초록 ▼

A device for purifying exhaust gas of diesel engines, in which an oxidizing catalyst, a diesel particulate filter, and an Nox occluding/reducing catalyst are successively disposed in an exhaust gas passage of the diesel engine from the upstream side of the passage, the device for purifying exhaust g

A device for purifying exhaust gas of diesel engines, in which an oxidizing catalyst, a diesel particulate filter, and an Nox occluding/reducing catalyst are successively disposed in an exhaust gas passage of the diesel engine from the upstream side of the passage, the device for purifying exhaust gas of diesel engines comprising a bypass that connects the upstream side of the oxidizing catalyst with the downstream side thereof in the exhaust gas passage, an exhaust gas passage change-over means for changing-over the exhaust gas flow into either the oxidizing catalyst or the bypass, an air-fuel ratio control means for controlling the air-fuel ratio of the exhaust gas, an NOx occlusion amount detector means for detecting the amount of NOx occluded by the NOx occluding substance, and a controller. The controller controls the air-fuel ratio control means and the exhaust gas passage change-over means so that the exhaust gas having a lean air-fuel ratio flows into the oxidizing catalyst when the amount of NOx occluded by the NOx occluding substance does not reach a predetermined value, and so that the exhaust gas having a rich air-fuel ratio flows through the bypass when the amount of NOx occluded by the NOx occluding substance exceeds the predetermined value.

대표청구항 ▼

1. A device for purifying exhaust gas of diesel engines, in which an oxidizing catalyst, a diesel particulate filter for trapping particulate matters contained in the exhaust gas, and an NOx occluding/reducing catalyst comprising an NOx occluding substance and a catalytically active component, are s

1. A device for purifying exhaust gas of diesel engines, in which an oxidizing catalyst, a diesel particulate filter for trapping particulate matters contained in the exhaust gas, and an NOx occluding/reducing catalyst comprising an NOx occluding substance and a catalytically active component, are successively arranged in an exhaust gas passage of the diesel engine from the upstream side thereof, said device for purifying exhaust gas of diesel engines comprising:a bypass that connects the upstream side of said oxidizing catalyst with the downstream side thereof in said exhaust gas passage to bypass said oxidizing catalyst; an exhaust gas passage change-over means for changing-over the exhaust gas flow into either said oxidizing catalyst or said bypass; an air-fuel ratio control means for controlling the air-fuel ratio of the exhaust gas; an NOx occlusion amount detector means for detecting the amount of NOx occluded by said NOx occluding substance; and a controller for controlling said air-fuel ratio control means and said exhaust gas passage change-over means based on a detection signal from said NOx occlusion amount detector means; wherein said controller controls said air-fuel ratio control means so that the exhaust gas will have a lean air-fuel ratio and controls said exhaust gas passage change-over means so that the exhaust gas will flow through said oxidizing catalyst when the amount of NOx occluded by said NOx occluding substance does not reach a predetermined value, and controls said air-fuel ratio control means so that the exhaust gas will have a rich air-fuel ratio and controls said exhaust gas passage change-over means so that the exhaust gas will flow through said bypass when the amount of NOx occluded by said NOx occluding substance exceeds the predetermined value.