Internal-combustion engines – Combustion chamber – Having catalytic cambustion aid
Reexamination Certificate
2001-09-18
2003-08-19
Yuen, Henry C. (Department: 3747)
Internal-combustion engines
Combustion chamber
Having catalytic cambustion aid
Reexamination Certificate
active
06606983
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates generally to pistons for diesel engine application, and particularly to, pistons for use in diesel engine applications utilizing an exhaust gas recirculation system.
2. Related Art
Diesel engines are widely utilized for providing power for trucks, ships and construction machines as well as for use in electrical power generation. In an effort to abate air pollutants such as nitrogen oxides (NO
x
) present in exhaust gases produced by diesel engines, government regulations may soon require the recirculation of exhaust gases in diesel engines. An exhaust gas recirculation system (EGR) may be utilized as a means of controlling NO
x
emissions, but also produces an environment within the engine that is characterized by increased corrosive potential compared to a non-EGR combustion system. Such an EGR system would likely introduce organic acids and other corrosive elements into the combustion chamber and could present a corrosive environment that would be harmful to conventional ferrous pistons.
U.S. Pat. No. 5,450,784 discloses a piston having an electro-deposited tin-based plating for wear resistance. There is no disclosure as to corrosion resistance to an EGR environment.
It is an object of the present invention to provide a ferrous piston which is resistant to attack by a corrosive EGR environment of a diesel engine.
SUMMARY OF THE INVENTION
A piston for a diesel engine having exhaust gas recirculation(EGR) system comprises a piston body fabricated of ferrous metal and a coating of electroless nickel formed on at least a portion of the piston body providing a continuous, non-porous barrier to the EGR environment.
The piston of the present invention has the advantage of providing a continuous barrier layer or coating that protects the ferrous piston from the corrosive EGR environment.
The piston has the further advantage of providing a continuous barrier layer that does not require additional machining or finishing after the barrier layer has been applied. Because there is no additional machining, the coating remains continuous to protect the piston from the corrosive EGR environment.
The electroless coating can be applied in a uniform, thin layer such that the dimensional tolerances of the piston can be maintained without the use of further finishing operations after the coating has been applied. This arrangement allows for an economical corrosion resistant part to be produced without complex machining of the piston or the cylinder of a diesel engine to accommodate the thickness of a coating.
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Bedwell Tom
De Azevedo Miguel N. D.
Ribeiro Carmo
Ali Hyder
Federal-Mogul World Wide Inc.
Howard & Howard
Yuen Henry C.
LandOfFree
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