Dynamic magnetic information storage or retrieval – Record transport with head stationary during transducing – Disk record
Reexamination Certificate
2000-09-30
2002-10-15
Evans, Jefferson (Department: 2652)
Dynamic magnetic information storage or retrieval
Record transport with head stationary during transducing
Disk record
Reexamination Certificate
active
06466398
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to disk drives for computer systems. More particularly, the present invention relates to a disk drive comprising a cover having slots near a shaft aperture for reducing resonance.
2. Description of the Prior Art
A computer system usually includes one or more disk drives for economical, non-volatile data storage.
FIG. 1
shows a prior art disk drive
100
disclosed, for example, in U.S. Pat. No. 5,282,100 to Tacklind et al. which includes a housing formed by fitting a cover comprising an inner layer
102
and an outer layer
104
to a base
106
to create a sealed head disk assembly (HDA) chamber. The HDA includes one or more disks
108
stacked in a spaced-apart relationship on a spindle motor hub and rotated by a spindle motor (not shown). The disks
108
rotate in close proximity to a head
114
that is disposed by means of a head gimbal assembly (HGA) attached to one of a plurality of actuator arms
110
.
The spindle motor includes a stationary element such as a fixed spindle shaft
116
affixed to the disk drive housing at the base and cover to define and stabilize a spindle axis about which a hub rotates the disks
108
. A stator of the spindle motor, as well as bearings and seals, are secured between the fixed spindle shaft
116
and the rotating hub. To create this stabilized spindle axis, inner layer
102
includes shaft aperture
118
for receiving a fastener, such as a screw
120
, for rigidly attaching the inner layer
102
to the fixed spindle shaft
116
.
The actuator arms
110
are part of a head stack assembly (HSA) which is rotated about a pivot bearing assembly by a voice coil motor (VCM)
112
. The pivot bearing assembly includes a stationary element such as a pivot shaft
122
that is fixed to the disk drive housing at the base
106
and inner layer
102
of the cover to define and stabilize a pivot axis for the HSA. Typically, the pivot shaft
122
is rigidly coupled to the cover (e.g., by screw
124
) and to the base
106
. The rigid attachment of the spindle and pivot shafts fixes and stabilizes the relationship of the spindle axis and the pivot axis to control head positioning error. As the spindle motor rotates, the bearings and the fixed spindle shaft
116
tend to vibrate at a first set of characteristic frequencies associated with the bearings. The spindle motor and disk pack also tend to vibrate creating a resonance at a second set of frequencies associated with forward and reverse pitch modes of the spindle motor. If the first set frequencies line up with the second set of frequencies (vibration modes), the resulting resonance can perturb the actuator arms
110
impairing the ability of the disk drive
100
to maintain the heads
114
over the centerline of data tracks during read and write operations. If the heads
114
move off track, the fidelity of data written to and read from the disks
108
degrades and may result in failures. Thus, it is desirable to prevent vibration frequencies characteristic of the bearings and fixed spindle shaft
116
from lining up with vibration modes characteristic of the spindle motor and disk pack.
FIG. 2
shows a cover of a prior art HDA intended to reduce the resonances by shifting vibration frequencies characteristic of the fixed spindle shaft
116
away from the vibration frequencies characteristic of the spindle motor bearings. A washer
126
is attached to the inner layer
102
of the cover using a visco damping adhesive (the cover of
FIG. 2
is inverted). The washer
120
is aligned concentric with the shaft aperture
118
and abuts the fixed spindle shaft
116
creating a damping effect. The damping effect of the washer
126
shifts the vibration mode frequencies characteristic of the motor and disk pack away from the vibration frequencies characteristic of the spindle motor bearings. However, incorporating the washer
126
requires an additional component in the disk drive
100
, and requires an additional manufacturing step. Further, the visco damping adhesive for attaching the washer
126
to the inner layer
102
of the cover may creep and become less secure with time and temperature.
There is, therefore, a need to reduce resonances in a disk drive in a secure, cost-effective manner.
SUMMARY OF THE INVENTION
The present invention may be regarded as a disk drive with reduced resonance, comprising a disk, a fixed spindle shaft disposed axially through the disk, a spindle motor for rotating the disk about the fixed spindle shaft, wherein a resonance is associated with the spindle motor rotating the disk. The disk drive further comprises a head, an actuator arm for actuating the head radially over the disk, a base, and a cover attached to the base to form a head disk assembly chamber. The cover comprises a shaft aperture positioned over the fixed spindle shaft, the shaft aperture for receiving a fastener for attaching the cover to the fixed spindle shaft. The cover further comprises a plurality of slots proximate the shaft aperture, wherein the shaft aperture and slots provide a flexible support for the fixed spindle shaft which reduces the resonance associated with the spindle motor.
In one embodiment, the slots comprise a plurality of slot apertures. In another embodiment, the slots comprise a plurality of grooves. In yet another embodiment, the cover comprises an inner and outer layer, and the inner layer comprises the slots. In yet another embodiment, the slots comprise at least one spoke extending substantially radially from the shaft aperture. In yet another embodiment, the slots comprise at least one arc substantially concentric with the shaft aperture. In yet another embodiment, the slots comprise at least one spoke extending substantially radially from the shaft aperture, and at least one arc substantially concentric with the shaft aperture.
The present invention may also be regarded as a method for manufacturing a disk drive with reduced resonance. A shaft aperture is formed in a cover, and plurality of slots are formed in the cover proximate the shaft aperture. A head disk assembly is disposed into a base of a head disk assembly chamber. The head disk assembly comprises a disk, a fixed spindle shaft, and a motor for rotating the disk about the fixed spindle shaft. The cover is attached to the base of the head disk assembly chamber by attaching a fastener to the fixed spindle shaft through the shaft aperture. The slots provide a flexibility in the cover which reduces a resonance associated with the spindle motor rotating the disk.
REFERENCES:
patent: 5282100 (1994-01-01), Tacklind et al.
patent: 5781373 (1998-07-01), Larson et al.
patent: 5790344 (1998-08-01), Allen
patent: 5875067 (1999-02-01), Morris et al.
patent: 6177173 (2001-01-01), Nelson
patent: 6249400 (2001-06-01), Hong et al.
patent: 6266207 (2001-07-01), Iwahara et al.
patent: 6275352 (2001-08-01), Tadepalli et al.
patent: 6308961 (2001-10-01), Kunikane et al.
patent: 9-73741 (1997-03-01), None
patent: 11-328945 (1999-11-01), None
Butler Walter W.
Foisy Gregory G.
Gustafson John R.
Evans Jefferson
Kim Esq. W. Chris
Shara, Esq. Milad G.
Western Digital Technologies Inc.
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