing grease. The grease may then warm to a minimum threshold temperature, thus providing a safe environment for normal operation of spindle motor assembly.
The amount of time required for the current, including any one of a constant DC current AC current and pulsed current, to be applied to the windings of the stator of the disk drive unit may be determined utilizing one of the following. First, in consideration of a voltage measurement of the spindle motor assembly, experimental measurements may be made on spindle motor assembly to determine the change in the resistance of the windings as they change with temperature depending on the change in current or voltage on a given winding. Such measurements may be stored in a table within a controller of the disk drive unit and once the given resistance value is obtained, normal spinning operation of spindle motor assembly may commence.
Secondly, a thermistor may be provided on a card of the disk drive unit. The controller first determines the disk drive card temperature prior to power up. If the temperature disk drive unit card is less than the minimum threshold temperature, the controller performs a table look up for the temperature that is closest to the measured temperature. The controller then applies a current to the stator windings for the given time as specified within the table prior to spin-up of the spindle motor assembly.
The spin-up times would be experimentally determin
Smith Gordon James
Van Leeuwen George Willard
Hudspeth David
International Business Machines - Corporation
Olson Jason
Rabin & Berdo PC
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