| 摘要 |
PROBLEM TO BE SOLVED: To provide a detecting apparatus for the functional state of an NOx occlusion catalyst, by which the functional state of the NOx occlusion catalyst by an NOx sensor can be judged surely. SOLUTION: When an operation control procedure in a lean air-fuel ratio is started (S120), a timer is started. A second minimum pumping current among from second pumping currents IPs detected repeatedly until a waiting time Tw elapses is stored as a reference second pumping current IP2s, and a timer value at this time is stored as a reference timer value Ts (S110 to S160). When the relative value ΔIP2(=IP2-IP2s) of the second pumping current IP2 detected after that to the reference pumping current IP2s becomes larger than a fixed value Ic (S240-Y), a measuring time ΔT(=Te-Ts) is found on the basis of a timer value Ts at this time and on the basis of the reference timer value Ts, a refresh request is output when the measuring time ΔT is smaller than a time threshold value Tth, and a catalyst burning-off request is output when the measuring time ΔT is larger than the time threshold value Tth (S250 to S280, S220). |
