Patent ID: 8549845

Claim:
An exhaust purification device for an internal combustion engine provided with a NOx purification catalyst that is disposed in an exhaust path of the internal combustion engine, and purifies NOx in exhaust, the device comprising: a fuel reformer that is provided separately from the exhaust path, reforms fuel and produces a reducing gas containing carbon monoxide, hydrogen, and hydrocarbons, and supplies the reducing gas upstream of the NOx purification catalyst into the exhaust path; a temperature detection means for detecting a temperature of exhaust flowing in the exhaust path, or a temperature of the NOx purification catalyst; a reformer control means for starting supply of reducing gas to the exhaust path by starting control of the fuel reformer in a case where the temperature detected by the temperature detection means is no higher than a predetermined first temperature, and stops supply of reducing gas to the exhaust path by stopping control of the fuel reformer in a case where the temperature detected by the temperature detection means becomes at least a second temperature that is higher than the first temperature; an intake control valve provided in an intake path of the internal combustion engine; an exhaust-gas recirculation amount control valve provided in an exhaust-gas recirculation path that recirculates a portion of exhaust flowing in the exhaust path into the intake path; and a space velocity control means for decreasing an intake amount by closing the intake control valve, or increasing an exhaust-gas recirculation amount by opening the exhaust-gas recirculation amount control valve, so that a space velocity of exhaust gas in the NOx purification catalyst falls below a predetermined lower limit target velocity, while supplying reducing gas to the exhaust path by way of the fuel reformer.