Disk drive and head suspension unit

Details Disk drive and head suspension unit Disk drive and head suspension unit

1999-02-05

2002-11-05

Klimowicz, William (Department: 2652)

Dynamic magnetic information storage or retrieval

Head mounting

For shifting head between tracks

C360S266100

Reexamination Certificate

active

06477017

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a disk drive, and, in particular, to a small-sized disk drive and a head suspension unit loaded in a small-sized computer.
Recently, reduction in thickness, improvement in a processing performance and improvement in shock resistance in consideration of erroneous dropping are demanded for a portable small-sized computer. For a 2.5-inch-size magnetic disk drive which is loaded in a portable small-sized computer, not only reduction in thickness but also a large storage capacity in response to improvement in a CPU's processing performance, and superiority in shock resistance such that, when the computer is erroneously dropped, an arm supporting a head slider is prevented from hitting a magnetic disk are demanded.
In order to increase the storage capacity without increasing the size of the magnetic disk, it is necessary to reduce the pitch of the recording tracks and thus increase the number of the recording tracks. When the pitch of the recording tracks is reduced from 3 &mgr;m which is the pitch in the current magnetic disk to 1 &mgr;m, for example, it is necessary to improve the positioning accuracy of the head slider to the order of nanometers. In order to improve the positioning accuracy of the head slider, it is necessary to reduce the amplitude of vibration in directions parallel to the data recording surface of the magnetic disk (directions in which the head slider performs the seeking operation) of the arm supporting the head slider when resonance occurs. For this purpose, it is necessary to increase the resonance frequency of the vibration by improving the rigidity of the arm.
In order to improve the shock resistance, it is necessary to reduce the amount of bending of the arm in the direction in which the extending end of the arm approaches the magnetic disk, by improving the rigidity of the arm.
2. Description of the Related Art
A 2.5-inch-size magnetic disk drive
10
in the related art has an arrangement, as shown in
FIGS. 1A and 1B
, in which two 2.5-inch-size magnetic disks
12
-
1
,
12
-
2
are assembled in a housing
11
, these magnetic disks being rotated by a motor (not shown in the figures). Further, a head suspension unit
13
is assembled in the housing
11
, the head suspension unit
13
being rotated by an actuator
14
.
FIG. 1B
shows a magnified sectional view taken along the B—B line shown in FIG.
1
A.
As shown in
FIG. 2
, in the head suspension unit
13
, an arm
21
-
1
, a spacer
22
-
1
, an arm
21
-
2
, an arm
21
-
3
, a spacer
22
-
2
and an arm
21
-
4
are fitted around a sleeve
20
, are stacked in the stated order, and are fixed by a screw member
23
. The sleeve
20
is assembled around a fixed central shaft
25
via bearings
24
-
1
,
24
-
2
so that the sleeve
20
can rotate.
At the extending ends of the arm
21
-
1
through
21
-
4
, suspensions
26
-
1
through
26
-
4
are fixed, respectively. At the extending ends of the suspensions
26
-
1
through
26
-
4
, head sliders
27
-
1
through
27
-
4
are fixed, respectively.
The arm
21
-
1
is positioned below the magnetic disk
12
-
2
, the arms
21
-
2
,
21
-
3
are positioned between the magnetic disks
12
-
1
and
12
-
2
, and the arm
21
-
4
is positioned above the magnetic disk
12
-
1
. The head slider
27
-
1
is in contact with the bottom surface of the magnetic disk
12
-
2
, the head slider
27
-
2
is in contact with the top surface of the magnetic disk
12
-
2
, the head slider
27
-
3
is in contact with the bottom surface of the magnetic disk
12
-
1
and the head slider
27
-
4
is in contact with the top surface of the magnetic disk
12
-
1
.
The vibration-frequency responding characteristics in directions parallel to the data recording surfaces of the magnetic disks (the directions in which the head sliders perform the seeking operation) of the extending ends of the respective arms
21
-
1
through
21
-
4
in the condition where the suspensions and head sliders are attached thereto in the above-described head suspension unit
13
will now be considered.
In
FIG. 8
, the curve II indicated by the broken line shows the vibration-frequency responding characteristics in the directions parallel to the data recording surfaces of the magnetic disks (the directions in which the head sliders perform the seeking operation) of the extending ends of the upper arm
21
-
1
and the lower arm
21
-
4
when a test the same as that which will be described later is performed. The peak P
2
appears at the frequency f
2
and the amplitude of the peak P
2
is L
2
.
Both the vibration-frequency responding characteristics in the directions parallel to the data recording surface of the magnetic disks (the directions in which the head sliders perform the seeking operation) of the extending end of the arm
21
-
2
and the vibration-frequency responding characteristics in the directions parallel to the data recording surfaces of the magnetic disks (the directions in which the head sliders performs the seeking operation) of the extending end of the arm
21
-
3
are the same as those shown by the curve II indicated by the broken line. This is because the arms
21
-
2
and
21
-
3
merely lie on top of one another.
The frequency f
2
is somewhat low and the amplitude L
2
is somewhat high. This feature can be obtained both in the resonance characteristics of the vibration of the arm in the directions parallel to the data recording surfaces of the magnetic disks and in the resonance characteristics of the vibration of the arm in the directions perpendicular the data recording surfaces of the magnetic disks. Therefore, improvement in the positioning accuracy of the head sliders is difficult, and, also, it is difficult to reduce the pitch of the recording tracks, increase the number of recording tracks, and, thus, increase the storage capacity of the magnetic disks.
Further, because the arms
21
-
2
and
21
-
3
merely lie on top of one another, due to variation in dimension accuracies of the arms, variation in assembling, and so forth, there is a case where extending-end portions of the arms
21
-
2
and
21
-
3
are in contact with one another, as shown in
FIG. 3A
, and, also, there is a case where the extending-end portions of the arms
21
-
2
and
21
-
3
are away from and are not in contact with. one another, as shown in
FIG. 3B
, depending on particular magnetic disk drives
10
. In
FIG. 3B
, a space
28
is present between the arms
21
-
2
and
21
-
3
. Such variation in the assembling condition results in variation in the vibration characteristics of the head suspension unit
13
. Therefore, the servo circuit for performing the seeking operation should be designed in consideration of safety for preventing the servo system from oscillating. Also in this view point, it is difficult to improve the positioning accuracy of the head sliders, and, therefore, to increase the storage capacity of the magnetic disks.
A case where the magnetic disk drive
10
is erroneously dropped onto a floor will now be considered.
Due to a shock when the magnetic disk drive
10
is dropped onto a floor, a force F is applied to the extending end of each of the arms
21
-
1
through
21
-
4
, which force F depends on the weight of a respective one of the head sliders
27
-
1
through
27
-
4
.
Each of the top arm
21
-
4
and the bottom arm
21
-
1
bends as shown in
FIG. 4A
, and the bending amount of the extending end thereof is &dgr;
2
.
Similarly, each of the intermediate arms
21
-
2
and
21
-
3
bends as shown in
FIG. 4B
, and the bending amount of the extending end thereof is also &dgr;
2
.
In order to reduce the thickness of the magnetic disk drive
10
, the space ‘g’ between the magnetic disks
12
-
1
and
12
-
2
is approximately 1.8 mm, and, thus, is small. Also, the space ‘a’ between the extending end of each of the arms
21
-
1
through
21
-
4
and a respective one of the magnetic disks
12
-
1
and
12
-
2
is approximately 300 &mgr;m, and, thus, is small (see FIG.
1
B). Therefore, it is diffic

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