Dynamic magnetic information storage or retrieval – Head mounting – For adjusting head position
Reexamination Certificate
1999-03-18
2002-05-21
Klimowicz, William (Department: 2652)
Dynamic magnetic information storage or retrieval
Head mounting
For adjusting head position
C360S294600
Reexamination Certificate
active
06392848
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a head carriage assembly and a disk device incorporating thereof, and particularly relates to a magnetic head carriage assembly suitable for high-density recording and a magnetic disk device incorporating thereof.
2. Description of the Related Art
There is a continuous effort toward developing magnetic disk devices, for example, a 3.5-inch type, which devices are capable of implementing a high-density recording. In order to achieve a high-density recording, it is necessary to increase the value of tracks per unit length (TPI) of magnetic disks. With such an increased value of TPI, a width of each track will be narrowed, so that it is necessary to improve a positioning accuracy of the magnetic head. When the value of TPI is increased to 25000, a track pitch will be 1 &mgr;m, so that the positioning accuracy of the magnetic head needs to be less than 0.1 &mgr;m.
A basic way of improving the positioning accuracy of the magnetic head is to increase a loop gain in a positioning-servo system so as to obtain a higher crossover frequency in an open loop. An upper limit of the loop gain in the positioning-servo system depends on a natural frequency of the head carriage supported at a bearing so as to be pivotable about a shaft. Therefore, the magnetic disk device of the related art is designed such that the head carriage has a high rigidity, so that the natural frequency of the head carriage is increased and the loop gain in the positioning-servo system is as great as possible.
However, even if the rigidity of the head carriage is maximized, it is not possible to prevent a translational force from acting on a bearing in a direction influencing the positioning of the magnetic head. In other words, a translational mode occurs at the bearing. Therefore, it is difficult to achieve a positioning accuracy of less than 0.1 &mgr;m of the magnetic head.
Japanese Laid-Open Patent Nos. 59-116965 and 8-306142 disclose magnetic head carriage assemblies which can prevent such a translational mode from occurring at the bearing.
FIGS. 1A and 1B
are diagrams showing a magnetic head carriage assembly
10
described in Japanese Laid-Open Patent No. 59-116965. The magnetic head carriage assembly
10
includes a head carriage
11
having a magnetic head
15
at one end and a bearing
12
at the other end. The magnetic head carriage assembly
10
also includes magnetic driving mechanisms
13
,
14
provided on both sides of the bearing
12
. The magnetic driving mechanisms
13
,
14
are driven simultaneously in mutually equal and opposite directions, thus causing the head carriage
11
to pivot about the bearing
12
. The magnetic head
15
is moved in a radial direction of the rotating magnetic disk
16
so as to implement seeking and positioning operations. A translational force acting on the bearing
12
is cancelled by equal and opposite forces F
1
, F
2
which are exerted by the magnetic driving mechanisms
13
,
14
driven simultaneously.
FIG. 2
is a diagram showing a magnetic head carriage assembly
20
described in Japanese Laid-Open Patent No. 8-306142. The magnetic head carriage assembly
20
includes a head carriage
21
having a magnetic head
27
at one end and a bearing
22
at the other end. The magnetic head carriage assembly
20
also includes magnetic driving mechanisms
23
,
24
provided on both sides of the bearing
22
. In the figure, reference numeral
25
show an axis in a longitudinal direction of the head carriage
21
. Reference numeral
26
show a line passing through the bearing
22
and perpendicular to the axis
25
.
The magnetic driving mechanisms
23
,
24
are provided at positions on an opposite side of the head carriage
27
with respect to the line
26
(right hand side in FIG.
2
). Forces F
3
, F
4
are produced by actuating the magnetic driving mechanisms
23
,
24
, so that the head carriage
21
is pivoted about the bearing
22
. The magnetic head
27
is moved in a radial direction of the rotating magnetic disk
28
so as to implement seeking and positioning operations. A translational force acting on the bearing
22
is reduced by the forces F
3
, F
4
which are exerted by the magnetic driving mechanism
23
,
24
.
With the magnetic head carriage assembly shown in
FIGS. 1A and 1B
, since the translational force acting on the bearing
12
is cancelled out, it is possible to increase the loop gain in the positioning-servo system and thus accurately positioning the magnetic head. However, as can be seen from
FIG. 1A
, the magnetic driving mechanism
14
constrains a freedom of a layout of the magnetic disk
16
and the magnetic head carriage assembly
10
. Therefore, it is a problem that the magnetic head device cannot be assembled easily. Also, it is a problem that information recorded on the magnetic disc
16
may be degraded since the magnetic circuit of the magnetic driving mechanism
14
is too close to the magnetic disk
16
.
According to the magnetic head carriage assembly
20
shown in
FIG. 2
, the limitation of the layout between the magnetic disk
28
and the magnetic head carriage assembly
20
is reduced by a certain amount compared to the magnetic head carriage assembly
10
shown in FIG.
1
. However, since the forces F
3
, F
4
both include components in the direction of the line
26
, a translational force F
5
is produced which acts on the bearing
22
. Therefore, a translational mode is produced at the bearing
22
. The translational force F
5
acts in the direction of the line
26
, which direction influences the positioning accuracy of the magnetic head,
27
with respect to the track. Therefore, it is difficult to improve the positioning accuracy of the magnetic head.
SUMMARY OF THE INVENTION
Accordingly, it is a general object of the present invention to provide a head carriage assembly and a disk device incorporating thereof which can solve the problems above.
It is another and more specific object of the invention to provide a magnetic head carriage assembly and a magnetic disk device which can achieve an increased recording density while achieving an accurate positioning of a magnetic head.
In order to achieve the above objects, a head carriage assembly includes:
a head carriage having a magnetic head at a first end part and a bearing between the first end part and a second end part, the head carriage being pivotable about a shaft cooperating with the bearing in such a manner that the head moves in a radial direction of a rotating disk to be read;
first driving means provided at the second end of the head carriage and generating a force for pivoting the head carriage; and
second driving means generating a further force for pivoting the head carriage.
In one aspect of the above-described head carriage assembly, the second driving means is provided at a location on a line passing through the shaft and perpendicular to a longitudinal axis of the head carriage. Further, such a location may be on the opposite side of a center of rotation of the disk with respect to the longitudinal axis.
In another aspect of the above-described head carriage assembly, the second driving means is provided at a location on a longitudinal axis of the head carriage between the first end and the bearing.
With the head carriage assembly described above, it is possible to improve an accuracy of a track-following operation while preventing the disk and the head carriage assembly from interfering with each other.
It is still another object of the present invention to provide a disk device which can achieve an increased recording density while achieving an accurate positioning of a magnetic head.
In order to achieve the above object, a disk device includes:
1) a chassis base;
2) a disk to be rotated about a spindle fixed on the chassis base;
3) a head carriage assembly comprising:
a head carriage having a magnetic head at a first end part and a bearing between the first end part and a second end part, the head carriage being pivotable about a shaft cooperating with the be
Fujitsu Limited
Greer Burns & Crain Ltd.
Klimowicz William
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