FR3086330A1 - DETERMINATION OF A PRESSURE LOSS GENERATED BY A PARTICLE FILTER - Google Patents

Abstract

Control method for a thermal engine based on the determination of a pressure drop (AP) of a particulate filter, comprising: - estimation of the pressure drop by a sensor measuring a pressure drop (ΔPc) up to a maximum limit value, - control of an engine actuator as a function of the estimated pressure drop (ΔPE). Said estimate comprising: - measurement of a current exhaust gas flow rate, - if the measured pressure drop is less than said limit value, determination of the estimated pressure drop from the measured pressure drop, and determination of '' a degree of efficiency of the particle filter by a first function (f1) based on the flow rate and the pressure drop measured, - otherwise, determination of the pressure drop estimated by a second function (f2) based on the current flow rate and on the last degree of efficiency.

Description

DETERMINATION OF A PRESSURE LOSS GENERATED BY A PARTICLE FILTER

TECHNICAL AREA

The present invention relates, in general, to the field of heat engines and relates more specifically to the determination of a pressure drop generated by a particle filter coupled to a heat engine.

In terms of controls applied to combustion engines, in particular anti-pollution controls, it becomes necessary to know the state of the systems linked to the exhaust of gases in order to be able to meet requirements which are becoming more and more severe. These checks are not limited to an ecological function but can affect any engine control system using a function for controlling the air flow in the air and exhaust gas circuit linked to the engine.

To do this, the present invention provides a control method for an internal combustion engine based on a determination or an estimate of the pressure drop generated by a particulate filter coupled to an engine. The invention also relates to a heat engine controlled by this method and to a motor vehicle comprising such an engine.

The engines concerned are typically diesel type engines, preferably supercharged or atmospheric engines.

PRIOR ART

The pressure drop generated by a particulate filter fitted to a thermal engine, typically of the diesel type, is information used in the control and / or command of the engine. This pressure drop corresponds to the dissipation, by friction, of the mechanical energy released by the exhaust gases when they pass through the particle filter to be, as far as possible, rid of the fine particles which these gases contain. This pressure drop is typically determined by a pressure difference between two points situated on either side of the particle filter, generally at the inlet and at the outlet of this filter, respectively.

This pressure drop is also known by the name delta P (ΔΡ) and is typically measured in millibars.

Currently, the pressure drop of the particulate filter is determined, by measurement, by means of a pressure sensor, more specifically a differential pressure sensor also known by the name of delta-P sensor or DP sensor. This sensor is the known means for determining the pressure drop of the particulate filter. This pressure drop is most often below a limit value corresponding to the maximum end of the measurement range of this sensor. Any differential pressure value going beyond this maximum limit value cannot therefore be measured by this sensor. In this case, the sensor will be in a so-called "saturated" state and will only be able to return this limit value in response to these measurements. It will be necessary to wait for the differential pressure to return to the level accepted by the measurement range of this sensor so that the latter can indicate a value representative of reality.

However, if the value given by this sensor, in this saturated state, is no longer representative of the actual pressure drop of the particulate filter, any control or command system based on such a value will remain unsatisfactory. This will result in a loss of information or incomplete information which may affect many devices depending on the value of the pressure drop generated by the particle filter.

The document FR3014948 describes a method for detecting the malfunction of a filter element for the exhaust gases of a motor vehicle. To this end, this method comprises a monitoring means using differential pressure sensors disposed downstream of the filters and adapted to detect any drop in the pressure drop. However, the solution suggested in this document does not solve the problem of the saturated state of the sensor.

Consequently, there is an advantage in finding a new, more suitable solution which at least partially makes it possible to resolve the abovementioned drawbacks.

SUMMARY OF THE INVENTION

To this end, the first object of the present invention relates to a method of controlling a heat engine based on the determination, in particular an estimate, of a pressure drop generated by a particle filter coupled to the heat engine.

This method includes a step of estimating the pressure drop using a sensor configured to be able to measure a pressure drop up to a maximum limit value. This method also includes a step of controlling an actuator of the heat engine as a function of the estimated pressure drop.

According to the invention, the step of estimating the pressure drop further comprises:

- a measurement of a current exhaust gas flow rate, and

- a comparison of the pressure drop measured by the sensor with the maximum limit value; the result of this comparison being treated as follows:

If the measured pressure drop is less than the maximum limit value, then carry out:

a determination of the estimated pressure drop from the pressure drop measured by the sensor, and

- a determination of a degree of effectiveness of the particulate filter by means of a first function based on the exhaust gas flow rate and the pressure drop measured by the sensor. The degree of effectiveness of the particulate filter referring to the quantification of the capacity of this filter to be able to fulfill its function, namely to filter the particles contained in the exhaust gases before the latter are discharged into the open air .

On the other hand, if the pressure drop measured is greater than or equal to the maximum limit value, then we carry out:

- a determination of the estimated pressure drop by means of a second function which is based on the current flow rate of the exhaust gases and on a previously determined degree of efficiency, preferably on the last degree of efficiency which may have been to be determined.

Preferably, the steps relating to the estimation of the pressure drop according to the invention are intended to be able to be repeated, for example in accordance with a circular procedure which can be typically implemented by an algorithm. Such an algorithm could be materialized by programming steps intended for software or by flip-flops within a logic or electronic circuit. Such a circuit can be obtained from a plurality of electronic components interconnected by means of a printed circuit for example.

Advantageously, the solution proposed by the present invention makes it possible to obtain an estimate of the pressure drop at the level of the particle filter without having to resort to models or strategies that are complex to manage or to implement.

Advantageously also, this solution makes it possible to obtain information which is on the one hand continuous over time and on the other hand close to reality, in particular when the value of the pressure drop given by the sensor is greater than the value maximum limit defined by its measuring range.

Advantageously, this results in an improvement in the quality of the regulation of the boost pressure, in particular of the air and of the exhaust gas recirculation of the EGR system (Exhaust Gas Recirculation), which generates a reduction. pollutant emissions from the engine.

In addition, the solution of the present invention is advantageously inexpensive to implement and makes it possible to preserve the existing differential pressure sensors while at least partially remedying the drawbacks that they present.

Preferably, the first function used to determine the degree of efficiency of the particulate filter is a linear function corresponding to the current flow rate of exhaust gas the pressure drop measured by the sensor. In a preferred variant, the degree of efficiency is determined from the slope of this linear function.

Alternatively, the degree of efficiency of the particulate filter is determined only if the difference between the maximum limit value and the pressure drop measured by the sensor is less than a threshold value.

Preferably, in the case where the measured pressure drop is less than said maximum limit value, the estimated pressure drop is determined to be equal to the pressure drop measured by the sensor.

The sensor can be configured to determine a pressure variation between the upstream and downstream of the particulate filter.

According to the preferred embodiment, at least one previously determined degree of efficiency, preferably the last determined degree of efficiency, is stored in a register or a memory, for example a temporary memory or a random access memory.

Preferably, the current flow is determined upstream of the particulate filter and more preferably the current flow of exhaust gas is a volume flow.

According to another aspect, the present invention also relates to a heat engine controlled according to any one of the embodiments of the method. More preferably, the internal combustion or internal combustion engine is a supercharged or atmospheric type engine.

Finally, according to a last aspect, the present invention also relates to a motor vehicle comprising a heat engine such as that briefly described above.

BRIEF DESCRIPTION OF THE FIGURES

Other characteristics and advantages of the present invention will appear more clearly on reading the detailed description which follows and which presents different embodiments of the invention given by way of non-limiting examples and illustrated by the appended figures in which :

- Figure 1 shows schematically the flow of gases within an engine and through the main elements associated with it;

- Figure 2 is a first graph showing an example of a curve from the pressure drop measurements taken by a sensor used for this purpose;

- Figure 3 is a second graph showing, for six different capacity degrees of a particulate filter, the pressure drop caused by this filter as a function of the exhaust gas flow;

- Figure 4 shows the same graph as that of Figure 2 to which have been added portions of curves representative of reality and the estimate of the pressure drop obtained according to the present invention.

- Figure 5 shows, in the form of a block diagram, the process of determining or estimating the pressure drop according to the invention.

DETAILED DESCRIPTION

With reference to FIG. 1, this illustrates the well-known circulation of gases, through a motor 10, more precisely of a motor system comprising an air intake at inlet 1 and an exhaust at outlet 2. As illustrated in this figure, the air admitted at the inlet successively passes through an air filter 11, a compressor 12 and a charge air cooler 13 before entering the engine block 15 through the intake manifold 14. The gases exit from the engine block 15 through the exhaust manifold 16. A portion of these gases can be reinjected into the intake manifold 14 by means of the exhaust gas recirculation system 17 followed by an exchanger 17a. This system reduces emissions of nitrogen oxides (NOx) and better meets emission standards without having to modify the engine's structure. The part of the exhaust gases which is not reinjected into this system is directed to a turbine 18 which makes it possible to drive the compressor by a mechanical connection. At the outlet of the turbine, the gases pass through a pollution control system before leaving the exhaust circuit. The pollution control system consists precisely of a particulate filter 19, in particular for diesel engines 10.

As schematically represented in FIG. 1, a measurement of the air flow or of the exhaust gases is, for example, carried out near the particulate filter 19, preferably upstream or at the inlet of this filter, by a device configured or capable of determining this quantity. This device can typically be a flow meter 8. Preferably, the flow Q measured or obtained by this device or flow meter 8 is a volume flow, for example in m ³ / s, but could also be a mass flow, for example in kg / s. The flow rate Q could also be determined from a flow rate of intake air and an amount of fuel injected.

As shown in FIG. 1 in a very schematic way, the pressure drop ΔΡ induced by the particle filter 19 can be measured or determined by a sensor 20. This pressure drop is preferably expressed in mbar will be more particularly noted APc where the index C precisely refers to the sensor so that the pressure APc corresponds to that given by the sensor 20. To do this, this sensor 20 can be a differential pressure sensor which, for example, could be able to measure a first pressure upstream of the particle filter 19 and a second pressure downstream of this particle filter before determining the pressure difference ΔΡ between this first pressure and the second pressure. More preferably, the first and second pressures are respectively measured at the inlet and at the outlet of the particulate filter 19. As a variant, the sensor could be a pressure sensor configured on the one hand to measure the first pressure upstream, preferably at the inlet, the particle filter 19 and on the other hand configured to subtract, from this first pressure, the value of atmospheric pressure. Indeed, this atmospheric pressure being that which one generally has at the outlet of the pollution control system, it could be an estimate value taken by default or a value obtained by another suitable means of measurement.

FIG. 2 illustrates a measurement curve 21 of the pressure characteristic of the pressure drop measured by a conventional sensor, such as the sensor 20, over time. As illustrated in this first graph, it is noted that the values of this pressure curve do not exceed a maximum limit value 25 which is illustrated in phantom in this figure. It follows that the measurement curve 21 has horizontal portions 25a of constant values situated at the level of the maximum limit value 25. These horizontal portions 25a arise from the fact that the sensor 20 is simply not configured to be able to measure pressure values ΔΡ going beyond this limit. In the example illustrated in FIG. 2, the maximum limit value 25 that the sensor 20 can measure is fixed at 1000 mbar. In other words, the sensor 20, taken as an example in this figure, has a measurement range the upper limit of which is 1000 mbar. For this reason, the values returned by this sensor in these horizontal portions are limited to 1000 mbar. In these horizontal portions 25a, it is generally said that the sensor saturates, that it is saturated or is in a state of saturation.

Thus, the problem arising from the measurements taken by such a sensor 20 resides in the fact that, when the latter is in a saturated state, it is no longer possible to know or to estimate the real pressure drop generated by the filter. with particles. The only indication that can be deduced from this is that the pressure drop is greater than the maximum limit value 25 of the measurement range of this sensor. To compensate for this incomplete information, the present invention proposes a solution which is in particular based on the characteristics illustrated by the graph in FIG. 3.

FIG. 3 represents the characteristics of a particle filter 19 in six different states. Each of these states is representative of the capacity of the filter to fulfill its primary function, namely to filter fine particles in exhaust gases. This capacity therefore depends on the physical state in which the particulate filter 19 is located. This state or capacity is quantified by what will be called, in the remainder of this description, the rate or degree of efficiency 29 of the particle filter 19. This degree of efficiency can for example be expressed as a percentage in a ratio between the current or current efficiency of the particle filter compared to its efficiency when it is new. In FIG. 3, the pressure drop characteristics ΔΡ as a function of the flow rate Q of a particle filter 19 are shown for six different degrees of efficiency 29, noted 29a to 29f.

The first degree of efficiency 29a corresponds to that of a new and empty particle filter 19. In this case the degree of efficiency 29a is 100%. The second degree of efficiency 29b corresponds to that of an aged and empty particle filter 19. The degree of efficiency 29b could typically be quantified at 95%. The third degree of efficiency 29c illustrated as an example in this figure is that of a new and charged particle filter and amounts to 70%. The fourth degree of efficiency 29d is quantified at 60% and corresponds to an aged and charged particle filter. The fifth degree of efficiency 29e is representative of a new and clogged particulate filter which can correspond to a value of 40%. Finally, the last degree of efficiency 29f illustrated here is that of an aged and clogged particle filter. In the latter case, the degree of efficiency 29f is zero and therefore corresponds to 0%. Of course, there are a multitude of intermediate degrees of efficiency between 0% and 100% which each correspond to a different physical state of the particulate filter.

In the example given by the graph in FIG. 3, each degree of efficiency 29 is illustrated by a first function fi based on the flow rate Q of exhaust gas and on the pressure drop ΔΡ measured by a sensor, typically by the sensor 20. The flow rate Q preferably being the volume flow rate of the gases having to pass through or having passed through the particle filter 19. The function fi can be expressed by the expression fi (Q, ΔΡ). Thus, for each state or degree of efficiency 29 of the particle filter, there is the expression Efficiency = fi (Q, ΔΡ). As shown in this FIG. 3, the function fi is typically a linear function whose slope is representative of the degree of efficiency 29 of the particle filter. The lower the slope, the better the efficiency of the filter. Consequently, the more the slope of this function increases, the more the physical state of the particulate filter degrades.

The degrees of efficiency 29 can, for example, be determined empirically and be the subject of graphs, such as that of FIG. 3, of charts or tables of values which can then serve as a basis of information for an automated system. Indeed, these graphs, charts or tables of values could be modeled in the form of programs, algorithms or databases accessible or used by an automated system, such as software or a logic circuit, in order to be able to extract information from them. from input data. For example, by knowing as input data the value of the flow rate Q and that of the pressure drop ΔΡ of a particle filter in an instant, it becomes possible to find the degree of efficiency of this particle filter at this point. instant using the information illustrated in FIG. 3 and in this case the first function fi (Q, ΔΡ).

Furthermore, it is assumed that the state of the particle filter remains constant in the time interval that each horizontal portion 25a illustrated in FIG. 2 lasts. In other words, it is assumed that the degree of efficiency 29 of the particulate filter remains constant between a first instant when the sensor 20 reaches the maximum limit value 25 of its measurement range and a second instant when this sensor is again able to return in response to its measurements a value below this maximum limits 25.

Thus, the solution of the present invention in particular suggests being able to estimate the pressure drop values during the time intervals corresponding to the horizontal portions 25a, namely during the time intervals when the sensor 20 is in a saturated state. To do this, the solution of the present invention is based on the one hand on the aforementioned assumption and on the other hand on the three characteristics, which are the degree of efficiency 29, the flow rate Q and the pressure drop ΔΡ, which are linked to each other for a particle filter at a given time.

Indeed, if from the flow Q and the pressure drop APc, measured respectively by the flow meter 8 and the sensor 20, it is possible to determine the degree of efficiency 29 by means of the first function fi (Q, ΔΡ ) as shown by the various illustrations of this function fi in FIG. 3, conversely it is then also possible to determine the pressure drop ΔΡ as a function of the flow rate Q and of a certain degree of efficiency 29, more particularly the current (or also commonly used) degree of efficiency of the particulate filter. Since, according to the aforementioned hypothesis, this degree of efficiency 29 does not change between the moment when the sensor 20 reaches the maximum limit value 25 and the first subsequent instant when it leaves its state of saturation, then it determining the degree of efficiency 29 of the particle filter before, preferably just before, the sensor 20 goes into a saturated state, it is possible to determine the estimated pressure losses (denoted ΔΡε) during each time interval l 'saturation state of the sensor 20. To do this, the function that should be used in this case is a second function that we will denote by f2 (Q, Efficiency) and which be expressed by the expression ΔΡε = f2 (Q, Efficiency). In general, we can consider that the second function is the inverse of the first.

Figure 4 is a figure comparable to Figure 3 but to which have been added the pressure drop estimates ΔΡε determined from the second function mentioned above. These estimates appear above each of the horizontal portions 25a and are illustrated by the estimation curve 22 drawn in dotted lines. For comparison with the real pressure drop values, this estimation curve 22 is compared with the real curve 23 of the pressure drop. It will thus be appreciated that the information gain in terms of pressure drop provided by the estimation curve 23 relative to the measured curve 21 in the areas where the sensor 20 is in a saturated state.

On the basis of the above, the first object of the present invention relates to a method making it possible to determine or estimate the pressure drop generated by a particulate filter at any time or continuously, namely including in the time intervals in which the sensor 20 is in a so-called saturated state. More particularly, this method refers to a control method for a heat engine 10, based on the estimation of the pressure drop generated by the particle filter 19 coupled to this heat engine 10. This method comprises the following steps:

- an estimate of the pressure drop by means of the sensor 20, which is configured to be able to measure a pressure drop up to a maximum limit value 25, and

- a control of an actuator 5 of the heat engine 10 as a function of the estimated pressure drop.

According to the invention, the step for estimating the pressure drop further comprises the following steps:

- the measurement of the current flow rate Q of exhaust gases,

- comparison of the pressure drop measured ΔΡο by the sensor 20 with the maximum limit value 25.

From this comparison result the following two cases:

First scenario:

1) If the pressure drop ΔΡο measured is less than the maximum limit value 25, then we are in the case where the sensor 20 is not in a saturated state. In this case, we determine:

a) the pressure drop estimated ΔΡε as being derived from the pressure drop ΔΡο measured by the sensor 20, and

b) the degree of efficiency 29 of the particulate filter 19 by means of the first function fi based on the current flow rate Q of exhaust gas and the pressure drop ΔΡο measured by the sensor 20.

Second scenario:

2) If the pressure drop ΔΡο measured is greater than or equal to the maximum limit value 25, then we are in the case where the sensor 20 is in a saturated state. In this case, we determine:

a) the estimated pressure drop ΔΡε by means of the second function f2 based on the current flow rate Q of exhaust gas or air and on a previously determined degree of efficiency. The degree of efficiency previously determined is preferably the last degree of efficiency 29 which has been able to be determined so far.

Preferably, this last degree of efficiency 29 or previously determined degree may have been noted in different ways, the simplest being able to be to memorize this value, for example by means of a register or a memory such as a memory. long live for example. This embodiment could be replaced by an index placed in a table of values, in particular next to a value corresponding to the state or the degree of efficiency that one wishes to temporarily memorize. Whatever the variants used to find the value corresponding to this last degree of efficiency (or at least degree of efficiency previously determined), electronic voice will be preferred, which has the advantage of being reliable, easy to implement and therefore inexpensive.

According to the preferred embodiment and as illustrated in FIG. 3, the functions used are linear functions. Typically the first function h is a linear function corresponding to the flow rate Q current of exhaust gas the pressure drop ΔΡο measured by the sensor 20. Advantageously, said degree of efficiency 29 can then be easily determined from the slope that gives this first linear function fi. Therefore, it is easily possible to calculate by calculation the value of the degree of efficiency corresponding to such a function which can just as easily be determined by means of the two current values of gas flow and pressure drop .

In one embodiment, the degree of efficiency 29 of the particle filter is determined at all times. As a variant, this degree of efficiency is determined only if the difference between the maximum limit value 25 and the pressure drop ΔΡο measured by the sensor is less than a threshold value 26, illustrated by way of example in FIG. 4. In a similar variant, one could imagine that the degree of efficiency 29 is determined only if the pressure drop APc measured by the sensor 20 is greater than a threshold value 26 'situated below the maximum limit value 25. L' importance of the withdrawal of the level of the threshold value 26 'relative to that of the maximum limit value 25 could be a predetermined constant or a configurable value.

In the first case mentioned above, namely in the case where the measured pressure drop APc is less than said maximum limit value 25, it has been mentioned that the estimated pressure drop APe is derived from the pressure drop APC measured by the sensor 20. In this first case, the estimated pressure drop APe is preferably directly derived, more particularly equal to the pressure drop APc measured by the sensor 20.

With reference to FIG. 5, this represents, in the form of a schemabloc, the process for determining or estimating the estimated pressure drop APe according to the invention. This block diagram shows in particular the constituent elements which make it possible to implement the method of the present invention, according to any one of its variants.

In this FIG. 5, it is noted that different parameters P, denoted P1, P2, ... Px, can be introduced, just like the pressure drop APc measured by the sensor 20, as input data in a first unit 31. This first unit 31 is typically a logic unit which is configured to be able to determine the degree of efficiency 29 of the particle filter 19 from the first function h (Q, APc) and in particular from the relationship Efficiency = fi (Q, APc). Thus, at least one of the parameters P will refer to the flow rate Q which can be measured or determined by an appropriate device, such as the flow meter 8 illustrated in FIG. 1.

The pressure drop APc measured by the sensor 20 (namely the current pressure drop) is also introduced as input data into a comparator 33. The latter also acquires as second input data the maximum limit value 25, denoted APm with the index m set for the maximum term. As a variant, this maximum limit value 25 could be permanently predefined in the comparator 30 instead of being entered as input data. The comparator 33 is configured to compare the pressure drop measured APc by the sensor 20 with the maximum limit value 25. The result of this comparison can be of different forms. It can be a numerical value equivalent to this difference or a binary value of type 1 or 0 respectively representative of a true or false result. The value of this result is contained in the variable X from the comparator 33. This result or this value X is routed in a first logical entity 34 and in a second logical entity 35. The first logical entity 35 also receives the value corresponding to the degree efficiency 29 which was determined by logic unit 31.

The first logical entity 34 integrates a memory M or at least has access to such a memory. This memory stores at least one previously determined degree of efficiency 29, preferably the last degree of efficiency 29 which could have been calculated by the logic unit 31 when the sensor 20 was in an unsaturated state. Thus, the first logical entity 34 is able to determine, by virtue of the value X, whether the sensor 20 is currently in a saturated state or not. In the case where the value X is 0, the sensor 20 is not in a saturated state and the degree of efficiency 29 which will result from this first logical entity 34 will be the current degree of efficiency 29 as it has could have just been determined by the logical unit 31. On the other hand, if the value of X is 1, the sensor 20 is in a saturated state and the degree of efficiency 29 originating from the first logical entity 34 will correspond to said degree d efficiency previously determined which has been stored in memory M, which will preferably be the last degree of efficiency 29 determined and stored in this memory.

Whatever the age of the degree of efficiency 29 originating from the first logical entity 34, this degree of efficiency 29 will be introduced into a second logical unit 32 with at least some of the parameters P mentioned above. Among these parameters P, it will be noted that the current flow Q is one of the values introduced into the second logic unit 32. The latter is therefore configured to be able to determine the estimated pressure drop ΔΡε from the second function f2 (Q, Efficiency) and in particular of the relation ΔΡε = f2 (Q, Efficiency).

The value of this estimated pressure drop ΔΡε is introduced, together with the value X and the value ΔΡο, into the second logical entity 35. The latter can then be configured to give, in response to these input values, either the value APc if the value of X is 0 (sensor 20 unsaturated), or the value ΔΡε if value of X is 1 (sensor 20 saturated).

The entire process shown diagrammatically in FIG. 5 can advantageously be implemented by software programming steps or by flip-flops and / or other electronic or logic components which may be part of a printed circuit for example. Such a circuit or software could be implemented in a motor control such as the actuator 5.

The second object of the present invention relates to a heat engine 10 configured to be controlled by any of the embodiments of the method described above. To do this and as illustrated in FIG. 1, the heat engine 10 can be controlled by an actuator 5 configured according to this method.

Finally, the last object of the present invention relates to a motor vehicle comprising a heat engine 10 according to the second object mentioned above.

Although the objects of the present invention have been described with reference to specific examples, various obvious modifications and / or improvements could be made to the embodiments described without departing from the spirit and scope of the invention. invention defined by the appended claims.

Claims (10)

1. Control method for a heat engine (10) based on the determination of a pressure drop (ΔΡ) generated by a particle filter (19) coupled to said heat engine (10), the method comprising the following steps: - estimation of said pressure drop by means of a sensor (20) configured to be able to measure a pressure drop (APc) up to a maximum limit value (25), - control of an actuator (5) of the heat engine (10) as a function of the estimated pressure drop (ΔΡε), characterized in that the step of estimating the pressure drop further comprises: - measurement of a flow rate (Q) of exhaust gas, - comparison of the pressure drop (APc) measured by the sensor (20) with said maximum limit value (25), and - if the pressure drop (APc) measured is less than said maximum limit value (25), then the method comprises the following sub-steps: - determination of the estimated pressure drop (ΔΡε) from the pressure drop (ΔΡο) measured by the sensor (20), and - determination of a degree of efficiency (29) of the particle filter, to be able to filter said particles, by means of a first function (fi) based on the flow rate (Q) of exhaust gas and the pressure drop (APc) measured by the sensor (20), - if the pressure drop (APc) measured is greater than or equal to the maximum limit value (25)), then the method comprises the following sub-steps: - determination of the estimated pressure drop (ΔΡε) by means of a second function (f2) based on the current flow rate (Q) of the exhaust gas and on a degree of efficiency (29) previously determined. 2. Method according to claim 1, characterized in that the first function (fi) is a linear function making correspond to the flow (Q) current of exhaust gas the pressure drop (ΔΡο) measured by the sensor (20), and in that said degree of efficiency (29) is determined from the slope of the linear function. 3. Method according to one of the preceding claims, characterized in that the degree of efficiency (29) of the particulate filter (19) is only determined if the difference between the maximum limit value (25) and the loss of load (ΔΡο) measured by the sensor (20) is less than a threshold value (26). 4. Method according to one of the preceding claims, characterized in that in the case where the pressure drop (ΔΡο) measured is less than said maximum limit value (25), the estimated pressure drop (ΔΡε) is determined to be equal to the pressure drop (ΔΡο) measured by the sensor (20). 5. Method according to one of the preceding claims, characterized in that said sensor (20) is a sensor configured to determine a pressure variation (ΔΡ) between the upstream and downstream of the particulate filter (19). 6. Method according to one of the preceding claims, characterized in that said previously determined degree of efficiency (29) is stored in a register or a memory (M). 7. Method according to one of the preceding claims, characterized in that the current flow rate (Q) is determined upstream of the particle filter (19). 8. Method according to one of the preceding claims, characterized in that the current flow rate (Q) of exhaust gas is a volume flow rate. 9. Heat engine (10) controlled according to the method of any one of claims 1 to 8. 10. Motor vehicle comprising a heat engine (10) according to claim 9.