Verfahren zur adaptiven Prüfung einer Strömungsbegrenzung für Abgasrückführsystem

摘要

An improved test method for an EGR system (22, 24) reliably detects debilitating EGR system restrictions without significantly degrading combustion stability and exhaust emissions. The EGR valve test opening for diagnostic purposes is initialized at a relatively low value, which is progressively increased if the resulting change in intake manifold pressure fails to exceed a threshold based on the minimum expected change in intake manifold pressure for an EGR system that is regarded as functioning within acceptable limits (110, 120, 130, 170). As soon as the measured pressure change exceeds the threshold, the EGR system is deemed to pass the restriction test, and the test method is terminated (130, 140, 180). If the EGR valve opening reaches a maximum value without the measured pressure exceeding the threshold, the EGR system is deemed to fail the restriction test, and a fault indication is generated (130, 150, 160). Consequently, the test opening of the EGR valve (22) is adaptively determined based on the measured intake manifold pressure change, and is never larger than required to reliably detect a debilitating EGR restriction. This allows reliable detection of a borderline failing EGR system, while preventing degradation of combustion stability and emissions in a substantially unrestricted EGR system.