Gas dynamic foil bearing

Details Gas dynamic foil bearing Gas dynamic foil bearing

2000-03-15

2001-07-17

Hannon, Thomas R. (Department: 3682)

Bearings

Rotary bearing

Fluid bearing

C384S106000

Reexamination Certificate

active

06261002

ABSTRACT:

TECHNICAL FIELD
The present invention relates to bearings, and more particularly, to gas dynamic foil bearings with gas lubrication, used for axial and radial suspension of rotors which rotate at a high speed in a turbomechanism such as a turbocooler, a turboexpander, a turbocompressor, a turbocharger, a turbogenerator, and a turbopump.
BACKGROUND ART
A gas dynamic foil bearing is simple in its structure and can be produced economically. Therefore, it has been widely applied to small-sized machines. In U.S. Pat. No. 3,893,733, issued on Jul. 8, 1975, entitled “Foil Bearing Arrangements” to Silver et al., a self-pressurizing hydrodynamic foil bearing is described in which the foil bearing comprises resilient foils providing support between a movable and stationary bearing member and resilient foil supports for supporting and stiffening the foils.
A conventional thrust gas foil bearing disclosed in Soviet Union Patent No. 1754949, issued on Aug. 15, 1992, is illustrated in FIG.
1
. As shown in
FIG. 1
, the thrust gas foil bearing includes a plate
1
attached to a base
10
, support members
2
fixed on the plate
1
by welding, and elastic foils
3
attached to the supporting members
2
by welding such that the elastic foils
3
overlap as shown. Here, the elastic foil
3
has a support portion
3
a
which is a tail thereof and is not attached to the support member
2
, and an edge
3
b
of the elastic foil
3
is in contact with the adjacent foil
3
. The radius of curvature of the elastic foil
3
decreases from R1 to R2 toward the edge
3
b
. Also, a thrust disk
11
connected to a rotor (not shown), for example, a rotating shaft is placed on the elastic foils
3
.
As the thrust disk
11
connected to the rotor rotates, the gas is drawn into the space between the thrust disk
11
and the elastic foils
3
, thereby lifting the thrust disk
11
from the elastic foils
3
. Here, the thrust disk
11
remains in contact with the elastic foils
3
until the speed of rotation thereof reaches a normal lift-off speed. At this time, the elastic foil
3
is pressed downward by the edge
3
b
of the adjacent foil
3
and is elastically deformed to thereby contact the upper surface of the plate
1
at the position A (FIG.
2
). At the same time. the lower surface of the deformed foil
3
is in contact with and is elastically supported by the support portion
3
a
of the adjacent foil
3
at position B.
However, the conventional thrust gas foil bearing has several shortcomings. Since the support portion
3
b
supporting the adjacent elastic foil
3
is integrally formed with the elastic foil
3
of the same material, it cannot additionally provide sufficient rigidity to each foil
3
elastically deformed by the axial load. Accordingly, the elastic foil
3
is deformed downward until it contacts the upper surface of the plate
1
, which causes an axial displacement of the thrust disk
11
or the rotor connected thereto to increase during the initial operation of the bearing.
Also, the damping capacity against the axial load and a bearing load capacity are poor because the elastic foils
3
contact the plate
1
during operation at normal lift-off speed. Further, the elastic foil
3
has a radius that gradually gets smaller toward the edge
3
b
, thereby making the manufacturing process thereof complicated and difficult.
DISCLOSURE OF THE INVENTION
It is an object of the present invention to provide a gas dynamic foil bearing which decreases the displacement of the thrust disk or axis during the initial operation, increases the bearing load capacity, and simplifies the manufacture thereof.
According to an embodiment of the present invention, there is provided a gas dynamic foil bearing comprising a plate attached to a base, support members fixed on the plate by a predetermined distance, elastic foils fixed to the support members at one end thereof to overlap each other, and a thrust disk connected to a rotating rotor and placed on the elastic foils, characterized by comprising bent springs interposed between the elastic foils and the plate in the overlapping area of the elastic foils for supporting the elastic foils.
The elastic foil has the same curvature through its overall length and the bent spring is comprised of a working portion which supports the elastic foil and is elastically deformed, and coupling portions, at one side or both sides thereof, connected to the plate at the position off a bearing operating zone being between the internal radius and the external radius of the elastic foil.
Alternatively, the bent spring rests on a groove formed in a positioning plate connected on the plate and prevented from falling out of the groove by the elastic foils.
According to another embodiment of the present invention, there is provided a gas dynamic foil bearing comprising a plate attached to an inner circumferential surface of a base, support members fixed on the plate by a predetermined distance, elastic foils fixed to the support members at one end thereof to overlap each other, and a rotation axis contacting the elastic foils, characterized by comprising bent springs interposed between the elastic foils and the plate in the overlapping area of the elastic foils for supporting the elastic foils.
According to the present invention, the rigidity of the elastic foil package is determined by the rigidity of the elastic foils during the initial operation, and by the rigidity of the bent spring during normal lift-off operation.


REFERENCES:
patent: 3893733 (1975-07-01), Silver et al.
patent: 4451163 (1984-05-01), Glaser
patent: 4475824 (1984-10-01), Glaser et al.
patent: 5498082 (1996-03-01), Nadjafl
patent: 5498083 (1996-03-01), Brown
patent: 5634723 (1997-06-01), Agarawal
patent: 1754949 (1990-11-01), None
patent: 92/10689 (1992-06-01), None

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