Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – With indicator or control of power plant
Reexamination Certificate
1999-05-05
2001-04-03
Wolfe, Willis R. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
With indicator or control of power plant
C701S108000, C123S568210
Reexamination Certificate
active
06212467
ABSTRACT:
BACKGROUND AND SUMMARY OF THE INVENTION
This application claims the priority of German patent document 198 19 937.6, filed May 5, 1998, the disclosure of which is expressly incorporated by reference herein.
The invention relates to an electronic engine control system for an internal-combustion engine.
An engine control system of this type is used in modern internal-combustion engines for automatically controlling the operating performance of the internal-combustion engine. For example, such an engine control system interacts with a fuel injection system, a throttle valve in the air intake region of the internal-combustion engine, an exhaust gas recirculation system and an exhaust gas cleaning system. In addition, with a correspondingly constructed engine control system, the air/fuel mass ratio of the mixture fed to the combustion can be varied; in particular, a change-over can be permitted between rich and lean operations of the internal-combustion engine.
Modern internal-combustion engines (such as direct-injection gasoline engines, direct-injection diesel engines, common-rail injection diesel engines) may be equipped with an exhaust gas recirculation system in order to reduce the emission of pollutants and reduce the fuel consumption. In such systems,a portion of the engine exhaust gases is returned to the combustion mixture. Such an external exhaust gas recirculation changes the air-fuel mass ratio of the mixture charged into the combustion space and therefore has considerable influence on the combustion taking place there. As a result, the composition of the exhaust gases is changed, and the power and the smooth operation of the engine are influenced. In addition to being influenced by such an external exhaust gas recirculation, the operating performance of the engine can also be affected by internal exhaust recirculation. Such internal exhaust gas recirculation is performed, for example, by providing a dead volume which cannot be driven out of the combustion space by a piston of a cylinder. In addition, during charging of the mixture into the combustion space, an overlap between the closing movement of the exhaust valves and the opening movement of the intake valves leads to a return flow of exhaust gases already displaced from the combustion space into the exhaust gas system.
In order to obtain optimal values for engine performance, particularly for fuel consumption, pollutant emission and engine efficiency, the fraction of exhaust gases which exists in the combustion space before the next combustion operation must be known. only then, can the mixture composition in the combustion space be determined with sufficient precision and, as a result, by means of a suitable automatic control or control, the operating performance of the engine can be influenced.
The fraction of exhaust gas which remains in the combustion space before the next combustion (called a residual gas fraction) is taken into account with respect to characteristic diagrams in the case of conventional engine control systems. For this purpose, characteristic diagrams stored in a memory of the engine control system represent experimental values for adjustment of the exhaust gas recirculation system or of a mixing valve which influences the exhaust gas quantity externally fed to the combustion, as a function of different load condition of the internal-combustion engine. Because both internal and external exhaust gas recirculation can change during constant engine operation in order, for example, to be able to ensure a smooth engine running performance, considerable safety factors must be taken into account. As a result, the influence of the residual gas fraction by means of characteristic diagrams can be considered only in a relatively rough manner.
Other methods, which measure the residual gas fraction in the combustion space relatively precisely, have high equipment-related expenditures, and can therefore be used only in experiments within the scope of the engine development.
One object of the present invention, therefore, is to provide a system which can determine the residual gas fraction in the combustion space, at low expenditures.
These and other objects and advantages are achieved by the present invention, in which the residual gas fraction is determined exclusively from a conventionally measurable air/fuel mass ratio in the exhaust gases and from an air/fuel mass ratio adjusted by the engine control system in the carbureted fuel. Thus, for the system according to the invention, a normally existing engine control system can be used. By means of such an engine control system, an already existing signal value for the air/fuel mass ratio in the carbureted fuel is detected and is combined with a signal value for the air/fuel mass ratio in the exhaust gas sensed by a sensor system. Such a sensor system also already exists in internal-combustion engines with a modern exhaust gas cleaning system. The engine control system according to the invention can therefore easily be integrated into an existing engine control system.
In a preferred embodiment of the invention, the engine control system can influence the engine operation as a function of the signal value correlating with the residual gas fraction, when the engine control unit detects the existence of steady-state or quasi-steady-state engine operation and/or engine operation with an extrastoichiomeetric air/fuel mass ratio in the carbureted fuel. These measures are based in particular on the recognition that, in extrastoichiometric engine operation, either the fuel mass in the exhaust gas after combustion is essentially equal to zero (overstoichiometric air/fuel mass mixture in the carbureted fuel during lean operation) or the air or oxygen mass in the exhaust gas after the combustion is equal to zero (understoichiometric air/fuel mass ratio in the carbureted air in the rich operation). In addition, the invention takes into consideration that, in the case of an extrastoichiometric operation of the engine, because of the internal and external exhaust gas recirculation, HC (in the case of a rich understoichiometric operation) or O
2
(in the case of a lean overstoichiometric operation) builds up in the combustion space. That is, the mixture available in the combustion space for the combustion on its own becomes increasingly richer or leaner within certain limits.
Under these conditions, the following therefore applies to the fuel:
m
kz
(
k
)=
m
kf
(
k
)+
r
R
m
ka
(
k
−1)
wherein:
m
ka
(
k
-
1
)
=
{
m
kz
(
k
-
1
)
-
m
lz
(
k
-
1
)
Δ
,
for
m
kz
(
k
-
1
)
≧
m
lz
(
k
-
1
)
Δ
(
rich
operation
)
0
,
for
m
kz
(
k
-
1
)
≦
m
lz
(
k
-
1
)
Δ
(
lean
operation
)
Analogously, the following applies to the air:
m
lz
(
k
)=
m
lf
(
k
)+
r
R
m
la
(
k
−1)
wherein:
m
la
(
k
-
1
)
=
{
m
lz
(
k
-
1
)
-
m
kz
(
k
-
1
)
·
Δ
,
for
m
lk
(
k
-
1
)
≧
m
kz
(
k
-
1
)
·
Δ
(
lean
operation
)
0
,
for
m
lk
(
k
-
1
)
≦
m
kz
(
k
-
1
)
·
Δ
(
rich
operation
)
The following legend applies to all formulas and equations contained in the description:
m
lz
=air mass in the cylinder combustion space
m
lf
=air mass in the carbureted fuel
m
la
=air mass in the exhaust gas
m
kz
=fuel mass in the cylinder combustion space
m
kf
=fuel mass in the carbureted fuel
m
ka
=fuel mass in the exhaust gas
r
R
=residual gas fraction
&Dgr;=stoichiometric air/fuel mass ratio
&phgr;
z
=air/fuel mass ratio in the mixture contained in the cylinder combustion space or in the exhaust gas
&phgr;
f
=air/fuel mass ratio in the carbureted fuel
k=discrete point in time in the combustion space shortly before a combustion
k−1=point in time k of the preceding combustio
Guzella Lino
Koch Charles Robert
Scherer Matthias
Daimler-Chrysler AG
Evenson, McKeown, Edwards & Lenahan P.L.L.C.
Wolfe Willis R.
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