Internal-combustion engines – Valve – Packing
Reexamination Certificate
2000-10-10
2001-11-20
McMahon, Marguerite (Department: 3626)
Internal-combustion engines
Valve
Packing
Reexamination Certificate
active
06318328
ABSTRACT:
FIELD OF INVENTION
The present invention relates to a valve stem seal and more particularly to a seal that prevents oil flow down a valve stem toward a combustion chamber.
BACKGROUND OF THE INVENTION
In conventional overhead valve internal combustion engines, at least two valves reciprocate to provide intermittent communication between intake and exhaust manifolds and a combustion chamber. The valves include valve stems that are disposed in valve stem guides, supporting axial motion in an engine component such as an engine head. Lubrication is provided to upper portions of the valve stems by a spray of lubricating oil within a valve cover disposed over the engine head or by gravity flow from an associated rocker arm. Oil flows by the force of gravity and may be encouraged by a pressure differential in the manifold versus crankcase pressure along a free upper end of the valve stem toward the manifolds and valve heads.
Valve stem seals located between the valve stem and the valve guide serve various purposes. First, they minimize engine oil consumption by metering oil entry into the manifold and the combustion chamber. Second, they help to minimize exhaust particles that contribute to pollution. Third, they are helpful in minimizing guide wear.
However, increasingly stringent environmental protection regulation requires that vehicle emissions be reduced to produce lower pollution levels. Exhaust particles, as noted above, contribute to this pollution. Emission levels increase by allowing even minuscule amounts of oil past the valve stem seal and down the valve stem and into the combustion chamber. Current valve stem seals, however, are designed only to meter or limit oil flow and are incapable of completely eliminating oil flow down the valve stem and into a combustion chamber.
Accordingly, a valve stem seal is needed that prevents the flow of any oil down a valve stem past the valve guide and into the combustion chamber.
SUMMARY OF THE INVENTION
A valve stem seal assembly is provided to prevent oil flow down a valve stem into a combustion chamber that includes two annular hydraulic (zero-leak) seals separated by a generally flat support member, where the seals are axially positioned back to back on an upper free end of a valve stem. The seals and the washer are secured along a radially outer circumference by a retainer, a portion of which contacts an upper surface of a valve guide. The valve stem is slideably sealed by an inner annular surface of both seals.
Preferably, each hydraulic seal includes a generally U- or V-shaped radial cross-section formed by inner and outer legs separated by a radial transverse portion. The seal may include a support such as a spring in the radial cross-section of each seal. The spring provides an inwardly radial force to hold the seal in place against the valve stem while giving the seal assembly a longer life-span during reciprocation of the valve stem. When assembled, the transverse portions of each respective hydraulic seal are placed in adjacent relationship and are separated by the support member, such that the inner legs of each respective seal define upper and lower sealing lips that contact the valve stem, and such that the outer legs of each respective seal contact the retainer. The support member may be a rigid precision washer.
The upper sealing lip acts to prevent the flow of all overhead oil down the valve stem. In particular, the retainer provides sufficient radial pressure on the upper seal to cause the upper sealing lip to completely seal the valve stem against downward oil flow. Additionally, during reciprocating action of the valve, the upper sealing lip scrapes oil off the valve stem, collecting the oil within a U- or V-shaped reservoir portion of the upper seal such that the oil within the reservoir exerts a further radially inward pressure on the upper seal. Similarly, the lower sealing lip prevents pressure from the exhaust and intake manifolds from upsetting the sealing action of the upper seal. The upper and lower sealing lips thus combine to completely eliminate an oil leak path into the combustion chamber, thereby reducing harmful emissions.
REFERENCES:
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patent: 2264413 (1941-12-01), Siegerist
patent: 2509436 (1950-05-01), Isenbarger
patent: 3306621 (1967-02-01), Fisher
patent: 3480286 (1969-11-01), Kosatka
patent: 3599992 (1971-08-01), Kammeraad
patent: 4502696 (1985-03-01), Kammeraad
patent: 5873337 (1999-02-01), Binford
patent: 6006778 (1999-12-01), Kim
patent: 6123054 (2000-09-01), Netzer
patent: 6202616 (2001-03-01), Gracyalny
patent: 6209504 (2001-04-01), Hegemier et al.
Dana Corporation
McMahon Marguerite
Rader & Fishman & Grauer, PLLC
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