Control device for an internal combustion engine
AssigneeMitsubishi Jidosha Kogyo Kabushiki Kaisha
InventorsKenji Saito, Yoshiaki Higuchi, Hitoshi Kamura
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Abstract
Prior to failure determination of a three-way catalyst, which is carried out on the basis of a reverse frequency ratio of upstream and downstream O2 sensors, deterioration determination is performed at the point when the reverse frequency ratio of the O2 sensors starts to increase, and low NOx control is then implemented. The implement of the low NOx control makes it possible to compensate for the deterioration of the three-way catalyst with respect to NOx purification and to keep NOx emissions from the three-way catalyst equal to or less than the regulation value.
Claims6
A control device for an internal combustion engine, comprising:
- failure determining means for making a failure determination of a three-way catalyst of an internal combustion engine on the basis of an output of air-fuel ratio detecting means disposed upstream and downstream of said catalyst;
- deterioration determining means for determining a deterioration of said catalyst before said failure determining means makes a failure determination;
- and
- low NOx control means for controlling said internal combustion engine to be operated in an operating state where NOx emissions are lowered when said deterioration determining means determines a deterioration of the catalyst.
Dependencies are inferred from the claim text.