Operating exhaust gas purification device comprises operating engine in rich operating mode with reduction catalyst and oxidation catalyst and adjusting secondary air pump to specified lambda value

摘要

Operating an exhaust gas purification device comprises operating the engine (10) in a rich operating mode ( lambda = 1) with a reduction catalyst (32) and an oxidation catalyst (34) and adjusting a secondary air pump (40) to lambda 1. An Independent claim is also included for an exhaust gas purification device comprising a catalyst system arranged in the exhaust gas channel for reducing hydrocarbons, carbon monoxide and nitrogen oxides in the gas, and a secondary air pump having an injector (37) between the catalysts. The catalyst system consists of a reduction catalyst and an oxidation catalyst. Preferred Features: Regulation of the air pump is carried out with the aid of a model for the exhaust gas composition streams and/or a signal of an exhaust gas sensor (28), preferably a lambda sensor or a NOx sensor, arranged upstream of the oxidation catalyst. The lambda value before the reduction catalyst is 0.995-0.999 and before the oxidation catalyst is 1.001-1.005.