Power plants – Internal combustion engine with treatment or handling of... – Having means analyzing composition of exhaust gas
Patent
1996-02-09
1998-03-31
Hart, Douglas
Power plants
Internal combustion engine with treatment or handling of...
Having means analyzing composition of exhaust gas
60277, 60285, F01N 320
Patent
active
057325529
ABSTRACT:
A deterioration diagnostic apparatus for a three-way catalyst includes an electronic control unit, which obtains a frequency of reversals of the changing direction in which the output of an upstream-side O.sub.2 sensor changes, based on the number of times the output voltage of the O.sub.2 sensor crosses a threshold. Also, the control unit obtains a frequency of reversals of the changing direction in which the output of a downstream-side O.sub.2 sensor changes, based on the number of times the output voltage of the downstream-side O.sub.2 sensor crosses upper and lower reversal reference values which are obtained by adding and subtracting a hysteresis constant to and from an average value of input values of the downstream-side O.sub.2 sensor output voltage. The control unit further obtains the ratio of the reversal frequency of the downstream-side sensor output to the reversal frequency of the upstream-side sensor output, and diagnoses deterioration of the three-way catalyst when the reversal frequency ratio has become greater than a predetermined value.
REFERENCES:
patent: 5228287 (1993-07-01), Kuronishi
patent: 5337558 (1994-08-01), Komatsu
patent: 5341642 (1994-08-01), Kurihara et al.
patent: 5400592 (1995-03-01), Mukaihira et al.
Hashimoto Toru
Kanao Hidetsugu
Matsumoto Takuya
Miyake Mitsuhiro
Nomura Toshiro
Hart Douglas
Mitsubishi Jidosha Kogyo Kabushiki Kaisha
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