Exhaust gas converter system for a diesel engine

摘要

The computer effects changeover from lean to rich running when regeneration temperature is reached in the storage catalyst (27) and it has reached predetermined loading. Weak running is resumed when rich running criteria absent, or regeneration time expired, or catalyst (27) regenerated to predetermined degree, or on reaching predetermined reductant concentration following (27), or when exhaust temperature lies below a given threshold. Regeneration time is a function of catalyst loading at the start of regeneration. Preferred Features: For change to rich running, the engine is operating in steady, quasi-steady or stationary state. States are deduced from one or more sensors measuring: r.p.m., accelerator setting, injection quantity, exhaust temperature especially ahead of the turbocharger (1), torque and load. Time profiles of the signals are taken into account. Differing thresholds and intervals (i.e. differing profiles) are used to characterize non-steady state operation. A temperature sensor ahead of the storage catalyst monitors regeneration temperature. The temperature sensor (30) intervenes between an oxidizing catalyst (28) and the storage catalyst (27). Characteristic stored data and measured values determine catalyst loading. NOx sensors (31, 32) are used for the purpose. Sensor determines loading from the NOx quantity emitted. Regeneration time and state are determined from characteristic curves as a function of engine operational state and loading of the storage catalyst. Initial and final states and the stored characteristics are taken into account. Exhaust reductants are monitored following the storage catalyst using an HC, CO or lambda sensor. Reductant sensor monitors between storage catalyst and DeNOx catalyst (29). Temperature sensor measures exhaust gas temperature ahead of the storage catalyst. Exhaust gas temperature sensor is located between storage catalyst and the preceding oxidation catalyst.