Exhaust gas emission control device comprises nitrogen oxides absorption device, control device, nitrogen oxides absorption device deterioration determining device, device for shortening operation time and blocking device

摘要

An exhaust gas emissions control device comprises a nitrogen oxide (NOx) absorption device (21) in the exhaust gas channel of an IC engine; a normal operation control device for implementing an operation control of the engine; a NOx absorption device deterioration determining device to decide the deterioration of the NOx absorption device; a device for shortening the operation time of an air-fuel ratio of the exhaust gas in the NOx absorption device; and a device for blocking the operation with an oxygen excess-air-fuel ratio when it is decided that the degree of deterioration exceeds a prescribed value. An exhaust gas emissions control device comprises a NOx absorption device (21) arranged in the exhaust gas channel of the IC engine to absorb NOx when the in-coming exhaust gas is in an oxygen excess and emit NOx during reduction when there is a fall in the oxygen content; a normal operation control device for implementing an operation control of the engine by switching between a operation with an oxygen excess-air-fuel ratio, an operation with a theoretical air-fuel ratio and an operation with a fuel excess-air-fuel ratio according to the operating conditions of the engine; a NOx absorption device deterioration determining device to decide the deterioration of the NOx absorption device based on the amount of NOx absorbed by the absorption device; a device for shortening the operation time of an air-fuel ratio of the exhaust gas in the NOx absorption device; and a device for blocking the operation with an oxygen excess-air-fuel ratio when it is decided that the degree of deterioration exceeds a prescribed value. Preferred Features: The blocking device decides whether the operation is to be blocked with the oxygen excess-air-fuel ratio or not, based on the absorption permissible value, which makes the NOx absorption device available.