FR2774427A1 - System for regenerating a particle filter in a diesel engine exhaust pipe - Google Patents

Abstract

The injection (6) of additional fuel into the engine cylinder (1) during expansion increases the hydrocarbon and carbon monoxide present in the exhaust (2). This produces an exothermic reaction in an oxidation catalyst (8) upstream of the filter (4), thus providing the heat to burn particles off the filter and help to regenerate it. System for helping regeneration of a particle filter (4) fitted into an exhaust pipe (2) for a diesel engine (1), in particular for a vehicle engine. The particle filter is connected to an oxidation catalyst (8) to assist in regeneration, fitted upstream of the filter in the exhaust pipe. Means (5, 6, 7) of injecting an additional quantity of fuel into at least certain engine cylinders, after the main injection and during expansion, causes an increase in the hydrocarbon and carbon monoxide fraction of the exhaust gases to activate the catalyst and start the regeneration of the filter by increasing the temperature of the gases entering the filter after passage through the catalyst. The timing of the injection is calibrated to obtain a required temperature on exit from the cylinders. The means of injection include electrically controlled injectors (6) connected to the cylinders, and are fed by a fuel supply (5) common to all the injectors. The means of injection also have a central unit (7) for data collection and injector control.

Description

 The present invention relates to a system for assisting the regeneration of a particulate filter integrated in a diesel engine exhaust line, in particular for a motor vehicle.

 We know that one of the most important concerns of equipment manufacturers and motor vehicle manufacturers is the reduction of the pollution generated by their operation.

 This is particularly the case for diesel engines.

 Different solutions have therefore been envisaged in an attempt to reduce the level of pollution of these engines.

 Thus, for example, it has already been proposed in the prior art, to integrate particulate filters into the exhaust lines of these diesel engines.

 These are then adapted to trap particles or soot contained in the exhaust gases of these engines and burn them during a regeneration phase of the filter.

 Various means of assisting in the regeneration of these filters have already been developed in the state of the art.

 However, none of these are fully satisfactory.

 The object of the invention is therefore to solve these problems.

 To this end, a subject of the invention is a system for assisting the regeneration of a particulate filter integrated in a diesel engine exhaust line, in particular for a motor vehicle, characterized in that the particulate filter is associated with a oxidation catalyst for its regeneration, arranged upstream of this filter in the exhaust line and in that it comprises means for injecting an additional quantity of fuel into at least some of the engine cylinders , after the main injection of fuel into them and during the expansion phase of the cycle of these cylinders in order to cause at least an increase in the rate of hydrocarbon and carbon monoxide in the exhaust gases of these cylinders for activate the catalyst and initiate the regeneration of the particulate filter by increasing the temperature of the gases entering it after passage through the catalyst.

 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 of a system for assisting in the regeneration of a filter according to the invention.

 We recognize indeed in this figure, a system for assisting the regeneration of a particulate filter integrated in an exhaust line of a diesel engine in particular of a motor vehicle.

 In this figure, the engine is designated by the general reference 1 and the exhaust gases from the latter are caused to circulate in an exhaust line designated by the general reference 2.

 This exhaust line is optionally associated with a turbocharger designated by the general reference 3 and the gases therefore pass through this turbocharger and more particularly into the turbine portion thereof.

 Then, the gases are caused to circulate in a particle filter designated by the general reference 4 in this figure.

 The engine is also associated with a fuel supply system designated by the general reference 5 in this figure, this supply system comprising, for example, a supply system common to all the engine cylinders, of the COMMON RAIL type for example. , comprising for each cylinder of the engine, an injector with electrical control, for example such as that designated by the general reference 6 in this figure.

 These injectors are controlled by a central information processing unit designated by the general reference 7.

 According to the invention, the particulate filter designated by the general reference 4, is associated with an oxidation catalyst designated by the general reference 8 in this figure, to aid its regeneration and disposed upstream of this filter in the line exhaust.

 In addition, this system includes means for injecting an additional quantity of fuel into at least some of the engine cylinders, after the main injection of fuel into them and during the expansion phase of the cycle of these cylinders in order to to cause at least an increase in the rate of hydrocarbon and carbon monoxide in the exhaust gases of these cylinders to activate the catalyst and initiate the regeneration of the particulate filter by increasing the temperature of the gases entering it after passage through the catalyst.

 In fact, these injection means can be formed by the main fuel supply system of the engine, the central information processing unit 7 then being adapted to pilot the injectors for the first time in order to ensure a main injection. of fuel in the engine cylinders and a second time after this main injection and during the expansion phase of the cycle of these cylinders, to ensure post-injection of an additional quantity of fuel.

 This post-fuel injection is carried out at the end of the combustion of the fuel of the main injection and the instant of injection of this additional quantity of fuel during the expansion phase, can be calibrated to obtain a determined temperature of the gases. exhaust at the cylinder outlet.

 In fact, the temperature of the exhaust gases depends on the instant of injection of the additional quantity of fuel into the cylinder.

 It can therefore be seen that it is possible, for example, to obtain an increase in the temperature of the exhaust gases by partial combustion of the post-injected fuel, but above all an increase in the hydrocarbon and carbon monoxide content of these gases d exhaust, by unburnt fuel.

 In fact, if the post-injection of additional fuel is delayed sufficiently compared to the main injection, at least part of the post-injected fuel can be used to produce hydrocarbons and carbon monoxide.

 It can therefore be seen that the passage of such exhaust gases through the oxidation catalyst 8 causes catalysis according to an exothermic reaction.

 Of course, the importance of this reaction depends on the amount of post-injected fuel.

 An increase in the temperature of the exhaust gases is then obtained during their passage through the oxidation catalyst, which allows these gases during their passage through the particulate filter, to initiate the regeneration of the latter.

 This is particularly advantageous when the vehicle engine is operating in unfavorable conditions such as for example during city driving or at low load.

 It will be noted that a possible increase in the temperature of the gases entering the catalyst by partial afterburning makes it possible to improve the efficiency of the latter and to further increase the temperature of the gases leaving the latter.

 In addition, the hydrocarbons in the exhaust gases also make it possible to wet, in particular, the soot trapped in the particulate filter, which makes it possible to further facilitate the regeneration of this filter.

 It goes without saying of course that still other embodiments of this system can be envisaged.

Claims (6)

 1. System for assisting the regeneration of a particulate filter (4) integrated in an exhaust line (2) of a diesel engine (1) in particular for a motor vehicle, characterized in that the particulate filter (4) is associated with an oxidation catalyst (8) for its regeneration, placed upstream of this filter in the exhaust line (2) and in that it comprises means (5,6,7) d injection of an additional quantity of fuel into at least some of the engine cylinders, after the main injection of fuel into them and during the expansion phase of the cycle of these cylinders in order to cause at least an increase in the rate of hydrocarbon and carbon monoxide in the exhaust gases of these cylinders to activate the catalyst (8) and initiate the regeneration of the particulate filter (4) by increasing the temperature of the gases entering it after passing through the catalyst.  2. System according to claim 1, characterized in that the instant of injection of the quantity of additional fuel during the expansion phase is calibrated to obtain a determined temperature of the exhaust gases leaving the cylinders.  3. System according to claim 1 or 2, characterized in that the means for injecting the additional quantity of fuel include injectors (6) electrically associated with the engine cylinders.  4. System according to claim 3, characterized in that the injectors (6) are formed by injectors of a supply system (5) with engine fuel.  5. System according to claim 4, characterized in that the engine supply system (5) is a common supply system for all the injectors.  6. System according to any one of the preceding claims, characterized in that the injection means comprise a central unit (7) for processing information and controlling the injectors.