Patent ID: 8176730

Claim:
An exhaust gas purification device of an internal combustion engine applied to an exhaust gas purification system that has a NOx catalyst provided in an exhaust passage of the internal combustion engine for adsorbing a reducing agent and for selectively purifying NOx in exhaust gas with the reducing agent and that adds the reducing agent upstream of the NOx catalyst with respect to a flow direction of the exhaust gas by using a reducing agent adding unit, the exhaust gas purification device comprising: an electronic control unit configured to: obtain temperature of the NOx catalyst or temperature information correlated with the temperature of the NOx catalyst through measurement or estimation; switch an execution mode of the control of reducing agent addition quantity based on the obtained catalyst temperature or the temperature information; calculate a basic value of the reducing agent addition quantity, which is added by the reducing agent adding unit, based on NOx quantity introduced into the NOx catalyst at each time; and calculate a correction value of the reducing agent addition quantity, which is added by the reducing agent adding unit, based on reducing agent adsorption quantity, wherein the addition quantity control is performed based on an addition quantity control value calculated from the basic value and the correction value of the reducing agent addition quantity in a case where the catalyst temperature or the temperature information is lower than a predetermined value, the addition quantity control is performed based on an addition quantity control value calculated from the basic value in a case where the catalyst temperature or the temperature information is higher than a predetermined value, and wherein the exhaust gas purification device calculates the reducing agent adsorption quantity in the NOx catalyst and controls the reducing agent addition quantity, which is added by the reducing agent adding unit, based on the reducing agent adsorption quantity.