FR3045102A1 - METHOD FOR CONTROLLING A MOTORIZATION DEVICE AND ASSOCIATED MOTORIZATION DEVICE - Google Patents

Abstract

The invention proposes a method for controlling a motor vehicle engine device comprising a diesel engine and a particulate filter, which is intended to compensate for a loss of efficiency (ε) of the filter and to delay the ignition of a fuel cell. OBD indicator on the instrument panel. When the efficiency becomes lower than a second threshold (εdefault), which is strictly greater than the vehicle failure threshold, a fault is recorded in an engine computer; the motor setting is changed so that it emits fewer soot particles (PM) to compensate for the loss of filter efficiency. This backup setting is applied as long as the efficiency does not become less than a failure threshold (εOBD), which then requires reporting a vehicle failure, for example by lighting a warning light.

Description

METHOD FOR CONTROLLING A MOTORIZATION DEVICE AND DEVICE

MOTORIZATION SYSTEM

TECHNICAL FIELD OF THE INVENTION The invention relates to a method for controlling a motorization device, more particularly to a device comprising an internal combustion engine operating in a lean mixture and a particulate filter mounted on the exhaust of said engine. It also relates to a motorization device for implementing such a method. It finds an advantageous application in the form of a control method embedded in a motor vehicle equipped with a motorization device comprising a diesel engine and a particulate filter, and further comprising a device for reducing nitrogen oxides.

STATE OF THE ART

Modern diesel engines in motor vehicles are equipped with a particulate filter at the exhaust.

In a known manner, such a particulate filter operates in a sequential manner: during normal operation of the lean-burn engine, it stores the soot particles (PM) emitted in the combustion gases of the engine without treating them; then, for example when the mass of stored soot reaches a predetermined threshold, an engine computer triggers a regeneration phase of the filter. To do this, it raises the temperature of the filter above the minimum soot combustion temperature and it brings to the filter inlet reducers, for example unburned fuel in the engine cylinders, through a post- injection of fuel not participating in the normal combustion cycle, so as to burn the soot accumulated within the filter.

A particulate filter thus makes it possible to reduce the emissions of soot particles (PM) into the atmosphere and to comply with the legal standards that limit the exhaust emissions of polluting species by motor vehicles. For example, the so-called "euro6b" European standard limits PM emissions to 5 milligrams per kilometer traveled, on the so-called "NEDC" cycle. On the other hand, the legislation requires motor vehicles to be equipped with an on-board diagnostic system, also known as an OBD (On Board Diagnostic), capable of continuously verifying that polluting emissions do not exceed the legal limits, and report if necessary such an overtaking to the driver, typically by the ignition of a warning light on the dashboard, so that the driver can proceed to the repair of the vehicle.

Such an OBD control system also monitors the proper functioning of the various components of the vehicle that contribute to compliance with the pollutant emission levels, and it causes the ignition of a light, said OBD indicator, on the dashboard of the vehicle. where these levels are exceeded. Thus, the driver of the vehicle is alerted that the vehicle no longer complies with the legislation and is encouraged to have it refurbished.

The OBD control system controls in particular the components involved in the formation of combustion gases at the engine outlet (air intake valve, fuel injectors, etc.) and the components that participate in the depollution of said combustion gas in the exhaust line.

In the case of a diesel engine equipped with a particulate filter, the OBD control system more particularly monitors the effectiveness of the filter, that is to say the ratio of the quantity of soot effectively retained in the filter, divided by the amount of soot emitted into the combustion gases of the engine and entering said filter during normal operation of the lean-burn engine.

For this, the OBD control system determines the value of a parameter representative of the effectiveness of the filter, then, when said value is greater than a threshold, said threshold OBD, which corresponds to the vehicle exceeding the authorized emissions, it records a fault in a memory of an engine computer and it causes the ignition of a light on the dashboard of the vehicle. The illumination of this OBD light indicates to the driver that the vehicle no longer complies with the legislation and encourages him to have it repaired. The refurbishment includes all the maintenance or repair operations necessary to restore the efficiency of the filter, and then clear the fault in the computer's memory.

As the refurbishment of the vehicle may be costly, particularly when it is necessary to replace the filter, there is interest in delaying the appearance of the fault and lighting of the OBD indicator on the dashboard of the vehicle, of course ensuring that releases of pollutants into the atmosphere remain within legal limits.

Several processes are known from the state of the art which aim to compensate to a certain extent the loss of efficiency of a particulate filter. For example, EP-B1-0 921 285 discloses a device and method for cold compensation of the inefficiency of a particulate filter. It discloses a diesel engine in which the amount of soot produced increases gradually and then goes through a maximum when the amount of inert gas in the combustion chamber increases and in which a further increase in the amount of inert gas in the combustion chamber has As a result, the temperature of the fuel and the surrounding gas in the combustion chamber at the time of combustion becomes lower than the soot production temperature and so there is almost no more soot production.

The engine comprises: a catalyst disposed in an exhaust manifold and having an oxidation function, and a switching means for selectively passing a first combustion in which the amount of inert gas in the combustion chamber is greater than the quantity of inert gas for which the quantity of soot produced passes through a maximum and in which almost no soot is produced, to a second combustion in which the quantity of inert gas in the combustion chamber is less than amount of inert gas for which the amount of soot produced passes through a maximum, said switching means first running the second combustion and then passing to the first combustion when the engine is started.

Such a method, which provides an alternative setting of the engine compared to its normal setting which is the first combustion, aims to compensate temporarily, ie only cold, the loss of soot storage efficiency of a filter to particles, so as not to increase the polluting emissions of the vehicle that are due to this degradation of the cold efficiency of the filter. It plans to significantly increase the rate of recirculation of gases, including more than 55%, so that the engine emits virtually no soot, but this is only possible when the temperature of the fuel and the surrounding gas is low.

This method is therefore not applicable to compensate for a loss of efficiency of a particulate filter in general, for example a loss of efficiency due to aging, which is apparent in all the operating conditions of the vehicle and in particular in all the temperature conditions, and it does not allow to delay the appearance of a nonconformity of the polluting emissions of the vehicle.

There is therefore a need for a mode of compensation of the soot emissions of the vehicle which is able to delay the appearance of the fault and the ignition of the OBD indicator on the dashboard, while ensuring that the emissions of soot remain in compliance with the legislation.

SUMMARY OF THE INVENTION The invention proposes to remedy the defects of known methods for compensating for the loss of efficiency of a particulate filter.

It proposes for this purpose a control method of a motor vehicle engine device comprising a diesel-type internal combustion engine and a particulate filter mounted in the exhaust system of the engine, said method comprising at least:

A nominal motor setting step, in which engine soot particle emissions are set to a nominal concentration value;

A step of determining the efficiency of the filter and comparing said efficiency with a vehicle failure threshold, said threshold OBD;

A step in which, when the effectiveness of the filter becomes lower than said OBD threshold, a motor calculator stores in memory a malfunction of the filter and alerts the driver of the vehicle of a vehicle failure.

Said method is characterized in that it further comprises:

A step in which the efficiency of the filter is compared with a second threshold strictly greater than the OBD threshold;

A step in which, when the effectiveness of the filter becomes lower than said second threshold, the computer stores in memory a malfunction of the filter; and,

When the efficiency of the filter becomes lower than said second threshold, a motor backup setting step in which the emissions of engine soot particles are set to a value lower than the nominal concentration value, said setting being maintained at least so much that the efficiency of the filter does not become lower than the OBD threshold.

BRIEF DESCRIPTION OF THE FIGURES Other features and advantages of the invention will appear on reading a non-limiting embodiment thereof, with reference to the accompanying drawings, in which: FIG. 1 represents an example of a motorization device adapted to the implementation of the method according to the invention; and FIG. 2 is a logic diagram of the steps of a control method of the motorization device according to the invention.

DETAILED DESCRIPTION OF THE FIGURES

In Figure 1, there is shown a motorization device adapted to implement the method according to the invention. It comprises an internal combustion engine 1 of a motor vehicle, of the diesel type (compression ignition), which is here in a non-limiting manner in the form of a four-cylinder engine supercharged line. The engine 1 is supplied with air by an air intake circuit 2, and fuel, for example diesel, by a plurality of injectors 3 mounted on a common fuel supply rail 4.

The air intake circuit 2 comprises from upstream to downstream, that is to say in the direction of air circulation, an air intake pipe 5, a compressor 6 of a turbocharger 7 of the engine 1, a connecting line compressor-intake manifold 8 on which is mounted a flow meter 9 and an intake manifold 10. Of course, the intake circuit 2 may comprise other components not shown here, for example an air filter, a supercharged air cooler, a flow control valve admitted into the intake manifold 9, a flow meter, etc.

The engine 1 is also equipped with an exhaust system 11 for exhaust gases, comprising from upstream to downstream, that is to say in the direction of flow of the gases, an exhaust manifold 12, a turbine 13 of the turbocharger 7, a turbine-oxidation catalyst connection line 14, an oxidation catalyst 15, an oxidation catalyst-particle filter line 16, a particulate filter 17, a filter connection pipe particulate trap - nitrogen oxide trap 18, a nitrogen oxide trap 19, also called NOx trap trap 19, and an exhaust pipe 20.

Alternatively, and in a manner known per se, at least two of the emission treatment devices among the oxidation catalyst 15, the particulate filter 17 and the nitrogen oxide trap 19 can be combined in one and the same envelope (or "canning"), mainly for thermal reasons.

Alternatively not shown also, the nitrogen oxide trap 19 can be replaced by another device for reducing nitrogen oxides 19, more precisely by a selective reduction catalyst of nitrogen oxides 19, also called SCR catalyst.

The arrow shown on the turbine 13 indicates that it is a turbine whose fins are tilting. In other words, the turbocharger 7 is here in the form of a turbocharger 7 with variable geometry. Of course, in a variant not shown, the turbocharger 7 may be a turbocharger fixed geometry.

The particle filter 17 is here associated with two pressure sensors 21, 22: a first pressure sensor 21, called an upstream pressure sensor 21, mounted at the inlet of the particulate filter 17 on the oxidation catalyst connecting pipe. - Particle filter 16, and a second pressure sensor 22, said downstream pressure sensor 22, mounted at the outlet of the particulate filter 17 on the particulate filter-nitrogen oxide trap line 18.

Conventionally, these pressure sensors 21, 22 can be used to trigger the regeneration steps of the particulate filter 17.

More specifically, from a normal mode of operation of the lean-burn engine in which the soot particles of the combustion gases of the engine accumulate in the filter 17 without being treated, control means (not shown) of the device 1, for example an engine computer, trigger, when the difference between the pressure measured by the downstream pressure sensor 22 and the pressure measured by the upstream pressure sensor 21 exceeds a predetermined threshold, a sequence of increase of the temperature of the engine exhaust gas and fuel supply in the particle trap 17, so as to burn the accumulated soot. On the other hand, in combination with the flowmeter 9, pressure sensors 21,22 cases allow to determine a value of the efficiency ε of the filter, as will be described later.

The nitrogen oxide trap 19 is here associated with at least one nitrogen oxide sensor 23, more specifically a downstream nitrogen oxide sensor 23, which is mounted at the outlet of the nitrogen oxide trap. 19 on the exhaust pipe 20, and which is able to measure the concentration of nitrogen oxides [NOx] out of the trap 19.

In a conventional manner, this downstream nitrogen oxide sensor 23 may be used, in combination with an upstream nitrogen oxide sensor or with a model able to determine the concentration of nitrogen oxides [NOx] m entering the trap 19, to trigger the regeneration steps of the trap 19.

More specifically, from a normal mode of operation of the lean-burn engine in which the NOx particles of the engine combustion gases accumulate in the trap 19 without being treated, the control means (not shown) of the device of motorization 1 are able to calculate the storage efficiency Eff of trap 19 according to the equation: (Equ.1) Eff = ([NOx] in - [NOx] out) / [NOx] in,

When the current efficiency value of the trap Eff falls below a predetermined threshold, the control means trigger a sequence of operation of the engine in a rich mixture, capable of reducing the NOx stored in the trap in harmless molecules.

The exhaust circuit 11 further comprises a partial recirculation circuit of the exhaust gas at the intake. It is here in the form of a low-pressure partial recirculation circuit 24, also called EGR circuit BP 24 (from the acronym in English for: Exhaust Gas Recycling). It originates at a point in the exhaust circuit 11 located downstream of the turbine 13, here on the oxidation catalyst - particle filter line 16. Its other end opens at a point of the intake circuit 2 located upstream of the compressor 6, here on the air intake pipe 5. It is equipped with a partial recirculation valve of the low-pressure exhaust gas 25, also called EGR valve BP 25, the adjustment of which allows adjust the proportion of recycled gases on admission. Other embodiments of the motorization device are possible without harming the generality of the invention. For example, the exhaust circuit may comprise a partial recirculation circuit of the exhaust gas at the high pressure inlet (HP EGR circuit, not shown), or a BP EGR circuit 24 and an HP EGR circuit.

The control means, for example a computer, are generally able to adjust the operating parameters of the motorization device, in particular the motor 1, as a function of a torque setpoint C corresponding to a depression of the pedal. accelerator by the driver of the vehicle and at a given speed N. In a manner known per se, the computer regulates the admission of air and the amounts of recycled exhaust gas to the intake, the injection of fuel into the engine, the triggering (on threshold) regenerations of the particulate filter 17 and the nitrogen oxide trap 19.

In normal operation, i.e. in the absence of failure of the particulate filter 17, the motor setting is a nominal setting. For example, for a given speed-torque operating point, and at least for a temperature representative of the operation of the given engine, for example a coolant temperature, an exhaust gas temperature or a particulate filter temperature, the concentration of soot particles [ΡΜ], η emitted in the exhaust gas, and then entering the filter 17, can be adjusted by choosing a particular phasing of the fuel injection pattern, and by choosing a particular rate of exhaust gas recirculation at the intake.

By the term "injection pattern" is meant all of the fuel injection sequences during a combustion cycle in the engine, which may comprise: a pilot injection (pre-injection); a main injection; and, one or more late injections. Each of these individual sequences is characterized by the amount of fuel injected, which can be quantified in degrees of engine crankshaft angle, and by the moment this amount is injected, which can be quantified by the crankshaft angle relative to at a top dead center of the engine as the injection sequence begins. By the term "phasing of an injection" is meant the moment when an injection sequence begins.

It is known that the choice of the phasing of an injection pattern, that is to say the moments when each individual sequence of injections constituting the pattern begins, is the result of a compromise aimed at limiting the emission different types of engine emissions: HC, CO, NOx and PM soot particles.

In other words, in the nominal setting, the engine injection pattern is not adjusted so as to minimize the formation of PM particles in the combustion gases of the engine, but on a nominal concentration of soot particles [ PM] in, NOM greater than the minimum concentration value of particles [PM] m, MiN achievable, so as to limit the formation of the other polluting molecules: CO, HC and NOx in the combustion gases of the engine.

Similarly, it is also known that exhaust gas recirculation at intake is used to reduce NOx emissions, but this decrease occurs at the expense of emissions of soot particles, which tend to increase when the exhaust gas recirculation rate is increased on admission. The choice of the recirculation rate, called EGR rate, during the nominal setting of an engine, therefore results from a compromise between NOx and PM particles.

It is understood that for the same operating point speed -couple, and for the same representative temperature of the engine operation, a backup setting, decreasing the concentration of particles [ΡΜ], η relative to the nominal concentration, is possible by modifying one or the other of the compromises.

For this purpose, the computer may, for example, phase out at least one injection sequence of the pattern. In particular, it can regulate the phasing of all the injection sequences composing the pattern, so as to reach the minimum concentration of unburned hydrocarbons [PM] m, MiN. This adjustment can be obtained by preliminary tests on the engine test bench.

Alternatively or in combination, the computer can for example reduce the rate of recirculation of the exhaust gas at the inlet compared to the nominal setting rate.

The computer is able to switch the motor operation from its nominal setting mode to its backup setting mode when the filter 17 loses its efficiency ε PM particle treatment. Thus, the loss of efficiency of the filter is compensated by a lower emission of PM at the source, that is to say in the combustion gases of the engine.

Such a tilting may be provided for all or part of the engine speed-load operating points and for all or part of the temperatures representative of the operation of the engine. In particular, the temperature range for which the backup setting is applied is not necessarily limited to cold operation, i.e. at temperatures for which the filter is not yet primed. On the contrary, there is an interest in applying the hot backup setting, that is to say at the usual operating temperatures (excluding starting) of the motor, for which a loss of efficiency of a filter can also be noted. when it is primed.

Since the decrease in PM is offset by an increase in other pollutants, the backup control mode results in a faster increase of NOx storage in the nitrogen oxides trap 19, leading to an increase in the frequency of regenerations. of it.

We now describe a non-limiting embodiment for determining the efficiency ε of PM soot particles of the oxidation catalyst 14, or the value of a parameter representative of said efficiency. Reference will be made for a detailed description to the publication FR-A1-2 939 474.

The computer is connected to the pressure sensors 21 and downstream 22 associated with the particle filter 17 and the flow meter 9. It determines a value of the upstream pressure Pam and downstream Pav, from which it deduces the differential pressure ΔΡ at the terminals of the filter 17. It determines a value of the flow rate of the exhaust gas QeCh, for example by adding to the measurement of the flow of the intake gas Qadm from the flow meter 9 a value of the fuel flow Qcarb. It determines the quantity of Qpart particles entering the filter 17, and thus theoretically stored therein if its operating state is correct, from the flow of the QeCh exhaust gas and a soot concentration model [ΡΜ ], η in the combustion gases which is a function of the operating point of the engine. It determines, from the volume flow rate QeCh of the exhaust gas and the quantity Qpart of particles representative of the theoretical loading state of the filter, the theoretical differential pressure APth to be established across the filter in normal operation, presenting the theoretical loading state determined and traversed by a flow rate equal to the flow rate of the exhaust gas Qech. The values of real differential pressure ΔΡ and theoretical APth make it possible to deduce a parameter PPD which is calculated according to the equation: (Equ.2) PPD = APth - ΔΡ

This PPD parameter makes it possible to evaluate the difference between the operation of a particulate filter 17 and that of a particulate filter in good condition. The greater the difference between the theoretical differential pressure and the actual pressure, the more the filter is degraded. The parameter PPD is therefore a parameter which is representative of the efficiency of the filter 17. From this method, which provides an indirect quantification of the efficiency of the filter 17, it is possible to deduce the value of the efficiency ε in the manner next :

A series of filters having different known efficiency values ε are prepared. To do this, we artificially age a series of new filters with different durations. Each filter is then mounted on a motor bench provided with an analysis chamber capable of measuring the concentrations of PM particles directly in the combustion gases of the engine [ΡΜ], η and leaving the filter [PM] out, the efficiency ε being calculated according to the following equation: (Equ.2) ε = ([PM] in - [PM] out) / [PM] in

Then, for each of the filters 17 whose efficiency is known, the differential pressure ΔΡ is determined according to the method which has been described above. For a new filter in perfect condition, the measured differential pressure is equal to the theoretical differential pressure APth. This establishes a correspondence table between the differential pressure ΔΡ and the efficiency ε, and thus between the parameter PPD and the efficiency. This correspondence table, after preliminary tests, is stored in a memory of the computer and conversely allows to deduce the efficiency of a filter 17 from a differential pressure value ΔΡ.

The computer comprises means for comparing the efficiency ε of the filter 17 with a second threshold Sdefault, called the filter fault recording threshold, said second threshold being strictly greater than a second threshold, said threshold of vehicle failure or threshold OBD Sobd for which a vehicle failure must legally be reported to the driver, for example by lighting a warning light on the instrument panel.

The calculator comprises means capable of tilting the motor setting, for all or part of the engine speed-load operating points and for all or part of the temperatures representative of the engine operation, from its nominal mode to its backup mode when the efficiency ε of the filter becomes less than said second threshold S deficiency of recording fault, and means adapted to register a malfunction of the filter 17 in a memory. This defect will be used to diagnose the operator device during vehicle maintenance and to guide repairs quickly.

The computer comprises means for triggering an alarm on the dashboard of the vehicle, typically in the form of the lighting of a light, said OBD light, when the efficiency ε of the filter 17 becomes lower than the failure threshold of the vehicle. vehicle, or threshold OBD Sobd.

FIG. 2 is a logic diagram of the steps of the control method of the motorization device according to one embodiment of the invention.

The process starts with a step 100 in which the drive device is set in a nominal setting mode, in which the PM concentration in the combustion gases of the engine 1 is set to a nominal concentration value [PM] m, NOM greater than the minimum concentration value [PM] in, MIN.

The method continues with a step 200 in which the computer determines a value of the efficiency ε of the filter 17 according to the method described above, and compares it to the second threshold Sdefault. This Sdefault threshold is strictly greater than the OBD SoBD threshold

If the efficiency is greater than or equal to the second threshold, the method resumes in step 100. In the opposite case, the method is directed to a step 300 in which a malfunction of the filter 17 is entered in a memory of the calculator at this point, however, without the driver of the vehicle being alerted of a vehicle failure.

The method then continues with a step 400 in which the adjustment of the motorization device is modified with respect to the nominal setting. More specifically, the computer switches the drive device to the backup setting to compensate for the loss of efficiency, still moderate at this stage, of the filter 17 by a reduction of PM soot particulate emissions at source.

For example, it is possible to modify the phasing of at least one fuel injection sequence in the engine cylinders. In particular, it is possible to modify the phasing of all the injection sequences that make up the injection pattern, so that the concentration of PM in the combustion gases of the engine is equal to the minimum concentration value.

Alternatively or in combination, the rate of recirculation of the exhaust gas at the engine intake can be reduced.

The method continues with a new step 500 of determining the efficiency ε of the filter 17 and of comparing with the threshold OBD £ obd.

As long as the efficiency remains above said OBD threshold, the process continues with the application of the save setting (step 400), in which the loss of efficiency ε of the filter 17 is compensated by a decrease in PM emissions at the source.

In other words, the application of this backup setting makes it possible to ensure that the vehicle's polluting emissions remain limited, even in the presence of a loss of efficiency of the filter. As the reduction of soot emissions at the source is permanent, it is thus possible to reduce the value of the OBD threshold Sobd, or threshold of vehicle failure, from which it is necessary to alert the driver of the vehicle to a vehicle failure, compared to the value of the threshold that would have been expected if the adjustment had not been modified. This allows to delay the alert and the repair of the vehicle, without breaking the law.

When the efficiency ε of the filter 17 becomes less than the threshold OBD, Sobd, the method orients to a step 600 during which a fault is recorded again in the memory of the computer. In other words, the defect already recorded in step 600 is confirmed, and the driver of the vehicle is alerted of a vehicle failure. Following step 600, the method may finally continue with a step 700 during which the fault is cleared from the computer memory when the repair is performed (this step is usually performed in the garage). After clearing the fault, the motor setting returns to the nominal setting (step 100).

Claims (8)

1. A method for controlling a motor vehicle engine device comprising a diesel-type internal combustion engine (1) and a particulate filter (17) mounted in the exhaust system (11) of the engine, said method comprising at least one minus: a motor nominal setting step (100), in which engine soot particle emissions are set to a nominal concentration value ([PM] m, NOM); a step (500) for determining the efficiency (ε) of the filter (17) and for comparing said efficiency (ε) with a threshold (sobd) of vehicle failure; a step (600) in which, when the efficiency (ε) of the filter (17) becomes less than said threshold (sobd) of vehicle failure, an engine calculator stores in memory a malfunction of the filter (17) and alert the driver of the vehicle of a vehicle failure, CHARACTERIZED IN THAT it further comprises: a step (200) in which the efficiency (ε) of the filter is compared with a second threshold (Sdefault) strictly greater than the threshold of vehicle failure (sobd); a step (300) in which, when the efficiency (ε) of the filter (17) becomes lower than said second threshold (Sdefault), the computer stores in memory a malfunction of the filter; and, when the efficiency (ε) of the filter (17) becomes less than said second threshold (default), a motor backup adjustment step (400) in which the soot particle emissions (PM) of the engine are regulated. at a value lower than the nominal concentration value ([PM] m, NOM), said backup setting being maintained at least until the efficiency (ε) of the filter (17) does not fall below the vehicle failure threshold (£ oBD). 2. Method according to claim 1, characterized in that the driver of the vehicle is not alerted to a vehicle failure when the efficiency (ε) of the filter becomes lower than the second threshold (Sdefault). 3. Method according to any one of the preceding claims, characterized in that the driver is alerted to a vehicle failure by lighting a warning light on the dashboard of the vehicle. 4. Method according to any one of the preceding claims, characterized in that the engine backup setting is obtained from the nominal setting by changing the phasing of at least one fuel injection sequence in the engine cylinders by ratio to the phasing of the nominal setting. 5. Method according to claim 4, characterized in that the backup setting is obtained by changing the phasing of the various fuel injection sequences in the engine cylinders which minimizes the concentration ([PM] m, MiN) of soot particles from the engine. 6. Method according to any one of the preceding claims, characterized in that the backup setting is obtained from the nominal setting by decreasing a recirculation rate of the engine exhaust gas at the engine intake. 7. Method according to any one of the preceding claims, characterized in that the backup setting is applied at least over a temperature range representative of the operation of the motor in which the filter (17) is initiated. Motor vehicle drive device for carrying out the method according to any one of claims 1 to 7, comprising a diesel engine (1) and particulate filter (17) mounted in the exhaust circuit (10). the engine, CHARACTERIZED IN THAT it further comprises: means for determining the efficiency (ε) of the filter (17); means and comparing said efficiency with a threshold (Sdefault; £ obd); means for recording a fault relating to the filter (17) when the efficiency (ε) becomes less than a threshold (Sdefault; Cobd); means adapted to alert the driver of the vehicle of a vehicle failure when the efficiency (ε) becomes less than a threshold (sobd); engine tilting means in a backup adjustment mode adapted to reduce the emissions of soot particles (PM) compared to the nominal setting of the engine.