Power plants – Internal combustion engine with treatment or handling of... – By means producing a chemical reaction of a component of the...
Patent
1998-06-16
2000-05-30
Denion, Thomas
Power plants
Internal combustion engine with treatment or handling of...
By means producing a chemical reaction of a component of the...
60274, 60276, 60277, 123691, 123696, F01N 300
Patent
active
060677945
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to internal combustion engines of the fuel-injection type equipped with a catalytic exhaust converter and, more particularly in such engines, a system and a process for slaving the fuel-to-air ratio by a double feedback loop operating in real time.
2. Discussion of the Background
It is known how to use systems for modifying the quantity of fuel injected into an engine as a function of the exhaust-gas composition and, more particularly, of the oxygen content of these gases. To this end, the oxygen content is measured by means of a nonlinear sensor known as the "lambda" sensor or EGO sensor, where EGO is an English-language acronym for "Exhaust Gas Oxygen". Such a sensor is disposed upstream from the catalytic exhaust converter which treats the exhaust gases, and the signal delivered by this sensor is used to modify the quantity of fuel injected upstream from the engine cylinders via a first feedback loop.
In certain applications, it is known how to dispose a second lambda sensor downstream from the catalytic exhaust converter and to use the signal delivered by that sensor to measure, for example, the performances of the catalytic exhaust converter.
In other applications, the signal of this second sensor is used for slow regulation of the fuel-to-air ratio of the first loop by changing its operating point or by changing its transfer function. This slow regulation compensates for the aging of the first sensor on the basis of an average, but does not achieve real-time regulation of the fuel-to-air ratio, or in other words richness regulation, such that it is maintained at the stoichiometric value or close thereto, thus ensuring good operation of the catalytic converter and in turn less pollution.
SUMMARY OF THE INVENTION
One object of the present invention is therefore to provide, for internal combustion engines, a system and process with double control loop which permit real-time regulation of the fuel-to-air ratio.
Richness regulation is achieved, for example, by a fuel-injection calculator by virtue of the signal voltage delivered by the nonlinear sensor, to the effect that it modifies the injection time by means of a correction term. This correction term is a function of the sign of the difference between the sensor voltage and a threshold voltage. For example, when the sensor voltage is smaller than the threshold voltage, this means that the oxygen content is too high, and the correction comprises lengthening the fuel-injection time to increase the quantity of fuel, or in other words the richness. In the opposite case, the correction comprises shortening the fuel-injection duration to reduce the richness.
With such regulation, the physical characteristics of the sensor, such as the response time during lean-to-rich or rich-to-lean transitions and the dependence of the voltage characteristic as a function of richness according to the composition of the exhaust gases, may lead to a mean regulating richness different from the stoichiometric value.
In addition, to achieve maximum effectiveness of the catalytic exhaust converter or for any other aspect of tuning the engine, it may be necessary to choose a mean richness which is appreciably different from the stoichiometric value.
Another object of the present invention is therefore to provide, for internal combustion engines, a system and process with double control loop which permit modifying the mean richness and slaving it to a predetermined value. The invention therefore relates to a system with double loop for richness control for internal combustion engines of the fuel-injection type controlled by an electric computer and equipped with a catalytic converter which comprises: electrical signal V.sub.upstream representative of the proportion of one of the components of the engine exhaust gases at the inlet of the catalytic converter and a first correction circuit to process the said first electrical signal in such a way as to deliver to the computer a first signal KCL for correc
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Givois Bernard
Simon Edouard
Denion Thomas
Renault
Tran Binh
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