Method of controlling the state of clogging of a catalytic converter for a vehicle by measuring the richness of exhaust gases upstream of the converter for a known richness from the engine

摘要

The richness of the exhaust gases from an engine is modified so it is in a range of predetermined values and during at least one predetermined period an electrical voltage leaving a probe (8) measuring the richness of the exhaust gases upstream of the converter (6) is analyzed. Comparison with preset threshold voltage values allows the amount of clogging to be determined : The modification stage is controlled following reception of data about the state of the vehicle, or independently of the state of the vehicle. The range is for a ratio of theoretical air mass supplied to the engine during a predetermined period in stoichiometric quantity for combustion of a fuel and a mass of air supplied to the engine over the same time, and is between 0.8 and 1.1. The analysis is carried out over two predetermined periods. One period starts when a measure of the richness is for the first time in the preset range after modification, or after this moment. If the probe is a Lambda probe, the method involves determining if, between preset instants Tx and T1, the voltage is at least once below a preset threshold U1 and if, between preset instants T0 and T2, the tension becomes less than a preset threshold U2. Alternatively, the method involves determining if, between preset instants T0 and T1 the voltage becomes greater than a preset threshold U1 and if between preset instants T0 and T2 the voltage becomes less than a preset threshold U2. If the probe is a proportional probe, the method involves determining if, between preset instants T0 and T3 the voltage becomes greater than a preset threshold U3 and if between preset instants Ty and T4 the voltage becomes greater than a preset threshold U4. The driver of the vehicle is informed of the state of the converter. The converter is a first converter and the vehicle has a second catalytic converter upstream of the probe. The engine is a compression ignition engine. An independent claim is made for a control system to carry out the above process, with means of modifying the richness of the exhaust gases so they are in a predetermined range of values and means of analyzing an electrical voltage over a predetermined period to measure the richness of the exhaust gases upstream of the converter.