US 5,964,088 AGranted

Device for purifying exhaust gas of engine

AssigneeToyota Jidosha Kabushiki Kaisha

InventorsYukio Kinugasa, Takaaki Itou, Koichi Hoshi, Naoto Suzuki, Koichi Takeuchi, Takehisa Yaegashi, Kouhei Igarashi

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Abstract

A device for purifying the exhaust gas of an engine having a plurality of cylinders divided into first and second cylinder groups, the first and the second cylinder groups being connected to first and second exhaust passage, respectively, and performing a lean operation, comprises an NH.sub.3 synthesizing catalyst arranged in the first exhaust passage, and an exhaust gas purifying catalyst arranged in an interconnecting passage, which interconnects the first passage downstream of the NH.sub.3 synthesizing catalyst and the second exhaust passage, for purifying the inflowing NO.sub.X and NH.sub.3. An additional engine performing a rich operation is provided and the exhaust gas thereof is fed to the first exhaust gas passage upstream of the NH.sub.3 synthesizing catalyst to make the exhaust gas air-fuel ratio of the exhaust gas flowing into the NH.sub.3 synthesizing catalyst rich, to thereby synthesize NH.sub.3 therein. An amount of NH.sub.3 or NO.sub.X flowing into the exhaust gas purifying catalyst is obtained, and the additional engine is controlled in accordance with the obtained NH.sub.3 or NO.sub.X amount to control the amount of the reducing agent flowing to the exhaust gas purifying catalyst.

Claims43

Dependent claims

A device for purifying an exhaust gas of an engine having a plurality of cylinders divided into first and second cylinder groups, the first and the second cylinder groups being connected to first and second exhaust passage, respectively, and performing a lean operation, 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 a part of NO.sub.X in the inflowing exhaust gas when the exhaust gas air-fuel ratio of the inflowing exhaust gas is rich, and passing through NO.sub.X in the inflowing exhaust gas when the exhaust gas air-fuel ratio of the inflowing exhaust gas is lean;
an interconnecting exhaust passage interconnecting the first passage downstream of the NH.sub.3 synthesizing catalyst and the second exhaust passage;
an exhaust gas purifying catalyst arranged in the interconnecting passage for purifying the inflowing NO.sub.X and NH.sub.3 ;
rich gas forming means, which is different from the engine, for supplying a reducing agent to the first exhaust gas passage upstream of the NH.sub.3 synthesizing catalyst to make the exhaust gas air-fuel ratio of the exhaust gas flowing into the NH.sub.3 synthesizing catalyst rich;
and
reducing agent amount control means for obtaining an amount of NH.sub.3 or NO.sub.X flowing into the exhaust gas purifying catalyst, and controlling the rich gas forming means in accordance with the obtained NH.sub.3 or NO.sub.X amount to control the amount of the reducing agent supplied into the first exhaust passage to control the amount of the reducing agent flowing to the exhaust gas purifying catalyst.

3 more elements

A device for purifying an exhaust gas of an engine performing a lean operation, the device comprising:

rich gas forming means, which is different from the engine, for forming the exhaust gas of which the exhaust gas air-fuel ratio is rich;
an NH.sub.3 synthesizing catalyst connected to the rich gas forming means, the NH.sub.3 synthesizing catalyst synthesizing NH.sub.3 from at least a part of NO.sub.X in the inflowing exhaust gas when the exhaust gas air-fuel ratio of the inflowing exhaust gas is rich, and passing through NO.sub.X in the inflowing exhaust gas when the exhaust gas air-fuel ratio of the inflowing exhaust gas is lean;
an interconnecting exhaust passage interconnecting the exhaust gas of the engine and that discharged from the NH.sub.3 synthesizing catalyst;
an exhaust gas purifying catalyst arranged in the interconnecting passage for purifying the inflowing NO.sub.X and the inflowing NH.sub.3 ;
and
reducing agent amount control means for obtaining an amount of NH.sub.3 or NO.sub.X flowing into the exhaust gas purifying catalyst, and controlling the rich gas forming means in accordance with the obtained NH.sub.3 or NO.sub.X amount to control the amount of the reducing agent supplied into the interconnecting passage upstream of the exhaust gas purifying catalyst.

3 more elements

Dependencies are inferred from the claim text.