Method for operating an internal combustion engine and device for implementing the method

Abstract

A method for operating an internal combustion engine and a device for implementing the method may allow a catalytic converter diagnosis with a high degree of accuracy. At least one catalytic converter is positioned in the exhaust-gas region of the internal combustion engine, and a lambda sensor, which is configured as broadband lambda sensor, is positioned downstream from the catalytic converter or downstream from a section of the catalytic converter. The catalytic converter diagnosis is based on the evaluation of a measure for the oxygen storage capacity of the catalytic converter / within the catalytic converter. An at least approximately empty / filled oxygen reservoir of the catalytic converter is assumed. A change in the lambda setpoint value of the internal combustion engine to an excess air factor lambda that is greater than 1 / less than 1 follows. Subsequently, a first change of the lambda signal is detected initially. Determined is a measure for the oxygen stored / discharged following the first change of the lambda signal. The determination of the stored / discharged oxygen is terminated if either a second change in the lambda signal is detected or if the measure of oxygen exceeds a threshold value.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] The present application claims priority to Application No. 10 2005 002 237.5, filed in the Federal Republic of Germany on Jan. 18, 2005, which is expressly incorporated herein in its entirety by reference thereto. FIELD OF THE INVENTION [0002] The present invention relates to a method for operating an internal combustion engine and to a device for implementing the method. BACKGROUND INFORMATION [0003] One possibility for diagnosis of the catalytic converter is based on determining the oxygen storage capacity of the catalytic converter. A decrease in the oxygen storage capacity is considered a measure for the decline in the conversion capacity of the catalytic converter. The oxygen storage capacity of a catalytic converter can be determined by subjecting the excess-air factor lambda in the exhaust gas upstream from the catalytic converter to a cyclic change about the value 1.0 and comparing the lambda signal measured downstream from the ...

AI Technical Summary

Benefits of technology

[0006] Example embodiments of the present invention may provide a method for operating an internal combustion engine and a device for implementing the method, which may allow a reliable diagnosis of the catalytic converter.

[0008] Due to the use of a broadband lambda sensor, the method may provide relatively high accuracy in the determination of at least one measure for the oxygen storage capacity of the catalytic converter, which may be utilized as a measure for the ageing condition of the catalytic converter. High oxygen storage capacity is a sign of a good catalytic converter.

[0014] Low-pass filtering of the lambda signal may be provided to block interference signals and rapid changes of the lambda signal due to dynamic processes during determination of the change.

Problems solved by technology

Due to this measure, an unsteady operating state of the internal combustion engine during the catalytic converter diagnosis may have an only negligible effect on the diagnosis result.

Images