Internal-combustion engines – Charge forming device – Including exhaust gas condition responsive means
Reexamination Certificate
1999-08-10
2001-06-26
Dolinar, Andrew M. (Department: 3747)
Internal-combustion engines
Charge forming device
Including exhaust gas condition responsive means
C123S698000
Reexamination Certificate
active
06250291
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process for controlling an internal combustion engine, and relates more particularly to such a process designed to control the recirculation of exhaust gases.
Because of the requirements to reduce the pollution of internal combustion engines, exhaust gases have to be recirculated to the inlet side of the engine in certain operating regimes.
2. Description of the Related Art
Document FR 2 677 123, for example, discloses a process for controlling and diagnosing an internal combustion engine comprising an exhaust gas recirculation device. The engine is controlled conventionally by controlling an amount of fuel delivered by an injector placed in the inlet manifold to suit the operating parameters such as the pressure in the inlet manifold and the engine speed. An oxygen probe placed in the exhaust manifold allows the richness of the mixture to be regulated to keep it around the stochiometric value. The engine further comprises an exhaust gas recirculation device consisting of a recirculation pipe connecting the exhaust manifold to the inlet manifold, said pipe being equipped with a valve that allows the amount of exhaust gases reintroduced in the inlet side to be regulated.
In certain operating regimes in which it is necessary to obtain a reduction in the temperature of combustion in the engine cylinder, the recirculation valve is therefore made to open so that neutral gas can be introduced into the mixture. In this way it becomes possible to reduce the omissions of polluting gases, such as oxides of nitrogen for example, in the exhaust gases.
Document JP-A-54 124 119 suggests synchronizing the control of the recirculation valve with the transitions of a signal from an oxygen probe placed in the exhaust manifold. However, the intended objective is to minimize variations in torque and does not take account of the pollution generated by synchronization of this kind.
It has been found that when the recirculation valve is made to open or to close, a peak of pollutants liable to exceed the purification capability of a catalytic converter placed in the exhaust manifold occurred.
The object of the present invention is therefore to provide a process for controlling an internal combustion engine which is more particularly suited to reducing these pollution peaks. The objects of the invention are achieved by means of a process for controlling an internal combustion engine equipped with an exhaust gas recirculation device comprising a recirculation valve and with a device for regulating the air-fuel mixture injected into the inlet circuit as a function of the signal from an oxygen probe placed in the exhaust circuit. According to the invention, control of the recirculation valve is synchronized with at least one transition of a correction of the richness of the mixture so that opening and/or closure of the recirculation valve occur respectively during a phase in which the air/fuel mixture is being enriched and/or a phase during which it is becoming more lean.
According to the invention, the control of the recirculation valve is synchronized with at least one transition of a correction of the richness of the mixture.
In a first embodiment of the invention, the valve is made to open in a first time window, the start and the end of which are determined such that the actual opening of the valve, which is defined by an increase in the inlet pressure at the inlet to a cylinder of the engine as a result of the opening of the valve, occurs during a phase in which the air/fuel mixture is enriched. Advantageously, this first time window for allowing the valve to be opened is determined by two durations measured from a transition of the mixture from rich to lean, these durations being a function of the speed and of a value representing the load of the engine.
Likewise, the valve is made to close in a second time window, the start and end of which are determined such that the actual closure of the valve, which is defined by a decrease in the inlet pressure at the inlet to a cylinder of the engine as a result of the closure of the valve, occurs during a phase in which the air/fuel mixture becomes more lean. Advantageously, this second time window for allowing the valve to be closed is determined by two durations measured from a transition of the mixture from lean to rich, these durations being a function of the speed and of a value representing the load of the engine.
In a second embodiment, the time windows begin respectively upon a transition from lean to rich, in the case of opening, and from rich to lean, in the case of closing, and end after a fifth, or respectively sixth, duration, said durations being a function of the speed and of a value representing the load of the engine.
SUMMARY OF THE INVENTION
Other features and advantages of the process according to the invention will become clear on reading the description which will follow and on examining the appended drawings, in which:
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Japanese Patent Application No. 54124119 (Keiso), dated Sep. 26, 1997.
Japanese Patent Application No. 63124849 (Yoshiharu), dated May 28, 1988.
Japanese Patent Application No. 05302548 (Yoji), dated Nov. 16, 1993.
Japanese Patent Application No. 57193739 (Nobuaki), dated Nov. 29, 1982.
Kerjean Jean-Jacques
Rembaud Françoise
Salafia Dominique
Castro Arnold
Dolinar Andrew M.
Greenber Laurence A.
Lerner Herbert L.
Siemens Automotive S.A.
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