Exhaust purification device for internal combustion engine

Abstract

　In this internal combustion engine, an exhaust purification catalyst and a hydrocarbon supply valve are disposed within an exhaust passage. If the temperature of the exhaust purification catalyst belongs to a first catalyst temperature range (I), a first NOx purification method is performed. If the temperature of the exhaust purification catalyst belongs to a second catalyst temperature range (II), a second NOx purification method is performed. If the temperature of the exhaust purification catalyst belongs to a range (IIP), which is within the second catalyst temperature range and near the first catalyst temperature range, the temperature of the exhaust purification catalyst is raised so as to shift the range to which the temperature of the exhaust purification catalyst belongs to the first catalyst temperature range, and the NOx purification method to be used also switches from the second NOx purification method to the first NOx purification method as a result.

Description

technical field [0001] The present invention relates to an exhaust purification device for an internal combustion engine. Background technique [0002] There is known an exhaust purification device of an internal combustion engine, in which an exhaust purification catalyst is arranged in an exhaust passage of the internal combustion engine, and a hydrocarbon feed valve is arranged in the exhaust passage of the internal combustion engine upstream of the exhaust purification catalyst, and on the exhaust gas flow surface of the exhaust purification catalyst A noble metal catalyst is supported and a basic exhaust gas flow surface portion is formed around the noble metal catalyst. The exhaust purification catalyst has an amplitude and a predetermined range if the concentration of hydrocarbons flowing into the exhaust purification catalyst is within a predetermined range. The periodic vibration within the range reduces the NOx contained in the exhaust gas, and has the property tha...

AI Technical Summary

Problems solved by technology

As a result, if the second NOx purification method is used because the temperature of the exhaust purification catalyst is lower than the limit temperature, and the rich air-fuel ratio control is not performed for a long time, the stored NOx cannot be released from the exhaust purification catalyst, and thus It becomes impossible to purify NOx well

[0005] In other words, even if it is decided to use the first NOx purification method or the second NOx purification method according to a certain criterion, it may not be possible to perform good NOx purification.

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