Fuel cut control apparatus of internal combustion engine

Abstract

The exhaust gas purifying catalysts sometimes generate HS which emits exhaust odor under reducing atmosphere. However, in the ordinary air-fuel ratio control, it takes much time to establish sufficient oxygen atmosphere for suppressing HS emission when the maximum oxygen storage amount which the exhaust gas purifying catalyst can store is large. Thus, the fuel cut control apparatus of an internal combustion engine executes fuel cut to bring oxygen in the exhaust gas into an excessive state when the maximum oxygen storage amount is a predetermined amount or more. As a result, sufficient oxygen can be stored in the exhaust gas purifying catalyst. Even when the maximum oxygen storage amount of the exhaust gas purifying catalyst is smaller than the predetermined amount, if the temperature of the exhaust gas purifying catalyst is lower than predetermined temperature, fuel cut is executed. In this case, influence which is given to deterioration of the catalysts is small even if the fuel cut is executed and the inside of the catalysts is under the oxygen atmosphere. On the other hand, if the temperature of the exhaust gas purifying catalyst is the predetermined temperature or higher, the fuel cut is not executed. Since the deterioration of the catalyst is promoted when the catalyst is under the oxygen atmosphere at high temperature, priority is given to prevention of deterioration of the exhaust gas purifying catalyst.