WO2014174169A1

WO2014174169A1 - Method for the triggering of regeneration of a particle filter

Info

Publication number: WO2014174169A1
Application number: PCT/FR2014/050720
Authority: WO
Inventors: Sebastien Faure; Patrice MARECHAL
Original assignee: Peugeot Citroen Automobiles Sa
Priority date: 2013-04-25
Filing date: 2014-03-27
Publication date: 2014-10-30
Also published as: EP2989308A1; FR3005103A1; FR3005103B1

Abstract

The method according to the invention involves calculating a threshold value (Seuil Teau) of the water temperature of the vehicle engine from a minimum temperature value (Tmin) below which regeneration (RG) is not authorised and a desired temperature value (Tsouh) above which the triggering of regeneration (RG) is preferred, this calculation being made on the basis of the driving conditions, it being possible to take one or more parameters individually or in combination to represent these conditions, said parameters being the driving time (t) taken in combination with the distance (D) travelled, the average speed, the proportion of idle operation time or the proportion of time driving at a speed lower than a predefined speed, the engine speed or torque, the number of times the driver lifts his foot per minute, and the average water temperature for the time during which the engine is running.

Description

METHOD FOR TRIGGERING A REGENERATION OF A

PARTICLE FILTER

The invention relates to a method of early triggering a regeneration of a particulate filter as a function of the engine water temperature of a motor vehicle.

At present, pollutant emission levels, motor vehicles are regulated, especially the level of particulate emissions. It is therefore known to equip vehicles comprising a heat engine, in association or not with another non-thermal engine such as for example hybrid vehicles, depollution means which may comprise a set of catalysts transforming the toxic constituents of the exhaust gases. exhaust, such as carbon monoxide, unburned hydrocarbons or oxides of nitrogen, into less toxic elements such as water vapor and carbon dioxide.

These means of pollution also include, especially for diesel engines but also for gasoline engines or hybrid engines in accordance with the new standards, a particulate filter that traps particles from combustion in the cylinders. The particles, mainly in the form of soot, accumulate in the particulate filter so that only purified gases are discharged. However, a particulate filter should be cleaned regularly to remove any particles that have accumulated from inside. This filter cleaning operation is called filter regeneration.

[0004] A regeneration of a particulate filter is based on soot combustion by raising the temperature of the particulate filter to the temperature at which the carbon particles burn. The most conventional method for regenerating a particulate filter requires post injection and particular engine settings. The post injection makes it possible to inject an additional quantity of fuel into at least one of the cylinders. The fuel thus injected late ignites by producing an increase in temperature of the exhaust gas.

The impact of these adjustments on the approval of the motor vehicle is even more sensitive that the cooling water of the engine is cold. For this reason, the particulate filter is usually not regenerated when the cooling water of the engine is too cold, this first temperature being hereinafter referred to as the minimum regeneration temperature. Without this being limiting, a Engine coolant temperature below 30 ° C is considered disadvantageous for regeneration of the particulate filter. It is this value of 30 ° C which is often taken as a mirimal temperature of water.

One of the negative impacts of post injection on the engine is the phenomenon of dilution which results in the presence of fuel in the engine oil. Indeed, the fuel injected late and does not burn in the combustion chamber can cause the formation of a liquid fuel film on the inner walls of the engine cylinders. This unburned fuel can then pass under a piston and mix with the engine lubricating oil. Such dilution adversely affects the lubricating properties of the oil and can be detrimental to engine reliability, resulting in premature wear or at least degrading the lubricating qualities of the engine oil.

The dilution phenomenon is all the more important that the cooling water of the engine is cold. It is for this reason that it is preferred to carry out regenerations of the particulate filter above a predetermined temperature called the desired regeneration temperature. Without this being limiting, this second so-called desired engine cooling water temperature is generally not less than 60 ° C. and can vary between 60 and 90 ° C.

In return, it is not always desirable to wait for these cooling water temperature conditions of the engine to initiate a regeneration of the particulate filter. Indeed, regardless of the cooling water temperature of the engine, the particulate filter is loaded with soot particles, and this, disadvantageously, the faster the water temperature is cold. After a while, the loading of the particulate filter is so high that regeneration must be initiated absolutely to avoid cracking of the particulate filter.

This cracking is mainly due to the excessive heat released by too many particles accumulated in the filter and being burned together. Such cracking may result in destruction of the particulate filter.

At the moment of regeneration of a particulate filter, the first and second cooling water temperatures of the engine, in particular the minimum regeneration temperature, are therefore carefully monitored and even become a condition for triggering regeneration. of the filter. This regeneration is advantageously triggered by a particle filter supervisor during the rolling of the vehicle.

[001 1] Such a supervisor calculates the regeneration opportunities of the particle filter according to measured data. These data, measured in particular by means of particle filter control sensors, may concern the mass of particles in the particulate filter, a pressure difference across the particle filter, the combustion mode, the current dilution, the outside temperature. When a predetermined saturation value of the particulate filter is reached, a regeneration is triggered. Another data that can be taken into account by the particle filter supervisor is the mileage traveled since the last regeneration.

It is also possible, from a temperature sensor or by estimation from other information, to collect the cooling water temperature of the engine to see if this temperature is higher than the first and second temperatures. previously mentioned. According to the state of the art, it is possible to progressively reduce the second water temperature, referred to as the desired regeneration temperature, advantageously above 60 ° C. as a function of the soot mass inside the estimated particulate filter. . In the case of a critical mass of particles in the filter, this desired regeneration temperature can then go down and reach the first minimum temperature of regeneration water, advantageously 30 ° C.

Therefore, according to the state of the art, it is preferred to wait for the overload of the particulate filter before allowing the desired temperature of water to drop. However, this can be very disadvantageous with regard to the risks of cracking of the particulate filter.

Indeed, when we finally allow regenerations at the minimum water temperature, that is to say towards 30 ° C, it may be that it is too late to prevent cracking of the particulate filter. The holding of the dilution objectives in relation to the overload of the filter is therefore the result of a global compromise, a compromise that may prove to be deficient as regards the protection of the particulate filter.

This solution only works because the motor vehicles overload particle filter are also those who have a severe rolling average speed and average duration. On the one hand, the loading of the particulate filter which is done for several hundreds of kilometers and in several hours and, on the other hand, the driving habits of a motorist, which are a few tens of minutes and a few tens However, kilometers do not have the same temporal and distance dynamics.

This implies that the solution of the state of the art, disclosed in particular by FR-A-2 970 040, does not optimize the minimum water temperature of authorization of a regeneration on the whole. cases of life that can be encountered during the taxi of a motor vehicle. This is the case, for example, for the change of road behavior of the vehicle just after a regeneration.

Therefore, the problem of the present invention is to index the minimum cooling water temperature for the beginning of a regeneration on an indicator taking into account the road behavior of the motorist in order to anticipate a particle filter overload, very often also related to the type of running of the motor vehicle.

To achieve this objective, there is provided, according to the invention, an early triggering process of a regeneration of a particulate filter present in the exhaust line of a motor vehicle according to a temperature threshold value. of the cooling engine of the engine of the vehicle, the method taking into account for the calculation of this threshold value of water temperature a minimum temperature value of water below which a regeneration is not allowed and a value desired water temperature at which or above which the initiation of a regeneration is preferred, characterized in that the threshold value is calculated according to the driving conditions of the vehicle, one or more parameters which can be taken individually or in combination to represent the driving conditions:

- the driving time taken in combination with the distance traveled by the vehicle,

- the average speed of the vehicle,

the proportion of operating time at idle or the proportion of time with a running speed lower than a predetermined speed,

- engine speed or torque,

- the number of feet per minute of the driver,

- the average of the cooling water temperature over the duration of the rotating engine

the temperature measured or estimated in the vicinity of the particulate filter.

It is preferable to first choose the driving time taken in combination with the distance traveled by the vehicle, then, to a lesser extent the average of the cooling water temperature over the duration of the engine running, then again in a lesser measure the engine speed or torque. Finally, all other parameters can also be chosen but are less relevant than the previous ones. Preferably, said threshold value (Water Threshold) of water temperature is therefore between said minimum temperature value (Tmin) and said desired temperature value (Tsouh) of water (up to being equal to one of these temperatures).

The technical effect is to make the rolling of the automobile depend on the threshold of the triggering water temperature of a regeneration then necessary. This makes it possible to adapt the threshold to each behavior of the motorist. It is thus obtained that the regenerations triggered with anticipation are as complete as possible, avoiding their interruption by a shutdown of the vehicle engine.

Advantageously, it is proceeded to the measurement or the estimation of the prevailing water temperature at a given moment, this measurement or estimate being compared with the threshold temperature value, a regeneration that can be triggered if necessary in the case where this measurement or estimate of the temperature is greater than the threshold value.

Advantageously, when the temperature threshold value is calculated as a function of the running time and the distance traveled by the vehicle, two pairs of rolling time and distance traveled values are determined, the first pair of values being determined. corresponding to obtaining a minimum water temperature below which a regeneration is not allowed and the second pair of values corresponding to obtaining a desired water temperature at or above which triggering a regeneration is preferred.

[0023] Advantageously, the first and second pairs of values in respective correspondence with the minimum temperature value and the desired temperature value are obtained by mapping.

Advantageously, it is taken into account n vehicle journeys with for each of these n trips a specific pair of running time and distance traveled, it is calculated an average of n running times and an average of n distances traveled. , the threshold value of water temperature being calculated according to the following equations:

Water threshold = 2. (Tmin-Tsouh) / (A. MD.Mt + B) + 2. (Tsouh - Tmin)

with

A = 1 /(D2.t2 -D1 .t1) and B = 1 - A.D1 .t1

MD being the average of the n distances traveled and Mt the average of n running times, Tmin the minimum water temperature and Tsouh the desired water temperature, D1 and t1 being respectively the distance and duration of the first pair and D2 and t2 the distance and duration of the second pair.

Advantageously, the temperature threshold values and the minimum temperature and desired temperature values are corrected as a function of the mass of particles inside the particle filter, these temperature values being lowered when the mass of the particles increases. the temperature-corrected threshold values forming a curve as a function of the mass of particles between the curve of the minimum temperature values and the curve of the desired temperature values.

Advantageously, a critical mass of particles inside the filter is defined for which a regeneration of the filter even at a predetermined minimum temperature value is imperative, this predetermined minimum temperature value being reached by the curve of the values of the minimum temperature for a predetermined mass of particles smaller than the critical mass.

[0027] Advantageously, the curve of the temperature-corrected threshold values oscillates between the curve of the minimum temperature values and the curve of the desired temperature values, the curve of the desired temperature values meeting the curve of the minimum temperature values from the critical mass. of particles reached.

Advantageously, the curve of the threshold values of temperature goes down when the rolling of the vehicle in duration and average distances becomes shorter and goes back up when this rolling becomes longer.

Advantageously, it is proceeded to the measurement of the outside temperature, the outside temperature thus measured being used to determine a water-corrected minimum temperature value as a function of the outside temperature, this minimum temperature value corrected from the outside temperature. water being compared with the temperature-corrected threshold value calculated as a function of the mass of particles, the minimum value between the corrected temperature threshold value and the water-corrected temperature value being taken as a new temperature threshold value to be compared to the measured or estimated water temperature value.

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 as non-limiting examples and in which:

FIG. 1 is a schematic representation of the steps of the determination of a temperature threshold value according to an embodiment of a method of early triggering of a regeneration according to the present invention, FIG. 2 is a schematic representation of minimum cooling water temperature curves as a function of the running time and the distance traveled by the motor vehicle,

FIG. 3 shows three temperature curves as a function of the charge of the particulate particle filter, the curve of the corrected temperature threshold being interposed between the desired temperature curve of water and the minimum temperature curve of water for a given temperature. regeneration, the curve of the corrected temperature threshold being obtained by a method of early initiation of a regeneration according to the present invention,

FIG. 4 shows a minimum temperature curve of regeneration water as a function of the charge of the particulate filter, this curve being obtained by a method of triggering a regeneration according to the state of the art,

FIG. 5 shows a schematic representation of the steps of the determination of a temperature threshold value according to a variant of the method of early triggering of a regeneration according to the present invention, the outside temperature being taken into account in this variant.

The present invention relates to a method of early triggering a regeneration of a particulate filter present in the exhaust line of a motor vehicle. Such a method can be implemented by elements embedded in the engine computer or in the particle filter supervisor present in the motor vehicle. The main steps of the method of early triggering of a regeneration are illustrated in Figure 1.

When the supervisor determines that a regeneration of the particulate filter is necessary, the anticipated triggering method according to the present invention provides for determining a threshold temperature threshold SeuilTeau water cooling engine for which or above which a regeneration RG of the particulate filter can be triggered. The method takes into account for the calculation of this threshold value Threshold Water temperature water a minimum temperature value Tmin of water below which a regeneration RG is not allowed and a desired temperature value Tsouh of water to which or above which the triggering of a regeneration RG is preferred.

According to the present invention, the threshold threshold WaterSeal is calculated according to the vehicle running conditions, one or more parameters can be taken individually or in combination to represent the driving conditions: the duration of driving taken in combination with the distance traveled by the vehicle, the average speed of the vehicle, the proportion of idling time or the proportion of time with a speed of travel below a predetermined speed, engine speed or torque, the number of feet per minute of the driver, the average of the cooling water temperature over the duration of the engine running.

In Figure 1, it is the driving distance D and the running time t are taken into account. Thus, among the parameters previously mentioned as being representative of the running conditions of the vehicle, the pair associating rolling time t and distance D traveled by the vehicle is preferred.

In parallel with the determination of this threshold value SeuilTeau of cooling water temperature, at a given moment, it is proceeded to the measurement, advantageously by a temperature sensor, or to the estimation of the water temperature. Water my reigning then. This measured or estimated temperature water is compared with the threshold value ThresholdTemperature, a regeneration RG can be triggered if necessary in the case where the measured or estimated water temperature mes is greater than the threshold value ThresholdTeauTemperature.

FIG. 2 shows the obtaining of minimum cooling water temperature curves for triggering a regeneration as a function of the running time t on the ordinate and the distance D traveled on the abscissa. Such curves can be obtained by mapping. The minimum cooling water temperature curves can be of the hyperbolic type. Indeed, the less the vehicle rolls, so with a rolling time t and a distance D traveled low, the lower the threshold value of minimum water temperature must be reduced to have the time to regenerate the particle filter in case of launch of a regeneration. In this figure, the scale on the right is the temperature scale of 35 to 90 ° C.

In this Figure 2, there is defined two specific points forming a pair associating a distance traveled with a rolling time. In FIG. 2, a first pair of distances D1 and of short duration t1 is defined which imposes all the scenarios below which it is desired for the particulate filter to regenerate from the minimum temperature of water. for a regeneration, for example 30 ° C in Figure 2. This temperature is the minimum temperature to perform a regeneration is called Tmin. Below this temperature Tmin, no regeneration is performed.

It is also defined a second pair of distance D2 and duration t2 which imposes the set of scenarios beyond which it is desired to wait for a water temperature. hot enough to practice a satisfactory regeneration, for example 90 ° C in Figure 2. This temperature is the minimum desired temperature to perform a regeneration under satisfactory temperature conditions is called Tsouh.

Referring again to Figure 1, from these two temperatures Tmin and Tsouh, it is calculated in block 1 the threshold value SeuilTeau cooling water temperature, this according to the distances D and durations t. The distance D and the duration t used for this calculation are advantageously respectively the respective mean of the distances MD and the durations Mt on n motions of the motor vehicle, the averages MD and Mt being calculated respectively in the blocks 2 and 3.

Advantageously, the threshold value SeuilTeau cooling water temperature is calculated according to the following equations:

Water threshold = 2. (Tmin-Tsouh) / (A. MD.Mt + B) + 2. (Tsouh - Tmin)

with

A = 1 /(D2.t2 -D1 .t1) and B = 1 - A.D1 .t1

For which equations:

MD represents the average distance of the last n trips of the vehicle,

Mt represents the average duration of the last n trips of the vehicle,

Tmin the minimum water temperature and Tsouh the desired water temperature,

D1, t1; D2, t2 having previously been defined as the respective distance and duration of the first and second pairs of distance and duration.

In order to overcome a possible overload of the particulate filter not associated with a severe rolling profile, a saturation dependent on the estimated mass M of particles inside the particulate filter can be introduced to correct by refining the value. threshold ThresholdTemperature water. This is done in blocks 4, 5 and 6 shown in FIG. In block 5 it is the desired temperature value Tsouh of water, in block 4 it is the minimum temperature value Tmin of water and in block 6 it is the threshold value Threshold Water of the temperature of water which are respectively corrected, the latter giving the threshold value corrected SeuilTeau cor.

It should be noted that any other form of correction may also be possible, in particular as a function of another parameter than the estimated mass M of particles in the filter. As previously mentioned, if this threshold value corrected SeuilTeau cor is less than the measured or estimated water water value, a regeneration RG can be triggered if necessary.

FIG. 3 shows the respective temperature curves Tsouh, Threshold Water cor and Tmin as a function of the charge of the particulate filter in soot particles, these values having been corrected as a function of the mass M of particles in the filter. In this figure, the threshold values corrected SeuilTeau cor of water temperature as well as the minimum temperature values Tmin and desired Tsouh have been corrected according to the mass M of particles inside the particulate filter, these temperature values. being lowered when the mass M of the particles increases. The threshold values corrected Threshold Water coral temperature form a curve as a function of the mass M of particles between the curve of the minimum temperature values Tmin and the curve of the desired temperature values Tsouh, the latter being above the curve of Threshold values corrected Threshold Water cor.

These curves are to be compared with the minimum water curve Tmin et tech regeneration as a function of the mass M particles in the filter, this curve being obtained by a method according to the state of the art. In FIG. 4, according to the state of the art, a critical mass Me of particles inside the filter is defined for which a regeneration of the filter even at a predetermined minimum temperature value is imperative.

In this FIG. 4, this critical mass Me is set at 30 g, which is not limiting. As soon as this mass Me is obtained, a regeneration is triggered even when the water temperature is equal to the minimum water temperature, in this figure for example 30 ° C.

According to the state of the art, illustrated by Figure 4, the minimum regeneration temperature Tmin et tech was the minimum temperature desired to perform a regeneration, in this figure for example 60 ° C. The temperature of this minimum temperature Tmin et tech regeneration falls below the desired temperature to trigger a regeneration from the accumulation of a predetermined limit mass Ml, less than the critical mass Me, this predetermined limit mass Ml being by example of 20g to this figure. The curve of this minimum temperature Tmin et tech then reaches the minimum temperature of water during the accumulation of the critical mass Me in particles.

The predetermined mass Ml, accumulated in the filter, may be the largest accumulated mass value judged not to present a further danger for perform a regeneration but can become if the mass continues to increase, especially up to the critical mass Me, without regeneration.

Referring to Figure 3, according to the method according to the present invention, the minimum temperature value Tmin predetermined to perform a regeneration is reached from the accumulation of a mass of particles equal to the lower limit mass Ml to the critical mass Me by the curve of the minimum temperature values. This makes it possible to anticipate the triggering of a regeneration at a minimum temperature before the accumulation of the critical mass Me. Thus, it is ensured a protection of the particulate filter against a possible cracking which can occur when the regeneration is triggered at from the accumulation of the critical mass Me.

The intermediate curve of threshold values corrected Threshold Water cor water temperature, with an arrow pointing downwards between the two curves of minimum temperature Tmin and desired water Tsouh for regeneration, shows the evolution of the value threshold corrected Threshold Water coral of the water temperature according to the particle filter loading and the way of driving of the motorist.

This curve threshold values corrected SeuilTeau water temperature cor descends when the driving of the motorist, in terms of duration and average distance of travel, becomes shorter. Conversely, this curve rises when the rolling becomes longer, while remaining in an intermediate zone between the minimum temperature curves Tmin and desired Tsouh water.

The curve of the threshold values corrected SeuilTeau horn of temperature oscillates between the curve of the minimum temperature values Tmin and the curve of the desired temperature values Tsouh, the curve of the desired temperature values Tsouh meeting the curve of the minimum temperature values Tmin from the critical mass Me of particles reached.

This has the great advantage of triggering an anticipated regeneration compared to the triggering of a regeneration according to the state of the art thus to protect the particulate filter. In addition, this makes it possible to increase the number of regenerations actually effected, since they are triggered earlier and they are likely not to be interrupted as much by motor vehicle engine shutdown as regenerations triggered later by the state of the art.

It is also obtained a global gain in dilution with less regeneration recovery. These regeneration enhancements are indeed even more generating dilution with more post injections required for the upstream temperature rise of the particulate filter compared to a post injection at cold engine cooling water temperature.

A variant of the method according to the invention is shown in FIG. 5. Such a variant makes it possible to refine the triggering of the regenerations, during prolonged uses of the vehicle in very cold conditions, for example between -30 ° C. and 0 ° C. ° C, as may be the case during the winter months in Northern Europe.

According to this variant, it is then advantageously proceeded to a correction of the threshold value corrected SeuilTeau cor cooling water temperature to trigger a regeneration as a function of the ambient temperature Text. This makes it possible to lower the threshold threshold corrected SeuilTeau cor of the cooling water temperature for triggering regenerations RG.

According to this advantageous embodiment, it is first measured to the outside temperature Text. The external temperature Text thus measured serves to determine a minimum temperature value corrected Tmin of water as a function of the external temperature Text. This corrected minimum temperature value Tmin of water is then compared with the threshold value corrected Threshold Water coral temperature, this threshold threshold corrected SeuilTeau cor having been previously corrected as a function of the mass M of particles.

According to the variant of the method, the minimum value between the threshold value corrected SeuilTeau horn of temperature and the corrected temperature value Tmin horn of water is then taken as a new temperature threshold value and is then compared to the measured value. or estimated water temperature, similar to what was described with reference to Figure 1.

Such a correction is based on the observation that, under very cold outside temperature conditions, the engine of the vehicle has difficulty heating its water, the driver does not otherwise change his driving habits, estimated in duration and average distances.

In addition to the advantages of performing complete regenerations and of protecting the particulate overload particle filter, another of the main advantages of the present invention, in all its embodiments, is that the anticipation of certain regenerations with a cooler cooling water temperature, even without overloading the particulate filter, makes it possible to gain engine dilution. Indeed, engines are often limited to about 10% dilution overall and regeneration in the city can be responsible up to 1% dilution for the engine.

Other advantages of using a method of anticipating a regeneration according to the present invention are:

an increase in the vehicle emptying intervals for the same particle filter size, which results in an increase in the quality perceptible to the driver of the motor vehicle,

a reduction in the size of the particulate filters for the same regeneration interval, which may allow the use of less robust and therefore less expensive materials and may consequently lower the cost of manufacturing the filters,

- a reduction in the volume of oil for the same dimension of particle filter, which enhances the satisfaction of the user of the vehicle and the brand image of the vehicle.

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

Claims

1. A method for early triggering of a regeneration (RG) of a particulate filter present in the exhaust line of a motor vehicle according to a threshold value (ThresholdTo) of the cooling water temperature of the engine of the vehicle , the method taking into account for the calculation of this threshold value (Water Threshold) of water temperature a minimum temperature value (Tmin) of water below which a regeneration (RG) is not allowed and a value of desired temperature (Tsouh) of water at which or above which the initiation of a regeneration (RG) is preferred, characterized in that the threshold value (Water Threshold) is calculated according to the driving conditions of the vehicle, a or the following parameters that can be taken individually or in combination to represent the driving conditions:

the duration (t) of driving taken in combination with the distance (D) traveled by the vehicle,

the average speed of the vehicle,

engine speed or torque,

the number of feet per minute of the driver,

the average of the cooling water temperature over the duration of the rotating engine

2. Method according to claim 1, characterized in that said threshold value (ThresholdTeau) water temperature is between said minimum temperature value (Tmin) and said desired temperature value (Tsouh) of water.

3. Method according to claim 1 or claim 2, for which the measurement or estimation of the water temperature (Mes water) is carried out at a given moment, this measurement or estimate (water mes) being compared with the threshold value (Water Threshold), a regeneration (RG) that can be triggered if necessary in the case where this measurement or estimation of the temperature (water mes) is greater than the threshold value (water threshold).

4. Method according to one of the preceding claims, wherein, when the threshold value (SeuilTeau) temperature is calculated based on the duration (t) of rolling and the distance (D) traveled by the vehicle, it is determined two pairs of values (D1, t1, D2, t2) of running time and distance traveled, the first pair of values (D1, t1) corresponding to obtaining a minimum temperature (Tmin) of water below of which a regeneration (RG) is not allowed and the second pair of values (D2, t2) corresponding to obtaining a desired temperature (Tsouh) of water at or above which the triggering of Regeneration (RG) is preferred.

5. Method according to the preceding claim, wherein the first and second pairs of values (D1, t1; D2, t2) corresponding respectively to the minimum temperature value (Tmin) and the desired temperature value (Tsouh) are obtained by mapping.

The method of claim 4 or 5, wherein:

- n vehicle journeys are taken into account with, for each of these n journeys, a specific pair of driving time and distance traveled,

an average of the n durations (Mt) of rolling and an average of n distances (MD) traveled are calculated,

the threshold value (Water Threshold) of water temperature is calculated according to the following equations:

Water threshold = 2. (Tmin-Tsouh) / (A. MD.Mt + B) + 2. (Tsouh - Tmin)

with

A = 1 / (D2.t2 -D1 .t1) and B = 1 - A.D1 .t1

MD being the average of the n distances traveled and Mt the average of the n running times, Tmin the minimum water temperature and Tsouh the desired water temperature, D1 and t1 being respectively the distance and duration of the first pair and D2 and t2 the distance and duration of the second pair.

7. Process according to any one of claims 4 to 6, for which the temperature threshold values (Water Threshold) and the minimum temperature (Tmin) and desired temperature (Tsouh) values are corrected as a function of the mass (M). of particles within the particle filter, these temperature values being lowered when the mass (M) of the particles increases, the corrected threshold values (ThresholdCalc) of temperature forming a curve as a function of the mass (M) of particles between the curve of the minimum temperature values (Tmin) and the curve of the desired temperature values (Tsouh).

The method according to claim 7, wherein a critical mass (Me) of particles within the filter is defined for which a regeneration (RG) of the filter even at a predetermined minimum temperature value (Tmin) is imperative, this predetermined minimum temperature value (Tmin) being reached by the curve of the minimum temperature values (Tmin) for a predetermined mass (Ml) of particles smaller than the critical mass (Me).

The method of claim 8, wherein the temperature threshold value curve oscillates between the minimum temperature value curve (Tmin) and the desired temperature value curve (Tsuh), the desired temperature value curve (Tsouh). ) meeting the curve of the minimum temperature values (Tmin) from the critical mass (Me) of particles reached.

10. The method of claim 7, wherein the curve of the corrected threshold values (ThresholdCal Water) temperature goes down when the rolling of the vehicle in duration and average distances (Mt, MD) becomes shorter and goes back when this rolling becomes longer.

11. A method according to any one of claims 7 to 10, for which the measurement of the external temperature (Text) is carried out, the external temperature (Text) thus measured serving for the determination of a corrected minimum temperature value. (Tmin cor) of water as a function of the outside temperature (Text), this corrected minimum temperature value (Tmin cor) of water being compared with the corrected threshold value (ThresholdCalc) of temperature calculated as a function of the mass ( M) of particles, the minimum value between the corrected threshold value (ThresholdCalc) of temperature and the corrected temperature value (Tmin cor) of water being taken as a new temperature threshold value to be compared with the measured or estimated value of temperature (water).