Checking NOx sensor in engine exhaust system, initiates rich running to detect low initial ramping rate and low maximum value of ammonia produced

• Main Authors: ARLT TINO, ROSEL GERD
• Format: Patent
• Language: English; French
• Published: 21.06.2002
• Edition: 7
• Subjects: BLASTING; COMBUSTION ENGINES; CONTROLLING COMBUSTION ENGINES; HEATING; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS; INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIRCHEMICAL OR PHYSICAL PROPERTIES; LIGHTING; MEASURING; MECHANICAL ENGINEERING; PHYSICS; TESTING; WEAPONS

The NOx sensor (4) is located downstream of the catalyst (3). Initially the engine is run with lambda = 1. Subsequently, the engine is run with lambda less than unity, under which condition, more NH3 is produced. Defective NOx sensor operation is recognized when the signal change at the start of the second interval has a lower gradient and/or the maximum value reached is too low. Preferred features: The engine management system determines the mode of running in terms of a system variable. Rich running is initiated when the engine management system determines from a system variable, that the torque developed exceeds a maximum threshold. It is initiated when a second variable indicates that the catalyst temperature has exceeded a maximum value. The catalyst is designed for NOx storage. Outside regeneration phases, the engine is run weak when the engine management system reports from the first system variable, that the torque to be developed by the engine is less an intermediate threshold. It is also run weak when the engine management reports, from the second system variable, that the catalyst has sufficient NOx storage capacity. In addition, the engine is operated with lambda = 1 when it is similarly determined that the torque to be developed lies between the intermediate and maximum thresholds in accordance a second variable indicating that the catalyst is not above the maximum nor below the minimal temperature. Alternatively, if the temperature of the catalyst is between an upper intermediate temperature, less than the maximum, and the maximum temperature, or is between a lower intermediate temperature, above the minimum temperature, and the minimal temperature, that the torque to be developed by the engine does not exceed a maximum threshold. Using a three-way catalyst, the engine is run at lambda = 1 when the engine management reports from the first system variable that the torque to be developed by the engine is below a maximum threshold and from a second system variable that the temperature of the catalyst is below the maximum temperature, or above the minimum temperature. Le capteur de NOx (4) présente une sensibilité transversale vis-à-vis de NH3 et est disposé en aval d'un catalyseur (3) qui produit davantage de NH3 lorsque le moteur (1) fonctionne avec lambda < 1 que lorsqu'il fonctionne avec lambda = 1.Pendant une première période, le moteur fonctionne avec lambda = 1. Pendant une deuxième période qui fait suite à la première période, le moteur fonctionne avec lambda < 1. Un fonctionnement défectueux du capteur de NOx (4) est diagnostiqué lorsque la modification du signal du capteur de NOx, au début de la deuxième période, ne présente pas un flanc de pente suffisamment raide ou que la grandeur maximale atteinte du signal du capteur de NOx au cours de la deuxième période est trop faible.