EXHAUST PURIFICATION SYSTEM FOR INTERNAL COMBUSTION ENGINE (AS AMENDED)

摘要

Provided is an exhaust purification system for an internal combustion engine. The exhaust purification system comprising: a NOX purifying catalyst arranged in an exhaust passage of the internal combustion engine, wherein the NOX purifying catalyst comprises a base metal supported on a catalyst support; an oxygen sensor arranged at the downstream side of the NOX purifying catalyst in the exhaust passage; and an air-fuel, ratio control means for controlling the air-fuel ratio of exhaust gas flowing into the NOX purifying catalyst; wherein when the NOX purifying catalyst suffers from predetermined oxygen poisoning, the air-fuel ratio control means controls the air-fuel ratio of the exhaust gas, which flows into the NOX purifying catalyst, to a first air-fuel ratio wherein the first air-fuel ratio is richer than a theoretical air-fuel ratio, and then the air-fuel ratio control means switches the air-fuel ratio of the exhaust gas, which flows into the NOX purifying catalyst, to a second air-fuel ratio on the basis of an output value from the oxygen sensor wherein the second air-fuel ratio is leaner than the first air-fuel ratio.

主权项

1. An exhaust purification system for an internal combustion engine comprising:
a NOX purifying catalyst arranged in an exhaust passage of said internal combustion engine, wherein said NOX purifying catalyst comprises a base metal supported on a catalyst support; an oxygen sensor arranged at the downstream side of said NOX purifying catalyst in the exhaust passage; and an air-fuel ratio control means for controlling the air-fuel ratio of exhaust gas flowing into said NOX purifying catalyst; wherein when said NOX purifying catalyst suffers from predetermined oxygen poisoning, said air-fuel ratio control means controls the air-fuel ratio of the exhaust gas, which flows into said NOX purifying catalyst, to a first air-fuel ratio wherein said first air-fuel ratio is richer than a theoretical air-fuel ratio, and then said air-fuel ratio control means switches the air-fuel ratio of the exhaust gas, which flows into said NOX purifying catalyst, to a second air-fuel ratio on the basis of an output value from said oxygen sensor wherein said second air-fuel ratio is leaner than said first air-fuel ratio.