Rolling bearing for supporting rotary shaft of disk memory...

Details Rolling bearing for supporting rotary shaft of disk memory... Rolling bearing for supporting rotary shaft of disk memory...

1999-08-27

2001-12-25

Footland, Lenard A. (Department: 3682)

Bearings

Rotary bearing

Antifriction bearing

C384S527000, C384S523000

Reexamination Certificate

active

06332717

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates to a rolling bearing for supporting a rotary shaft of a disk memory device such as an optical disk or a magnetic disk, and more particularly to a rolling bearing for supporting a rotary shaft of a spindle motor or a swing arm in a disk memory device such as a compact disk, a hard disk drive (HDD), or a mass storage floppy disk drive.
FIG. 1
shows a support structure for supporting the rotary shaft of a typical hard disk drive (HDD for short). This support structure comprises a pair of ball bearings
6
for supporting a rotary shaft
3
rotatably supporting a magnetic disk
2
through a hub
1
, and another pair of ball bearings
7
supporting a rotary shaft
5
of an arm
4
carrying at its tip a magnetic head (not shown).
The pair of ball bearings
6
supporting the rotary shaft
3
of the magnetic disk
2
have their inner rings
8
mounted to the rotary shaft
3
so as to rotate together, and their outer rings
9
fixedly fitted in a fixed tubular member
11
of a spindle motor
10
. The rotary shaft
3
is fixed to the center of a dish-shaped rotary member
12
, and is rotated by a spindle motor
10
.
The magnetic disk
2
rotatably supported by this structure is rotated at a high speed by the motor
10
through the shaft
3
, while the swing arm
4
is, as its name suggests, swung so that its head can read and write data into and out of the disk.
The arm
4
is supported at its end remote from the head on the top of the rotary shaft
5
. The rotary shaft is rotated about its axis by an actuator (not shown) such as a coil to pivot the arm
4
a predetermined angle to move its magnetic head to a predetermined position. As the shaft
5
swings, the head can thus read and write magnetic data in the effective memory area of the magnetic disk
2
.
Heretofore, high-precision small ball bearings (miniature ball bearings: JIS B 0104 “bearing having outer diameter of less than 9 mm”) have been used to support rotary shafts of hard disk drive. Bearings with dimensional accuracy and rotation accuracy of JIS 5 or over have been used.
Such rolling bearings have a retainer having the shape of a crown as shown in
FIG. 3A
or
3
B. They comprise an annular retainer body having on its top surface a plurality of pairs of claws
21
arranged circumferentially at a predetermined pitch, each adjacent pair having opposed curved surfaces, defining a rolling element retaining pocket
22
. A flat surface
23
as a reference surface from which the claws
21
protrude is formed between adjacent pockets
22
.
The retainer of
FIG. 3B
has a plate-shaped upright wall
24
formed on each flat surface
23
to prevent leakage of grease.
If semisolid lubricant such as grease is used for lubrication of such roller bearings having retainers, lubricating (or stirring) resistance will be produced according to the viscosity of the lubricant. This increases the torque required to turn the rotary shaft supported by the bearing, and also causes torque fluctuations.
To prevent this problem, unexamined Japanese patent publication 8-21450 proposes to make the retainer itself from a lubricative composition comprising a mixture of a polyolefin resin and a lubricating oil.
One problem of the retainer disclosed in the abovesaid publication is that since the lubricating oil is retained by the highly oil-absorptive polyolefin resin, oil scarcely exudes onto the surface of the retainer. It is also difficult to keep oil exuded uniformly at a constant rate over a long period of time even if the oil is dispersed uniformly in the resin.
An object of the present invention is to provide a rolling bearing for supporting a rotary shaft of a disk memory device, which includes a retainer having good lubricative properties and which can lower and stabilize the torque required to turn the rotary shaft so that the disk memory device will exhibit high optical or magnetic recording performance over a long period of time.
SUMMARY OF THE INVENTION
According to this invention, there is provided a rolling bearing for supporting a rotary shaft of a disk of a disk memory device, comprising a retainer made from an oil-containing resin composition containing a synthetic resin as a main component to which are added fibrous oil conducting material and lubricating oil.
There is also provided a rolling bearing for supporting a rotary shaft of an arm carrying a head of a disk memory device, comprising a retainer made from an oil-containing resin composition comprising a synthetic resin as a main component, fibrous oil conducting material and lubricating oil.
The oil-containing resin composition forming the retainer may comprise 40-94 wt % of a synthetic resin, 1-40 wt % of fibrous oil conducting material, and 5-30 wt % of lubricating oil. Also, as the rolling bearing, a miniature bearing having an inner ring having an inner diameter of 8 mm or less may be used.
The fibrous oil-conducting material may be solid fibers, or hollow fibers.
The retainer of the rolling bearing used in this invention contains lubricating oil in a uniformly dispersed state to a deep portion. The lubricating oil bleeds through the fibrous oil conducting material onto the surface from inside the retainer, so that the retainer shows good lubricating properties.
By providing solid fibers in the retainer as the conducting material for lubricating oil, the lubricating oil present inside passes the surfaces of the fibers as the conducting material (that is, interface between the synthetic resin and fibers), and bleeds stably onto the surface of the retainer over a long period of time, so that it shows good lubricating properties.
Also, if hollow fibers (each having a through hole extending in the axial direction of the fiber) are used as the conducting material for lubricating oil, the lubricating oil present inside passes the holes of the hollow fibers, and the fiber surfaces (that is, interfaces of the base resin and fibrous filler), and bleeds onto the surface of the retainer at a stable rate over a long period of time, so that it shows good lubricating properties.
If the fibrous oil conducting material and lubricating oil are sufficiently mixed together beforehand, oil will be always present on the surface and/or in hollow portions of the fibrous oil conducting material, so that the lubricating oil bleed onto the sliding surface at a stable speed, so that the rolling bearing shows better lubricating properties. Thus, the rotary shaft of the disk memory device rotates stably with low torque.
Other features and objects of the present invention will become apparent from the following description made with reference to the accompanying drawings, in which:


REFERENCES:
patent: 5558448 (1996-09-01), Yabe et al.
patent: 5575570 (1996-11-01), Uchiyama et al.
patent: 8-21450 (1996-01-01), None

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