Method of influencing temperature of catalytic system in direct injection internal combustion engine exhaust involves determining oxygen storage capacity in system and its components

摘要

Values of the oxygen storage capacity in the pre-catalyzer, OSCVK, the main catalyzer OSCHK and the catalytic system OSCK are determined, and, as a function of these values, selective dispositions are made to influence the temperature of at least one of the components of the exhaust system : There is a pre-catalyzer and at least one main catalyzer. The exhaust system includes at least a pre-catalyzer and at least one main catalyzer downstream of the pre-catalyzer. The storage capacity of the pre-catalyzer is determined by finding the oxygen storage capacity of the system OSCVK and OSCK during two time intervals using a curve of the variation against time of the oxygen concentration downstream of the main catalyzer. During the first time interval TVK, OSCVK must reach a level above a threshold OSCVKS1 and the capacity of the main catalyzer is less than a threshold OSCHKS1, During the second time interval, OSCVK is chosen approximately equal to OSCK; OSCHK is greater than a threshold OSCHLS2 and OSCVK is greater than a threshold OSCVKS2. The capacity OSCHK of the main catalyzer is the difference between OSCK and OSCVK. The time interval TVK is fixed so between its limits, the temperature tempVK of the pre-catalyzer is greater than a light-off temperature TempLOVK and the temperature TempHK of the main catalyzer is less than a light-off temperature TempLOHK. At least one parameter of the catalyzer measuring the sulfur load SHK or NOx storage capacity NOxSFHK is determined and desulfurization or improvement in NOx conversion is carried out as a function of this value or values. desulfurization is carried out when SHK is greater than a threshold SW1 and when SFHK is below a threshold SKSF, preferably as a function of a desulfurization parameter DeS. When DeS is greater than a threshold SW2 desulfurization is carried out and if DeS is less than a threshold SW2 at least one measure is taken to increase NOx conversion. If SFHK is less than SWSF and TempHK is less than a threshold SW3 or SW4, at least one measure is taken to raise the temperature TempK of the catalytic system. SW3 is coordinated with SHK greater than SW1 and SW4 is coordinated with SHK less than SW1. The variation with time of oxygen concentration is used to determine an OSC after passage of at least one lambda value of the engine lambdaM, from a preset poor value, lambda leanto a preset rich value, lambda rich, to a preset poor value, lambda lean. The delay T1, T2 after lambda changes is used for a reaction of lambda downstream of the main catalyzer. At least one of the following arrangements is made as a function of OSCVK, OSCHK and/or OSCK, to know throttled operation with a stratified fuel charge, optimal heating of the catalyzer after the engine is started, abandoning the stratified fuel charge operation in favor of a homogenous function with a poor mixture or offsetting the spark later. An independent claim is made for a device to carry out the above process by measuring the oxygen storage capacity of the pre-catalyzer and main catalyzer and selective arrangements are made to influence the temperature of at least part of the exhaust system as a function of these values.