Bearings – Rotary bearing – Fluid bearing
Reexamination Certificate
2001-08-15
2003-08-12
Schwartz, Christopher P. (Department: 3683)
Bearings
Rotary bearing
Fluid bearing
C384S113000, C384S123000
Reexamination Certificate
active
06604858
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a hydro dynamic gas bearing and a disk drive using the bearing.
BACKGROUND OF THE INVENTION
In recent years, there is a tendency to increase speed and storage capacity of a recording/reproducing disc drive such as a magnetic disk, and particularly, achieving high-density recording is essential in increasing the storage capacity. To this end, highly accurate rotation technique of a main rotary shaft is required, and there is a move afoot to adopt a highly accurate hydro dynamic gas bearing in place of a conventional ball bearing or a cylindrical slide bearing.
FIGS. 4 and 5
show disk drives using a conventional hydro dynamic gas bearing.
In
FIG. 4
, a plurality of zigzag-shaped hydro dynamic pressure grooves
8
are formed on an outer peripheral surface of a shaft
9
to generate a hydro dynamic pressure subject to loads in radial and thrust directions. The shaft
9
is secured to a base
7
and inserted into a sleeve
10
so as to rotatably support the sleeve
10
.
A circular coil
6
is provided on the base
7
by being inserted into a recess
10
A formed in the sleeve
10
. On an inner wall of the recess
10
A, an annular magnet
5
is provided opposite the coil
6
. Mounted to the sleeve
10
is a disk
14
which can magnetically or optically record/reproduce signals.
The bearing shown in
FIG. 4
is accommodated in an inner space
13
a
defined by a casing
13
and the base
7
as shown in FIG.
5
.
At the time of feeding a current through the coil
6
, an electromagnetic force is generated between the magnet
5
and the coil
6
to rotate the sleeve
10
in a direction of arrow B. By this rotation, under a pumping action of the hydro dynamic pressure generating grooves
8
formed on the shaft
9
, an air pressure in a sleeve inner space
11
between the shaft
9
and the sleeve
10
is locally increased to be higher than an outside air pressure. By the increased air pressure, the sleeve
10
is supported in a radial direction (direction of arrow R) of the shaft
9
.
The hydro dynamic pressure generating grooves
8
are formed in an asymmetrical pattern with respect to radial-directional lines passing vertexes of each zigzag pattern. The pumping action thus caused generates an airflow which flows from a bottom to a top in the sleeve inner space
11
to increase an air pressure in a space
11
A at a top of the shaft
9
to be higher than the outside air pressure. As a result, the sleeve
10
moves upward with respect to the shaft
9
in an axial direction (thrust direction) of the shaft.
A vent plate
1
of a cap
3
provided above the sleeve
10
has an air vent
2
, so that the high-pressure air in the space
11
A is discharged outward through the air vent
2
. Setting a diameter of the air vent
2
to a predetermined value allows the air pressure to be kept at a constant value and allows an amount of upward movement of the sleeve
10
in the thrust direction to be kept at a predetermined value. In this way, the sleeve
10
is rotated in a contactless fashion with the shaft
9
.
And, recording signals on the disk
14
or reading signals from the disk
14
is performed by means of a head
16
mounted to a head arm
17
which is driven to oscillate around an oscillation shaft
18
in a direction of arrow C by a voice coil motor
19
provided on the base
7
.
In a disk device like this, at the time of inserting the shaft
9
into the sleeve
10
, it is not seldom that foreign matters such as scrap metal powder of burr or wear powder generated at the time of metal processing sometimes enter the sleeve inner space
11
. Further, at the time of rotating the sleeve
10
, the sleeve
10
sometimes makes contact with the shaft
9
and others, causing the foreign matters to be generated.
These foreign matters
12
are conveyed to the space
11
A at the top of the shaft
9
by the airflow which flows from the bottom to the top in the sleeve inner space
11
. The foreign matters
12
having been conveyed to the space
11
A are carried in the airflow which flows from the bottom to the top of the sleeve inner space
11
and discharged from the air vent
2
into an inner space
13
a
of a casing, and are driven to be discharged outside by passing through the air vent
2
.
The foreign matters
12
thus discharged into the inner space
13
a
through the air vent
2
adhere to the surface of the disk
14
mounted to the sleeve
10
, causing a problem of reduction in functional performance, such as a crush of the head
16
or a recording/reproducing error.
The present invention has an object to prevent the discharge of the foreign matters into the inner space
13
a
and to improve movement stability and reliability of the disk drive.
DISCLOSURE OF THE INVENTION
A hydro dynamic gas bearing according to claim
1
of the present invention is a hydro dynamic gas bearing, in which a sleeve with one end closed is connected to a front end of a shaft supported at its proximal end to a base on a fixed side, a plurality of hydro dynamic pressure generating grooves are formed on at least one of an outer peripheral surface of the shaft and an inner peripheral surface of the sleeve opposite the outer peripheral surface, and the sleeve is supported in a radial direction of the shaft by a pumping action of the hydro dynamic pressure generating grooves, the pumping action being made accompanying rotation of the sleeve, wherein the bearing comprises: a through hole formed to extend from the front end to the proximal end of the shaft and communicating with an outside of the base; and an air vent formed in the through hole and adjusting a pressure between the shaft and sleeve.
According to this configuration, by providing a hollow shaft having an air vent at its top, the rotation of the sleeve increases an air pressure in a sleeve inner space to be higher than an atmospheric air pressure, so that the sleeve is supported at a correct position in the radial direction of the hollow shaft. Fine foreign matters entering between the shaft and the sleeve at the time of assembly of the shaft and the sleeve or foreign matters generated as the sleeve contacts with the shaft and others at the time of rotation of the sleeve are carried in a gas passing through the air vent and guided to the outside of a casing through the through hole of the shaft. Therefore, it is possible to prevent the foreign matters from being discharged into an inner space of the casing and improve reliability of the bearing.
A disk drive according to claim
2
of the present invention is a disk drive comprising a hydro dynamic gas bearing and a casing accommodating therein the bearing, wherein the hydro dynamic gas bearing is configured such that a sleeve with one end closed is connected to a front end of a shaft supported at its proximal end to a base on a fixed side, a plurality of hydro dynamic pressure generating grooves are formed on at least one of an outer peripheral surface of the shaft and an inner peripheral surface of the sleeve opposite the outer peripheral surface, and the sleeve is supported in a radial direction of the shaft by a pumping action of the hydro dynamic pressure generating grooves, the pumping action being made accompanying rotation of the sleeve, and wherein the casing, part of which is formed by the base, includes in an inner space thereof: a recording medium mounted to the sleeve; driving mechanisms for rotatably driving the sleeve with respect to the shaft; and a head making access to the recording medium to execute reading and writing of information, the inner space of the casing being communicated with an atmospheric outside through a through hole of the shaft.
REFERENCES:
patent: 5516212 (1996-05-01), Titcomb
patent: 5658080 (1997-08-01), Ichiyama
patent: 5777403 (1998-07-01), Yuan
patent: 6097121 (2000-08-01), Oku
patent: 6196722 (2001-03-01), Asada et al.
Asada Takafumi
Kusaka Keigo
Parkhurst & Wendel L.L.P.
Schwartz Christopher P.
Torres Melanie
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