CONTROL SYSTEM OF INTERNAL COMBUSTION ENGINE

摘要

An internal combustion engine comprises an exhaust purification catalyst. The control system comprises a temperature detecting means for detecting or estimating a temperature of the exhaust purification catalyst, performs feedback control so that an air-fuel ratio of exhaust gas flowing into the exhaust purification catalyst becomes a target air-fuel ratio, and performs target air-fuel ratio setting control which alternately sets the target air-fuel ratio to a rich set air-fuel ratio and a lean set air-fuel ratio. In addition, the control system increases a variation difference, obtained by subtracting a rich degree of the rich set air-fuel ratio from a lean degree of a lean set air-fuel ratio, when a temperature of the exhaust purification catalyst detected or estimated by the temperature detecting means is a predetermined upper limit temperature or less compared with when it is higher than the upper limit temperature. As a result, a sulfur ingredient storage amount of an exhaust purification catalyst is maintained low.

主权项

1. A control system of an internal combustion engine, the internal combustion engine comprising an exhaust purification catalyst which is arranged in an exhaust passage of the internal combustion engine and which can store oxygen,
said control system of an internal combustion engine comprising a temperature detecting means for detecting or estimating a temperature of said exhaust purification catalyst, performing feedback control so that an air-fuel ratio of exhaust gas flowing into said exhaust purification catalyst becomes a target air-fuel ratio, and performing target air-fuel ratio setting control which alternately sets said target air-fuel ratio to a rich set air-fuel ratio richer than a stoichiometric air-fuel ratio and a lean set air-fuel ratio leaner than the stoichiometric air-fuel ratio, wherein when the temperature of said exhaust purification catalyst which has been detected or estimated by said temperature detecting means is a predetermined upper limit temperature or less, compared to when it is higher than said upper limit temperature, a variation difference, obtained by subtracting a rich degree which is a difference of said rich set air-fuel ratio and stoichiometric air-fuel ratio from a lean degree which is a difference of said lean set air-fuel ratio and stoichiometric air-fuel ratio, is increased.