Patent ID: 6226982
Filing Date: 2001-05-08
Classification: F02D

Abstract:
Method for controlling the strength of the air/fuel mixture supplied to an internal-combustion engine after the engine has been in a fuel cut-off operating condition during which a catalytic converter arranged along the exhaust pipe of the engine is acted on by a flow of air and stores oxygen; the method being comprising the steps of:measuring the strength of the mixture supplied to the engine by means of a first oxygen sensor arranged along the exhaust pipe upstream of the catalytic converter;estimating the quantity of oxygen stored by the catalytic converter on the basis of the strength (Mm) measured upstream of the catalytic converter itself; andexecuting, at the end of the fuel cut-off condition, a first correction of the target strength of the mixture to be supplied to the engine, with respect to an approximately stoichiometric value, in relation to the estimated quantity of oxygen stored so as to ensure controlled enrichment of the mixture aimed at allowing rapid disposal of the oxygen stored by the catalytic converter; said step of executing said first correction of the target strength being achieved by applying a correction parameter to the target strength when the engine is no longer in the fuel cutoff condition; and correction being maintained until the quantity of oxygen stored in the catalytic converter is greater than a given threshold value;executing a second correction of the target strength by processing an output signal of a second oxygen sensor arranged along the exhaust pipe downstream of the catalytic converter;disabling said second correction during said step of executing said first correction;enabling said second correction when the quantity of oxygen stored in the catalytic converter is equal to the said given threshold value, indicating that disposal of the oxygen stored by the catalytic converter during the fuel cut-off condition has occurred.