| 摘要 |
PROBLEM TO BE SOLVED: To provide a catalyst deterioration determination device capable of accurately determining the deterioration of a catalyst without being affected by NH3 generated in the catalyst during the supply of a reducing agent. SOLUTION: This catalyst deterioration determination device 1 is provided in an exhaust system 5 of an internal combustion engine 3, and reduces NOx in exhaust gas by a reducing agent when the reducing agent is supplied so as to determine the deterioration of the catalyst 7 to be purified. A NOx concentration sensor 14 for detecting a NOx concentration in exhaust gas is provided at the downstream side from the catalyst 7 in the exhaust system 5. Whether or not the reducing agent is supplied is determined (Step 4), and timing when NH3 is generated in the catalyst 7 during the supply of the reducing agent is estimated (Fig. 3, Steps 10, 31). Based on the NOx concentration CNOx detected during the supply of the reducing agent and before the estimated generation timing, the deterioration of the catalyst 7 is determined (Steps 11, 13, 14 and 16). COPYRIGHT: (C)2007,JPO&INPIT
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