Abstract: An exhaust-gas after-treatment device having an oxygen storage capacitor substance which releases oxygen when the exhaust-gas is rich in air-fuel ratio and stores oxygen and heats up by itself when the exhaust-gas is lean in air-fuel ratio. The air-fuel ratio for the exhaust-gas flowing into the device is regulated so as to alternately come into the rich condition and the lean condition when the temperature of the exhaust-gas is not higher than a given temperature and when the device is not in a regeneration condition. Thus, when the device having a deNOx catalyst and a diesel particulate filter is not in a regeneration condition, the temperature of the device is raised by utilizing the self-heating function of the oxygen storage capacitor substance during oxygen absorption. As a result, the purification rate for NOx and particulate matter at the time when the temperature of the exhaust-gas is low is improved.

Abstract: In an exhaust-gas after-treatment device (10,10A) having an oxygen storage capacitor substance which releases oxygen when the exhaust-gas is rich in air-fuel ratio and storages oxygen and heats up by itself when the exhaust-gas is lean in air-fuel ratio, the air-fuel ratio for the exhaust-gas flowing into the exhaust-gas after-treatment device (10,10A) is regulated so as to alternately come into a rich condition (R) and a lean condition (L) when the temperature (Tg) of the exhaust-gas is not higher than a given temperature (Tc) and when the exhaust-gas after-treatment device (10,10A) is not in the condition of being regenerated. Thus, when an exhaust-gas after-treatment device (10,10A) having a deNOx catalyst and a DPF is not in the condition of the regeneration of deNOx catalyst, DPF regeneration, or the like, the temperature of the exhaust-gas after-treatment device (10,10A) is raised by utilizing the self-heating function of the oxygen storage capacitor substance during oxygen absorption.