Exhaust gas purification device for an internal combustion engine
DCFirst Claim
1. An exhaust gas purification device for an internal combustion engine comprising:
- conversion means for converting, when the air-fuel ratio of exhaust gas supplied to the conversion means is rich, at least a portion of NOX contained in the exhaust gas to NH3 ;
NOX purification means disposed in an exhaust gas passage of the engine for causing the NOX in the exhaust gas to react with the NH3 produced by the conversion means and for causing the NOX to be reduced to N2 by the NH3 ; and
NOX increasing means for adjusting an air-fuel ratio of the exhaust gas supplied to the conversion means to a rich air-fuel ratio and, at the same time, increasing a concentration of NOX in the exhaust gas supplied to the conversion means to a value higher than a normal concentration of NOX in the exhaust gas of the engine, the normal concentration of NOX being defined as a concentration of NOX when the engine is operated at an air-fuel ratio the same as that of the exhaust gas adjusted by the NOX increasing means.
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Abstract
In an exhaust gas purification device, a No. 1 cylinder of the engine is operated at a rich air-fuel ratio and other cylinders (No. 2 to No. 4) are operated at a lean air-fuel ratio. The exhaust gases from the No. 1 and No. 2 cylinders are mixed with each other to form a rich air-fuel ratio exhaust gas mixture. Further, since the air-fuel ratio of the No. 2 cylinder is lean, the exhaust gas from the No. 2 cylinder contains a relatively large amount of NOx. This rich air-fuel ratio exhaust gas mixture which contains a relatively large amount of NOX is supplied to a three-way catalyst. At the three-way catalyst, part of the NOX in the exhaust gas mixture is converted to NH3. The exhaust gas mixture flowing out from the three-way catalyst and the lean exhaust gas from the No. 3 and No. 4 flow into a common exhaust gas passage where they mix with each other to form a lean exhaust gas containing NH3 from the three-way catalyst and NOX from the No. 3 and No. 4 cylinders. This lean exhaust gas flows into a denitrating catalyst disposed on the common exhaust gas passage in which NOX in the exhaust gas is reduced by the NH3.
185 Citations
15 Claims
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1. An exhaust gas purification device for an internal combustion engine comprising:
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conversion means for converting, when the air-fuel ratio of exhaust gas supplied to the conversion means is rich, at least a portion of NOX contained in the exhaust gas to NH3 ; NOX purification means disposed in an exhaust gas passage of the engine for causing the NOX in the exhaust gas to react with the NH3 produced by the conversion means and for causing the NOX to be reduced to N2 by the NH3 ; and NOX increasing means for adjusting an air-fuel ratio of the exhaust gas supplied to the conversion means to a rich air-fuel ratio and, at the same time, increasing a concentration of NOX in the exhaust gas supplied to the conversion means to a value higher than a normal concentration of NOX in the exhaust gas of the engine, the normal concentration of NOX being defined as a concentration of NOX when the engine is operated at an air-fuel ratio the same as that of the exhaust gas adjusted by the NOX increasing means. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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Specification