EP1766213A1

EP1766213A1 - System for evaluating the charge state of an exhaust line depollution means

Info

Publication number: EP1766213A1
Application number: EP05781810A
Authority: EP
Inventors: Christophe Colignon
Original assignee: Peugeot Citroen Automobiles SA
Current assignee: PSA Automobiles SA
Priority date: 2004-06-23
Filing date: 2005-06-22
Publication date: 2007-03-28
Also published as: WO2006005875A1; FR2872212A1; US7824481B2; US20070157818A1; FR2872212B1

Abstract

The inventive system for evaluating the charged state of depollution means integrated into the exhaust line of a motor vehicle engine is characterised in that it comprises means (7) for determining a pressure in the depollution means, means (8) for determining the volume gas flowrate upstream said depollution means (10) and means for comparing the depollution means state defined by the thus determined pressure and the volume flowrate with a predetermined diagram (11) of the absent, overcharged and clogged states of the depollution means in order to evaluate the state thereof.

Description

System for evaluating the state of charge of depollution means of an exhaust line.

The present invention relates to a system for evaluating the state of charge of depollution means. More particularly, the invention relates to such a system wherein the pollution control means are integrated in an exhaust line of a motor vehicle mo¬ tor.

Such an engine may be associated with common rail fuel supply means of the cylinders thereof, according to at least one post-injection.

Such a post-injection is, in a conventional manner, an injection of carbu¬ rant after top dead center of the cylinder considered.

These power supply means are adapted to implement, at iso¬ torque, by modifying engine operating control parameters, different regeneration strategies to obtain different thermal levels in the exhaust line.

Thus for example, feeding means implementing regeneration strategies called normal, level 1, level 2 and / or ni¬ calf 2 overcalibrated have already been proposed. It is known that in order to ensure the regeneration of depol¬ lution means such as a particulate filter, the soot trapped in it is burned thanks to the heat supplied by the engine and the exotherm produced by the combus¬ tion HC and CO on oxidation catalyst means, placed for example upstream of the particulate filter. This combustion can be assisted by a catalyst element melan¬ with soot, resulting for example from a regeneration aid additive, mixed with the engine feed fuel or by a catalyst deposited directly on the walls of the filter to particles (catalyzed particle filter).

The higher the thermal levels in the exhaust line at the inlet of the particulate filter, the shorter the regeneration time of the filter.

However, the state of charge of the depollution means must be eva¬ read as reliably as possible, for reasons of safety func¬ tioning thereof and the engine, and to optimize the triggering of regeneration. The object of the invention is therefore to propose such a system.

For this purpose, the subject of the invention is a system for evaluating the state of charge of depollution means integrated in an exhaust line of a motor vehicle engine, characterized in that it comprises means for determining a pressure at the level of the depollution means, means for determining the volume flow rate of the gases upstream of these depol¬ lution means and means for comparing the state point of the depollution means, defined by the pressure and the volume flow thus determined, a prede terminated abacus of states absent, overloaded and clogged means of pollution control, to evaluate the state thereof.

According to other features of the invention:

- the pressure is a differential pressure across the depollution means and the volume flow rate upstream of the depollution means is déter¬ mined according to the following relation: Qv i = _o (R * (AT2 + 273.15) / (.DELTA.P + P atmo ) * Air mass flow rate) in which Q _VO ι represents the volume flow rate, R is a constant, AT2 is the temperature of the gases upstream of the pollution control means, ΔP is the differential pressure across these depollution means, delivered by a Differential pressure sensor, Patmo is the atmospheric pressure and air mass flow rate is the flow of gases passing through the means of depollution;

the pressure is an absolute pressure upstream of the depol¬ lution means and the volume flow rate upstream of the depollution means is determined according to the following relationship:

Q _VOI = (R * (AT2 + 273.15) / P4 * Air mass flow rate) in which Q _VO ι represents the flow rate, R is a constant,

AT2 represents the temperature of the gases upstream of the pollution control means, P4 is the absolute pressure of the gases delivered by an absolute pressure sensor at the inlet of the pollution control means, and air mass flow rate is the flow rate of the gases passing through the depollution means. ; the states of the depollution means are defined by absentee state, overloaded state and clogged state curves, the state curve of which is absent from the depollution means is multiplied by an altimetric correction coefficient as a function of the atmospheric pressure ; the comparison means comprise means for comparing the volume flow rate determined with a low volume flow rate threshold value to allow the determination of the state of the depollution means only if the determined volume flow rate is greater than the value. low threshold; the comparison means comprise means for validating the state if the latter is maintained for a period of time greater than a predetermined period of confirmation time;

the depollution means comprise a particulate filter;

the particulate filter is catalyzed; the depollution means comprise a NOx trap;

the fuel comprises an additive intended to be deposited with parti¬ cules to which it is mixed, on the means of depollution to facilitate their regeneration;

the depollution means are impregnated with an SCR formulation, ensuring a CO / HC oxidation function;

the fuel comprises an additive forming a NOx trap; and

the engine is associated with a turbocharger.

The invention will be better understood on reading the description which follows, given solely by way of example and with reference to the appended drawings, in which:

FIG. 1 represents a block diagram illustrating the general structure and operation of an engine equipped with depollution means;

FIG. 2 represents a block diagram illustrating the general structure and operation of an evaluation system according to the invention; FIG. 3 represents a predetermined abacus of states of the depollution means; and

FIGS. 4 and 5 illustrate two alternative embodiments of means for determining the volume flow rate of the gases upstream of the depollution means.

It has indeed been shown in Figure 1, the pollution control means which are designated by the general reference 1 and which are integrated in an exhaust line 2 of a motor vehicle engine 3.

The engine may for example be a diesel engine of an auto-mobile vehicle, the pollution control means comprising for example a particulate filter or others, associated with oxidation catalyst means or the like, as already known in the state of the art.

This engine is associated with common rail fuel supply means, designated by the general reference 4 in this figure, adapted to implement, under the control of for example a calculator designated by the general reference 5, strategies regeneration of the depollution means by using post-injections of fuel in the engine cylinders.

These different strategies are for example stored in storage means designated by the general reference 6 and associated with the computer 5.

This calculator also comprises means for evaluating the state of charge of the depollution means.

Indeed, and as illustrated in FIG. 2, this calculator includes means for determining the differential pressure at the terminals of the depollution means, or the absolute pressure upstream of the pollution control means, designated by the general reference 7 in this figure 2 and means for determining the volume flow rate of the gases upstream of these depol¬ lution means, these means being designated by the general reference 8. In addition, the calculator comprises means for defining a state point of the depollution means from this volume flow rate and this differential pres¬ tion, designated by the general reference 9 and means 10 for comparing the state point and defined means of pollution control, to a predetermined abacus state of absence, overloaded or clogged with these depollution means, this abacus being for example stored in storage means designated by the general reference 11.

By comparison of the state point defined with this predetermined abacus of states, it is then possible for the computer 5, for example, to deliver an information of depollution means that are absent, overloaded or clogged. This is indeed illustrated in FIG. 3, which represents an embodiment of such an abacus where, as a function of the position of the state point on this chart, it is possible to determine the state of these depollution means by monitoring the exhaust back pressure. For example, it is possible to use a differential pressure sensor at the terminals of the depollution means.

In this case, and as illustrated in FIG. 4, the density determination means 8 receive as input the temperature of the gases upstream of the particulate filter, from a sensor designated by the general reference 12 on this figure, the differential pressure from a sensor designated by the general reference 13, the atmospheric pressure measured from a sensor designated by the general reference 14 and a gas mass flow rate information passing through these means of decontamination, from corresponding determination means designated by general reference 15.

In this case, the volume flow is calculated according to the following relation:

Qv _o i = (R * (AT2 + 273.15) / (ΔP + P atmo) * Air mass flow rate) in which Q _VO ι represents the volume flow rate, R is a constant, AT2 is the temperature of the gases upstream of the means of depollution, ΔP is the differential pressure at the terminals of the pollution control means, Patmo is the atmospheric pres¬ sion and air mass flow rate is the flow of gas passing through the means of depollution.

However, an absolute pressure sensor upstream of the depollution means can also be envisaged. In this case, and as shown in FIG. 5, the density determination means 8 then receive, at the inlet, the temperature of the gases upstream of the particulate filter from the sensor 12, the mass flow rate. of air passing through the means of decontamination from the means of determination 15, and the absolute pressure of the gases at the inlet of the depollution means from a corresponding sensor designated by the general reference 16.

Thus, the determining means 8 can determine the volumetric flow rate by the following relation:

Q _vo i = (R * (AT2 + 273.15) / P4 * Air mass flow rate) in which Q _VO ι represents the volume flow rate, R is a constant, AT2 is the gas temperature upstream of the particulate filter, P4 is the absolute pressure at the inlet of the pollution control means and air mass flow rate is the flow rate of the gases passing through the depollution means.

The abacus then has three curves, respectively C Absent, C Overloaded, C Plugged, which respectively enable the presence or the absence of the depollution means, a clogged state of the pollution control means making it possible to ensure the protection of the engine and an overloaded state of the depollution means securing the charge indicator coming for example from other charge determination modules of these depollution means in case of drift thereof and thus ensuring the protection of the depollution means vis-à-vis too critical regeneration temperatures.

The determination of the state of charge can of course be subject to a condition of maintaining this state during a predetermined state confirmation time.

So Si 0 <(Qvol, ΔP) <C Absent

For a longer time confirmation state

Then the state of the FAP is absent or State FAP = 25%

If C Absent <(Qvol, ΔP) <C Overloaded

For a longer time confirmation state

Or if RestEtatFAP = 1

Then the state of the FAP is normal or State FAP = 0%

If C Overloaded <(Qvol, ΔP)> C Clogged

For a longer time confirmation state

Then the state of the FAP is overloaded or State FAP = 75%

If (Qvol, ΔP) <C Clogged

For a longer time confirmation state

Then the state of the FAP is clogged or state FAP = 100%

The state of the depollution means must of course be memorized at each power failure of the computer 5.

Various additional functions can be envisaged. For example, in order to obtain a satisfactory accuracy and avoid false detections, the Absent C curve can for example be multiplied by an altimetric correction coefficient as a function of the atmospheric pressure.

To avoid false detections, the detection of the different states can also be subjected to a comparison of the volume flow rate determined with a low threshold value of volume flow, this threshold being for example calibratable. Thus, the comparison means 10 can also be adapted to compare the determined volume flow rate with this low limit threshold value ca¬ librable, to allow the determination of the state of the pollution control means only if the determined volume flow is higher at the low threshold value. Additional conditions may also be set for detecting the absence of the depollution means.

For example, if a differential pressure sensor is used, the learning phase of the offset of the latter must be completed, the rate of the post-injections must be zero for a predetermined minimum duration and that a time counter allows the detection of such a state.

The various state curves mentioned above can be calibrated according to a similar methodology.

Thus, for example, the Absent C curve can be obtained by characterization on a motor bed of a catalyst + FAP assembly in the absence of FAP. The curve is then constructed by taking the different values of ΔP according to Q vol.

For the C-shaped clogged curve, it is possible, for example, to load a sooty par¬ particle filter until the maximum value ΔP is reached, that is to say a permissible limit value before the reopening of the engine exhaust valves. . Curve C overloaded can be, for example, a trans¬ position of the C-shaped curve.

Of course, other embodiments may be envi¬ sages.

In particular, various embodiments of the depollution means may be provided.

Thus, for example, the depollution means and the oxidation catalyst means may be integrated into one and the same element, in particular on the same substrate. By way of example, a particulate filter incorporating the oxidation function can be envisaged.

These depollution means may also be impregnated with a SCR formulation providing a CO / HC oxidation function in a conventional manner.

Similarly, a NOx trap incorporating an oxidation function can also be envisaged, whether or not it is additive.

This oxidation function and / or NOx trap can be filled for example by an additive mixed with the fuel. In this case, the fuel may in fact comprise an additive intended to be deposited with the particles to which it is mixed on the means of pollution, to facilitate their regeneration.

Similarly, the engine may or may not be associated with a turbocharger.

Claims

1. System for evaluating the state of charge of depollution means (1) integrated in an exhaust line (2) of an engine (3) of an auto-mobile vehicle, characterized in that it comprises means (7) for determining a pressure at the level of the depollution means (1), means (8) for determining the volume flow rate of the gases upstream of these depollution means (1) and means (10) for comparison the state point of the depollution means, defined by the pressure and the volume flow rate thus determined, to a predetermined abacus of absent, overloaded and clogged states of the pollution control means (1) for evaluating the state thereof.

2. System according to claim 1, characterized in that the pressure is a differential pressure across the pollution control means and the volume flow upstream of the pollution control means (1) is determined according to the following rela¬ tion: Qv _o i = (R * (AT2 + 273.15) / (ΔP + P atmo) * Air mass flow rate) in which Q _VO ι represents the volume flow rate, R is a constant, AT2 is the temperature of the gases upstream of the depollution means, ΔP is the differential pressure at the terminals of these depollution means, delivered by a differential pressure sensor, Patmo is the atmospheric pressure and air mass flow rate is the flow rate of the gases passing through the depollution means.

3. System according to claim 1, characterized in that the pressure is an absolute pressure upstream of the pollution control means and volumi¬ flow upstream of the pollution control means (1) is determined according to the following rela¬ tion: Qv _o i = (R * (AT2 + 273.15) / P4 * Air mass flow rate) in which Q _VO ι represents the volume flow rate, R is a constant, AT2 represents the temperature of the gases upstream of the pollution control means, P4 is the absolute pressure gas delivered by an absolute pressure sensor at the inlet of the pollution control means, and air mass flow rate is the flow rate of the gases passing through the pollution control means.

4. System according to any one of the preceding claims, characterized in that the states of the pollution control means (1) are defined by absentee state curves, overloaded state and clogged state, whose curve the state of absence of the pollution control means is multiplied by an altimetric correction coefficient as a function of the atmospheric pressure.

5. System according to any one of the preceding claims, characterized in that the comparison means (10) comprises means for comparing the volume flow rate determined with a low threshold value of volume flow rate to allow the determination of the state of the pollution control means (1) if the determined volume flow rate is greater than the low threshold value.

6. System according to any one of the preceding claims, characterized in that the comparison means (10) comprise means for validating the state if it is maintained for a period of time greater than a period of time. predetermined confirmation time.

7. System according to any one of the preceding claims, characterized in that the pollution control means (1) comprise a particulate filter.

8. System according to claim 7, characterized in that the particulate filter is catalyzed.

9. System according to any one of the preceding claims, characterized in that the pollution control means comprise a NOx trap.

10. System according to any one of the preceding claims, characterized in that the fuel comprises an additive intended to be deposited with particles to which it is mixed, on the depollution means to faci¬ bed their regeneration.

11. System according to any one of the preceding claims, characterized in that the pollution control means (1) are impregnated with a formulation SCR ensuring a CO / HC oxidation function.

12. System according to any one of claims 1 to 9, caracté¬ ized in that the fuel comprises a NOx trap additive.

13. System according to any one of the preceding claims, characterized in that the engine (3) is associated with a turbocharger.