Oxygen level controlling method for internal combustion engine, involves modulating exhaust gas composition between threshold values such that lean and fat adjustments of composition are terminated, when amount reaches values, respectively

摘要

The method involves measuring exhaust gas composition in front of and behind an exhaust gas purification system (16) in flow direction of exhaust gas using exhaust sensors (14, 17). Oxygen entering into the system is summed to an oxygen amount. The composition in front of the system is modulated between upper and lower threshold values such that lean and fat adjustments of the composition are terminated, when the amount reaches the upper and lower values, respectively. The values are fixed based on aging of the system and operating parameters of an internal combustion engine (10).