Method for determining the total pressure in the cylinder of an engine

Abstract

A method (45) for determining the total pressure in a cylinder (P.sub.cyl) of an engine as a function of the angular position (crk) of a crankshaft (14) and from a quantity of fuel to be injected in possibly several injections, includes: determining the pressure in the cylinder when there is no combustion, the pressure being called the pressure without combustion (P.sub.cyl.sub._.sub.m), determining, for each injection (inj.sub.i), a curve of sub-variation of pressure (P.sub.comb.sub._.sub.i) caused by the combustion of the fuel quantity injected during the such injection (inj.sub.i), the shape of the curve being estimated as a function of the quantity of fuel to be injected (MF.sub.i) and of the angular position for start of injection (SOI.sub.i) of the corresponding injection, determining the total pressure in the cylinder (P.sub.cyl) by adding together the pressure without combustion (P.sub.cyl.sub._.sub.m) and the pressures given by the pressure sub-variation curves (P.sub.comb.sub._.sub.i) of each injection (inj.sub.i).

Claims

1. A method for determining a total pressure in a cylinder (P.sub.cyl) of an engine as a function of an angular position (crk) of a crankshaft (14) and from a quantity of fuel to be injected in possibly several injections, and for controlling a quantity of fuel injected into the engine, the method comprising: determining the pressure in the cylinder when there is no combustion, said pressure being called the pressure without combustion (P.sub.cyl.sub._.sub.m), determining, for each injection (inj.sub.i), a curve of sub-variation of pressure (P.sub.comb.sub._.sub.i) caused by a combustion of the fuel quantity injected during the injection (inj.sub.i) in question, a shape of the curve being estimated as a function of the quantity of fuel (MF.sub.i) to be injected and of an angular position for start of injection (SOI.sub.i) of the corresponding injection, determining the total pressure in the cylinder (P.sub.cyl) by adding together the pressure without combustion (P.sub.cyl.sub._.sub.m) and the pressures given by the pressure sub-variation curves (P.sub.comb.sub._.sub.i) of each injection (inj.sub.i), adjusting an injector opening duration based on the total pressure of the cylinder.

2. The method as claimed in claim 1, wherein the pressure without combustion (P.sub.cyl.sub._.sub.m) is determined by considering that a compression and an expansion of the gas mixture contained in the cylinder are adiabatic and that said mixture behaves like an ideal gas, said determination being linearly corrected as a function of a cooling temperature (TCO) and of an exhaust gas recirculation rate (EGR).

3. The method as claimed in claim 1, wherein each pressure sub-variation curve (P.sub.comb.sub._.sub.i) is determined by a relationship between a combustion efficiency (), the quantity of fuel to be injected (MF.sub.i), a volume of the cylinder relative to the angular position (crk) of the crankshaft (14), the combustion start slope (.sub.i) of the pressure sub-variation curve (P.sub.comb.sub._.sub.i), an angular position for the start of combustion (SOC.sub.i) of the crankshaft (14), a combustion end slope (.sub.i) of the pressure sub-variation curve (P.sub.comb.sub._.sub.i) and an angular position for the end of combustion (EOC.sub.i) of the crankshaft (14).

4. The method as claimed in claim 3, wherein the combustion efficiency () is determined from a base value (ctse.sub.) which is corrected as a function of a cooling temperature of the fuel (TCO.sub.i) and of a pressure of the fuel (FUP.sub.i) at injection.

5. The method as claimed in claim 3, wherein each combustion start slope (.sub.i) is determined from a base value (ctse.sub.) which is corrected as a function of the quantity of fuel to be injected (MF.sub.i), an exhaust gas recirculation rate (EGR) and a time (T.sub.DIFFi) between a previous injection (inj.sub.i-1) and the corresponding injection (inj.sub.i).

6. The method as claimed in claim 3, wherein the angular position for start of combustion (SOC.sub.i) of the crankshaft is determined by adding together the angular position for start of injection (SOI.sub.i) and a time constant (.sub.i) which is, itself, determined from a base value (ctse.sub.) which is linearly corrected as a function of the quantity of fuel to be injected (MF.sub.i) and of an exhaust gas recirculation rate (EGR).

7. The method as claimed in claim 3, wherein the combustion end slope (.sub.i) is determined by a linear relationship as a function of the angular position for start of injection (SOI.sub.i).

8. The method as claimed in claim 3, wherein the angular position for end of combustion (EOC.sub.i) is determined by a linear relationship between the angular position for start of combustion (SOC.sub.i), a rate of the combustion () and the quantity of fuel to be injected (MF.sub.i).

9. A device for determining a total pressure of an engine cylinder (P.sub.cyl) as a function of an angular position (crk) of a crankshaft (14), comprising: means for determining the pressure in the cylinder when there is no combustion, said pressure being called the pressure without combustion (P.sub.cyl.sub._.sub.m), means for determining, for each injection (inj.sub.i), a curve of sub-variation of pressure (P.sub.comb.sub._.sub.i) caused by a combustion of the fuel quantity injected during the injection (inj.sub.i) in question, a shape of the curve being estimated as a function of the quantity of fuel (MF.sub.i) to be injected and of an angular position for start of injection (SOI.sub.i) of the corresponding injection, means for determining the total pressure in the cylinder (P.sub.cyl) by adding together the pressure without combustion (P.sub.cyl.sub._.sub.m) and the pressures given by the pressure sub-variation curves (P.sub.comb.sub._.sub.i) of each injection (inj.sub.i).

10. A device for controlling a quantity of fuel to be injected into an engine cylinder as a function of the total pressure in the cylinder (P.sub.cyl), comprising a control unit (12) in which the device for determining according to claim 9 is installed.

11. The method as claimed in claim 2, wherein each pressure sub-variation curve (P.sub.comb.sub._.sub.i) is determined by a relationship between a combustion efficiency (), the quantity of fuel to be injected (MF.sub.i), a volume of the cylinder relative to the angular position (crk) of the crankshaft (14), a combustion start slope (.sub.i) of the pressure sub-variation curve (P.sub.comb.sub._.sub.i), an angular position for the start of combustion (SOC.sub.i) of the crankshaft (14), a combustion end slope (.sub.i) of the pressure sub-variation curve (P.sub.comb .sub._.sub.i) and an angular position for the end of combustion (EOC.sub.i) of the crankshaft (14).

12. The method as claimed in claim 4, wherein each combustion start slope (.sub.i) is determined from a second base value (ctse.sub.) which is corrected as a function of the quantity of fuel to be injected (MF.sub.i), an exhaust gas recirculation rate (EGR) and a time (T.sub.DIFFi) between a previous injection (inj.sub.i-1) and the corresponding injection (inj.sub.i).

13. The method as claimed in claim 4, wherein the angular position for start of combustion (SOC.sub.i) of the crankshaft is determined by adding together the angular position for start of injection (SOI.sub.i) and a time constant (.sub.i) which is, itself, determined from a second base value (ctse.sub.) which is linearly corrected as a function of the quantity of fuel to be injected (MF.sub.i) and of an exhaust gas recirculation rate (EGR).

14. The method as claimed in claim 5, wherein the angular position for start of combustion (SOC.sub.i) of the crankshaft is determined by adding together the angular position for start of injection (SOI.sub.i) and a time constant (.sub.i) which is, itself, determined from a second base value (ctse.sub.) which is linearly corrected as a function of the quantity of fuel to be injected (MF.sub.i) and of an exhaust gas recirculation rate (EGR).

15. The method as claimed in claim 4, wherein the combustion end slope (.sub.i) is determined by a linear relationship as a function of the angular position for start of injection (SOI.sub.i).

16. The method as claimed in claim 5, wherein the combustion end slope (.sub.i) is determined by a linear relationship as a function of the angular position for start of injection (SOI.sub.i).

17. The method as claimed in claim 6, wherein the combustion end slope (.sub.i) is determined by a linear relationship as a function of the angular position for start of injection (SOI.sub.i).

18. The method as claimed in claim 4, wherein the angular position for end of combustion (EOC.sub.i) is determined by a linear relationship between the angular position for start of combustion (SOC.sub.i), a rate of the combustion () and the quantity of fuel to be injected (MF.sub.i).

19. The method as claimed in claim 5, wherein the angular position for end of combustion (EOC.sub.i) is determined by a linear relationship between the angular position for start of combustion (SOC.sub.i), a rate of the combustion () and the quantity of fuel to be injected (MF.sub.i).

20. The method as claimed in claim 6, wherein the angular position for end of combustion (EOC.sub.i) is determined by a linear relationship between the angular position for start of combustion (SOC.sub.i), a rate of the combustion () and the quantity of fuel to be injected (MF.sub.i).

Description

(1) Details and advantages of the present invention will emerge more clearly upon reading the following description, with reference to the appended schematic drawings in which:

(2) FIG. 1 is a block diagram illustrating a determining device according to an embodiment of the present invention,

(3) FIG. 2 is a general graph of the pressure in a cylinder as a function of the angular position of the crankshaft according to an exemplary embodiment of the present invention,

(4) FIG. 3 is a validation graph for the present invention, and

(5) FIG. 4 is an activity diagram illustrating a method according to the present invention.

(6) FIG. 1 illustrates the general structure of an embodiment of a determining device 10 for determining the pressure within a cylinder P.sub.cyl in an engine as a function of the angular position crk of a crankshaft 14 of said engine.

(7) FIG. 1 also schematically illustrates the general structure of an embodiment of a device 11 for controlling the quantity of fuel to be injected into said engine cylinder as a function of the pressure in the cylinder P.sub.cyl.

(8) A control device 11 comprises a control unit 12, for example a microprocessor, in which the determining device 10 is installed. The control device 11 receives information from the user through a command 13, for example the vehicle pedals, which information is transmitted to the control unit 12. This information allows for determining the torque required of the engine and thus for managing various blocks such as an injector 15, and optionally an intake valve 16 and an exhaust valve 17. In addition, the control unit 12 comprises a unit 18 arranged to define the quantity of fuel to be injected MF.sub.i into the cylinder for each injection inj.sub.i.

(9) The determining device 10 comprises: a unit 19 arranged to determine, by calculation, a pressure sub-variation curve P.sub.comb.sub._.sub.i corresponding to a combustion for each injection inj.sub.i, a unit 20 arranged to determine, by calculation, the pressure, called the pressure without combustion P.sub.cyl.sub._.sub.m, in the cylinder when there is no combustion, and a unit 22 arranged to determine, by calculation, the pressure in the cylinder P.sub.cyl from the information provided by the aforementioned units.

(10) The unit 19 is, preferably, formed from several blocks for each determining a parameter necessary for determining the pressure sub-variation curve P.sub.comb.sub._.sub.i. It therefore comprises: a block 23 arranged to determine the combustion efficiency , a block 24 arranged to determine the angular position of the crankshaft 14 at the start of the combustion SOC.sub.i for each injection inj.sub.i, a block 25 arranged to determine the angular position of the crankshaft 14 at the end of combustion EOC.sub.i for each injection inj.sub.i, a block 26 arranged for determining the combustion start slope .sub.i of said curve for each injection inj.sub.i, and a block 27 arranged to determine the combustion end slope .sub.i of said curve for each injection inj.sub.i.

(11) FIG. 2 illustrates the result of an example of implementing the determining device 10. FIG. 2 therefore shows a graph for the total pressure in the cylinder P.sub.cyl, in bar, and the quantity of fuel MF.sub.i to be injected in mg (MF.sub.1=0.8 mg, MF.sub.2=0.8 mg, MF.sub.3=14.2 mg) as a function of the angular position crk, in degrees, of the crankshaft 14. The angular position range has been chosen such as to only represent the cycle about the fuel injections. Thus, in FIG. 2 (as for FIG. 3), the angular position of the crankshaft 14 varies from 40 to +40 with the point 0 corresponding to the upper dead center (PMH) of a piston corresponding to the cylinder in question.

(12) A curve 30 represents the total pressure in the cylinder P.sub.cyl, which pressure is estimated by the determining device 10 before the engine cycle takes place. The gas mixture introduced into the cylinder is compressed by a piston and fuel is injected. In the present exemplary embodiment, it is assumed that there are three consecutive injections: a first pilot pre-injection inj.sub.1, a second pilot pre-injection inj.sub.2, then a main injection inj.sub.3. It is clearly observed that the total pressure in the cylinder P.sub.cyl increases with each injection of fuel, especially during the main injection, then decreases when the combustion ends and the piston goes back down, the curve 30 tending to a minimum pressure.

(13) The estimation of the curve 30 is based on the calculation of the pressure without combustion P.sub.cyl.sub._.sub.m, illustrated by a curve 32, and on the calculation of pressure sub-variation curves P.sub.comb.sub._.sub.i brought about by each injection inj.sub.i.

(14) Each of the injections of FIG. 2 produces a significant pressure sub-variation during the combustion. Each injection inj.sub.1, inj.sub.2, inj.sub.3 starts at a certain angular position of the crankshaft 14 corresponding to each of the angular positions for start of injection SOI.sub.1, SOI.sub.2, SOI.sub.3, respectively. Shortly after each of the injections, the combustion begins, at angular positions for start of combustion SOC.sub.1, SOC.sub.2, SOC.sub.3, respectively, with an increase in the pressure to a certain point and then the combustion ends, at angular positions for end of combustion EOC.sub.1, EOC.sub.2, EOC.sub.3, respectively, with the pressure decreasing until approaching zero. Curves 33, 34, 35 illustrate the pressure sub-variations P.sub.comb.sub._.sub.i due to the injections inj.sub.i.

(15) The curve 35 has a large pressure variation due to the greatest quantity of fuel injected. The main injection therefore has a greater influence on the behavior of the pressure in the cylinder P.sub.cyl. However, it is observed that the pressure sub-variations of the curves 33, 34 are not zero during the main injection inj.sub.3. Therefore, they also influence this injection and, thus, the overall pressure in the cylinder P.sub.cyl.

(16) In order to calculate the total pressure in the cylinder P.sub.cyl, a method 45 for determining this pressure is proposed in this document, described using FIG. 4.

(17) As shown in FIG. 4, starting from a quantity of fuel to be injected MF.sub.i, a first step 37 is a step for determining the pressure without combustion P.sub.cyl.sub._.sub.m, followed by steps 38 for determining each pressure sub-variation curve P.sub.comb.sub._.sub.i. The chronological order between the step 37 and the steps 38 can vary: these steps can even take place in parallel since they are independent. Moreover, the pressure without combustion P.sub.cyl.sub._.sub.m and the pressure sub-variation curves P.sub.comb.sub._.sub.i are calculated as a function of the angular position crk of the crankshaft 14.

(18) The step 37 consists in calculating the pressure without combustion P.sub.cyl.sub._.sub.m from a relationship 50 corresponding to adiabatic compression and expansion and from a linear correction relationship 51.

(19) The relationship 50 considers the Laplace coefficient and is dependent upon the pressure of an intake inlet P.sub.intake of said cylinder and the volume relating to the angular position crk. In the relationship 50, the value V.sub.IVC refers to the volume of the combustion chamber when the intake valve closes, and the value V(crk) refers to the volume V relating to the angular position crk.

(20) $\begin{array}{cc}{P}_{\mathrm{cyl}\_m1}\left(\mathrm{crk}\right)={P_{\mathrm{intake}}\left(\frac{V_{\mathrm{IVC}}}{V\left(\mathrm{crk}\right)}\right)}^{}& \left(50\right)\end{array}$

(21) The relationship 51 is formed from a base value, corresponding to the result of the relationship 50, to which several linear corrections are added. The latter can be, each, formed from a constant and from a coefficient relating to the parameters of the injection inj.sub.i. In this case, a first correction cor.sub.TCO is dependent upon the cooling temperature TCO and a second correction cor.sub.EGR is dependent upon the exhaust gas recirculation rate EGR.

(22) $\begin{array}{cc}{P}_{\mathrm{cyl}\_m}\left(\mathrm{crk}\right)=P_{\mathrm{cyl}\_m1}\left(\mathrm{crk}\right)*\left(1+{\mathrm{cor}}_{\mathrm{TCO}}\frac{\mathrm{TCO}}{{\mathrm{TCO}}_{\max }}\right)*\left(1+{\mathrm{cor}}_{\mathrm{EGR}}\frac{\mathrm{EGR}}{{\mathrm{EGR}}_{\max }}\right)& \left(51\right)\end{array}$

(23) Each step 38 consists in calculating a pressure sub-variation curve P.sub.comb.sub._.sub.i and, more precisely, in determining the shape of the corresponding curve. To this end, each of the curves is estimated in the same way using a relationship 52 which is dependent upon the efficiency of the combustion , the quantity of fuel to be injected MF.sub.i, the volume V relating to the angular position crk, the volume of the cylinder when the piston is at the upper dead center V.sub.PMH and the combustion start slope .sub.i of said curve, the angular position for start of combustion SOC.sub.i, the combustion end slope .sub.i of said curve and the angular position for end of combustion EOC.sub.i.

(24) $\begin{array}{cc}{P_{\mathrm{comb}}\left(\mathrm{crk}\right)}_i=*{\mathrm{MF}}_i*\left[\frac{\left(\mathrm{crk}-{\mathrm{SOC}}_i\right)}{\left(\mathrm{crk}-{\mathrm{SOC}}_i\right)+{}_i}*\min \left(\frac{\left(\mathrm{crk}-{\mathrm{EOC}}_i\right)}{\left(\mathrm{crk}-{\mathrm{EOC}}_i\right)+{}_i},1\right)\right]*\frac{V_{\mathrm{PMH}}}{V\left(\mathrm{crk}\right)}& \left(52\right)\end{array}$

(25) The method 45 then comprises, within each step 38, several sub-steps, each consisting in calculating one of the parameters of the relationship 52.

(26) A sub-step 39 consists in calculating the combustion efficiency , in bar/mg, using a linear relationship 53. This relationship comprises a base value cste.sub. to which are added several linear corrections. Each of the corrections can be formed from a constant and from a coefficient relating to the parameters of the injection inj.sub.i. In this case, a first correction cor.sub.FUP is dependent upon the pressure of the fuel FUR at the injection and a second correction cor.sub.TCO is dependent upon the cooling temperature TCO.sub.i. Indeed, the more the engine is cooled, the more the combustion efficiency reduces, i.e. the number of unburnt residues increases.

(27) $\begin{array}{cc}={\mathrm{cste}}_{}*\left(1+{\mathrm{cor}}_{\mathrm{FUP}}\frac{{\mathrm{FUP}}_i}{{\mathrm{FUP}}_{\max }}\right)*\left(1+{\mathrm{cor}}_{\mathrm{TCO}}\frac{{\mathrm{TCO}}_i}{{\mathrm{TCO}}_{\max }}\right)& \left(53\right)\end{array}$

(28) In this example, the parameters of the relationship 55, of the relationship 56, 57 and of the relationship 58 are firstly estimated in seconds to simplify the calculations, then converted to angular degrees. For this purpose, the conversion is produced in this case from the relationship 54 where N is the engine speed.
x(*crk)=6*N*x(s)(54)

(29) The angular position for start of combustion SOC.sub.i is determined by the relationship 55 where .sub.i is a time period for auto-ignition of the fuel, as shown in FIG. 2.
SOC.sub.i=SOI.sub.i+.sub.i(55)

(30) The auto-ignition time period .sub.i can be estimated in seconds in a linear manner by the relationship 56 which comprises a base value cste.sub. to which several linear corrections are added. Each of the corrections can be formed from a constant and from a coefficient relating to the parameters of the injection inj.sub.i. For the auto-ignition time period .sub.i, a first correction cor.sub.MF is dependent upon the quantity of fuel MF.sub.i and a second correction cor.sub.EGR is dependent upon the exhaust gas recirculation rate EGR.sub.i. These two corrections are each approximately 40% with respect to the overall correction value. The auto-ignition time period .sub.i also comprises a third correction cor.sub.TDIFF dependent upon the time T.sub.DIFFi between the previous injection inj.sub.i-1 and the injection inj.sub.i, a fourth correction cor.sub.FUP dependent upon the fuel pressure FUP.sub.i at injection and a fifth correction cor.sub.TCO is dependent upon the cooling temperature TCO.sub.i.

(31) $\begin{array}{cc}{}_i={\mathrm{cste}}_{}*\left(1+{\mathrm{cor}}_{\mathrm{MF}}\frac{{\mathrm{MF}}_i}{{\mathrm{MF}}_{\max }}\right)*\left(1+{\mathrm{cor}}_{\mathrm{EGR}}\frac{{\mathrm{EGR}}_i}{{\mathrm{EGR}}_{\max }}\right)*\left(1+{\mathrm{cor}}_{T_{\mathrm{DIFF}}}\frac{{T_{\mathrm{DIFF}}}_i}{{T_{\mathrm{DIFF}}}_{\max }}\right)*\left(1+{\mathrm{cor}}_{\mathrm{FUP}}\frac{{\mathrm{FUP}}_i}{{\mathrm{FUP}}_{\max }}\right)*\left(1+{\mathrm{cor}}_{\mathrm{TCO}}\frac{{\mathrm{TCO}}_i}{{\mathrm{TCO}}_{\max }}\right)& \left(56\right)\end{array}$

(32) To calculate the angular position for start of combustion SOC.sub.i, the auto-ignition time period .sub.i of the relationship 56 can be converted to degrees by the relationship 54.

(33) A sub-step 41 for determining the angular position for end of combustion EOC.sub.i is determined by the relationship 57 where gives the combustion rate initially in mg.Math.s.sup.1 and converted into crk.s.sup.1.

(34) $\begin{array}{cc}{\mathrm{EOC}}_i={\mathrm{SOC}}_i+\left(\frac{{\mathrm{MF}}_i}{}\right)& \left(57\right)\end{array}$

(35) A sub-step 42 consists in determining the slope .sub.i of the sub-variation curve in question at the start of combustion. It can be estimated in seconds in a linear manner by the relationship 58 which comprises a base value cste.sub. to which several linear corrections are added. The latter can be, each, formed from a constant and from a coefficient relating to the parameters of the injection inj.sub.i. In this case, the corrections are dependent upon the quantity of fuel MF.sub.i, the exhaust gas recirculation rate EGR.sub.i and the time T.sub.DIFFi between the previous injection inj.sub.i-1, and the injection inj.sub.i.

(36) $\begin{array}{cc}{}_i={\mathrm{cste}}_{}*\left(1+{\mathrm{cor}}_{\mathrm{MF}}\frac{{\mathrm{MF}}_i}{{\mathrm{MF}}_{\max }}\right)*\left(1+{\mathrm{cor}}_{\mathrm{EGR}}\frac{{\mathrm{EGR}}_i}{{\mathrm{EGR}}_{\max }}\right)*\left(1+{\mathrm{cor}}_{T_{\mathrm{DIFF}}}\frac{{T_{\mathrm{DIFF}}}_i}{{T_{\mathrm{DIFF}}}_{\max }}\right)& \left(58\right)\end{array}$

(37) A sub-step 43 allows the slope .sub.i to be calculated. It varies as a function of the angular position for start of injection SOI.sub.i for the injection in question inj.sub.i. Indeed, the further away the injection is from the position PMH of the piston, the more slowly the combustion end slope .sub.i progresses. The slope .sub.i can therefore be calibrated. For example, it is calculated using an interpolation table.

(38) A step 44 then allows the final pressure to be estimated by adding together the pressure without combustion P.sub.cyl.sub._.sub.m and each of the pressure sub-variations P.sub.comb.sub._.sub.i using the relationship 59 where n is the total number of injections inj.sub.i.
P.sub.cyl(crk)=P.sub.cyl.sub._.sub.m(crk)+.sub.i=1.sup.nP.sub.comb(crk).sub.i(59)

(39) FIG. 3 illustrates, for an injection similar to that of FIG. 2, the results obtained with the determining method described above. However, the injections inj.sub.1, inj.sub.2, inj.sub.3 of FIG. 3 differ slightly from those of FIG. 2. The curve 28 illustrates the various injections. As for FIG. 2, this example comprises three injections: a first pilot pre-injection, a second pilot pre-injection, then a main injection.

(40) A curve 29 shows a measurement of the pressure in the cylinder P.sub.cyl undertaken to validate the proposed method. The curve 30 diagrammatically shows the total pressure in the cylinder P.sub.cyl estimated by the determining device 10 before the engine cycle takes place (predictive estimate). It is observed that the curve 30 is very close to the curve 29. Indeed, the difference between these two curves does not exceed a threshold of +/5 bar, illustrated in the figure by an interval 31, in the pre-injection zone, also called the compression zone, and a threshold of +/10 bar in the combustion zone.

(41) The present invention therefore allows for simply predicting the pressure in an engine cylinder while achieving very good accuracy.

(42) The present invention also allows the pressure in the cylinder to be estimated by taking into account all of the injections of an engine cycle, i.e. both the pre-injections and the main injection or the injections subsequent to the main injection.

(43) Estimating the pressure in the cylinder at the time of commanding the injection allows the control of the quantity of fuel injected into the engine to be effectively adjusted by acting, for example, on the injector opening duration.

(44) The present invention can be used, for example, in devices implementing engines, for example, compression ignition engines also called diesel engines or also positive ignition engines also called gasoline engines. The present invention can therefore be easily applied to different engines.

(45) The correction parameters described above are dependent upon the engine and the desired level of accuracy. It will not therefore be a departure from the scope of the invention to add a correction coefficient to account for a parameter not stated here.

(46) Of course, the present invention is not limited to the embodiment shown above by way of non-limiting example. It also relates to the alternative embodiments within the capabilities of a person skilled in the art within the scope of the claims hereafter.