Bearings – Rotary bearing – Fluid bearing
Reexamination Certificate
2000-10-27
2002-08-20
Footland, Lenard A. (Department: 3682)
Bearings
Rotary bearing
Fluid bearing
C384S112000
Reexamination Certificate
active
06435721
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a spindle motor unit having a hydrodynamic bearing that can be used for a hard disk, and the like.
BACKGROUND OF THE INVENTION
A conventional spindle motor unit having a hydrodynamic bearing is described below.
FIG. 9
is a cross sectional view of a conventional spindle motor unit having a hydrodynamic bearing used for a hard disk, at rotation.
FIG. 10
is an enlarged partial view of
FIG. 9
illustrating a thrust bearing of the spindle motor unit at rest and placed in a normal position.
FIG. 11
illustrates the thrust bearing shown in
FIG. 10
at rest and placed in a vertically inverted position.
FIG. 12
is a top view of flange
3
used in the spindle motor unit, and cross sectional views of flange
3
shown in
FIGS. 10 and 11
are taken on lines
10
(
11
)—
10
(
11
) of FIG.
12
.
Referring to
FIGS. 9 through 12
, base
1
has radial bearing
1
a
and thrust support
1
b
. Rotating shaft
2
that co-axially rotates with respect to base
1
is supported by the radial bearing
1
a
. Flange
3
is secured to the lower end of rotating shaft
2
by a machine screw.
Flange
3
has grooves
3
a
and
3
b
formed of projections and depressions on its top and bottom faces, respectively. Plate
4
has thrust support
4
a
in a position opposed to grooves
3
b
on flange
3
, and is secured to a bottom face of base
1
by a machine screw. Lubricant
5
exists between radial bearing
1
a
and rotating shaft
2
, between thrust support
1
b
on base
1
and grooves
3
a
on flange
3
, and between grooves
3
b
on flange
3
and thrust support
4
a
on plate
4
. Hub
6
with magnetic disks
7
mounted thereon is co-axially fixed to rotating shaft
2
.
In a spindle motor unit having a hydrodynamic bearing structured as above, a rotating body including magnetic disks
7
and rotating shaft
2
floats up in a predetermined position during its rotation; thereby such information as picture, audio, and text, is recorded into magnetic disks
7
or recorded information is reproduced from magnetic disks
7
through a magnetic head (not shown).
However, while the flange is at rest as shown in
FIG. 10
, circumferential projection
3
d
on the periphery of the bottom face of flange
3
and thrust support
4
a
on plate
4
are in intimate contact with each other. Therefore, immediately after start-up of rotating shaft
2
, only a small amount of lubricant
5
exiting outside of the bearing can move into between grooves
3
b
and thrust support
4
a
. This phenomenon has caused the following problems: the rotating body including rotating shaft
2
does not float up in the predetermined position, the reliability of the bearing cannot be maintained, and a magnetic head (not shown) cannot correctly be positioned with respect to the magnetic disks to perform correct recording and reproduction of signals.
Similarly, when the motor is used in a vertically inverted position as shown in
FIG. 11
, circumferential projection
3
c
on the periphery of the top face of flange
3
and thrust support
1
b
on base
1
are in intimate contact with each other while the flange is at rest. Therefore, when rotating shaft
2
starts to rotate, lubricant
5
existing outside of the bearing cannot move into between grooves
3
a
and thrust support
1
b
easily. This phenomenon has also caused the following problems: the rotating body including rotating shaft
2
does not float up in the predetermined position, the reliability of the bearing cannot be maintained, and the magnetic head (not shown) cannot perform correct recording or reproducing to or from the magnetic disks
7
.
The present invention addresses the problems of conventional spindle motor units discussed above. Therefore, it is an object of the present invention to provide a spindle motor unit having a hydrodynamic bearing that allows lubricant to easily move from the outside into the inside of the bearing at start-up of rotation to thereby ensure the reliability as a thrust bearing and correct recording and reproducing operations.
SUMMARY OF THE INVENTION
A spindle motor unit having a hydrodynamic bearing in accordance with a first exemplary embodiment of the present invention has an escape formed at a corner of the base facing to the periphery of the top face of the flange and a circumferential recess formed in the plate in a position facing to the periphery of the bottom face of the flange as shown in FIG.
2
. At start-up of rotation, lubricant existing around the peripheries of the flange easily moves through the above escape in the base and the circumferential recess in the plate into the thrust bearing, thus floating up the rotating body in a predetermined position. Assuming the diameter of the escape in the thrust support on the base is &phgr;d
1
, the outermost diameter of the grooves on the top face of the flange is &phgr;d
2
, the outermost diameter of the grooves on the bottom face of the flange is &phgr;d
3
, the outer diameter of the flange is &phgr;d
4
, the outer diameter of the circumferential recess in the plate is &phgr;d
5
, the inner diameter of the circumferential recess is &phgr;d
6
, relations &phgr;d
1
<&phgr;d
2
, &phgr;d
6
<&phgr;d
3
, and &phgr;d
4
<&phgr;d
5
hold.
In a spindle motor unit having a hydrodynamic bearing in accordance with a second exemplary embodiment of the present invention, areas around the peripheries of the top and bottom faces of the flange are formed with depressions as shown in FIG.
6
. Since these depressions are continuous with the grooves on the top and bottom faces of the flange, lubricant existing around the peripheries of the flange moves into the thrust bearing easily at start-up of rotation, thus floating up the rotating body in the predetermined position.
REFERENCES:
patent: 5770906 (1998-06-01), Hazelton et al.
patent: 6126320 (2000-10-01), Ichiyama
patent: 6176618 (2001-01-01), Kawawada et al.
Inomata Hiromichi
Inoue Hiroshi
Omura Masashi
Footland Lenard A.
Matsushita Electric - Industrial Co., Ltd.
Wenderoth , Lind & Ponack, L.L.P.
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