| abstract |
In an internal combustion engine (100) providednwith an NO x absorbing reduction catalyst (2) in an exhaustngas passage (1), there are arranged: an oxygen sensor (3)nwhich is mounted downstream of the NO x absorbing reductionncatalyst (2) in the exhaust gas passage (1); and andetermination means for determining a condition ofndegradation of the NO x absorbing reduction catalyst (2) onnthe basis of a time length, during which a voltage value,nhaving a small amount of variation before the voltage valuenoutputted from the oxygen sensor (3) is recorded as anmaximum value when executing a rich spike, is recorded. |