Patent ID: 6477833
Filing Date: 2002-11-12
Classification: B01D,F01N,F02D,Y02A,Y02T

Abstract:
A control device for an engine, the engine comprising a fuel supply mechanism which supplies main fuel to generate an air-fuel mixture for combustion, an exhaust passage which discharges exhaust gas generated by the combustion of the air-fuel mixture, a first catalyst disposed in the exhaust passage which stores oxygen contained in the exhaust gas and releases stored oxygen for oxidizing a reducing agent component contained in the exhaust gas, the first catalyst comprising a noble metal which stores oxygen and an oxygen storage material which absorbs oxygen at a lower rate than the noble metal, and a second catalyst disposed downstream of the first catalyst in the exhaust passage which stores nitrogen oxides in the exhaust gas and releases stored nitrogen oxides by reducing the stored nitrogen oxides by the reducing agent component contained in the exhaust gas, the control device comprising:a first means for detecting a running condition of the engine; a second means for detecting an air-fuel ratio of the air-fuel mixture; a third means for calculating a storage amount of nitrogen oxides by the second catalyst based on the running condition; a fourth means for determining whether or not the storage amount is greater than a predetermined value; a fifth means for controlling the fuel supply mechanism to supply additional fuel to the engine after the combustion of the air-fuel mixture generated by the main fuel when the storage amount exceeds the predetermined value; a sixth means for calculating an oxygen storage amount of the noble metal based on the air-fuel ratio of the air-fuel mixture; a seventh means for determining, after a supply of the additional fuel to the engine has started, whether or not a predetermined condition is satisfied, the seventh means determining that the predetermined condition is satisfied when the oxygen storage amount of the noble metal falls below a predetermined amount; and an eighth means controlling the fuel supply mechanism to stop supply of the additional fuel and to increase an amount of the main fuel when the predetermined condition is satisfied.