Suspension for disc drive

Details Suspension for disc drive Suspension for disc drive

2001-03-23

2004-03-02

Cao, Allen (Department: 2652)

Dynamic magnetic information storage or retrieval

Head mounting

Disk record

Reexamination Certificate

active

06700744

ABSTRACT:

CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2001-079358, filed Mar. 19, 2001, the entire contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
The present invention relates to a suspension for disc drive incorporated in an information processing apparatus, such as a personal computer.
A hard disc drive (HDD) for recording in and reading information from a rotating magnetic disc or magneto-optical disc includes a carriage that can turn around a shaft. The carriage is rotated around the shaft by means of a positioning motor. The carriage is provided with an arm (actuator arm), a suspension mounted on the distal end portion of the arm, a head portion including a slider mounted on the suspension, etc.
When the disc rotates, air that gets into the space between the slider and the surface of the disc causes the slider slightly to lift off the disc surface. This suspension comprises a baseplate fixed to a suspension mounting surface of the arm, a beam portion formed of a precision plate spring, a flexure fixed to the beam portion, etc.
With the advance of compaction of information recorded in the disc and speed-up of the disc drive operation, the disc drive of this type has been requiring a shorter seek time. In order to shorten the seek time, the rotation of the disc must be speeded up further. If the disc rotates at high speed, however, an air turbulence that is generated near the disc surface causes the suspension to flutter, thus arousing a serious problem.
BRIEF SUMMARY OF THE INVENTION
In order to improve various properties that are required of suspensions, a suspension has been developed by the inventors hereof such that a baseplate and a beam portion are connected to each other by means of a hinge member that is formed of a thin spring member. For example, a suspension
1
shown in
FIG. 1
comprises a baseplate
2
, beam portion
3
, hinge member
4
, etc. The baseplate
2
is formed having a boss portion
7
that can be fixed to an actuator arm
6
. The hinge member
4
is provided with connecting portions
4
a
with a length L1 between the baseplate
2
and the beam portion
3
. The connecting portions
4
a
are bendable in the thickness direction of the hinge member
4
. The beam portion
3
is fitted with a flexure
8
, which is provided with a slider
9
.
In a hard disc drive
10
shown in
FIG. 2
, each suspension
1
is mounted on the actuator arm
6
. The actuator arm
6
is turned around a shaft (not shown) by means of a positioning motor (not shown). The slider
9
is opposed to a surface of a disc
11
. In this specification, a distance h
1
from the surface of the disc
11
to a baseplate mounting surface
6
a
of the actuator arm
6
is referred to as Z-height.
As shown in
FIG. 3
, a convex pivot portion
15
(dimple as it is called in the art) for supporting the slider
9
for rocking motion is formed on the distal end portion of the beam portion
3
. The slider
9
on the flexure
8
is rockable around a distal end
15
a
of the pivot portion
15
. Even if the suspension
1
flutters, the slider
9
never moves in the direction indicated by arrow F when the beam portion
3
swings around the distal end
15
a
of the pivot portion
15
.
Owing to variation in the Z-height, however, the beam portion
3
may possibly swing around a spot (e.g., pivot center designated by R
1
or R
2
in
FIG. 3
) that is off the distal end
15
a
of the pivot portion
15
. As the pivot portion
15
is displaced in the direction of arrow F, in this case, the slider
9
inevitably moves in the direction of arrow F, thereby causing a track miss.
As the rotation of the disc
11
is speeded up, according to the suspension
1
described above, it becomes more important to restrain fluttering. Essential factors to restrain fluttering include the thickness of the baseplate
2
, a width W1 of the baseplate
2
, a distance L2 (referred to as baseplate length herein) from a center C
1
of the boss portion
7
to a front end
2
a
of the baseplate
2
, etc., as well as the length L1 (referred to as hinge length herein) of the connecting portions
4
a
of the hinge member
4
.
Fluttering is not a problem with a suspension of which a length L3 from the center C
1
of the boss portion
7
to the pivot portion
15
is 11.0 mm, for example. Possibly, however, fluttering may interfere with the operation of a suspension that has the length L3 of 14.5 mm.
In some cases, fluttering can be effectively restrained by enhancing the torsion stiffness of the suspension
1
. It may be supposed, therefore, that fluttering can be restrained by increasing the width W1 of the baseplate
2
from, e.g., 4 mm to 4.5 mm. According to a diligent study made by the inventors hereof, however, fluttering cannot be satisfactorily restrained by only increasing the width of the baseplate
2
.
Accordingly, the object of the present invention is to provide a suspension capable of restraining generation of fluttering in a disc drive with a disc that rotates at high speed.
In order to achieve the above object, a suspension for disc drive according to the present invention comprises a baseplate having a boss portion, a beam portion with a flexure, and a hinge member fixed to the baseplate and the beam portion and including a connecting portion bendable in the thickness direction thereof between the baseplate and the beam portion, the thickness of the baseplate ranging from 0.175 mm to 0.25 mm, the width of the baseplate being greater than 4.0 mm and not greater than 5.0 mm, the length of the connecting portion of the hinge member ranging from 0.1 mm to 0.7 mm, and the baseplate length from the center of the boss portion to the front end of the baseplate ranging from 4.0 mm to 5.1 mm.
According to the suspension of this invention, generation of fluttering can be restrained even when the disc rotates at high speed, so that the disc rotation can be speeded up without hindrance. According to this invention, moreover, generation of fluttering can be restrained with a high-rotation disc in the suspension that has a length of 14.5 mm.
The following is a description of the reason why the dimensions according to present invention are restricted to aforementioned values.
In
FIG. 4
, A
1
represents the relationship between the thickness of the baseplate and the sway frequency of the suspension. The sway frequency is a resonance frequency in the sway direction (direction indicated by arrow S in
FIG. 1
) of the suspension. In
FIG. 4
, A
2
represents the relationship between the thickness of the baseplate and the torsion stiffness of the suspension. If the thickness of the baseplate is smaller than about 0.17 mm, the sway frequency and the torsion stiffness lower suddenly. If the thickness of the baseplate exceeds 0.25 mm, the baseplate is too heavy to be feasible for practical use. Preferably, therefore, the thickness of the baseplate ranges from 0.17 mm to 0.25 mm.
In
FIG. 5
, A
3
represents the relationship between the hinge length L1 and the sway frequency. In
FIG. 5
, A
4
represents the relationship between the hinge length L1 and the torsion stiffness. If the hinge length L1 exceeds 0.7 mm, as seen from
FIG. 5
, the torsion stiffness, as well as the sway frequency, lowers considerably. It is to be desired, therefore, that the hinge length should be 0.7 mm or shorter. The shorter the hinge length L1, the higher the sway frequency and the torsion stiffness are. If the hinge length L1 is shorter than 0.1 mm, however, the manufacture of the suspension, adjustment of its performance, etc. are difficult. Accordingly, 0.1 mm is the lower limit of the hinge length L1.
In manufacturing the disc drive, the Z-height inevitably varies owing to limited accuracy of assembly. If the Z-height is subject to variation, the beam portion
3
swings around the spot (e.g., pivot center designated by R
1
or R
2
in
FIG. 3
) that is off the distal end
15
a
of the pivot portion
15
. The longer a distance D
1

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