| 摘要 |
PROBLEM TO BE SOLVED: To inhibit deterioration of a NOx conversion rate and drop of NOx storage capacity by keeping the temperature of a NOx catalyst excessively high in an internal combustion engine provided with a storage reduction type NOx catalyst. SOLUTION: In fuel addition control relating to a NOx reduction process in a NOx catalyst, an integrated value of periods during which catalyst bed temperature Tn (NOx storage integration periodΣSs) is equal to or higher than NOx storage upper limit temperature Tj in a reference period Sdi is calculated (S102), and fuel addition pattern is changed to keep fuel addition interval Sin long (S104) when it is determined that NOx storage integration periodΣSs is shorter than a second reference period Sd2 (S103). COPYRIGHT: (C)2008,JPO&INPIT
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