초록 ▼

In an exhaust gas purification device, a three-way catalyst, an NO.sub.x absorbing-reducing catalyst and an NH.sub.3 adsorbing-denitrating catalyst are disposed in an exhaust gas passage of the internal combustion engine. The engine is provided with direct cylinder injection valves which inject fuel

In an exhaust gas purification device, a three-way catalyst, an NO.sub.x absorbing-reducing catalyst and an NH.sub.3 adsorbing-denitrating catalyst are disposed in an exhaust gas passage of the internal combustion engine. The engine is provided with direct cylinder injection valves which inject fuel directly into the respective cylinders. A control circuit controls the amount of fuel injected from the injection valve so that the air-fuel ratio of the combustion in the cylinders becomes a lean air-fuel ratio during the normal operation of the engine. Therefore, a lean air-fuel ratio exhaust gas is discharged from the cylinders during the normal operation and NO.sub.x, in the exhaust gas is absorbed by the NO.sub.x absorbing-reducing catalyst. When the amount of NO.sub.x absorbed in the NO.sub.x absorbing-reducing catalyst increases to a predetermined level, the control circuit performs an additional fuel injection during the expansion stroke or exhaust stroke of cylinders in order to adjust the air-fuel ratio of the exhaust gas leaving the cylinders to a rich air-fuel ratio. The rich air-fuel ratio exhaust gas leaving the cylinders flows into the three-way catalyst and NO.sub.x in the exhaust gas is converted into NH.sub.3 at the three-way catalyst. When the rich air-fuel ratio exhaust gas flows through the NO.sub.x absorbing-reducing catalyst, NO.sub.x is released from the NO.sub.x absorbing-reducing catalyst and is reduced to N.sub.2 by NH.sub.3 in the exhaust gas.

대표청구항 ▼

[ We claim:] [1.] An exhaust gas purification device for an internal combustion engine capable of operating on lean air-fuel combustion, the engine being provided with a direct cylinder injection valve for injecting fuel directly into a cylinder thereof and an exhaust gas passage extending through w

[ We claim:] [1.] An exhaust gas purification device for an internal combustion engine capable of operating on lean air-fuel combustion, the engine being provided with a direct cylinder injection valve for injecting fuel directly into a cylinder thereof and an exhaust gas passage extending through which exhaust gas travels away from the cylinder, said device comprising:exhaust gas air-fuel ratio adjusting means for adjusting an air-fuel ratio of exhaust gas produced by lean air-fuel ratio combustion in the cylinder from a lean air-fuel ratio to a rich air-fuel ratio by injecting additional fuel into the cylinder from the direct cylinder injection valve during one of an expansion stroke and an exhaust stroke of the cylinder;NH.sub.3 conversion means disposed in the exhaust gas passage downstream of the cylinder wherein, when additional fuel is injected to the cylinder by the exhaust gas air-fuel ratio adjusting means, the exhaust gas air-fuel ratio adjusting means provides rich air-fuel ratio exhaust gas to the NH.sub.3 conversion means, the NH.sub.3 conversion means producing NH.sub.3 by converting at least a portion of NO.sub.x contained in the exhaust gas to NH.sub.3 ; andpurification means disposed in the exhaust gas passage downstream of the NH.sub.3 conversion means for purifying both NO.sub.x and NH.sub.3 included in the exhaust gas by reacting the NO.sub.x with the NH.sub.3.