FR2840644A1 - METHOD FOR DETERMINING THE CHARGING STATE OF A PARTICLE FILTER OF AN INTERNAL COMBUSTION ENGINE - Google Patents

Abstract

Method for determining the state of charge of a catalytically coated particulate filter of an internal combustion engine, which is supplied by the exhaust gases of the internal combustion engine, comprising the following phases: a) determination of the mass of carbon black primary accumulated in the particulate filter, b) determination of the mass of carbon black converted in the particulate filter by a reaction with NO2, between accumulated particles and NO2 generated, etc) determination of the integral accumulation of carbon black from phases a) and b).

Description

exhaust gas.

  The invention relates to a method for determining a state of charge of a catalytically coated particle filter of an internal combustion engine, in particular of a diesel engine, which is supplied by the exhaust gases of the internal combustion engine. internal combustion. It is known to use particle filters for the elimination of solid particles contained in the exhaust gases of internal combustion engines, in particular for the elimination of carbon black compounds contained in the exhaust gases of engines. diesel so that

  these cannot reach the environment.

  Particle filters also fulfill the function of protecting a catalyst placed downstream against impurities which could deteriorate the latter, or at least

affect its effectiveness.

  To maintain their operating capacity, particulate filters must be subjected to a regular regeneration process in order to restore an initial charge capacity. Different wind regeneration methods known for this purpose. In the case of thermal regeneration, the temperature of the diesel particulate filter is increased to such an extent that the particles accumulated in the filter ignite and burn. The rise in temperature is for example obtained by heating an area in the initial part of the particle filter. Another method is to raise the temperature of the exhaust gas, which can be done either by heating a flow of exhaust gas upstream of the particulate filter by means of a heater, or by appropriate influence exerted on the running state of the engine, for example a re-injection, a modification of the position of a throttle valve and / or a modification of an exhaust gas recycling rate. The regeneration can moreover be carried out using an additive, a dose additive added to the fuel or an injection of additive upstream of the particle filter causing a reduction in the ignition temperature of the carbon black, or the diesel particulate filter is coated with a suitable catalyst. A regeneration filter filter control

  particles can work passively or actively.

  In the case of passive production, a high charge in particles of the filter leads to a strong increase in the pressure upstream of the filter, until the temperature lo of the exhaust gases is finally brought to a level such that spontaneous combustion of the particles is started. The extreme increase in the temperature of the exhaust gases, and the combustion of the particles, sometimes taking place very suddenly during regeneration, operating passively, represent a risk of irreversible deterioration of the particle filter. In the case of simple processes operating in an active manner, the regeneration of the filter at fixed intervals is generally based on a path traveled or on an operating time of the internal combustion engine. The regeneration cycle is in this case designed so that the operating capacity of the particle filter is ensured, even under extreme operating conditions in which an increased rejection of carbon black is generated. Regeneration is therefore performed more frequently than would be required for an actual load value of the filter. This leads to increased thermal wear of the particulate filter, as well as higher fuel consumption. With known methods, and in the absence of knowledge of the actual state of charge of the particle filter, the regeneration process is in its entirety carried out, either too rarely, as in the case of passive operation, or too

  frequently, as in the case of the active process.

  To take note of the state of charge of the particle filter, the document DE-A-199 61 159 proposes to calculate at predetermined time intervals a mass of carbon black passed during a real time interval, and this on the basis of the detection of at least one real operating parameter of the internal combustion engine, and calculating an integral load in carbon black of the particle filter by summing up the

  masses of carbon black during time intervals.

  The need for regeneration can thus be decided by a comparison between the integral charge in calculated carbon black and a predetermined threshold value. The mass flows of carbon black necessary for the calculation of the mass of carbon black are calculated only as a function of the operating parameter or parameters, using theoretical models or empirical values which are listed in suitable characteristic curves. For diesel particulate filters fitted with a catalytically active coating, the method described above for calculating the carbon black charge leads to imprecise results due to the effects of oxides

  nitrogen, NOx, contained in the exhaust gases.

  The objective of the invention therefore consists in proposing an improved method for determining the charge, in particular the charge in carbon black and in ash, as well as a method for the regeneration and the maintenance of a filter. particles provided with a catalytic coating. To this end, the invention provides a method comprising the following phases: a) determination of the mass of carbon black accumulated in a primary manner in the particle filter, b) determination of the mass of carbon black converted in the particle filter by a reaction with NO2 between the accumulated particles and NO2 generated in the diesel particulate filter, and c) determination of the full accumulation of carbon black from phases a) and b). The invention also provides a method for the regeneration and maintenance of a catalytically coated particle filter of an internal combustion engine, where a regeneration of the particle filter is carried out when the full accumulation of carbon black is greater than or equal to a predefined carbon black charge threshold value, and maintenance of the particulate filter is required when the ash residue in the

  particles exceeds an ash threshold value.

  The mass of carbon black accumulated in a primary manner can in particular be determined from a characteristic field. For the determination of the mass of carbon black converted by the reaction between accumulated particles and generated NO2, it is also possible to calculate the proportion of NO2 which is generated in the filter of particles with catalytic coating by the NO generated by the engine and entered in the particle filter, the proportion of NO2 being calculated in a preferred embodiment from a field

feature.

  From the proportion of NO2 generated in the particle filter, it is preferably calculated an active proportion of NO2 for the reaction between accumulated particles and of generated NO2, which takes into account the reduction of this reaction due to the SO2 contained in

the exhaust gas.

  In another preferred embodiment, the ash residue remains after a regeneration of the particle filter is integrated in tent as a function of the number of regenerations carried out. It is therefore advantageously possible to generate, for example, a maintenance signal, by which the owner of the vehicle is informed in the context of an OBD (On Board Diagnosis) that the particle filter will soon be no longer in working order. because of the ash residue, and that it should be

  therefore to carry out maintenance.

  A preferred embodiment of the invention is explained below in detail using a filter.

  particulate matter intended for an internal combustion diesel engine.

  In the case of diesel internal combustion engines, the NO2 contained in the exhaust gases leads in the particle filter to a combustion of carbon accumulated in carbon monoxide, which means that a reaction takes place, which consumes a part carbon black builds up in the diesel particulate filter. In the case of coated diesel particulate filters, a higher proportion of NO is oxidized to NO2, which is consumed for the conversion of particles, than if it were, for example, generated from the NO contained in the exhaust gases. crude through a diesel oxidation catalyst placed upstream. This is due to the fact that NO2 contained in the diesel particulate filter is reproduced according to the following formula:

2 NO + O2 NO2

  The NO2 thus generated in the diesel particulate filter reacts again with the accumulated C:

NO2 + C -> CO + NO

  means by which the carbon black load of the filter

particles is reduced.

  During a separate generation of NO2, taking place for example in a pre-catalyst, the active proportion of NO2 for the reaction between accumulated particles and NO2 generated would be 50% maximum, in the case of a filter of diesel particles coated with precious metal, this

  proportion is between 50 and 99%.

  For the detection of the accumulation of carbon black in the diesel particulate filter, it is advisable to determine the accumulation of carbon black for a coated diesel particulate filter, so that - from a characteristic field previously recorded, the carbon black content entered in a primary manner in the diesel particulate filter is either integrated (sum_C_primaire), - from a characteristic field previously recorded, or calculated the proportion of NO2 which is formed in the filter diesel particles coated with NO generated by the engine (f_NO2), - taking into account the inhibition of this reaction between accumulated particles and NO2 generated, due to SO2, CO or the hydrocarbons contained in the gas exhaust, the active proportion of corrected NO2 is calculated (f_NO2 *), and - taking into account the ideal NO2 / C ratio for the reaction between accumulated particles and NO2 generated, the content of carbon black converted d years the filter of

  diesel particles with NO2 either calculated (f_CRT).

  The result is the full accumulation of carbon black in the coated diesel particulate filter sum_C_DPF with respect to: sum_C_DPF = sum_C_primaire - f_CRT with f_CRT = f_NO2 * To sum_C_primaire, and

  sum_C_DPF = (l - f_NO2 *) To sum_C_primaire.

  The proportion of SO2, which inhibits the reaction between accumulated particles and generated NO2, can be set 2s from fuel data or generated from a fuel detector. The active proportion of NO2, designated above by f_NO2 *, can then be determined from data recorded in the characteristic field, such as the temperature of the exhaust gases, the volume flow of the exhaust gases and

  the temperature of the diesel particulate filter.

  The full accumulation of carbon black in the diesel particulate filter, which can be calculated in this way, is therefore a magnitude for the mass of 3s carbon black that can burn which has accumulated in the diesel particulate filter, and serves as the basis for the request to initiate a regeneration. In other words, as soon as the full accumulation of carbon black exceeds a predetermined threshold value of carbon black, a regeneration of the particle filter is triggered, and the particles of carbon black accumulated in the particle filter are burnt. according to one of

  known processes, and exposed above.

  The combustion of the accumulated charge of the particulate filter is however not complete because, in addition to the mass of carbon black which can be burned, an ash content increasing with the number of regenerations

  accumulated in the diesel particulate filter.

  This proportion of ash cannot be burnt, and

  increasingly fouls the diesel particulate filter.

  In order to be able to define a time for the maintenance of the diesel particulate filter, this proportion of ash from regenerations must also be integrated into the tent as ash residue. This means that a maintenance signal is for example generated when the residue of

  ash exceeds a predetermined threshold.

  The ash in the diesel particulate filter can come from several sources: - of unburned proportions of diesel fuel (f_CD) - of unburned proportions of lubricating oil (f_Oil) - of metallic abrasion (f_AM), and - of salts from combustion of the additive

  possibly added to fuel (f_Add).

  The integral proportion of ash to ash can be determined approximately in two ways: The average non-combustible ash residue_R of ash accumulated in the diesel particulate filter is expressed as the proportion of the total accumulation of black

  of carbon accumulates, and is expressed by a factor f_R.

  Express in other words: Ash_R = f R To sum C DPF_ _ The integral proportion of ash on a number i of regenerations sum_cendre then results from the integration of the residue of ash_R for the number i of regenerations, i being an integer : Ash sum = f R sum C DPF

_ _ _ _

  2.) Detailed integration of the different ash contents according to their sources: For a possible taking into account of different ash contents, the proportion of ash f_Add from additives, as well as the proportion of ash from

  diesel fuel f_CD, particularly suitable wind.

  These can be integrated from the fuel consumption which is accessible via the characteristic fields, which is to be determined through the mass injected in CD diesel fuel and the consumption of additive. Oil consumption and metal abrasion are more difficult to detect. These can, however, be determined, at least approximately, from wear and oil consumption measurements, as well as load detection and correlation with the characteristic wear and consumption fields. oil

recorded for this purpose.

  Thanks to the above measures, the state of charge of a catalytically coated particle filter can be determined precisely. As a result, the timing of regeneration of the particulate filter can be determined more precisely, which leads to a lower thermal stress on the particulate filter and a reduction in fuel consumption. The ash state of the particulate filter can also be determined, so that a more precise definition of the required maintenance interval of the particulate filter

particles is possible.

Claims (11)

REVENDI CAT I ONS   1. Method for determining the charge of a catalytically coated particle filter of an internal combustion engine, which is supplied by the exhaust gases of the internal combustion engine, the method being characterized in that it comprises the following phases: a) determination of the mass of carbon black accumulated in a primary manner in the particle filter, b) determination of the mass of carbon black converted in the particle filter by a reaction with NO2, between particles accumulated and NO2 generated, and c) determination of the total accumulation of black   carbon from phases a) and b).   2. Method according to claim 1, characterized in that the mass of carbon black accumulated in a primary manner is determined from a characteristic field. 3. Method according to claim 1 or 2, characterized in that, for the determination of the mass of carbon black converted by the reaction between accumulated particles and NO2 generated, the proportion of NO2 which is generated in the filter is calculated of particles with catalytic coating, from NO generated by the engine and entrainé in the particle filter. 4. Method according to claim 3, characterized in that the proportion of NO2 is calculated from a characteristic field.   5. Method according to claim 3 or 4, characterized in that, from the proportion of NO2 generated in the particle filter, an active proportion of NO2 is calculated for the reaction between accumulated particles and generated NO2, which account for the reduction in the reaction between accumulated particles and generated NO2 due to SO2, CO and   hydrocarbons contained in the exhaust gases.   6. Method according to claim 5, characterized in that the proportion of SO2 contained in the exhaust gases is parameterized from data from the   fuel or generated from a fuel detector.   7. Method according to claim 5 or 6, characterized in that the active proportion of NO2 is determined from data recorded in a characteristic field, such as for example the temperature of the exhaust gases, the volume flow of the gases exhaust   and the temperature of the diesel particulate filter.   S. Method according to claim 1 or 2, characterized in that the active proportion of NO2 is determined from a measurement with an appropriate nitrogen oxide probe, as well as from a measurement of the inlet temperature exhaust gas upstream of the diesel particulate filter or a combination of a measurement with previously recorded data from a field feature.   9. Method according to any one of the claims   precedents, characterized in that the proportion of carbon black converted by the reaction between accumulated particles and NO2 generated is calculated taking into account the 2s ideal NO2 / C ratio.   10. Method according to any one of the claims   previous, characterized in that the ash residue remains after regeneration of the particle filter is integrated only in function of the number of regenerations performed.   11. Method according to claim 10, characterized in that the ash residue by regeneration is determined in tent as a function of the integral mass of carbon black. 12. Method according to claim 11, characterized in that the ash residue by regeneration is determined in tent that average proportion of the integral mass of carbon black.   13. Method according to claim 10, characterized in that the ash residue by regeneration is determined from the proportional integration of the different non-combustible components of the charge of the particle filter. 14. Method according to claim 13, characterized in that the different non-combustible components of the wind ash made up of one or more elements of the quantity of additive used to promote the combustion of carbon black, diesel fuel, l oil   lubrication as well as metallic abrasion.   15. Method for regeneration and maintenance of a catalytically coated particle filter of an internal combustion engine, characterized in that a determination is made of the integral accumulation of carbon black and of the ash residue according to   any one of the preceding claims, and a   regeneration of the particle filter, when the full accumulation of carbon black is greater than or equal to a predetermined threshold value of carbon black charge, and in that maintenance of the particle filter is required when the ash residue in the   particle filter exceeds an ash threshold value.   16. Method according to claim 15, characterized in that the maintenance request is carried out by triggering a maintenance signal which is transmitted to