Bearings – Rotary bearing – Plural bearings one plain and one antifriction
Reexamination Certificate
1999-03-01
2001-01-23
Wright, Dirk (Department: 3681)
Bearings
Rotary bearing
Plural bearings one plain and one antifriction
Reexamination Certificate
active
06176620
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a composite ball bearing which and more particularly to a composite bearing structure is a combination of a single row ball bearing and a cylindrical bearing.
2. Description of the Prior Art
Single row ball bearings are simple in construction and low cost, and are therefore widely used for the bearings in the rotational support mechanism of the rotational axis in compact motors, etc.
FIG. 17
shows a sectional view through a single row ball bearing. In the single row ball bearing shown in
FIG. 17
, when a single bearing
100
is used, the outer ring
101
freely inclines through an angle of &thgr; on top of ball
102
. As a result, when a rotating element (not shown) such as the hub of a spindle motor is mounted on outer ring
101
, this rotating element will vibrate in both the axial and radial directions against the inner ring
103
, resulting in an unstable rotation.
Similarly, if outer ring
101
is fixed and when a rotating body (not shown) such as the rotational shaft of a spindle motor is mounted on inner ring
103
, this rotating body will vibrate in both the axial and radial directions against the outer ring
101
, also resulting in an unstable rotation.
In order to prevent this vibratory rotation of the rotating element, two single row ball bearings
100
and
110
are fixed together in a parallel assembly as shown in
FIG. 18
, or, to further reduce the rotational vibration, a spacer
120
is mounted between the two single row ball bearings
100
and
110
, increasing the space between ball bearing
100
and ball bearing
110
, preventing rotational vibration and achieving stable high precision rotation as shown in FIG.
19
.
However, in response to the trend for smaller size in many kinds of device, when a rotating element of more compact dimensions is to be employed, it is desired to reduce the dimension L in
FIGS. 18 and 19
as much as possible. Accordingly, to make the dimensions as compact as possible, the arrangement is often used as shown in
FIG. 18
where single row ball bearings
100
and
110
are mounted side by side, instead of the arrangement where a spacer
120
is used between single row ball bearings
100
and
110
as shown in FIG C. If it is desired to reduce the minimum dimensions even more than this, the only solution is to specially manufacture thin multiple row ball bearings. Even if such special thin multiple row ball bearings are used, the dimensions are limited by the size of the balls in the 2 side-by-side parallel rows.
A concrete example of this trend toward reducing the size of devices is the remarkable recent reduction in the size and thickness of floppy disk drives and hard disk drives for magnetic storage equipment. Demand is especially strong for more compact, thinner spindle motors for use in such drives. To respond to this demand for more compact, thinner spindle motors, a major point is to find some method for making the dimensions of the bearing section more compact (thinner). At present, the only way to meet these requirements is to use a side-by-side double row of ball bearings, or specially produced multiple row ball bearings as mentioned above, and these methods have their limitations. For the bearing on one side of a spindle motor, it is desirable to use a single ball bearing in order to make the motor thinner. However, this method will result in rotational vibration as described above and is therefore not practical. Also, the use of 2 single row ball bearings for this purpose would cause an undesirable cost increase.
The present invention has been accomplished in the light of the above-mentioned problems and it is an object of the invention to provide a bearing structure in which a single ball bearing is used in such a way as to prevent rotational vibration is the same way as if two ball bearings were used, and in addition to provide a low cost, thin type ball bearing structure.
SUMMARY OF THE INVENTION
In order to achieve the above-mentioned object, the invention described in the claims of the present invention provides the means described as follows.
The present invention provides a structure which prevents inclined rotation, using a single-row bearing, which is the minimum for an application of a ball bearing, where sintered, oil-impregnated bearings (or non-oil-impregnated dry bearings or fluid bearings) are arranged on either one side or both sides of either the inner ring or the outer ring of the said single-row bearing.
According to the present invention, the radial load is mainly received by the balls of the single-row bearing, and when the outer or inner ring is about to vibrate and incline, the sintered oil-impregnated bearing at either one side or both sides of either the inner ring or the outer ring, prevents the inclination by slidably contacting the inner or outer ring arranged oppositely at a gap, and since said inner and outer ring form the single-row bearing, their surface is finished very precisely thus reducing frictional loss relating to an inclinational load.
Furthermore, the thrust load is all received by the balls of the single-row ball bearing. In this way, practically the whole of the radial load is received by the balls, the thrust load is also all received by the balls, and the friction loss received by the inclination-preventing sintered, oil-impregnated bearing is very slight, and therefore there is no great influence on either the rotational precision or the lifetime reliability. The present invention makes possible a bearing with minimal width, which can be formed by a composite bearing having an anti-collapse function, and which does not require much increase of the width of the single row ball bearing.
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patent: 4226484 (1980-10-01), Glassow et al.
patent: 4309063 (1982-01-01), Weis
patent: 4394091 (1983-07-01), Klomp
patent: 4881828 (1989-11-01), Kato
patent: 4938610 (1990-07-01), Kato
patent: 5046863 (1991-09-01), Sakatani et al.
patent: 5332317 (1994-07-01), Niwa et al.
patent: 5806988 (1998-09-01), Dublin, Jr. et al.
patent: 1464889 (1967-03-01), None
patent: 1042549 (1965-08-01), None
patent: 1382037 (1975-01-01), None
patent: 10-064002 (1998-06-01), None
Minebea Co. Ltd.
Staas & Halsey , LLP
Wright Dirk
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