Patent ID: 7028464
Filing Date: 2006-04-18
Classification: F02D

Abstract:
1. A method for purifying the exhaust gas from an internal combustion engine which is operated under lambda-based closed loop control and which has an exhaust gas tract in which a catalytic converter is located, comprising: continuously sensing a pre-converter lambda value for the exhaust gas upstream of the catalytic converter, from which a pre-converter lambda signal is generated; using this pre-converter signal as a reference variable for the lambda control loop; continuously sensing a lambda value for the exhaust gas downstream from the converter, from which a post-converter lambda signal is generated, this being a monotonically decreasing function of the lambda value (λ) for the exhaust gas downstream from the catalytic converter; and applying a correction to the lambda control loop by using this post-converter lambda signal in a trimming control loop for correcting a signal level of the pre-lambda signal; wherein a measurement signal is generated which, at least below a certain value of lambda close to lambda=1, is a strictly monotonically increasing or monotonically decreasing function of the lambda value for the exhaust gas downstream from the catalytic converter, and for levels of the post-converter lambda signal which are above a threshold value, this supplementary measurement signal is used for trimming control, and for levels of the post-converter lambda signal which are below this threshold value, the post-converter lambda signal itself is used for trimming control.