EXHAUST GAS RECIRCULATION CONTROL DEVICE AND ITS FAILURE DIAGNOSIS DEVICE

摘要

An exhaust gas recirculation control device adapted to control a recirculation of part of exhaust gas of an internal combustion engine back to the engine which comprises a recirculation pipe for recirculating the exhaust gas of the internal combustion engine back to an intake air pipe; a recirculation valve for controlling a flow quantity of the exhaust gas flowing in the recirculation pipe; a recirculation valve passage area controlling means for controlling a passage area of the recirculation valve; a running condition detecting means for detecting a running condition of the internal combustion engine; a pressure difference detecting means for detecting a pressure difference between pressures at two arbitrary points in the recirculation pipe from an exit of the recirculation valve to the intake air pipe or a pressure difference between pressures at two arbitrary points in the recirculation pipe from an inlet of the recirculation valve to an exhaust pipe; a first exhaust gas recirculation ratio calculating means for calculating a first exhaust gas recirculation ratio from the pressure difference and a detected value of the running condition detecting means; and a second exhaust gas recirculation ratio calculating means for calculating a second exhaust gas recirculation ratio corresponding with the detected value of the running condition detecting means; wherein a feed back control is performed in which the passage area of the recirculation valve is increased or decreased so that a difference between the first exhaust gas recirculation ratio and a second exhaust gas recirculation ratio is nullified.