Patent ID: 6119452
Filing Date: 2000-09-19
Classification: B01D,F01N,F02B,F02D,Y02T

Abstract:
A device for purifying an exhaust gas of an internal combustion engine having a plurality of cylinders divided into first and second cylinder groups, and first and second exhaust passages connected to the first and the second cylinder groups, respectively, the device comprising:an NH.sub.3 synthesizing catalyst arranged in the first exhaust passage, the NH.sub.3 synthesizing catalyst synthesizing NH.sub.3 from at least of a part NO.sub.X in an inflowing exhaust gas when an exhaust gas air-fuel ratio of the inflowing exhaust gas is rich;first making-rich means for making the exhaust gas air-fuel ratio of the exhaust gas flowing into the NH.sub.3 synthesizing catalyst rich to synthesize NH.sub.3 ;an interconnecting exhaust passage interconnecting the first passage downstream of the NH.sub.3 synthesizing catalyst and the second exhaust passage to contact NH.sub.3 synthesized in the NH.sub.3 synthesizing catalyst and NO.sub.X from the second exhaust passage to each other, to reduce the NO.sub.X by the NH.sub.3 ; andfirst making-lean means for making the exhaust gas air-fuel ratio of the exhaust gas flowing into the NH.sub.3 synthesizing catalyst temporarily lean; wherein a cumulative amount of hydrocarbon (HC) flowing to the NH.sub.3 synthesizing catalyst when the exhaust gas air-fuel ratio of the exhaust gas flowing to the NH.sub.3 synthesizing catalyst is rich is obtained, and wherein the first making-lean means performs the making-lean operation when the cumulative amount of HC becomes larger than a predetermined upper threshold.