Dynamic magnetic information storage or retrieval – General recording or reproducing – Signal switching
Reexamination Certificate
2000-06-26
2004-03-30
Sniezek, Andrew L. (Department: 2651)
Dynamic magnetic information storage or retrieval
General recording or reproducing
Signal switching
C360S078040, C711S112000
Reexamination Certificate
active
06714373
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
The present application is based on Japanese priority application No.11-279943 filed on Sep. 30, 1999, the entire contents of which are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
The present invention generally relates to magnetic storage of information and more particularly to a magnetic disk device having an improved seek control.
In a magnetic disk device that stores information on a rotary magnetic disk, it is necessary for a magnetic head to scan over a surface of the rotary magnetic disk, when reading information from the rotary magnetic disk, until it reaches a specific cylinder or a target track on which the information to be read out is recorded. Such a scanning operation of the magnetic head is called a seek operation and the duration for the seek operation is called a seek time. The smaller the seek time, the higher the access speed of the magnetic disk device.
On the other hand, in the actual magnetic storage device, there arises a case in which the magnetic head, carried on a swing arm at a tip end thereof, may reach the target track with a timing offset from the nominal timing for the portion or sector of the target track (target sector) on which the information to be reproduced is recorded. In such a case, the magnetic head cannot reproduce the information immediately from the target sector but has to wait on that track for another turn of the magnetic disk until the target sector that carries the information to be read out comes right underneath the magnetic head. However, the existence of such a waiting time decreases the reading speed of the magnetic disk device.
FIG.1
is a diagram showing the construction of a magnetic disk device
1
called a hard disk device according to a related art.
Referring to
FIG. 1
, the magnetic disk device
1
includes a magnetic disk
14
accommodated in an enclosure
10
having a cover
12
and stores information on the magnetic disk
14
along concentric tracks or cylinders defined thereon. The magnetic disk
14
is mounted on a spindle motor
18
for rotation, and a floating magnetic head
16
scans over the surface of the magnetic disk
14
. The magnetic head
16
is mounted at an end of a swing arm
24
, wherein the arm
24
is connected to a voice coil motor
20
and the voice coil motor
20
actuates the arm
24
for the swinging motion. With the swinging motion of the arm
24
thus caused by the voice coil motor
20
, the magnetic head
16
scans over the surface of the magnetic disk
14
generally in a radial direction thereof. Thereby, the magnetic head
16
is controlled so as to trace a desired track on the magnetic disk
14
.
FIGS. 2A and 2B
show the magnetic disk
14
respectively in a plan view and in a cross-sectional view.
Referring to
FIG. 2A
, it can be seen that there are a number of concentric tracks
30
formed on a magnetic recording surface
26
of the magnetic disk
14
, wherein the magnetic recording surface
26
is formed on both sides of the magnetic disk
14
. Each of the tracks is divided into a number of sectors
28
, and the magnetic head
16
scans over the magnetic recording surface
26
so as to record or reproduce information on or from a selected target sector
28
of a selected target track
30
.
As represented in the cross-sectional view of
FIG. 2B
, the magnetic head
16
includes an upper head
16
(n) locating above the magnetic disk
14
and a lower head
16
(n−1) locating below the magnetic disk
14
, wherein the upper and lower magnetic heads are floating from the respective, corresponding magnetic recording surfaces
26
n and
26
n−1 by a thin air film. By actuating the arm
24
, the magnetic head
16
performs a seek operation across the tracks
30
from a first track to a next track.
In the magnetic disk device
1
of
FIG. 1
, it should be noted that the magnetic disk
14
in fact includes a plurality of magnetic disks held on the spindle motor
18
coaxially, and the swing arm
24
in fact includes a number of swing arms driven by the voice coil motor
20
as a unitary body. Thereby, the swing arms
24
, and hence the magnetic heads
16
held thereon, scan over the corresponding magnetic disks
14
simultaneously.
The concentric tracks
30
thus formed on the magnetic recording surfaces collectively constitute a cylinder. Thus, a track on the recording surface
26
n and a corresponding track on the recording surface
26
n+1 form together a cylinder.
FIG. 3
shows an example of the seek operation of the magnetic head
16
after the magnetic head
16
has reached a target track or a target cylinder HD(n).
Referring to
FIG. 3
, the magnetic head
16
assumes a state {circumflex over (
1
)} immediately after it reaches the target track HD(n), wherein it can be seen that the target sector or sectors, from which the information is to be read out, has or have already passed the position of the magnetic head
16
.
Under such a situation, it has been practiced to hold the magnetic head
16
on the target track HD(n) until a situation {circumflex over (
2
)} occurs in which the magnetic disk
14
makes another turn and the target sector or sectors comes to the position ready for scanning by the magnetic head
16
on the track HD(n). However, such a conventional seek control process inevitably wastes time and increases the seek time, and hence the access time, of the magnetic storage device.
In the conventional seek control of magnetic heads, a problem similar to the one explained with reference to
FIG. 3
can occur also when there occurred a switching of the magnetic head
16
from the first magnetic head
16
(n) scanning the first recording surface
26
n of the magnetic disk
14
to the second, different magnetic head
16
(n−1) scanning the second recording surface
26
n−1 of the magnetic disk
14
as represented in FIG.
2
B.
Referring to
FIG. 4
, there occurs a switching of the magnetic head
16
from a first magnetic head such as the magnetic head
16
(
0
) scanning a track HD(
0
) on a first recording surface of the magnetic disk
14
to a second magnetic head
16
(
2
) scanning a track HD(
2
) of a second recording surface of the magnetic disk
14
, with a timing such that the second magnetic head
16
(
1
) starts scanning of the first sector
0
of the track HD(
1
) in response to the completion of scanning of the last sector n of the first track HD(
0
).
In order to achieve such a successive cross over of the magnetic heads and hence the tracks, there is provided a predetermined skew between the tracks HD(
0
) and HD(
1
), so that the sector
0
of the track HD(
0
) comes to the position ready for scanning by the second magnetic head when the switching over is completed from the first magnetic head
16
(
0
) to the second magnetic head
16
(
1
) as represented in
FIG. 4
by a broken line.
Thus, as long as the skew thus set is appropriate, the first and second magnetic heads
16
(
0
) and
16
(
1
) constituting collectively the magnetic head
16
successively reproduce information from the sector n of the track HD(
0
) on the first recording surface and then from the sector
0
of the track HD(
1
) on the second recording surface.
In the case the actual skew between the magnetic tracks HD(
0
) and HD(
1
) is different from the predetermined skew as represented in
FIG. 4
by a continuous line, on the other hand, the second magnetic head
16
(
1
) fails to scan the heading part of the target sector
0
of the target track HD(
1
) or may even skip the target sector
0
entirely. Thereby, it has been necessary for the second magnetic head
16
(
1
) to wait on the track HD(
1
) until the magnetic disk
14
makes a further turn and the heading part of the target sector
0
returns again.
Further, such a waiting status may occur also in the seek operation of the magnetic head
16
scanning over the magnetic recording surface in a radial direction of the magnetic disk
14
by way of driving of the voice coil motor
20
in search of a target track. It should be noted that such a scanning of the ma
Fujitsu Limited
Greer Burns & Crain Ltd.
Sniezek Andrew L.
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