FR3048020A1 - METHOD FOR DETECTING REGENERATION OF A PARTICLE FILTER IN AN EXHAUST LINE OF AN ENGINE - Google Patents

Abstract

The invention relates to a method for detecting a regeneration of a particulate filter in an exhaust line of an internal combustion engine of a motor vehicle, the engine operating according to a plurality of richness values (R, P) of which a poor richness (P), a mean value of oxygen concentration being established for each of these richness values (R, P). During a poor richness interval (P) when the average effective oxygen concentration value (sdec) for this poor richness interval (P) has a negative oxygen concentration offset with the average value of oxygen concentration previously obtained or expected (savc) for such an interval and that this negative offset is greater in absolute value than a minimum predetermined oxygen concentration offset, it is diagnosed that a regeneration of the particulate filter is in progress. Application in the field of motor vehicles.

Description

METHOD FOR DETECTING REGENERATION OF A PARTICLE FILTER IN AN EXHAUST LINE OF AN ENGINE

The invention relates to a method for detecting a regeneration of a particulate filter in an exhaust line of an internal combustion engine. This detection can be done via an oxygen sensor positioned in the exhaust line downstream of the particulate filter by taking as a reference the path of the exhaust gases in the line.

Preferably, but not limited to, the exhaust line concerned by the present invention is an exhaust line of an internal combustion engine gasoline motor vehicle.

The technical field of the invention is also primarily the field of diagnostics carried on board the motor vehicle relating to the detection of a regeneration of the particulate filter.

The anti-pollution standards to come, especially in Europe with the next application of the regulations Emissions Euro 6 2nd stage, strongly harden the threshold to be respected for the particles emitted by the engines with Direct Injection of Gasoline or engines with ignition ordered.

Compliance with such a regulation could require the use of a particulate filter in the exhaust line of such engines. Such a particulate filter for gasoline engines, also commonly called GPF for the English name of "Gasoline Particle Filter", that is to say particulate filter gasoline, is relatively similar to those used for diesel engines but its characteristics are adapted so as not to penalize performance or consumption.

Such a particle filter is filled with particles and must be emptied at regular intervals. The particle filter is then regenerated during which the particles are burned. It is then desired a sharp increase in temperature in the exhaust system near the particle filter. The heating then continues until the regeneration is detected as complete. A particulate filter thus performs its regeneration passively in the presence of a high oxygen content where self-combustion of the particles takes place.

In a nonlimiting manner, in Figure 1, which shows an exhaust line 1 for a gasoline engine, the line 1 exhaust is equipped with a gasoline particle filter 3 and a catalyst three way 4 Other depollution elements may however be present in this line 1, for example but not only selective catalytic reduction elements. In Figure 1, the three-way catalyst 4 and the gasoline particle filter 3 are grouped in the same system, which is not mandatory.

The gasoline particle filter 3 is advantageously in the form of a porous system composed of cordierite, mullite or silicon carbide or other where the channels are plugged alternately at each end. It is characterized by a volume, a quantity of channels, a wall thickness and a porosity. The particulate filter 3 is advantageously positioned downstream of the three-way catalyst 4.

Conventionally, it can be provided at least one oxygen sensor or lambda probe, in Figure 1 two oxygen probes 5, 5a. A 5a of these two probes 5, 5a lambda can be placed in the exhaust line 1 between the exhaust manifold of the engine 2 and the catalyst 4. Its measurements can be transmitted to an injection computer provided in a control- control of the engine 2 to provide the possibility of determining the proportion of air-fuel mixture for which the efficiency of the engine 2 is optimal.

This keeps a low level of pollutants and positively influences a reduction in fuel consumption. The oxygen probes 5, 5a may be stoichiometric or linear.

The other oxygen sensor 5 may be provided downstream of the catalyst 4 and the gasoline particle filter 3 in the exhaust line 1. The main function of this oxygen sensor 5 downstream of the particulate filter 3 is, for a last-generation engine control, in addition to the oxygen sensor 5a disposed upstream of the particulate filter 3, to make it possible to evaluate the efficiency of the particulate filter 3 and the catalyst three way 4 permanently. Each oxygen sensor 5, 5a delivers wealth information through a potential difference provided by the sensing element that composes it.

In summary, the oxygen sensor 5a disposed upstream of the catalyst 4 measures the output richness of the engine, the three-way catalyst 4 oxidizes the gaseous agents and the oxygen sensor 5 disposed downstream of the catalyst 4 verifies the functionality of the catalyst 4.

Furthermore, it is necessary to monitor and recognize the regeneration phases of a particulate filter as soon as possible. This can help assist regeneration by making operational measurements to increase the oxygen supply in the exhaust line.

The document FR-A-2 829 798 describes a method of managing a combustion engine exhaust system of the type comprising a particle filter, by which the actuation of assistance means is initiated. the regeneration according to determined criteria, the operating parameters being adjusted according to the course of regeneration of the filter. The method includes monitoring the progress of the regenerations which comprises a step of detecting the beginning of a regeneration comprising a measurement and monitoring of the value of the richness downstream of the particulate filter. However, this document does not disclose means for implementing the method, in particular how the regenerations are detected.

The problem underlying the present invention is to detect as quickly as possible the beginning of a regeneration of a particulate filter in an exhaust line of an internal combustion engine using the already present means in the exhaust line for the control of engine efficiency.

To achieve this objective, it is provided according to the invention a method for detecting a regeneration of a particulate filter in an exhaust line of an internal combustion engine of a motor vehicle, the engine operating according to a plurality of richness values including a poor richness, an average value of oxygen concentration being established for each of these richness values, characterized in that, during a poor richness interval, when the average value of effective oxygen concentration for this poor richness interval has a negative oxygen concentration offset with the average value of oxygen concentration previously obtained or expected for such an interval and that this negative offset is greater in absolute value than a predetermined oxygen concentration shift minimal, it is diagnosed that a regeneration of the particulate filter is in progress.

The technical effect is to diagnose the regeneration phases of the particulate filter by monitoring the oxygen level downstream of the particulate filter, preferably via a downstream oxygen probe to the particulate filter in the d-line. 'exhaust.

Advantageously, as long as the negative offset remains greater in absolute value than the offset at minimum predetermined oxygen concentration, it is diagnosed that the regeneration of the particulate filter is still in progress.

Advantageously, the minimum predetermined offset is more than 2% of the average value of oxygen concentration previously obtained or expected for such an interval.

Advantageously, the detection is made by an oxygen sensor disposed downstream of the particulate filter, the oxygen probe delivering a voltage inversely proportional to the oxygen concentration, and when, during a poor richness interval , the average voltage value actually delivered by the oxygen sensor for a poor richness interval has a positive voltage offset with the previously obtained or expected average voltage value for such an interval and that this positive offset is greater than an offset by minimum predetermined voltage, it is diagnosed that a regeneration of the particulate filter is in progress.

Advantageously, when a depollution element of the exhaust gas flowing in the exhaust line is present with the particulate filter in the exhaust line and a second oxygen sensor is positioned upstream of the exhaust line. decontamination element and the particle filter, a mean voltage value is established for all the respective values of richness for the first and second oxygen probes, and when the average values of the second oxygen probe evolve for all the richnesses similarly. to the average values of the first oxygen sensor within a tolerance, it is diagnosed that the depollution element is in an out of service state while a functional state of the depollution element is diagnosed when the average values of the second oxygen sensor evolve for all the wealth differently than the average values of the first oxygen probe e Outside the tolerance, the average values in effective voltage and previously obtained or expected for the poor richness interval for the diagnosis of a regeneration of the filter being taken with a depollution element in the same state.

The invention also relates to a method of assisting the regeneration of a particulate filter, characterized in that it comprises such a method of detecting a regeneration of a particulate filter and in that, when a regeneration of the particulate filter is diagnosed, the regeneration aid method implements operational measures to increase the supply of oxygen in the exhaust line.

Advantageously, it is proceeded to a forced fuel supply cutoff during a foot release of the driver of the accelerator pedal.

The invention also relates to a set of an exhaust line of an internal combustion engine in a motor vehicle and a control system for the control of pollution in the exhaust line, the exhaust line comprising a particle filter and an oxygen sensor disposed downstream of the particulate filter, characterized in that the pollution control control system comprises a supervisor for detecting a regeneration of the particulate filter for the implementation of a such a detection method, the supervisor comprising elements for storing a minimum predetermined voltage offset, average value receiving elements in actual voltage and previously obtained or expected for a low richness interval, means for retrieving the value previously obtained or expected at the effective average value to obtain a difference and means of comparing the difference with the stored minimum predetermined voltage offset.

Advantageously, the exhaust line comprises at least one exhaust gas depollution element flowing in the exhaust line with the particulate filter and a second oxygen sensor positioned upstream of the depollution element and particle filter.

Advantageously, said at least one pollution control element is a three-way catalyst and the particulate filter is a particulate filter for gasoline engine.

Other features, objects and advantages of the present invention will appear on reading the detailed description which follows and with reference to the accompanying drawings given by way of non-limiting examples and in which: - Figure 1 is a schematic representation of an engine and part of an exhaust line of a motor vehicle according to the state of the art, - Figures 2 and 3 are respectively schematic representations of two voltage curves according to time respectively for the upstream oxygen sensor and the downstream oxygen sensor for an exhaust line comprising at least one particulate filter and a catalyst respectively functional or out of service, this during a succession of richness equal to one and of poor richness, a portion of the exhaust line showing the positioning of the oxygen sensors in the line being shown above the curves; - Figure 4 is a representation schematic representation of three voltage curves, the catalyst being functional, during a regeneration of the particle filter modifying the signal of the downstream probe by shifting it, this figure showing the signal of the upstream probe, the signal of the downstream probe without regeneration and the signal shifted by the regeneration, - Figure 5 is a schematic representation of three voltage curves in the configuration of the exhaust line with a catalyst being out of service, this during a regeneration of the particulate filter, this figure showing the signal of the upstream probe, the signal of the downstream probe without regeneration and the signal of the downstream probe offset by the regeneration.

It is to be borne in mind that the figures are given by way of examples and are not limiting of the invention. They constitute schematic representations of principle intended to facilitate the understanding of the invention and are not necessarily at the scale of practical applications. In particular, the dimensions of the various elements illustrated are not representative of reality.

In what follows, reference is made to all the figures taken in combination. When reference is made to one or more specific figures, these figures are to be taken in combination with the other figures for the recognition of the designated reference numerals. In what follows, the terms upstream and downstream are to be taken in the direction of gas flow in the exhaust line. For simplicity, the oxygen probes respectively upstream and downstream of the catalyst will be referred to respectively upstream or downstream oxygen sensor.

As regards FIGS. 2 to 5 with reference to FIG. 1 for some of the references, U (A) is the voltage of an oxygen probe, t (s) the time in seconds, the succession of R and P denote the rich phases and the fuel-poor phases, samc the signal of the oxygen probe upstream of the catalyst 4 and the particulate filter 3, therefore of the upstream probe 5a, the samc signal being in full line and savc the signal of the oxygen probe downstream of the catalyst 4 and the particle filter and therefore of the downstream probe 5, the signal savc being in dashed lines.

In Figure 2, with a functional catalyst, there is an oscillation of the signal of the upstream oxygen sensor 5a reflecting the regulation of the wealth on the engine. The signal from the downstream oxygen sensor 5 hardly changes because the catalyst 4 oxidizes the gaseous agents.

In Figure 3, with a catalyst out of service, there is an oscillation of the signal of the upstream sensor 5a reflecting the regulation of the wealth on the engine. The signal of the downstream probe 5 evolves almost like the upstream probe 5 because the catalyst 4 no longer oxidizes the gaseous agents.

Referring more particularly to Figures 1, 4 and 5, the present invention relates to a method for detecting a regeneration of a particulate filter 3 in a line 1 exhaust of an internal combustion engine 2 of a motor vehicle. The exhaust line 1 may comprise, for a selective pollutant, other depollution elements than the particulate filter 3, for example one or four or three-way oxidation catalyst or catalysts, a selective catalytic reduction system or a catalyst system. nitrogen oxide trap.

The particulate filter 3 may also be of several types, such as for example a diesel particulate filter 3 also known by the name of FAP or a particle filter 3 for gasoline engine also known by the name of FPE for gasoline particle filter 3, which corresponds to the Anglo-Saxon name of GPF for "gasoline particle filter" mentioned above.

In a known manner, the thermal combustion engine 2 operates according to several richness values R, P a poor richness P, an average value of oxygen concentration being established for each of these richness values R, P. This has been shown in particular in Figures 2 and 3.

According to the invention, during a poor richness interval P, when the average value of effective oxygen concentration for this poor richness interval P has a negative offset in oxygen concentration with the average value of concentration of oxygen. oxygen previously obtained or expected for such an interval and that this negative offset is greater in absolute value than a shift in minimum predetermined oxygen concentration, it is diagnosed that a regeneration of the particle filter 3 is in progress.

The average reference value may be that previously obtained under similar operating conditions of the engine or expected, that is to say estimated according to the engine operating conditions prevailing at this time.

The detection method can be implemented using the above-mentioned downstream oxygen probe 5. It is therefore the downstream oxygen sensor 5 serving to control the operation of the engine 2 with the upstream oxygen sensor 5a which is used according to the present invention for the detection of a regeneration.

The duration of the regeneration can also be diagnosed. As long as the negative offset remains greater in absolute value than the minimum predetermined oxygen concentration offset, it is diagnosed that the regeneration of the particle filter 3 is still in progress.

The minimum predetermined offset may be more than 2% of the average value of oxygen concentration previously obtained or expected for such an interval.

In a preferred embodiment of the present invention, the detection can be made by an oxygen probe 5 disposed downstream of the particulate filter 3. It is known that an oxygen probe delivers a voltage inversely proportional to the concentration of oxygen present in the exhaust gas. Referring to FIGS. 4 and 5, the shift signal upon regeneration of the downstream oxygen probe 5 is referenced sdec and is illustrated by a square bearing curve.

When, during a poor richness interval P, the average voltage value sdec actually delivered by the downstream oxygen probe 5 for a poor richness interval P has a positive voltage shift with the average voltage value savc. previously obtained or expected for such an interval and that this positive offset is greater than a minimum predetermined voltage offset, it can be diagnosed that a regeneration of the particle filter 3 is in progress.

The presence of at least one other pollution control element 4 in addition to the particulate filter 3 in the exhaust line 1 may affect the measurements of the oxygen sensor 5 positioned downstream of the particulate filter 3 in the line 1 exhaust. It is therefore advantageous to take into account the operating state of this or these elements for the comparison of the average values in effective voltage and previously obtained or expected.

This is illustrated in FIGS. 4 and 5. As previously mentioned, the signal from the downstream oxygen sensor 5 depends on the state of the catalyst, that being functional or out of service, the curve of the downstream oxygen probe 5 without regeneration approaching the curve of the upstream oxygen sensor 5a when the catalyst is out of service. The offset is more pronounced in a poor phase because the high voltage, approximately 800 mV, is a horizontal asymptote.

During a regeneration phase of the particulate filter 3, the regeneration of the particle filter 3 will consume oxygen to operate this intrinsic combustion phase. Because the oxygen level will drop, we will move to a slightly richer medium therefore tending the signal towards its high value when this signal is a voltage of a downstream oxygen sensor 5 or towards its low value. when we consider the oxygen concentration. In both cases, an offset will appear between the shift signal during a regeneration sdec of the downstream oxygen probe 5 and the signal without regeneration savc of the downstream oxygen sensor 5.

The measurements for the average of the signal can be done at least partly in rich phases. In this case, the probability of a regeneration is non-existent because one is in the absence of oxygen. These measurements for averaging the signal can be more advantageously in poor phases because the probability of regeneration is present because it is in the presence of oxygen. However, the presence of a regeneration is however not systematic.

When observing a significant difference in the average, confirming the presence of an offset, we can inform a supervisor monitoring the particle filter 3 that a regeneration is effective. Experimentally, the oxygen drop is about 5% at the end of regeneration but the fall is greater at the beginning of regeneration. In this case, the application of an integral calculation makes it possible to optimize this difference to take into account the beginning of the regeneration.

On a binary oxygen probe, the equilibrium point for a probe in natural respiration is 450 mV point to lambda = 1 approximately. The range generally ranges from 50 to 800 mV. In the presence of a working catalyst, the range of the downstream probe can range from about 400 to 500 mV. The equilibrium point is at 450 mV but the performance of the motor 2 can shift this average slightly. The regeneration of the particulate filter 3 results in additional oxygen consumption, which can be quantified as a percentage of additional oxygen or% O 2. The offset may be a few tens of millivolts at the signal of the probe 5a relative to the average signal previously obtained or expected savc.

The frequency of regulation of a probe that characterizes its ability to move from a rich / poor / rich R, P is about 3Hz to 4Hz. It is therefore wise to consider several failovers to average them. As a result, the acquisition of the average value previously obtained or expected can be a few seconds. The supervisor can compare acquisition periods of a few seconds to identify the phase in the presence of an offset.

It may then be useful to compare the average voltage values taken respectively by two oxygen probes 5, 5a, one placed upstream 5a of the depollution element 4 and the particle filter 3 and the other placed downstream 5 of the pollution control element 4 and the particle filter 3, to measure the influence of the pollution control element 4 on the average values in voltage and therefore in oxygen in line 1.

When there are several depollution elements, it can be placed a second oxygen probe 5a upstream of the first depollution element 4 and a first oxygen sensor 5 downstream of the last depollution element 4 which can be the filter 3. It may also be possible to place several additional oxygen probes, for example downstream of a depollution element 4 and upstream of the following depollution element 4 in the direction of the flow direction of the exhaust gases. 'exhaust.

Thus, in an optional embodiment of the detection method according to the present invention, when at least one depollution element 4 of the exhaust gas flowing in the exhaust line 1 is present with the particulate filter 3 in the exhaust line 1, a second oxygen probe 5a can be positioned upstream of the depollution element 4 and the particulate filter 3.

It can then be established a mean value in voltage savc, samc for all the values of richness R, P respectively of the first and second oxygen probes 5, 5a. When the average values samc of the second oxygen probe 5a, that is to say the upstream probe, evolve for all the richness R, P similar to the average values savc of the first oxygen probe 5, that is to say -desire the downstream probe, within a tolerance, it can be diagnosed that the depollution element 4 is in a state out of service, since it has no influence on the oxygen concentration in line 1 and that he does not do his work of depollution.

Conversely, a functional state of the depollution element 4 can be diagnosed when the average values samc of the second oxygen probe 5a, this probe being upstream of the depollution element 4 and the particle filter 3. , evolve for all the wealth R, P differently than the average values savc of the first oxygen sensor 5, this probe being downstream of the pollution control element 4 and the particulate filter 3. In both cases, it can be taken into account a tolerance.

In the detection method according to the invention, the average voltage values effective and previously obtained or expected for the poor richness interval P for the diagnosis of a regeneration of the filter can be taken with a depollution element 4 in the same state, so that there is no false comparison between the mean values in effective voltage sdec and previously obtained or expected savc, since the state of the pollution control element 4 can vary these average values.

The invention also relates to a method of assisting the regeneration of a particle filter 3 comprising such a method of detecting a regeneration of a particulate filter 3. When a regeneration of the particulate filter 3 is diagnosed, the method of assisting the regeneration implements operational measures to increase the supply of oxygen in the line 1 exhaust. For example, there may be a forced cut-off of fuel supply during a foot release of the driver of the accelerator pedal.

The invention also relates to an assembly of a line 1 for exhaust of internal combustion engine 2 in a motor vehicle and a control system for the control of pollution in the exhaust line 1. The exhaust line 1 comprises a particle filter 3 and an oxygen sensor 5 disposed downstream of the particulate filter 3. It may also comprise other pollution control elements that a particulate filter 3. The control system depollution which can initiate the regenerations comprises, as previously mentioned, a supervisor for detecting a regeneration of the particulate filter 3 for the implementation of the method as previously described.

The supervisor comprises elements for storing a minimum predetermined voltage offset, elements for receiving average values in effective voltage sdec and previously obtained or expected savc for a poor richness interval P. The supervisor also comprises means retracting the value previously obtained or expected at the effective mean value to obtain a difference and means for comparing the difference with the stored minimum predetermined voltage offset.

The exhaust line 1 may also comprise at least one pollution control element 4 of the exhaust gas flowing in the exhaust line 1 with the particulate filter 3 and a second oxygen sensor 5a positioned upstream of the exhaust pipe. depollution element 4 and the particulate filter 3.

In a preferred but non-limiting application of the present invention, the pollution control element 4 or one of the pollution control elements is a three-way catalyst. The particulate filter 3 may be a particulate filter for gasoline engine 2.

The invention is not limited to the described and illustrated embodiments which have been given as examples.

Claims (10)

Claims: 1. Method for detecting a regeneration of a particulate filter (3) in an exhaust line (1) of a motor vehicle internal combustion engine (2), the engine (2) operating according to several values of richness (R, P) with a poor richness (P), an average value of oxygen concentration being established for each of these richness values (R, P), characterized in that, during a richness interval poor (P), when the average effective oxygen concentration value (sdec) for this poor richness interval (P) has a negative oxygen concentration offset with the previously obtained or expected average oxygen concentration value (savc) for such an interval and that negative offset is greater in absolute value than a minimum predetermined oxygen concentration shift, it is diagnosed that a regeneration of the particulate filter (3) is in progress. 2. Detection method according to claim 1, wherein, as long as the negative offset remains greater in absolute value than the minimum predetermined oxygen concentration offset, it is diagnosed that the regeneration of the particulate filter (3) is still in progress . The detection method according to claim 1 or 2, wherein the minimum predetermined offset is more than 2% of the average value of oxygen concentration previously obtained or expected for such an interval. 4. Detection method according to any one of claims 1 to 3, wherein the detection is made by an oxygen sensor (5) disposed downstream of the particulate filter (3), the oxygen sensor (5) delivering a voltage inversely proportional to the oxygen concentration, and, when, during a poor richness interval (P), the average voltage value (sdec) actually delivered by the oxygen sensor (5) for a poor richness interval (P) has a positive voltage shift with the previously obtained or expected average voltage value (savc) for such an interval and that positive offset is greater than a minimum predetermined voltage offset, it is diagnosed that a regeneration of the filter with particles (3) is in progress. The method according to claim 4, wherein, when a depollution element (4) of the exhaust gas flowing in the exhaust line (1) is present with the particulate filter (3) in line (1). exhaust and that a second oxygen sensor (5a) is positioned upstream of the pollution control element (4) and the particulate filter (3), it is established a mean voltage value (samc, savc) for all the respective richness values (R, P) of the first and second oxygen probes (5, 5a), and when the average values (samc) of the second oxygen probe (5a) change for all the riches (R, P ) similar to the average values (savc) of the first oxygen sensor (5) with a tolerance, it is diagnosed that the depollution element (4) is in an out of service state while a functional state of the element (4) is diagnosed when the average values (samc) of the second oxygen probe (5a) evolve for all the riches (R, P) differently than the average values (savc) of the first oxygen probe (5) out of tolerance, the mean values in effective voltage (sdec) and previously obtained or expected (savc) for the poor richness interval (P) for diagnosing a regeneration of the filter (3) being taken with a depollution element (4) in the same state. 6. Process for assisting the regeneration of a particulate filter (3), characterized in that it comprises a method for detecting a regeneration of a particulate filter (3) according to any one of the claims. and in that, when a regeneration of the particulate filter (3) is diagnosed, the regeneration assisting method implements operational measures to increase the supply of oxygen in the exhaust line (1). . 7. Process for aiding regeneration according to claim 6, in which it is proceeded to a forced cut-off of fuel supply during a release of foot of the driver of the accelerator pedal. 8. A line (1) of an internal combustion engine exhaust (2) in a motor vehicle and a control system for the depollution in the exhaust line (1), the line (1) ) exhaust comprising a particle filter (3) and an oxygen sensor (5) disposed downstream of the particulate filter (3), characterized in that the pollution control control system comprises a detection supervisor of a regeneration of the particulate filter (3) for carrying out the method according to claim 4 or 5, the supervisor comprising elements for storing a minimum predetermined voltage offset, receiving elements of average values in effective voltage ( sdec) and previously obtained or expected (savc) for a poor richness interval (P), means for retrenching the value previously obtained or expected at the effective average value to obtain a difference e t means for comparing the difference with the stored minimum predetermined voltage offset. 9. The assembly of claim 8, wherein the line (1) exhaust comprises at least one element for the pollution control (4) of the exhaust gas flowing in the line (1) exhaust with the particulate filter (3). ) and a second oxygen sensor (5a) positioned upstream of the depollution element (4) and the particulate filter (3). 10. The assembly of claim 9, wherein said at least one pollution control element (4) is a three-way catalyst and the particulate filter (3) is a particulate filter for gasoline engine.