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A pair of particulate filters arranged in parallel in an exhaust passage and a combustion device for supplying to the filters exhaust gas having a temperature elevation capability higher than the temperature elevation capability of the engine exhaust gas able to raise the filter temperature are prov

A pair of particulate filters arranged in parallel in an exhaust passage and a combustion device for supplying to the filters exhaust gas having a temperature elevation capability higher than the temperature elevation capability of the engine exhaust gas able to raise the filter temperature are provided. An NOxcatalyst and oxidizing substance are carried on each filter. When the NOxabsorbed in an NOxcatalyst should be reduced, the flow of engine exhaust gas into the filter carrying the NOxcatalyst for reduction of the NOxis suppressed and a rich air-fuel ratio exhaust gas is supplied from the combustion device to the filter so that the filter temperature is maintained higher than a particulate continuous oxidation temperature in the NOxreduction temperature range.

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A pair of particulate filters arranged in parallel in an exhaust passage and a combustion device for supplying to the filters exhaust gas having a temperature elevation capability higher than the temperature elevation capability of the engine exhaust gas able to raise the filter temperature are prov

A pair of particulate filters arranged in parallel in an exhaust passage and a combustion device for supplying to the filters exhaust gas having a temperature elevation capability higher than the temperature elevation capability of the engine exhaust gas able to raise the filter temperature are provided. An NOxcatalyst and oxidizing substance are carried on each filter. When the NOxabsorbed in an NOxcatalyst should be reduced, the flow of engine exhaust gas into the filter carrying the NOxcatalyst for reduction of the NOxis suppressed and a rich air-fuel ratio exhaust gas is supplied from the combustion device to the filter so that the filter temperature is maintained higher than a particulate continuous oxidation temperature in the NOxreduction temperature range.