Testing lean burn engine exhaust lambda sensor is accomplished by evaluating its responsiveness when inlet manifold mixture is suddenly enriched as part of rich regeneration cycle for nitrogen oxide catalyst

摘要

Testing lean burn engine exhaust lambda sensor is accomplished by evaluating its responsiveness when inlet manifold mixture is suddenly enriched as part of rich regeneration cycle for nitrogen oxide catalyst. A gas transport interval (tGas) is calculated. This is the time required for (exhaust) gases to reach the lambda sensor from the fuel injection point in the inlet manifold. Total dead time (tTot) is measured. This is the time required for the sensor signal (LAMvor CAT) to jump between a desired lambda value and a given threshold value (SW1). The difference between gas transport time and total dead time is calculated. The difference is the inherent dead time (tSonde) of the sensor. This difference is compared with a threshold value (SW2). In accordance with the results of the comparison, the lambda sensor is assessed in terms of responsiveness. Preferred Features: The gas transport time (tGas) for a 6 cylinder engine is calculated from: tGas = (8-EBW/120) asterisk TN+tAbg TN = the time for 120 deg crankshaft rotation, EBW = the angle at which injection commences, tAbg = the exhaust passage time. This is given by: tAbg = (K asterisk TN)/(LM) LM = the mass of air in the inlet manifold in milligrams per stroke, K = a dimensional factor = f(LM), in kg/h. The factor (K) is stored as a function of air mass (LM) in a characteristic relationship (KF1) in a memory unit (21). Threshold values (SW1, SW2) are determined experimentally and stored in the memory.