Patent ID: 8725389
Filing Date: 2014-05-13
Classification: F02D,Y02T

Abstract:
1. A control device for a multi-cylinder internal combustion engine, comprising: an air-fuel ratio detecting unit that is provided in an exhaust passage of the multi-cylinder internal combustion engine; an air-fuel ratio control unit that is configured to execute air-fuel ratio feedback control such that an air-fuel ratio of exhaust gas, detected by the air-fuel ratio detecting unit, becomes a predetermined target air-fuel ratio; an EGR device that is configured to carry out external EGR by which exhaust gas in the exhaust passage is circulated to an intake passage of the multi-cylinder internal combustion engine; an abnormality detecting unit that is configured to, when an abnormal deviation that an air-fuel ratio of at least any one of cylinders deviates from the target air-fuel ratio while the air-fuel ratio control unit is executing the air-fuel ratio feedback control has occurred, detect the abnormal deviation and an abnormal cylinder that is the at least any one of the cylinders; and a deviation correction unit that is configured to, when the abnormal deviation has been detected while the air-fuel ratio control unit is executing the air-fuel ratio feedback control and the EGR device is carrying out the external EGR, correct the target air-fuel ratio in order to compensate for a detection error of the air-fuel ratio detecting unit due to an influence of specific components of exhaust gas and that is configured to change a mode of correction on the basis of whether the detected abnormal cylinder causes more intensive gas flow against the air-fuel ratio detecting unit than the other cylinders or causes equal or less intensive gas flow against the air-fuel ratio detecting unit than the other cylinders, wherein the abnormality detecting unit is configured to detect an abnormal lean deviation that the air-fuel ratio of the abnormal cylinder deviates from the target air-fuel ratio toward a lean side and an abnormal rich deviation that the air-fuel ratio of the abnormal cylinder deviates from the target air-fuel ratio toward a rich side as distinguished from each other, when the abnormal lean deviation has been detected, the deviation correction unit is configured to correct the target air-fuel ratio when the abnormal cylinder causes more intensive gas flow than the other cylinders and not to correct the target air-fuel ratio when the abnormal cylinder causes equal or less intensive gas flow than the other cylinders; whereas, when the abnormal rich deviation has been detected, the deviation correction unit is configured not to correct the target air-fuel ratio when the abnormal cylinder causes more intensive gas flow than the other cylinders and to correct the target air-fuel ratio when the abnormal cylinder causes equal or less intensive gas flow than the other cylinders.