Patent ID: 7225608

Claim:
A system for purging sulfate from a NOx trap associated with oxidation catalyst-forming means integrated in a common medium, and placed in an exhaust line of a motor vehicle diesel engine, in which the engine is associated with common rail means for feeding fuel to the cylinders of the engine, and responsive to modified engine-operation control parameters to cause the engine to switch between lean mixture operation and rich mixture operation, the feed means being adapted to define a normal operating strategy in which the engine is operated in a lean mixture and a purging control strategy in which the engine is operated to cause a purge of the NOx trap, the purging control strategy comprising a first sub-strategy for operating the engine with a rich mixture and at least two sub-strategies for operating the engine with a lean mixture referred to as “level 1” and “level 2” strategies, so as to obtain different temperature levels in the exhaust line, with the temperature level obtained by applying the level 2 strategy being higher than that obtained by applying the level 1 strategy, and wherein a temperature level obtained by applying the level 1 strategy is higher than a temperature obtained by applying the normal operating strategy, the system comprising: means for detecting a request to purge the NOx trap of sulfate; means for acquiring temperatures upstream and downstream from the medium of the NOx trap and of the catalyst-forming means in order to define a temperature operating point thereof; first comparator means for comparing said operating point with first and second predetermined low and high limit curves for controlling engine operation in rich mode if the operating point lies in the range defined between the first and second curves, or in lean mode if the operating point lies outside said range; and second comparator means for comparing said operating point with third and fourth predetermined low and high limit curves for controlling engine operation with the level 2 strategy if the operating point lies in the range defined by the third and fourth curves, or with the level 1 strategy if the operating point lies outside said range, wherein the first, second, third, and fourth curves are mapping curves as a function of upstream and downstream temperatures, wherein at least one of the first, second, third, and fourth curves is a non-linear curve.