WO2005064129A1

WO2005064129A1 - Support system for the regeneration of anti-pollution means arranged in an exhaust system of a motor vehicle engine

Info

Publication number: WO2005064129A1
Application number: PCT/FR2004/002884
Authority: WO
Inventors: Christophe Colignon
Original assignee: Peugeot Citroen Automobiles Sa
Priority date: 2003-11-25
Filing date: 2004-11-09
Publication date: 2005-07-14
Also published as: EP1702144A1; FR2862705A1; FR2862705B1

Abstract

The invention relates to a support system for the regeneration of anti-pollution means (1), arranged in an exhaust system (2) of a motor vehicle diesel engine (3) said engine having a common rail injection fuel supply and for carrying out at least two different regeneration strategies of a first and second level (8, 9), using at least one post-injection at constant torque, by modifying the engine control parameters in order to obtain different thermal conditions in the exhaust system, the thermal level corresponding to the second level strategy being higher than that of the first level strategy, characterised in further comprising temporary initiation means (6,7), for a second over-calibrated level strategy (10), at constant torque, to give a greater thermal level and thus accelerate the warm-up of the exhaust system (2) and/or the regeneration of the anti-pollution means (1).

Description

Aid system for the regeneration of pollution control means integrated in an exhaust line of a motor vehicle engine. The present invention relates to a system for assisting the regeneration of pollution control means integrated in an exhaust line of a diesel engine of a motor vehicle. More particularly, the invention relates to such systems in which the engine is associated with common rail supply means for injecting fuel into the engine cylinders, according to at least one post-injection, and suitable for implementing , at iso-torque, by modifying engine operating control parameters, at least two regeneration strategies of first and second levels, in order to obtain different thermal levels in the exhaust line, the thermal level corresponding to the second level strategy being greater than that corresponding to the first level strategy. It is known that systems of this type have already been developed in the state of the art for ensuring the regeneration, for example of a particle filter. In this case, the soot trapped on the particulate filter is burned thanks to the thermal supplied by the engine and to the exotherm achieved by the conversion of HC on an oxidation catalyst placed upstream of the particulate filter. This combustion can be assisted by a catalyst mixed with the soot coming from an additive mixed with the fuel for supplying the engine, this additive being intended to lower the combustion temperature of the trapped soot or by a catalyst deposited directly on the walls of the filter. , i.e. a catalyzed particulate filter. It can therefore be seen that the higher the thermal levels at the input of the particulate filter, the shorter the regeneration time of the latter. Likewise, and in the case where the depollution means comprise a NOx trap, the desulfation of which must be ensured, it is necessary to reach very high thermal levels in order to destock the sulfates which are adsorbed on the trap. The object of the invention is to propose a system which makes it possible to further optimize this regeneration. To this end, the subject of the invention is a system for assisting the regeneration of depollution means integrated in an exhaust line of an engine. Motor vehicle diesel, in which the engine is associated with common rail supply means for injecting fuel into engine cylinders, according to at least one post-injection, and suitable for implementing, iso-torque , by modifying engine operating control parameters, at least two first and second level regeneration strategies, in order to obtain different thermal levels in the exhaust line, the thermal level corresponding to the second level strategy being greater than that corresponding to the first level strategy, characterized in that it further comprises means for temporarily engaging an overbalanced second level strategy, with iso-torque, to obtain a higher thermal level and therefore accelerate the warming up of the exhaust line and / or the regeneration of the depollution means. According to other characteristics: - the depollution means comprise means forming an oxidation catalyst. - the depollution means include a particle filter. - the depollution means include a NOx trap. - The fuel includes an additive intended to be deposited with the particles with which it is mixed, on the depollution means to facilitate their regeneration. - the engine is associated with a turbocharger. The invention will be better understood with the aid of the description which follows, given solely by way of example, and made with reference to the appended drawing which represents a block diagram illustrating the structure and the operation of such a system. 'help. There has indeed been illustrated in this figure, a system for assisting the regeneration of pollution control means designated by the general reference 1 in this figure, integrated in an exhaust line 2 of a diesel engine 3 of a motor vehicle. This engine can be combined with a turbocharger. In the illustrated embodiment, these depollution means comprise means forming an oxidation catalyst designated by the general reference 4 placed upstream of a particulate filter designated by the general reference 5 in the exhaust line. The engine is in turn associated with means 6 for supplying common rail for injecting fuel into the engine cylinders according to at least one post-injection. These supply means are suitable for implementing under the control of control means 7, by modifying parameters for controlling the operation of the engine, and at iso-torque, at least two regeneration strategies of first and second levels such as designated by the references 8 and 9 in this figure. These strategies make it possible to obtain different thermal levels in the exhaust line, the thermal level corresponding to the second level strategy being higher than that obtained by the first level strategy. In this case, parameters for controlling the operation of the engine are modified, for example by acting on the air admitted thereto by controlling intake valve means or else the set pressure of the turbocharger possibly associated with the engine or again by acting on the quantity of fuel injected and / or the angle of start of injection and / or the number of injections, in a conventional manner. According to the invention, this system also includes means for temporarily engaging an overbalanced second level strategy 10 to obtain, at iso-torque, a higher thermal level and therefore accelerate the warming up of the exhaust line. and / or the regeneration of depollution means. These interlocking means are formed by the supply means 6 and the control means 7. This then makes it possible to use, in transient mode, a set of specific air and fuel parameters allowing iso-torque with respect to normal engine operation , by temporarily exceeding certain criteria of thermal resistance of engine elements, to further increase the thermal level throughout the exhaust line in order to more quickly reach the minimum temperature for initiating the combustion of particles trapped in the filter. particles or to desulfate the NOx trap or to regenerate the means forming an oxidation catalyst. This strategy then only applies to the level 2 regeneration aid, that is to say once the oxidation catalyst is primed. Thus, compared to the operating mode of regeneration of the particulate filter or of heating for the desulfation of a NOx trap, an operating mode of aid type for the regeneration of the level 2 particulate filter is added, making it possible to exceed temporarily the criteria for thermal resistance of certain elements of the engine (exhaust manifold, oxidation catalyst, NOx trap, etc.). The objective of this set of parameters is to accelerate the temperature rise of the entire exhaust line, particularly in engine operating conditions where the heating for the desulfation of the NOx trap or the aid for the regeneration of the conventional particle filter does not allow reaching sufficient thermal levels to trigger the regeneration of the particle filter, for example 500 ° C for a filter with additive and 570 ° C for a catalyzed filter, or the desulfation of the NOx trap, for example 625 ° C. It is known that the additive mentioned above is an additive which can be mixed with the engine supply fuel to deposit with the particles with which it is mixed, on the particle filter in order to favor the triggering of the combustion of soot trapped in it by lowering their combustion temperature. Conventionally, this additive is indeed present in the particles after combustion of the additive fuel in the engine. By way of example, the following criteria can be used for a standard calibration to aid in the regeneration of a second level particulate filter:

- maximum exhaust manifold temperature = 800 ° C - maximum catalyst exotherm = 150 ° C - maximum catalyst outlet temperature = 710 ° C - maximum internal catalyst temperature = 760 ° C - minimum oxygen content of gases at catalyst outlet = 3% the following criteria for an over-scaled second-level strategy - maximum exhaust manifold temperature = 830 ° C - maximum catalyst exotherm = 200 ° C - maximum catalyst outlet temperature = 730 ° C - maximum internal catalyst temperature = no maximum value - minimum oxygen content of gases at catalyst outlet 2%

With the following results:

It is therefore understandable that such a system makes it possible to accelerate the heating up of all the elements of the exhaust line, that is to say of the oxidation catalyst, of the NOx trap, of the particle filter, etc. by shortening the duration of this regeneration of a particulate filter or the desulfation of a NOx trap, particularly under unfavorable driving conditions such as in town or in traffic jams. Of course, other embodiments can be envisaged. Thus, for example, the means forming an oxidation catalyst and the NOx trap can be integrated into one and the same element, in particular on the same substrate. Furthermore, a particle filter integrating the oxidation function can be envisaged. Similarly, a NOx trap incorporating such an oxidation function can also be envisaged, whether this is additive or not. This oxidation and / or NOx trap function can be fulfilled, for example, by an additive mixed with the fuel.

Claims

CLAIMS 1. System for assisting the regeneration of pollution control means (1) integrated in an exhaust line (2) of a diesel engine (3) of a motor vehicle, in which the engine (3) is associated with common rail fuel supply means for injecting fuel into engine cylinders, according to at least one post-injection, and adapted to implement, at iso-torque, by modifying parameters of the engine operation control at least two first and second level regeneration strategies (8, 9), in order to obtain different thermal levels in the exhaust line, the thermal level corresponding to the second level strategy being higher than that corresponding to the first level, characterized in that it further comprises means (6,7) for temporarily engaging an overbalanced second level strategy (10), with iso-torque, in order to obtain a higher thermal level and therefore acc Lerer warming-up of the exhaust line and / or the regeneration of depollution means. 2. System according to claim 1, characterized in that the depollution means comprise means forming an oxidation catalyst (4). 3. System according to claim 1 or 2, characterized in that the pollution control means comprise a particle filter (5). 4. System according to claim 1, 2 or 3, characterized in that the pollution control means comprise a NOx trap. 5. System according to any one of the preceding claims, characterized in that the fuel comprises an additive intended to be deposited with the particles with which it is mixed, on the depollution means to facilitate their regeneration. 6. System according to any one of the preceding claims, characterized in that the engine is associated with a turbocharger.