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 (18) of an internal combustion engine (1) configured to be able to select a first mode which opens an exhaust valve (14) only during an exhaust stroke or a second mode which controls the exhaust valve (14 ) during the exhaust stroke and also during an intake stroke, the abnormality diagnosing device comprising: an intake air amount detecting device for detecting an intake air amount flowing in an intake passage (21); an exhaust pressure detecting device (32) for detecting a pressure an exhaust gas recirculation amount calculating device for calculating an exhaust gas recirculation amount that is recirculated into a cylinder (5) from an exhaust passage (31) in the second mode based on an intake air amount in the first mode detected by the intake air amount detection device d, and an intake air amount in the second mode when a predetermined diagnosis condition is satisfied; an exhaust gas recirculation amount estimating device for estimating an exhaust gas recirculation amount to be returned to the cylinder (5) from the exhaust passage (31) in the second mode based on the exhaust gas pressure which is detected by the exhaust pressure detecting device (32) when the predetermined diagnosis condition is satisfied; andan abnormality determination device for determining that the variable valve mechanism is abnormal when a difference between an exhaust gas recirculation amount calculated by the exhaust gas recirculation amount calculating device and an exhaust gas recirculation amount estimated by the exhaust gas recirculation amount estimating device is larger than a diagnosis threshold value (X1) wherein the exhaust gas recirculation amount estimating device estimates that the higher the exhaust gas pressure detected by the exhaust gas pressure detecting device (32) is, the larger the exhaust gas recirculation amount is.