US Patent 7247190 Engine exhaust gas cleaning apparatus

An engine exhaust gas cleaning apparatus is provided to minimize torque shock as during regeneration of an exhaust gas cleaning device. The engine exhaust gas cleaning apparatus comprises a fuel delivery device that delivers fuel to an engine at a lean excess air ratio during normal operation of the engine; a NOx trapping catalytic converter that adsorbs NOx from the exhaust gas during the lean operation; a regeneration control section that adjusts the excess air ratio to a rich target value to regenerate the NOx trapping catalytic converter; a feedback control section that feedback-controls the fuel delivery quantity to hold the excess air ratio at the target value during regeneration; a feedback control restricting section that restricts the feedback control during regeneration until the difference between the target value and the actual excess air ratio is less than a prescribed value.