Internal-combustion engines – Charge forming device – Including exhaust gas condition responsive means
Reexamination Certificate
2000-02-22
2001-08-14
Wolfe, Willis R. (Department: 3747)
Internal-combustion engines
Charge forming device
Including exhaust gas condition responsive means
C123S443000, C701S109000
Reexamination Certificate
active
06273077
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of operating an internal combustion engine, especially of a motor vehicle, in which an air mass and a fuel mass are fed into a combustion chamber in a combustion cycle, wherein the mixture composition ratio (lambda) of the air mass to the fuel mass is pre-adjustable. Further it also relates to a suitable control unit for this type of internal combustion engine.
2. Prior Art
In conventional combustion engines the air mass required for combustion is fed through an intake pipe to the combustion chamber. The fuel mass required for the combustion is similarly supplied to the combustion chamber by means of a fuel pipe and suitable injection valves in these engines or with direct gasoline injection (BDE) via a fuel intermediate reservoir (fuel rail), in which the highly compressed fuel is present at about 100 bar, in modern gasoline motors or diesel engines.
In an older previously published DE application (AZ R 32348-1) of the present inventor a method and apparatus for determination of the gas fill of a combustion engine is described. The gas mixture contained in the intake pipe is composed of fresh gas and exhaust gas. A process is described in this reference for determining the fresh gas portion in the gas flowing into the combustion chamber in order correspondingly to be able to exactly measure the amount of fuel to be made available for the combustion. To solve this problem the partial pressure of the fresh gas portion in the total mass flow flowing into the combustion chamber is determined by setting up a mass balance condition and then taking the time derivative of the general gas equation. This separate balancing of the fresh gas and the exhaust gas provides the advantage that the filled fresh gas volume can be exactly determined. The subject matter of the present patent application only concerns the residual air found in the exhaust pipe because of an external exhaust gas feedback, generally not to the internal residual gas present in the combustion chamber.
In the known internal combustion engine, especially combustion engines, the air portion in the residual gas still found in the residual gas after each combustion cycle is left completely out of consideration. Furthermore it is usually assumed that no residual air will be found in the residual gas from the combustion chamber. Of course considerable errors are thus present in the stoichiometry of air and fuel taken into the combustion cycle.
Furthermore in modem combustion engines with a 3-way exhaust gas catalyzer lean operation (lamba≧1) is basically avoided, since the nitrogen oxides (NOx) greatly increase during lean operation, which then enter the catalyzer and reduce its service life. However in contrast, the newest catalyzers also permit lean operation, since NOx fed into one of these catalyzers is reduced to N
2
and O
2
again by rich operation of the engine with &lgr;(lambda)<1. On account of this new catalyzer engineering advance gasoline engines may now be operated like Diesel engines, which besides has considerably improved the development of the BDE combustion engines.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method and apparatus for operation of the above-mentioned internal combustion engine, which overcomes the above-described disadvantages and permits an exact knowledge of the stoichiometry of the fuel/air mixture during combustion.
It is especially an object of the present invention to be able to exactly account for the portion of residual air in the respective mixture composition still found in the residual gas in the combustion chamber in lean operation.
The above-described objects of the invention are attained in a method, in which the portion of residual air present in the combustion chamber after combustion has occurred in the combustion chamber is determined in a combustion cycle with a mixture composition lambda &lgr; greater than 1 and the air mass fed to the combustion chamber in the combustion cycle following that is reduced by about that portion of residual air. The invention thus is based on the concept of considering the residual air available for a respective following combustion cycle in the &lgr;(lambda) determination.
The method of the invention thus includes the following method steps:
a) establishing the presence of a combustion cycle with a mixture ratio, &lgr;(lambda), of air/fuel>1;
b) determining a residual air portion remaining in the combustion chamber after combustion has occurred in the combustion chamber during the combustion cycle in which &lgr;(lambda)>1; and
c) reducing the air mass fed into the combustion chamber through the intake pipe in a combustion cycle following the combustion cycle in which &lgr;(lambda)>1 by about the residual air portion determined in step b).
The method according to the present invention thus takes the air portion in the residual gas into account and thus guarantees a more exact control of &lgr;(lambda) than in the state of the art and thus an improved exhaust gas and vehicle operation.
It should be emphasized that the present invention is not limited to BDE-operated internal combustion engines, but fundamentally includes engines, which have an NOx-fit catalyzer, i.e. also those engines with conventional fuel injection with a &lgr;(lambda) of about 1.6.
The control unit according to the invention, in an internal combustion engine having means for feeding an air mass and fuel mass into the combustion chamber, comprises means for controlling the mixture composition lambda &lgr; of air mass to fuel mass, means for establishing the presence of a combustion cycle with a mixture combustion lambda, &lgr;, >1; means for determining a residual air portion in the combustion cycle in which &lgr;(lambda)>1 after combustion has occurred in the combustion chamber prior to that cycle and means for calculating a reduced air mass to be fed into the combustion chamber through the intake pipe in a combustion cycle following that cycle approximately from the residual air portion determined to be present after combustion in the aforesaid combustion cycle in which &lgr;(lambda)>1.
REFERENCES:
patent: 4995258 (1991-02-01), Frank
patent: 5140850 (1992-08-01), Ellmann et al.
patent: 197 56 919 A1 (1998-10-01), None
patent: 0-454191-A1 (1991-10-01), None
Robert & Bosch GmbH
Striker Michael J.
Wolfe Willis R.
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