EXHAUST GAS CLEANING DEVICE FOR AN INTERNAL COMBUSTION ENGINE.

摘要

An exhaust gas cleaning device for an internal combustion engine comprising an NOx absorbing agent (18) disposed in the exhaust passage of the internal combustion engine for absorbing NOx when the air-fuel ratio of exhaust gas flowing thereinto is lean, while it discharges NOx so absorbed when the air-fuel ratio of exhaust gas flowing thereinto becomes a theoretical air-fuel ratio or rich, and an air-fuel ratio sensor (22) disposed downstream of the NOx absorbing agent (18) in the exhaust passage for judging that discharging of NOx from the absorbing agent (18) is completed when the air-fuel ratio detected by the air-fuel ratio sensor (22) has been switched from lean to rich after the air-fuel ratio of exhaust gas flowing into the absorbing agent (18) was switched from lean to rich.