EXHAUST EMISSION CONTROL DEVICE OF INTERNAL COMBUSTION ENGINES

摘要

An NOx sensor (27) detects an NOx concentration released to the atmosphere from an occlusion type NOx catalyst (25); a total NOx exhaust amount (A) is calculated based on the output from the NOx sensor (27); when a total NOx emission amount (A) reaches an NOx emission decision amount (A0) corresponding to an NOx emission decision amount specified by the NOx Emission Regulation before a running distance (C) reaches a preset running distance (C0), an exhaust air/fuel ratio is changed to a rich air/fuel ratio to thereby efficiently release NOx from the occlusion type NOx catalyst (25); and then a theoretical air/fuel ratio is changed to clean and reduce NOx by a three-way catalyst function.