Liquid seal structure

Details Liquid seal structure Liquid seal structure

2000-04-20

2002-08-06

Knight, Anthony (Department: 3626)

Seal for a joint or juncture

Seal between relatively movable parts

Circumferential contact seal for other than piston

C277S559000, C277S571000

Reexamination Certificate

active

06428015

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid seal structure for sealing oil and other liquid at a rotation shaft of an internal combustion engine, etc.
2. Description of Related Art
Conventionally, liquid seal structure has been used to with an internal combustion engine for preventing leaks of lubricant oil sealed inside a case at an output portion of a rotation shaft. Such liquid seal structure often also works for preventing invasion of dust from the outside.
U.S. Pat. No. 5,209,502 discloses a conventional liquid seal structure of rotation shaft.
As shown in
FIG. 7
herein, the seal mechanism has a seal member
71
composed of a seal lip
71
A made of Teflon (trademark of Dupont: polytetrafluoroethylene) or fluoropolymers in contact with an outer circumference of the rotation shaft
5
and dust seal lip
71
B standing back to back with the seal lip
71
A and in contact with the outer circumference of the rotation shaft
5
, the seal member
71
sandwiched by an inner case
73
and an outer case
74
constituting a seal lip support member
72
. The seal lip support member
72
is press-fitted to a housing
6
provided on a cylinder block of the engine.
The seal lip
71
A is disposed toward the inside of the engine (liquid side) to seal the oil in the engine and the dust seal lip
71
B is disposed toward the outside of the engine (gas side).
The seal lip
71
A of the seal mechanism is a disc shape having inner diameter smaller than the diameter of the rotation shaft
5
and outer diameter larger than the diameter of the rotation shaft
5
. The dust seal lip
71
B has a disc shape having inner diameter smaller than the diameter of the rotation shaft
5
and larger than the inner diameter of the seal lip
71
A and having the same outer diameter as the outer diameter of the seal lip
71
A. When the rotation shaft
5
is pressed into the inner diameter of the seal lip
71
A, the outer circumference of the rotation shaft
5
touches and slides on an end of the seal lip
71
A, the contact surface being a seal surface
71
C. At this time, inner end of the dust seal lip
71
B also touches to the outer circumference of the rotation shaft
5
. Further, a spiral groove
71
D is formed on the seal surface
71
C of the seal lip
71
A against the rotation shaft
5
, so that sealing can be made efficient using a pumping effect (an effect to push back oil etc.) of the groove
71
D.
However, in the above-described seal mechanism, since the pumping effect is lost when the spiral groove
71
D on the seal surface
71
C of the rotation shaft
5
and the seal lip
71
A is worn or when the groove
71
D is packed by sludge, sealing effect can be lost to allow an oil leak.
Further, when the oil oozes out or leaks from the seal lip
71
A, the oil can leak out to the outside through the dust seal lip
71
B.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a liquid seal structure capable of stably sealing for a long time.
A liquid seal structure according to the present invention is for preventing liquid on a liquid side from leaking toward a gas side, characterized in having: a tapered seal land provided on an outer circumference of a rotation shaft and having an outer circumference with a larger diameter on the liquid side than on the gas side; a tapered seal lip in contact with the outer circumference of the tapered seal land so that a contact surface forms a seal surface; and a seal lip support member for supporting the tapered seal lip.
According to the present invention, when the liquid, such as oil, invades into the seal surface between the tapered seal land and the tapered seal lip, since the seal surface is tapered, the liquid is returned to the side of the liquid to be sealed by moving elevationally, i.e. to the large diameter side of the tapered seal land on account of centrifugal force in accordance with the rotation of the rotation shaft. Accordingly, the liquid does not leak to the gas side, so that sealability can be secured for a long time to perform stable sealing. As a result, for instance, when the tapered seal lip has a groove. such as a helical groove, and sludge is packed in the groove or the groove is worn out, there is little influence on the sealing effect.
In the present invention, the tapered seal land is preferably independent from the rotation shaft and made of metal material, such as steel, sintered metal or metal sheets press-fitted to the rotation shaft. However, the rotation shaft itself may be carved to provide the tapered seal land. Plastic material may be used for the tapered seal land, however, since the tapered seal land can be heated during rotation, the aforesaid metal material is more preferable than the plastic material which is inferior in heat conduction.
The tapered angle of the tapered seal land is not specifically restricted but may be tapered in any manner from a gentle angle to a steep tapered angle, except for a right angle, as long as the liquid moves elevationally by the centrifugal force. Further, the width of the seal surface between the tapered seal land and the tapered seal lip is not specifically restricted but preferably as wide as possible. This is because the wider seal surface has a larger free-running effect (slinger effect) of the oil. Further, Teflon material is preferably used for the tapered seal lip, but other soft material having flexibility can also be used.
In the present invention, a groove may preferably be formed on at least one of the contact surfaces of the tapered seal land and the tapered seal lip.
According to the above arrangement, the leaked liquid goes into the groove and is unlikely to advance further outside in addition to the elevational movement of the liquid, such as oil, by the centrifugal force in accordance with rotation of the rotation shaft, thus obtaining further sealability. Further, when the groove is a helical groove, further improved sealability can be secured by the pumping effect of the groove
In the above, the groove includes helical grooves and multiple grooves. The depth of the groove is preferably approximately half (40 to 50%) of lip thickness. When the groove is a helical groove, the helix direction of the helical groove is the direction for pushing back the liquid, such as oil, though different in accordance with the rotation of the rotation shaft.
In the above, a dust seal lip for preventing invasion of dust from the gas side may preferably be provided on the outer circumference of the rotation shaft.
According to the above arrangement, since invasion of the dust or the like from the outside to the side of the liquid to be sealed can be prevented, damage on the seal surface between the tapered seal land and the tapered seal lip can be prevented, thus improving durability of the liquid seal structure.
In the above arrangement, the dust seal lip may be integrated with the tapered seal lip or may be provided as an independent body.
In the above liquid seal structure, the tapered seal lip and the dust seal lip may be integrated.
Accordingly, since the tapered seal lip and the dust seal lip are not necessary to be manufactured separately, production labor can be reduced.
Alternatively, the tapered seal lip and the dust seal lip may be independently formed.
Accordingly, since the tapered seal lip and the dust seal lip are separate bodies, the tapered seal lip and the dust seal lip can be manufactured easily. Further, since the dust seal lip can be formed in an appropriate form, the dust sealing property can be improved.
The liquid seal structure of the present invention may preferably have a liquid pool provided on the outer circumference of the tapered seal land for collecting the liquid.
Accordingly, even when the liquid leaks out from the seal surface between the tapered seal land and the tapered seal lip, the liquid is collected in the liquid pool, so that liquid leakage to the outside can be prevented by a self-collection function where the liquid moves to a lower part of the shaft through the groove and is collected again

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