| 摘要 |
A NOx sensor (24) following the three-way catalyst (22), provides a relationship between NOx concentration in the exhaust and its lambda value. This relationship and the measured NOx concentration are used to correct the signal level for lambda =1. Preferred features: The NOx sensor is used to control a NOx reduction or storage catalyst in the exhaust pipe. Mixture is controlled (25) such that at the NOx sensor, a predetermined NOx concentration is measured, corresponding to lambda = 1. The engine is controlled cyclically. During the cycle, slight, steady weakening of the mixture is caused. This results in slight, continuous NOx concentration ramping-up, at the sensor. On reaching a predetermined threshold, the mixture is again enriched. A NOx sensor is used, which in addition, delivers an oxygen-dependent signal. In a new departure, this signal is used in addition to the trimming control (26).
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