EP3420213B1 - Method for controlling the combustion of a combustion engine by way of an immediate load reduction method - Google Patents

Description

The present invention relates to a method of controlling the combustion of a heat engine by a method of immediate load reduction. The invention finds a particularly advantageous, but not exclusive, application in the field of motor vehicles equipped with a petrol-type heat engine.

Anti-pollution standards and the desire to limit the consumption of internal combustion engines as much as possible lead automobile manufacturers to produce low-displacement internal combustion engines with a decreasing number of cylinders (a trend known as "downsizing" in English). Also, to maintain a level of performance equivalent to that of a higher displacement engine, the engine must operate on operating points with a high rate of air filling in the cylinders.

This is favorable to the appearance of abnormal combustions for which the air / fuel mixture ignites at a location different from that initiated by the spark plug controlled. The mixture can ignite before the spark by candle (we speak then of "rumble" in English) or after the spark with candle (we speak then of "rumble" late). In addition, this type of abnormal combustion has the ability to self-maintain, that is to say that in case of appearance of "rumble" on a cylinder during an engine cycle, the following cycle may also see the same phenomenon.

The "rumble" generates vibrations called "rumble blows" in the following description associated with a thud in the combustion chamber constituting an inconvenience for the driver, with a high risk of engine failure. These vibrations have a frequency between 600 Hz and 1200 Hz. These vibrations are transmitted from the combustion chamber to the connecting rods and the crankshaft (unlike rattling, whose vibration between 5000 Hz and 15000 Hz is felt only in the chamber combustion). The "rumble" is caused by an increase in pressure in the combustion chamber, as well as an ignition too early or multiple hot spots in the combustion chamber.

A curative treatment process exists with the aim of eliminating the phenomenon of "rumble" when it appears.

This process consists of detecting abnormal combustions via an accelerometer placed on the engine block, then cutting the injection on the affected cylinders to remove the "rumble". In the event that the "rumble" persists, the method applies a load limitation on a driving cycle over the entire engine field. Such a process is disclosed in the document FR 2 942 006 , as well as in the document EP 2,662,216 .

The load limitation on a driving cycle, carried out during a series of one or more successive runs without resetting the engine computer (or "driving-cycle" in English), is a load limitation whose objective is to disappearance of the "rumble" phenomenon originating from reversible causes, for example in the case of fouling of the combustion chamber, and / or irreversible, for example during an engine part breakage. The load limitation is based on a slow dynamic rumble counter (several minutes or even several taxiings) and this load limitation is calculated by a map calibrated according to a number of injection cuts made.

However, the load limitation carried out on a driving cycle has several drawbacks. In particular, its action is not immediate since it is based on a slow dynamic "rumble" counter. In addition, the level of load limitation is a function of the number of injection cuts, which is not always representative of the number of "rumble" shots sustained. This level of limitation is therefore not adapted to what is necessary. In addition, by acting as a second curative action of "rumble", these load limitations have a reduced effectiveness insofar as the first curative action (injection cut) is effective in removing the "rumble", although that posing a problem of feeling for the driver (jolts, noise).

• une étape de détection de combustions anormales générant des vibrations dans un cylindre appelées "coups", les vibrations ayant une fréquence comprise entre 600 Hz et 1200 Hz,
• une étape de calcul d'une limitation de charge en fonction notamment, dans un plan régime/charge, d'une courbe d'iso-probabilité d'apparition de coups suite à la détection, courbe calibrée de sorte que la probabilité d'apparition de coups soit nulle ou très proche de zéro, et
• une étape d'application de la limitation de charge de manière à faire fonctionner le moteur thermique dans le plan régime/charge à des points de fonctionnement minimisant le risque de voir apparaître des coups,

cette étape de calcul d'une limitation de charge comprenant:

• une étape de calcul d'une limitation de charge de base à partir d'une courbe d'iso-probabilité d'apparition de coups translatée au niveau d'un point régime/charge d'apparition du premier coup,
• une étape de calcul d'une baisse de charge minimum réalisable en se basant sur un point régime/ charge courant,
• une étape de calcul d'une baisse de charge maximum réalisable en se basant sur un point régime/charge courant,
• une étape de calcul d'une charge minimum admissible, et
• une étape d'arbitrage entre la charge minimum admissible, la limitation de charge de base et les baisses de charge minimum et maximum précédemment calculées, et
• une étape d'application de ladite limitation de charge de manière à faire fonctionner ledit moteur thermique dans le plan régime/charge à des points de fonctionnement minimisant le risque de voir apparaître des coups.

The invention aims to effectively remedy these drawbacks by proposing a method for controlling the combustion of a heat engine, characterized in that the method comprises:

• a step of detecting abnormal combustions generating vibrations in a cylinder called "strokes", the vibrations having a frequency between 600 Hz and 1200 Hz,
• a step of calculating a load limitation as a function in particular, in a speed / load plan, of an iso-probability curve of appearance of strokes following detection, curve calibrated so that the probability of appearance of strokes either zero or very close to zero, and
• a step of applying the load limitation so as to operate the engine in the speed / load plane at operating points minimizing the risk of seeing blows appear,

this step of calculating a load limitation comprising:

• a step of calculating a base load limitation from an iso-probability curve of appearance of strokes translated at a speed / appearance point of charge on the first strike,
• a step of calculating a minimum load drop achievable based on a current speed / load point,
• a step of calculating a maximum load drop achievable based on a current speed / load point,
• a step of calculating a minimum admissible load, and
• an arbitration step between the minimum admissible load, the base load limitation and the previously calculated minimum and maximum load reductions, and
• a step of applying said load limitation so as to operate said heat engine in the speed / load plane at operating points minimizing the risk of seeing blows appear.

The invention thus allows rapid elimination of abnormal combustions in the heat engine without damaging the driving pleasure, insofar as the invention is implemented from the first blows of "rumble" and applies a level of load limitation corresponding to the just necessary to make disappear the phenomenon of "rumble" without requiring cuts of injection. In addition, the invention has the advantage of being inexpensive, since it can be integrated by software development into the engine control unit without adding any additional components.

• l'étape de calcul de la limitation de charge est réalisée lorsqu'apparaît un premier coup, et
• l'étape d'application de la limitation de charge est réalisée après N coup détectés en fonction d'une translation de la courbe d'iso-probabilité au niveau d'un point régime/charge correspondant au premier coup détecté.

According to one implementation:

• the step of calculating the load limitation is carried out when a first stroke appears, and
• the step of applying the load limitation is carried out after N detected strokes as a function of a translation of the iso-probability curve at a speed / load point corresponding to the first detected strike.

According to one implementation, the step of calculating the minimum load drop achievable requires the load limitation to be less than a load carried out during a request for application of the load limitation.

According to one implementation, the step of calculating the maximum achievable load reduction consists in determining a maximum variation in load reduction which cannot be exceeded during a request for application of the load limitation for reasons of 'approval.

According to one implementation, the step of calculating the minimum admissible load consists in introducing a torque threshold below which it is not possible to descend. This is to avoid operating the heat engine in an insufficient load area, for example not ensuring a take-off of the vehicle.

Où:

• C2 est la limitation de charge basée sur le premier coup,
• Del_min est le delta de baisse de charge minimum réalisable en se basant sur un point régime/charge courant,
• Del_max est le delta de baisse de charge maximum réalisable en se basant sur un point régime/charge courant,
• S_min est le seuil de charge minimum admissible.
• MIN est la fonction sélectionnant le minimum parmi deux valeurs,
• MAX est la fonction sélectionnant le maximum parmi deux valeurs.

According to one implementation, the arbitration step for determining the load limitation is carried out according to the following formula: $$\mathrm{Lim}\_\mathrm{ChCs}=\mathrm{MAX}\left(\mathrm{S}\_\min ;\mathrm{MIN}\left(\mathrm{Of\; the}\_\max ;\mathrm{MAX}\left(\mathrm{Of\; the}\_\min ;\mathrm{VS}2\right)\right)\right)$$

Or:

• C2 is the load limitation based on the first hit,
• Del_min is the minimum load drop delta achievable based on a current speed / load point,
• Del_max is the maximum load drop delta achievable based on a current speed / load point,
• S_min is the minimum admissible load threshold.
• MIN is the function selecting the minimum from two values,
• MAX is the function selecting the maximum from two values.

The invention also relates to an engine computer comprising a memory storing software instructions for the implementation of the combustion control method of a heat engine as defined above.

The invention also relates to a heat engine comprising such an engine computer.

The invention also relates to a vehicle equipped with such an engine.

The invention will be better understood on reading the description which follows and on examining the figures which accompany it. These figures are given only by way of illustration but in no way limit the invention.

The figure 1 is a functional schematic representation of a system according to the present invention implementing different types of actions to remedy abnormal combustions of the "rumble"type;

The figure 2 is a schematic representation of the steps of the control method according to the present invention making it possible to obtain an immediate load drop of the heat engine following the detection of "rumble"strokes;

The figure 3 is a schematic representation of an improved implementation of the method for limiting the immediate load of the heat engine according to the present invention;

The figure 4 represents curves in a speed / load plan illustrating a basic implementation of the immediate load limitation method according to the present invention;

The figure 5 to 8 represent curves in a speed / load plan illustrating life situations in which the basic implementation of the immediate load limitation method according to the invention has drawbacks;

The Figures 9 to 16 represent curves in a speed / load plan illustrating life situations in which the improved implementation of the load limitation method according to the present invention overcomes the drawbacks of the Figures 5 to 8 .

The figure 1 functionally illustrates a system 10 implementing a combustion engine combustion control method which can be fitted to a vehicle, this method making it possible to deal with a phenomenon known as "rumble" where the air / fuel mixture ignites at a place different from that initiated by the spark plug controlled. The mixture can ignite before the spark with the candle or after the spark with the candle (this is called late rumble).

The "rumble" generates vibrations, called "rumble" shots 101 in the following description, associated with a thud in the combustion chamber constituting an inconvenience for the driver, with a high risk of engine failure. These vibrations have a frequency between 600 and 1200 Hz. These vibrations are transmitted from the combustion chamber to the connecting rods and the crankshaft (unlike rattling, whose vibration between 5000Hz and 15000Hz is only felt in the combustion chamber) .

The "rumble" phenomenon generally appears in an engine speed zone of between 1000 and 3000 rpm and with high air filling, for example following the actuation of a turbocharger.

The rumble 101 shots are detected by means of a sensor 100 mounted on the engine block. This sensor 100 is also used to detect the rattling of the engine.

Among the actions likely to be implemented, there is an action 104 of preventive type consisting in avoiding the appearance of the "rumble" and actions 102, 103 of curative type aimed at treating the "rumble" following its appearance.

The preventive action 104 notably consists in limiting the load of the engine Lim_ChE as a function of a level of fouling of the combustion chamber.

Among the curative actions 102, 103, there is a set of curative actions 102, called immediate, and a set of curative actions 103 carried out on a driving cycle ("driving-cycle" in English) corresponding to a series one or more successive trips without resetting an engine control unit. For the immediate curative actions 102, the time scales, in particular the duration of monitoring before activation of the curative action 102, are very short, of the order of a few Top Dead Center (or TDC) or even a few seconds. For the curative actions 103 carried out on a driving cycle, the time scales, in particular the duration of monitoring before activation of the curative action 103, are longer than for the immediate curative actions 102, of the order of several minutes.

The curative actions 102, 103 could consist of a load limitation allowing the thermal engine to be brought back to a point of operation with unfavorable filling to the "rumble" (from a few filling points to full atmospheric load). The feeling for the driver then varies from almost zero feeling to a noticeable loss of performance. In the case of curative actions 103 carried out on a driving cycle, the load limitation Lim_ChR is applied temporarily when the causes of the "rumble" are reversible, for example in the event of fouling of the combustion chamber, or else of permanently Lim_ChI when the causes of the "rumble" are irreversible, for example when the engine part breaks. In the case of immediate curative actions 102, a current load limit Lim_ChC is configured which has a rapid effect with a level of limitation located just enough to make the "rumble" disappear. To this end, the drop in load Lim_ChC is determined from the use of the iso-probability curve for the appearance of the "rumble".

Activation of a specific fuel enrichment R_Spe makes it possible to cool the air / fuel mixture. Indeed, according to a new enrichment instruction, fuel is added to the air / fuel mixture so as to cool this mixture. This has the effect of improving the thermal conditions in the combustion chamber to reduce the risk of occurrence of the "rumble". This action R_Spe, quick to implement, presents no feeling for the driver, except for a very small increase in its fuel consumption.

The modification of injection patterns R_Inj associated with specific advance settings allows enough fuel to be injected into the cylinder to allow mixing with the air without, however, risking self-ignition. Thus, part of an amount of fuel to be injected is injected during an engine cycle during an intake phase and the remaining part of the amount of fuel during a combustion phase. This R_Inj action has no impact on the driver.

The C_Inj injection cut-off cuts off the fuel supply inside the combustion chamber of a cylinder in which the "rumble" appears. The combustion is therefore no longer done and the "rumble" ceases. This action C_Inj has the consequence of causing a feeling of jerk for the driver and is therefore generally implemented as a last resort.

A method 106 makes it possible to limit the load on the engine as a function of an advance efficiency at maximum ignition or a variation in advance at maximum ignition, referenced in both cases Lim_Low, minimizing the risk of appearance of rattling and the "rumble" phenomenon while taking into account an octane number of the fuel. The method 106 also makes it possible to limit the knocking Lim_Cli.

The invention presents a process for reducing the immediate current load Lim_ChC implemented by the system 10 and aiming to protect the heat engine from the "rumble" phenomenon. The immediate current load reduction Lim_ChC intervenes among the first curative actions before the injection cut-off C_lnj.

This immediate current load reduction process Lim_ChC is based on the notion of iso-probability curve C1 of appearance of "rumble" shots 101 in the speed / load plan (with R for the speed and Ch for the load - cf. . figure 4 ). By identifying a speed / load point P used during a first "rumble" 101 stroke, a load limitation is applied which is consistent with this iso-probability curve C1 of "rumble". Its action is immediate and the level of load limitation is just necessary to remove the "rumble". Below the curve C1, the probability of the appearance of the "rumble" is zero, or very close to zero (less than 5%). It depends on the way to calibrate this curve C1, and therefore on the acceptability of seeing "rumble" appear.

More specifically, as illustrated in the figure 2 , the iso-probability curve C1 of the appearance of the "rumble" is calculated Cal_C1 by a mapping as a function of the engine speed R. When a first stroke of the "rumble" 101 is counted by the sensor 100, a manager of the "rumble"", integrated for example in the engine ECU, issues a recording command Enr_P of the speed / load point P. The applicable load limitation Lim_ChC is then calculated via the Cal_C2 module by translation of the iso-probability curve C1 of appearance of the "rumble" at the speed / load point P recorded. A load limiting curve C2 is then obtained (cf. figure 4 ). A configurable safety margin is applied and the calculation of this margin is carried out by a map depending on the engine speed R.

When an N ^th stroke of "rumble" 101 appears, the "rumble" manager issues an order for applying the load limitation Lim_ChC. A time delay is applicable between the issuance of the application order and the completion of the action. This time delay is configurable, and can be zero. When the rumble manager issues an order to cancel the load limitation Lim_ChC, the maximum load level returns to its nominal level in a progressive manner, for example along a linear slope. A time delay is applicable between the issuance of the cancellation order and the completion of the cancellation, and this configurable time delay can be zero.

The control process thus allows a speed of the intervention because this load limitation Lim_ChC intervenes from the first blows of "rumble" 101. Its effect is immediate or almost immediate in the case of a short time delay. The level of load limitation being based on the first hit of "rumble" 101 detected, it corresponds to the reality of the engine and is not set in an excessively safe manner.

The method of implementing the process according to the figures 2 and 4 works correctly when the "rumble" appears in a situation of average acceleration of the heat engine. However, in the case of a weak or zero acceleration situation, of a decreasing load situation during the rise in R regime (for example, neck descent), or in the case of a very strong situation acceleration, the previously described method has drawbacks.

Thus, when the variation of the load Ch over the speed range R considered is less than the variation of the iso-probability curve C1 of appearance of the "rumble" over the same speed range R, the limitation curve of C2 charge obtained does not prevent the driver from returning to the potential "rumble" area. Indeed, as this is depicted on the figure 5 , the 3 ^rd and 4 ^th rumble shots, represented by stars, are in an area that the load limitation does not prevent from exploiting.

As shown in the figure 6 , when the load Ch decreases during the rise in speed R, the N ^th stroke of "rumble" 101 is in a less loaded zone than the 1 ^st stroke representing the calculation base Cal_C2 of the load limitation curve C2. Thus, the Lim_ChC load limitation is systematically found above these operating points where the "rumble" has appeared, and does not prevent the engine from operating a potential "rumble" area.

As shown in the figure 7 , when the load Ch increases very sharply during the rise in speed R, the N ^th blow of the "rumble" 101 is in a zone very far from the load limitation curve C2. When the Lim_ChC load limitation request is issued by the rumble manager, the load drop is too great (felt by the driver).

As shown in the figure 8 , when the load Ch is very low at the time of the request to drop the load, the N ^th stroke of "rumble" 101 may be in a zone very close to the minimum admissible load. The load limitation Lim_ChC which follows would bring the load below the minimum admissible level. This minimum load makes it possible, for example, to take off the vehicle when it is stationary.

To this end, the calculation of the load limitation Lim_ChC is not based solely on the engine speed / load point P during the ^1st "rumble" hit 101 but is also based on a current point when requesting application of load reduction Lim_ChC by the "rumble" manager.

• une étape de calcul de la limitation de charge Cal_C2 de base à partir de la courbe d'iso-probabilité C1 d'apparition de coups translatée au niveau du point régime/charge P d'apparition du premier coup,
• une étape de calcul d'une baisse de charge minimum réalisable en se basant sur un point régime/charge courant Cal_min,
• une étape de calcul d'une baisse de charge maximum réalisable en se basant sur un point régime/charge courant Cal_max,
• une étape de calcul d'une charge minimum admissible Cal_S_min, et
• une étape d'arbitrage entre la charge minimum admissible, la limitation de charge de base et les baisses de charge minimum et maximum précédemment calculées.

The introduction of new functionalities in the immediate current load reduction process Lim_ChC allows a consistent calculation of the applicable load limitation Lim_ChC so as to protect the heat engine in all phases of the life of the heat engine. For the cases mentioned above, the immediate current load reduction method Lim_ChC implemented by an improved control method further comprising a series of functionalities, the whole of which ensures the management of load limits in all phases of engine life thermal. For this, the determination of the applicable load limitation Lim_ChC, based on the diagram of the figure 3 includes:

• a step of calculating the basic load limitation Cal_C2 from the iso-probability curve C1 of appearance of strokes translated at the speed / load point P of appearance of the first strike,
• a step of calculating a minimum load drop achievable based on a current speed / load point Cal_min,
• a step of calculating a maximum drop in load achievable based on a current speed / load point Cal_max,
• a step of calculating a minimum admissible load Cal_S_min, and
• an arbitration step between the minimum admissible load, the base load limitation and the previously calculated minimum and maximum load reductions.

In the case of the calculation of the minimum achievable load drop Cal_min, a minimum load drop delta Del_min is introduced which must be carried out by the process when the application of the load limit Lim_ChC is applied by the "rumble" manager. The presence of this minimum delta Del_min forces the load limit to be lower than that achieved during the application request. This is useful in cases of load increasing slightly or zero, or decreasing during the rise in R regime. In these cases, as described above, the load limitation based on the ^1st stroke of "rumble" 101 would be greater than the charge carried out during the application request. The load drop delta Del_min would then be negative (because in the direction of the load increase). We then take into account a maximum between the load drop delta Del_Pre towards the load limit C2 based on the ^1st stroke of "rumble" 101 and the minimum load drop delta Del_min, which in this case is the delta of minimum load drop Del_min, as is well represented on the figure 9 .

In the nominal case of a moderate load growth during the R rise, the maximum will always be the delta of load drop Del_Pre towards the load limitation C2 based on the ^1st stroke of "rumble", as illustrated on the figure 10 . This part of the process can be inhibited by calibration. The minimum delta Del_min is calculated by a map indexed in engine speed R.

In the case of the calculation of the maximum achievable load drop Cal_max, a maximum delta of achievable load drop Del_max is introduced that can be carried out by the process when the application of the load limitation Lim_ChC by the "rumble" manager . Indeed, for reasons of approval, it is not admissible to lower the load too much. This is useful in the case of a strongly increasing load during the rise in engine speed R. A maximum is taken into account between the load drop delta Del_Pre towards the load limitation C2 based on the ^1st rumble hit 101 and the maximum load drop delta Del_max, which in this case is the maximum load drop delta Del_max, as is well represented on the figure 11 .

In the nominal case of a moderate load growth during the rise in R speed, the minimum will always be the delta of load drop Del_Pre towards the load limitation C2 based on the ^1st stroke of "rumble", as illustrated on the figure 12 . In addition, this part of the process can be inhibited by calibration and the maximum delta Del_max is calculated by a map indexed in engine speed R.

In the case of the calculation of the minimum admissible load Cal_S_min, a threshold S_min is introduced below which it is not possible to descend in order to avoid entering an area of insufficient load (for takeoff for example). This threshold S_min is calculated by a map indexed in engine speed R.

Où:

• C2 est la limitation de charge basée sur le 1^er coup de "rumble",
• Del_min est le delta de baisse de charge minimum réalisable en se basant sur un point régime/charge courant,
• Del_max est le delta de baisse de charge maximum réalisable en se basant sur un point régime/charge courant,
• S_min est le seuil de charge minimum admissible,
• MIN est la fonction sélectionnant le minimum parmi deux valeurs,
• MAX est la fonction sélectionnant le maximum parmi deux valeurs.

The arbitration between the load limitation curve C2, the maximum load drop delta Del_max, the minimum load drop delta Del_min, and the minimum admissible load Cal_S_min previously described makes it possible to determine the load limit Lim_ChC to be applied to the motor. thermal. Thus, the determination of the load limitation Lim_ChC is carried out according to the following formula: $$\mathrm{Lim}\_\mathrm{ChCs}=\mathrm{MAX}\left(\mathrm{S}\_\min ;\mathrm{MIN}\left(\mathrm{Of\; the}\_\max ;\mathrm{MAX}\left(\mathrm{Of\; the}\_\min ;\mathrm{VS}2\right)\right)\right)$$

Or:

• C2 is the load limitation based on the ^1st rumble hit,
• Del_min is the minimum load drop delta achievable based on a current speed / load point,
• Del_max is the maximum load drop delta achievable based on a current speed / load point,
• S_min is the minimum admissible load threshold,
• MIN is the function selecting the minimum from two values,
• MAX is the function selecting the maximum from two values.

This arbitration ensures the protection of the heat engine in all phases of life. Thus, in a nominal case, the curve C2 based on the ^1st stroke of "rumble" 101 is applied, as is well represented on the figure 13 , and in the event of a load increasing in a weak / null or decreasing way, the curve of minimum delta Del_min is applied, as it is clearly visible on the figures 14 and 15 . In addition, in the event of a strongly increasing load, the maximum delta curve Del_max is applied, as is clearly visible on the figure 16 .

Claims (9)

1. A method for controlling the combustion of a combustion engine, characterized in that said method comprises:

   - a step of detecting abnormal combustions generating vibrations in a cylinder, designated as "knocking" (101), said vibrations having a frequency comprised between 600Hz and 1200Hz,

   - a step of calculating a load limitation (Lim_ChC) as a function in particular, in a speed/load map, of an iso-probability curve (C1) of the occurrence of knocking following said detection, the curve being calibrated such that the probability of the occurrence of knocking is zero or very close to zero, this step of calculating a load limitation (Lim_ChC) including:

   - a step of calculating a base load limitation (Cal_C2) from an iso-probability curve (C1) of the occurrence of knocking translated at the level of a speed/load point (P) of the occurrence of the first knocking,

   - a step of calculating a minimum load decrease (Cal_min) able to be realized by being based on a current speed/load point,

   - a step of calculating a maximum load decrease (Cal_max) able to be realized by being based on a current speed/load point,

   - a step of calculating a minimum admissible load (Cal_S_min), and

   - a step of deciding between the minimum admissible load, the base load limitation and the decreases of minimum and maximum load previously calculated, and

   - a step of application of said load limitation (Lim_ChC) so as to cause said combustion engine to operate in the speed/load map at operating points minimizing the risk of knocking occurring.
2. The method according to Claim 1, characterized in that:

   - the step of calculating the load limitation is realized when a first knocking (101) occurs, and

   - the step of applying said load limitation (Lim_ChC) is realized after N knockings are detected as a function of a translation of the iso-probability curve (C1) at the level of a speed/load point (P) corresponding to the first detected knocking.
3. The method according to one of the preceding claims, characterized in that the step of calculating (Cal_min) the minimum load decrease able to be realized compels the load limitation (Lim_ChC) to be less than a load realized during a request for application of said load limitation (Lim_ChC).
4. The method according to one of the preceding claims, characterized in that the step of calculating (Cal_max) the maximum load decrease able to be realized consists in determining a maximum variation of load decrease not being able to be exceeded during a request for application of the load limitation (Lim_ChC) for reasons of amenity.
5. The method according to one of the preceding claims, characterized in that the step of calculating (Cal_S_min) of the minimum admissible load consists in introducing a torque threshold (S_min) below which is to not possible to fall.
6. The method according to one of the preceding claims, characterized in that the step of deciding for determining said load limitation (Lim_ChC) is realized according to the following formula: $$\mathrm{Lim}\_\mathrm{ChC}=\mathrm{MAX}\left(\mathrm{S}\_\min ;\mathrm{MIN}\left(\mathrm{Del}\_\max ;\mathrm{MAX}\left(\mathrm{Del}\_\min ;\mathrm{C}2\right)\right)\right)$$

   

   where:

   C2 is the load limitation based on the first knocking,

   Del_min is the minimum load decrease delta able to be realized, being based on a current speed/load point,

   Del_max is the maximum load decrease delta able to be realized, being based on a current speed/load point,

   S_min is the minimum admissible load threshold,

   MIN is the function selecting the minimum from two values,

   MAX is the function selecting the maximum from two values.
7. An engine control unit comprising a memory storing software instructions for the implementation of the method for controlling combustion of a combustion engine as defined according to any one of the preceding claims.
8. A combustion engine including an engine control unit according to Claim 7.
9. A vehicle equipped with a combustion engine according to Claim 8.

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