Apparartus for detecting deterioration of catalysts
First Claim
1. A deterioration detection apparatus for a catalyst located in an exhaust system of an internal combustion engine, said apparatus comprising:
- an upstream oxygen sensor and a downstream oxygen sensor located respectively upstream and downstream of said catalyst to detect whether an air/fuel ratio is rich or lean with respect to a stoichiometric air/fuel ratio;
amplitude detection means for detecting an amplitude of an output signal from said downstream oxygen sensor;
first deterioration determination means to determine whether deterioration of said catalyst is likely to be present on the basis of detection results of said amplitude detection means; and
second deterioration determination means to determine the presence of deterioration when possible deterioration is determined by said first determination means,wherein said second deterioration determination means includes;
response adjustment means to adjust a response of said upstream oxygen sensor to a preset value,response delay time summing means to sum a response delay time occurring within a specified period in said downstream oxygen sensor after adjusting the response of said upstream oxygen sensor, andfinal deterioration determination means to determine whether deterioration is present in said catalyst by comparing the sum from said response delay time summing means with a reference value indicating catalyst deterioration.
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Abstract
A catalyst deterioration determination is performed in two stages. In the first stage of determination, an amplitude of an output signal from a downstream oxygen sensor is detected and this amplitude is compared with a reference value in order to determine possible deterioration in a catalyst. When correct performance is expected, while taking into account variations (amplitude and response) in the upstream and downstream oxygen sensors, then the detection in a second stage is omitted. However when possible catalyst deterioration may be present, the determination at the seconds stage is performed. After adjusting the response of the upstream oxygen sensor to the characteristic of the slowest response, the total response delay time of the downstream sensor is obtained within a specified amount of time, and this sum then is compared with a reference value indicating catalyst deterioration. A final determination is made as to whether catalyst deterioration is present.
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Citations
7 Claims
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1. A deterioration detection apparatus for a catalyst located in an exhaust system of an internal combustion engine, said apparatus comprising:
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an upstream oxygen sensor and a downstream oxygen sensor located respectively upstream and downstream of said catalyst to detect whether an air/fuel ratio is rich or lean with respect to a stoichiometric air/fuel ratio; amplitude detection means for detecting an amplitude of an output signal from said downstream oxygen sensor; first deterioration determination means to determine whether deterioration of said catalyst is likely to be present on the basis of detection results of said amplitude detection means; and second deterioration determination means to determine the presence of deterioration when possible deterioration is determined by said first determination means, wherein said second deterioration determination means includes; response adjustment means to adjust a response of said upstream oxygen sensor to a preset value, response delay time summing means to sum a response delay time occurring within a specified period in said downstream oxygen sensor after adjusting the response of said upstream oxygen sensor, and final deterioration determination means to determine whether deterioration is present in said catalyst by comparing the sum from said response delay time summing means with a reference value indicating catalyst deterioration. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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Specification