Catalytic converter diagnostic
First Claim
1. A method for transforming an oxygen content signal into a signal indicating the oxygen storage and release capacity of a catalytic treatment means operative to catalytically treat internal combustion engine emissions passing through the catalytic treatment means, for diagnosing a fault in the catalytic treatment means, comprising the steps of:
- for each of a plurality of test periods, (a) sensing a predetermined event indicating a start of a test period, (b) sensing a predetermined event indicating an end of the test period, (c) periodically sampling, after the indicated start of the test period and before the indicated end of the test period, an oxygen content signal indicating the oxygen content of engine emissions that have passed through the catalytic treatment means, (d) estimating rates of change in oxygen content between successive samples of the oxygen content signal, (e) determining a maximum rate of change in oxygen content from the estimated rates of change;
generating an average rate of change signal indicating the oxygen storage and release capacity of the catalytic treatment means as a predetermined function of the determined maximum rates of change in oxygen content for each of the plurality of test periods;
comparing the generated average rate of change signal to a predetermined signal threshold value;
providing a diagnostic signal indicating a decreased oxygen storage and release capacity of the catalytic treatment means when the generated average rate of change signal exceeds the predetermined signal threshold value; and
carrying out a supplemental diagnostic according to a predetermined process when the generated average rate of change signal exceeds the predetermined signal threshold value.
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Accused Products
Abstract
A diagnostic for an internal combustion engine exhaust gas treatment means includes a series of enabling conditions for modelling temperature and operational stability of the treatment means and includes first and second stage tests alternately applied on an engine air/fuel ratio cycle-by-cycle basis in accord with the diagnosed performance of the treatment means using post-converter oxygen sensor information. When the treatment means performance is diagnosed as being degraded close to a failed condition, the first stage is disabled and the more statistically rigorous second stage is activated to closely scrutinize converter performance using a two phase approach for false alarm protection.
24 Citations
12 Claims
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1. A method for transforming an oxygen content signal into a signal indicating the oxygen storage and release capacity of a catalytic treatment means operative to catalytically treat internal combustion engine emissions passing through the catalytic treatment means, for diagnosing a fault in the catalytic treatment means, comprising the steps of:
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for each of a plurality of test periods, (a) sensing a predetermined event indicating a start of a test period, (b) sensing a predetermined event indicating an end of the test period, (c) periodically sampling, after the indicated start of the test period and before the indicated end of the test period, an oxygen content signal indicating the oxygen content of engine emissions that have passed through the catalytic treatment means, (d) estimating rates of change in oxygen content between successive samples of the oxygen content signal, (e) determining a maximum rate of change in oxygen content from the estimated rates of change; generating an average rate of change signal indicating the oxygen storage and release capacity of the catalytic treatment means as a predetermined function of the determined maximum rates of change in oxygen content for each of the plurality of test periods; comparing the generated average rate of change signal to a predetermined signal threshold value; providing a diagnostic signal indicating a decreased oxygen storage and release capacity of the catalytic treatment means when the generated average rate of change signal exceeds the predetermined signal threshold value; and carrying out a supplemental diagnostic according to a predetermined process when the generated average rate of change signal exceeds the predetermined signal threshold value. - View Dependent Claims (2, 3, 4, 5)
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6. A method for diagnosing a fault condition in a catalytic treatment means for catalytically treating internal combustion engine emission passing through the catalytic treatment means, by transforming an oxygen content signal into a signal indicating oxygen storage and release capacity of the catalytic treatment means and by analyzing such signal, comprising the steps of:
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periodically generating oxygen content signals by sampling an oxygen content of engine emissions that have passed through the catalytic treatment means; transforming the oxygen content signal into the signal indicating oxygen storage and release capacity, by a (a) passing the signals through a differentiation process for estimating a rate of magnitude change between oxygen content signals;
(b) grouping each of the differentiated signals into one of a plurality of test periods;
(c) determining a maximum differentiation signal for each of the plurality of test periods;
(d) generating an average signal value as a predetermined function of the determined maximum differentiation signals;carrying out a stage one diagnostic by comparing the average signal value to a predetermined stage one threshold value; carrying out a predetermined stage two diagnostic when the average signal value exceeds the predetermined stage one threshold value; and indicating a catalytic treatment means failure upon failing the stage two diagnostic. - View Dependent Claims (7, 8, 9, 10, 11, 12)
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Specification