| 摘要 |
PROBLEM TO BE SOLVED: To control the catalyst activity of NOx-occlusion catalyst by measuring the NOx-concentration in combustion gas during the regeneration period by a gas sensor for sensing NOx, which is installed in the rear of the NOx-occlusion catalyst, and taking the measured NOx-concentration into consideration as a barometer of catalyst activity of the NOx-occlusion catalyst. SOLUTION: Exhaust gas of an internal combustion engine supplied by an exhaust gas passage 11 reaches the inside of an NOx-occlusion catalyst 12. While combustion mixture exists due to lean state, nitrogen oxide existing in the exhaust gas is occluded and made react with a reducing compound such as hydrogen, hydrocarbon and carbon monoxide of a combustion mixture due to rich state by catalyst during the subsequent regeneration period. A gas sensor 14 for sensing NOx is used for measuring the NOx- concentration of exhaust gas after separation from the NOx-occlusion catalyst 12 during the regeneration period, and the shortage of catalyst activity is confirmed in the case where the absolute value of maximum value of NOx-concentration exceeds a designated value, in the case where the up gradient of NOx-concentration is below the designated vale, and further in the case where the integrated value of all NOx- concentration exceeds the designated value. |
