Patent ID: 7275364
Filing Date: 2007-10-02
Classification: F02D

Abstract:
1. An exhaust purification device for internal combustion engine, comprising: a catalytic converter provided in an exhaust passage of an internal combustion engine; an air/fuel ratio forcibly modulating element for forcibly modulating the air/fuel ratio of exhaust flowing into the catalytic converter, between a lean air/fuel ratio leaner than a target average air/fuel ratio and a rich air/fuel ratio richer than the target average air/fuel ratio, with a specific period, a specific amplitude, a specific modulation ratio and a specific waveform; an oxygen sensor provided in the exhaust passage for detecting the oxygen concentration of the exhaust and supplying an output corresponding to the detected oxygen concentration; a time ratio calculating element for obtaining one of, an air/fuel ratio adjusting element for adjusting the air/fuel ratio of the exhaust during the forcible modulation, such that an actual average air/fuel ratio, obtained on the basis of one of the ratio and the value correlating with the ratio obtained by the time ratio calculating element, matches the target average air/fuel ratio, wherein the period of the modulation is set to be one of equal and shorter than a maximum period which ensures the air/fuel ratio to be detected on the basis of the output of the oxygen sensor does not reach one of the upper and lower limits of a range of air/fuel ratios detectable by the oxygen sensor.