Rotation shaft seal

Details Rotation shaft seal Rotation shaft seal

2002-01-16

2004-07-20

Pickard, Alison K. (Department: 3676)

Seal for a joint or juncture

Seal between relatively movable parts

Circumferential contact seal for other than piston

C277S572000

Reexamination Certificate

active

06764080

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a rotation shaft seal, especially, a rotation shaft seal used for sealing high pressure fluid in a compressor for an air conditioner on an automobile.
2. Description of the Related Art
As a conventional rotation shaft seal of this kind, a shaft seal as shown in
FIG. 41
is known. This rotation shaft seal is disposed between a housing
31
such as a case of a compressor and a rotation shaft
32
for sealing fluid or gas in a fluid storing chamber
33
.
In the construction of the shaft seal, a seal member
35
made of rubber is adhered to an outer case
34
, and a first seal element
36
and a second seal element
37
made of synthetic resin (such as PTFE) having spiral grooves are unified with a first inner case
38
, a washer
39
, a second inner case
40
, etc. in the outer case
34
(by caulking).
The seal member
35
made of rubber is provided with a lip portion
42
protruding to the fluid storing chamber
33
side, the lip portion
42
has a concave portion
44
in a peripheral direction on the fluid storing chamber
33
side and a lip end portion
41
gradually diminishes in diameter to the fluid storing chamber
33
side, and, a tip of the lip end portion
41
contacts the rotation shaft
32
as to make a belt contact area to seal. That is to say, when the shaft is still, fluid is completely sealed by pressure of the fluid storing chamber
33
and elastic force of the lip end portion
41
itself.
And, when the rotation shaft
32
rotates, although slight leakage is generated in a sliding portion of the lip end portion
41
and the rotation shaft
32
, the leakage is pushed back (to the left side in
FIG. 41
) by hydrodynamic effect of the spiral grooves (screw threads) of the first seal element
36
and the second seal element
37
. The construction can seal the fluid as a whole.
To describe concretely, as shown in
FIG. 42A
, in the seal member
35
made of rubber in a non-attached state to the rotation shaft
32
(free state), an interference G is arranged on the lip end portion
41
to form an interference portion
46
inner to the periphery of the rotation shaft
32
. And, as shown in
FIG. 42B
, in the seal member
35
attached to the rotation shaft
32
, tightening force F
11
generated by elasticity of rubber works on a contact portion
43
(with the rotation shaft
32
) of the lip end portion
41
(the interference portion
46
) to a peripheral face of the rotation shaft
32
. And, as shown in
FIG. 42C
, in the seal member
35
pressurized (by pressure P of the fluid) in a pressurizing state of the fluid storing chamber
33
, self-sealing force F
12
(generated by pressurization) and the tightening force F
11
(working continuously) work on the contact portion
43
. Consequently, total force F
15
(=F
11
+F
12
) works on the contact portion
43
to the peripheral face of the rotation shaft
32
.
In the conventional seal described above, in case that the pressure in the fluid storing chamber
33
is high, the lip end portion
41
contacts the rotation shaft
32
with a large area for great deformation (by high pressure working in an arrow P direction in FIG.
42
C), sealability becomes unstable, and sealability of the first seal element
36
is also influenced. This causes problems that leakage is generated early, and abrasion of the contact portion of the lip end portion
41
with the rotation shaft
32
is large.
Further, root of the lip portion
42
has larger pressure receiving area and smaller amount of rubber (in comparison with other parts of the lip portion
42
) for the concave portion
44
. Therefore, fissures on the root of the lip portion
42
and exfoliation of the seal member
35
from the outer case
34
are generated because the root of the lip portion
42
is greatly deformed by the high pressure and stress is successively generated from the surface of the lip portion
42
to the outer case
34
. Further, there is a problem that the contact portion of the lip end portion
41
with the rotation shaft
32
becomes larger, and lifetime of the seal is shortened.
Further, in case that carbon dioxide, having high permeability against rubber and resin, is used as a cooling medium, carbon dioxide permeates the seal member
35
made of rubber, the first seal element
36
, and the second seal element
37
and leaks from the seal. That is to say, when leakage of the cooling medium is large, the cooling medium becomes short early, and inconvenience such as reduction of cooling effect for shortage of cooling medium is caused thereby.
It is therefore an object of the present invention to provide a rotation shaft seal used especially under high pressure (around 3 to 10 MPa, for use of high pressure cooling media such as CO
2
), with which leakage of the cooling medium is restricted, deformation of the lip end portion is small, the lip end portion has good durability for prevention of early abrasion, and sealability is stable with the contact area prevented from being enlarged.


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