Exhaust-gas purification device for internal combustion engine
AssigneeHonda Giken Kogyo Kabushiki Kaisha
InventorsNobuaki Takaoka, Hiroshi Oono
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Abstract
A proportional oxygen sensor, a three-way catalyst, a binary O2 sensor, a NOx purification device, and a binary O2 sensor are positioned in the named order in the exhaust system of an internal combustion engine. A correction coefficient KMON2, which is set in accordance with the degree of deterioration of a three-way catalyst, is used to correct the timer value tmMON2 used to measure the time extending from the time at which the output of the O2 sensor is changed when the air-fuel ratio is increased, until the time at which the output of the O2 sensor is changed. When the corrected timer value tmMON2 is smaller than a reference time TNOxREF, it is ascertained that deterioration of the NOx purification device has occurred.
Claims4
An exhaust-gas purification device, which is provided for the exhaust system of an internal combustion engine, comprising:
- nitrogen oxide purifying means for absorbing nitrogen oxide in exhaust gases in a lean exhaust-gas condition;
- a three-way catalyst, which is provided upstream of said nitrogen oxygen purifying means;
- a first oxygen sensor, which is provided between said nitrogen oxide purifying means and said three-way catalyst, for detecting the oxygen density in said exhaust gases;
- a second oxygen sensor, which is provided downstream of said nitrogen oxygen purifying means, for detecting said oxygen density in said exhaust gas;
- first deterioration determination means, for evaluating the deterioration of said three-way catalyst;
- and
- second deterioration determination means, for evaluating the deterioration of said nitrogen oxide purifying means, based on the deterioration of said three-way catalyst and a first determination time period, after a lean air-fuel ratio of the exhaust gas has been shifted to a rich air-fuel ratio by an decrease in the air-fuel ratio of a mixture to be supplied to the internal combustion engine, from a time at which the value output by first oxygen sensor changes to a value indicating a rich air-fuel ratio until the value output by said second oxygen sensor changes to a value indicating a rich air-fuel ratio.
Dependencies are inferred from the claim text.