Anomaly diagnosis device and abnormality diagnosis method for a variable valve mechanism, internal combustion engine and computer program product

摘要

An abnormality diagnosis apparatus for a variable valve mechanism configured to open an exhaust valve even during an intake stroke, and capable of selecting a first mode wherein the exhaust valve opens only during an intake stroke or a second mode, the exhaust valve both during an exhaust stroke as well as an intake stroke opens. The abnormality diagnosis by the apparatus determines that the mechanism is abnormal when a difference between an exhaust gas recirculation amount calculated to recirculate from an exhaust passage into a cylinder in the second mode based on intake air amounts in the first and second modes and an exhaust gas recirculation amount which is estimated to recirculate from an exhaust passage in the second mode based on an exhaust pressure exceeds a diagnostic threshold. The higher an exhaust gas pressure, the greater an exhaust gas recirculation amount is estimated to be.