Exhaust gas cleaner for internal combustion engine

Abstract

In an internal combustion engine (100) provided with an NOx absorbing reduction catalyst (2) in an exhaust gas passage (1), there are arranged: an oxygen sensor (3) which is mounted downstream of the NOx absorbing reduction catalyst (2) in the exhaust gas passage (1); and a determination means for determining a condition of degradation of the NOx absorbing reduction catalyst (2) on the basis of a time length, during which a voltage value, having a small amount of variation before the voltage value outputted from the oxygen sensor (3) is recorded as a maximum value when executing a rich spike, is recorded.

Description

technical field [0001] The present invention relates to an exhaust purification device of an internal combustion engine having a NOx storage reduction catalyst in an exhaust passage. Background technique [0002] In an internal combustion engine with a NOx occlusion reduction catalyst (hereinafter referred to as an occlusion catalyst) in the exhaust passage, once the NOx occlusion in the occlusion catalyst reaches a certain level, the air-fuel ratio must be temporarily and sharply changed from "lean" to "lean". The so-called rich boost (Japanese: リッチスパイク) operation of switching to "rich" reduces and removes the occluded NOx. [0003] As a method for regenerating the storage catalyst by this rich strengthening, there is Japanese Patent Application Laid-Open No. 2000-45752 (Method for Purifying a Nitrogen Oxide Storage and Reduction Catalyst in an Internal Combustion Engine) filed by the applicant of the present application. In the invention of JP 2000-45752, it is considered...

AI Technical Summary

Problems solved by technology

The term "deterioration of the storage catalyst" here refers to the degradation of the purification performance of the storage catalyst due to sulfur poisoning and thermal deterioration.

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