Page 172 - Methods For Monitoring And Diagnosing The Efficiency Of Catalytic Converters A Patent - oriented Survey

154 Methods for Monitoring and Diagnosing the Efficiency of Catalytic Converters

3) judging the deterioration of the catalytic converter according to the steps 4 to 8 of the
method of USS4OOS92 (1 995) described above, where the judgment is based on the data
sampled by the angular-based sampler in step 1 of the present method
4) sampling an output signal from the upstream air/fiel sensor at every lapse of a
predetermined constant time by means of a time-based data sampler e.g. a sampler sampling
data at every lapse of a constant time interval
5) judging deterioration of the upstream sensor on the basis of data sampled by the time-based
data sampler

The method of JP7063107 (1995) uses the output signals of an air quantity sensor, a rotational
speed sensor and the oxygen sensors placed upstream and downstream of the catalytic
converter to assess the deterioration degrees of an ignition plug, the upstream oxygen sensor
and the catalytic converter.

The method of JP7116469 (1995) comprises a monolithic catalytic converter with a lot of
exhaust gas channels located in the middle of the monolith. Exhaust gas on both upstream and
downstream sides of the catalytic converter is introduced to the inside electrode and the
outside electrode of an oxygen sensor respectively, which is located close to the exit end face
of the monolith (fig. 71). Electromotive force is generated corresponding to the difference in
the oxygen concentration of the exhaust gas on the upstream and downstream sides which are
in contact with the inside electrode and the outside electrode of the oxygen sensor respectively
to be extracted from lead wires as electric output signals. The output signals are compared
with predetermined values to diagnose the degree of deterioration of the catalytic converter.

The method of JP8296428 (1996) inhibits the deterioration detection of the catalytic converter
until the catalytic converter is activated. An initial deterioration index is calculated by means
of the output signals of the upstream and downstream oxygen sensors, as described in other
methods of this chapter. A final deterioration index is then calculated based on the initial
deterioration index and a correction value obtained by a correction value calculating means.