EP2399015A1

EP2399015A1 - Method and estimator for a fresh air mass in a combustion chamber, method for estimating total filling, recording medium for said methods, and vehicle provided with such an estimator

Info

Publication number: EP2399015A1
Application number: EP10707320A
Authority: EP
Inventors: Emmanuel Sedda; Frédéric TRELLE
Original assignee: Peugeot Citroen Automobiles SA
Current assignee: PSA Automobiles SA; GM Global Technology Operations LLC
Priority date: 2009-02-23
Filing date: 2010-01-19
Publication date: 2011-12-28
Anticipated expiration: 2030-01-19
Also published as: EP2399015B1; FR2942503A1; FR2942503B1; WO2010094870A1; RU2011138956A; RU2525862C2

Abstract

The invention relates to a method for estimating the mass Ma of fresh air taken into the combustion chamber of an engine cylinder during an engine cycle, characterised in that said method includes estimating (128) a total mass Mtot of gases contained in the combustion chamber at the end of the fresh air intake, estimating (120, 124) a mass Mb of burnt gases contained in the combustion chamber at the end of the exhaust of the burnt gases, and estimating (128) the mass Ma of fresh air from the difference between the estimated total mass Mtot and the estimated mass Mb of burnt gases.

Description

METHOD AND ESTIMATOR OF FRESH AIR MASS IN A COMBUSTION CHAMBER, TOTAL FILLING ESTIMATING METHOD, RECORDING MEDIUM FOR THESE METHODS AND VEHICLE

TEAM OF THIS ESTIMATOR

The present invention claims the priority of the French application 0951 133 filed February 23, 2009 whose content (text, drawings and claims) is here incorporated by reference.

The invention relates to an estimating method and an estimator of a mass Ma of fresh air admitted inside a combustion chamber of a cylinder of a motor during a motor cycle. The invention also relates to a method of estimating the total charge of fresh air supercharged from the combustion chamber and a vehicle equipped with the estimator.

[0003] An engine cycle successively comprises the exhaust of the burnt gases from the combustion chamber, the admission of fresh air and fuel into the combustion chamber and the explosion of the mixture in this combustion chamber. In the case of a four-stroke engine, an engine cycle is two round trips of piston in the cylinder between the two extreme positions of its stroke, that is to say the top dead center (TDC) and the point low death (PMB).

[ooo4] The exhaust of burned gases lasts as long as the exhaust valve (s) are open. Similarly, the fresh air intake lasts as long as the intake valve (s) are open.

[Oooδ] As is known, the power delivered by an internal combustion engine is a function of the amount of air introduced into the combustion chamber of the engine. This quantity of air is itself proportional to the density of this air. Therefore, in case of high power demand, it is expected to increase the amount of air by means of compression of the air before it is admitted into the combustion chamber. This operation is more commonly known as supercharging and can be performed by a supercharging device such as a turbocharger or a driven compressor such as a screw compressor.

In order to further increase this amount of air admitted into the cylinder, it can be expected to achieve an admission mode with a flue gas scavenging residual. This sweep makes it possible to evacuate the burnt gases present in the combustion chamber to replace them with supercharged air.

As explained in US Pat. No. 4,217,866, this scanning is obtained by simultaneously opening the exhaust and intake valves of the same combustion chamber for a few degrees to a few tens of degrees of angle. rotation of the crankshaft. Typically, this occurs at the end of the flue gas exhaust and at the beginning of the intake of fresh air. Specifically, the fact that the air pressure at the open intake valve is higher than the pressure at the exhaust valve creates a flow of air that passes directly from the intake to the exhaust valve. exhaust resulting in passing part of the residual burnt gases present in the combustion chamber. This period during which the intake and exhaust valves are simultaneously open is called "valve crossing".

[oooδ] In the case of atmospheric engines, that is to say engines without supercharging, a valve crossover can also be provided. In this case, during the crossing of valves, flue gases are sucked into the combustion chamber. It is said that the flue gases are re-aspirated. This feature is known by the acronym IGR (Internal Gas Recirculation) or Internal Recirculation of Exhaust Gas.

Methods for estimating the flow of fresh air admitted inside a combustion chamber of a cylinder of an engine are known. However, these methods are imprecise and do not really allow to obtain an estimate of the amount of fresh air admitted into each combustion chamber. But this estimate is important to properly control the engine. For example, this estimate is useful for determining the amount of fuel to be injected or for setting the ignition timing.

[Ooio] The invention aims to overcome this disadvantage by providing a more accurate method for estimating the amount of fresh air admitted into a combustion chamber.

It therefore relates to a method for estimating a mass Ma of fresh air admitted inside a combustion chamber of a cylinder of a motor during a motor cycle, in which this method comprises the estimation of a total mass Mtot of gas contained in the combustion chamber at the end of the intake of fresh air, the estimate of a mass Mb of burnt gases contained in the combustion chamber at the end of the exhaust of the flue gases, and estimating the mass Ma of fresh air from the difference between the total mass Mtot and the mass Mb of estimated burned gases.

The estimates of the total mass Mtot and the mass Mb of burnt gases can be established precisely without measuring the pressure or the temperature inside the combustion chamber. Therefore, this method of estimating the mass Ma is more accurate.

The embodiments of this method of estimating the mass Ma may comprise one or more of the characteristics corresponding to the variants described hereinafter.

In a variant, the estimate of the mass Mb of burnt gas comprises the estimation of a mass Mb_resi of residual burnt gas contained in the combustion chamber at the end of the exhaust of the burnt gases, and the estimating a mass Mb_reasp of burnt gases re-aspirated inside the combustion chamber during the crossing of valves. This embodiment makes it possible to obtain a more accurate estimation of the mass Mb since the residual mass of flue gases and the mass of the flue gases sucked back during a crossover of valves are simultaneously taken into account.

In a variant, the estimation of the mass Mb_resi is obtained from a pressure P _ECH of the burnt gases, an internal volume of the combustion chamber at the end of the exhaust of the burnt gases, d a temperature T _ECH of the burnt gases and a correction coefficient A _ECH of the pressure P _ECH whose value is a function of an end-of-exhaust angle and the engine speed. This mode also makes it possible to obtain an accurate estimate of the mass of residual burnt gases in the combustion chamber at the end of the exhaust without it being necessary to measure the pressure or the temperature inside the combustion chamber. combustion.

In a variant that makes it possible to increase the accuracy of the estimate by taking compote of the crossing of the valves, the estimation of the mass Mb_reasp is obtained using the following relation:

Mb _ reasp = x POND or :

- Mb _reasp is the flow of burned gas re-aspirated,

- P _ECH is the exhaust gas exhaust pressure,

- P _ADM is the air intake pressure,

- TECH is the temperature of the flue gases,

r is a constant equal to the following ratio R / M where R is the universal constant of perfect gases and M is the molar mass in kg. mol ^"1 of flue gases,

- Sbase is a corrective value depending on the engine speed and the difference between angles FE and OA, respectively, of exhaust closure and intake opening and,

- Scor is a corrective value according to the difference between the angles FE and OA and the engine speed,

- POND is a corrective value depending on the engine speed and a position of the valve crossing given by the following relation (FE + OA) / 2,

- Γ (P _A DM / PECH) is defined by the following relation:

where γ is the ratio of the heat capacity at constant pressure of the flue gases to the heat capacity at constant volume of the flue gases, - Γ _O (PADM / PECH) is defined by the following relation:

In a variant, the estimate of the total mass Mtot is obtained from an admission pressure P _ADM of the air, a volume of the combustion chamber at the end of the admission, of a temperature T _m _{ang ang} du of the mixture of fresh air and flue gas contained in the combustion chamber at the end of the intake of fresh air, and a correction coefficient A _ADM whose value is obtained from a prerecorded cartography according to an angle FA end of admission and the engine speed. This makes it possible to obtain an accurate estimate of this mass Mtot since it takes into account the exchanges of materials during the crossing of valves.

In a variant that makes it possible to estimate the mass Ma without knowing the temperature and the pressure inside the combustion chamber, the estimate of the mass Ma of fresh air is a solution of the system of equations. next :

V X - * mixture)

Ma = MtOt -Mb

_ MaxcpaxTa + MbxcpbxTb mix, ^ -, ^ _{7 7}

My x cpa + Mb x cpb

or :

- AADM is a correction coefficient whose value depends on the engine speed and the end of intake angle,

- PADM is the air intake pressure,

- Vcyl_FA is the geometric volume of the combustion chamber calculated at the end angle of admission,

- Tmixture is the temperature of the mixture of fresh air and flue gases contained in the combustion chamber,

r is a constant equal to the ratio R / M where R is the universal constant of perfect gases and M is the molar mass in kg mol -1 of the mixed gases,

cpa and cpb are the constant pressure mass heat capacities, respectively, of fresh air and flue gases, and

Ta and Tb are the temperatures, respectively, of fresh air and flue gases. The invention also relates to a method of estimating the total filling fill_tot supercharged fresh air of a combustion chamber of a cylinder of a motor during a motor cycle, wherein this method comprises estimating a mass Ma of fresh air admitted into the combustion chamber using the above method, estimating a mass Mbal_tot of gas swept (air or flue gas) during the crossing of the valves, and estimating the total filling repl_tot fresh air supercharged from the fresh air mass Ma and the mass Mbal_tot estimated gas swept

The above method is more accurate because we take into account the mass of gas swept to the exhaust at the crossing of valves.

In a variant of the invention, the estimate of the total filling is a solution of the following equation system:

or :

Mtot is the total mass of gas contained in the combustion chamber at the end of the admission of the fresh air defined above,

Mo is an air reference mass under normal conditions of temperature and pressure

Mb is a mass of burnt gases contained in the combustion chamber at the end of the exhaust of the burned gases

Mbal_tot is the total mass of swept gas (air or flue gas) during the valve crossing, Mbal is the mass of gas swept (air) between the intake and the exhaust during the crossing of valves,

Max (...) and Min (...) are respectively the functions returning the maximum and the minimum, and

I ... I is the absolute value.

The use of a solution of the equation above increases the accuracy since it takes into account that the admitted air mass fills the volume of the combustion chamber until that there is no more gas burned in it.

The invention also relates to an information recording medium comprising instructions for performing one of the above methods, when these instructions are executed by an electronic computer.

The invention also relates to an estimator of a mass Ma of fresh air admitted inside a combustion chamber of a cylinder of a motor during an engine cycle, in which this estimator comprises a module for estimating a total mass Mtot of gas contained in the combustion chamber at the end of the admission of fresh air, a module for estimating a mass Mb of burnt gases contained in the chamber at the end of the flue gas exhaust, and a module for estimating the mass Ma of fresh air from the difference between the total mass Mtot and the estimated mass Mb of flue gases.

Finally, the invention also relates to a vehicle comprising the estimator above.

The invention will be better understood on reading the description which follows, given solely by way of nonlimiting example and with reference to the drawings in which:

FIG. 1 is a schematic illustration of a vehicle in which the mass Ma and the total fillage fill_tot are estimated;

FIG. 2 is a graph schematically illustrating movements of the exhaust and intake valves during an engine cycle, FIG. 3 is a more detailed illustration of the architecture of an electronic calculator implementing an estimator of the mass Ma and of the total fill, fill_tot, and

FIG. 4 is a flowchart of a method for estimating the mass Ma and the total filling in the vehicle of FIG. 1.

[0027] Figure 1 schematically shows a vehicle 2 equipped with an internal combustion engine. For example, the vehicle 2 is a motor vehicle such as a car.

The engine of the vehicle 2 is equipped with several cylinders. However, to simplify the illustration, only a cylinder 6 of this combustion engine is shown in Figure 1. Inside the cylinder 6, a piston 8 is mounted movably in translation between a top dead center (TDC) and a bottom dead center (PMB). This piston 8 rotates a crank 10 of a crankshaft 12 via a connecting rod 14. The crankshaft 12 drives in rotation, through a mechanism (not shown), the driving wheels of the vehicle 2 such that the wheel 16.

The cylinder 6 defines a combustion chamber 18 defined by the upper part of the piston 8 and a cylinder head not shown. A fresh air intake duct 20 opens into the chamber 18 through an inlet opening. An inlet valve 24 is movable between a closed position in which it closes the intake opening in a fresh airtight manner, and an open position in which fresh air can be admitted into the interior of the chamber. chamber 18 through the intake opening. The valve 24 is moved between its open position and its closed position by an actuator 26 of intake valves.

In the particular case shown here, a fuel injector 28 is provided in the conduit 20 to inject fuel into the fresh air admitted to the interior of the chamber 18. Thus, the fresh air / fuel mixture starts at occur inside the intake air duct.

The conduit 20 is fluidly connected to a compressor 30 of a turbocharger 32 adapted to compress the fresh air admitted to the interior of the chamber 18. The fresh air thus compressed is called fresh air supercharged. A candle 34 clean to ignite the fresh air / fuel mixture opens into the chamber 18. This candle is controlled by an ignition device 36.

An exhaust duct 40 also opens into the chamber 18 through an exhaust opening. This exhaust opening is closable by a valve 44 movable between a closed position, and an open position in which the burnt gases contained inside the chamber 18 can escape via the conduit 40. This valve 44 is moved between these open and closed positions by a valve actuator 46.

The valve actuators 26 and 46 may be mechanical valve actuators.

The end of the duct 40 opposite its opening which opens into the chamber 18 is fluidly connected to a turbine 48 of the turbocharger 32. This turbine 48 allows in particular to relax the exhaust before sending them in a line d exhaust 50.

The various engine equipment that can be controlled such as the actuators, the ignition device or the fuel injector are connected to a motor control unit 60 also known by the acronym ECU (Engine Control Unit). To simplify FIG. 1, the connections between this unit 60 and the various equipment items ordered have not been represented.

The unit 60 is also connected to many sensors such as for example a sensor 62 of the position of the crankshaft 12 and a sensor 64 of the engine speed. The engine speed is defined here as being the number of revolutions per minute performed by the motor drive shaft.

Figure 2 shows, in the form of a graph, the movements of the valves 24 and 44 relative to the movements of the piston 8 during a motor cycle. In this graph, an axis 70 of the abscissa represents the displacement of the piston 8 between its top dead center and its bottom dead center, noted respectively, PMH and PMB on this graph. The y-axis represents the amplitude of the displacement of the intake and exhaust valves. This amplitude is zero when the intake valve or the exhaust valve is closed. It is maximum when these same valves are completely open. Here, the displacement of the valve 44 is represented by a curve 72 and the displacement of the valve 24 is represented by a curve 74.

The axis 70 is graduated in degrees of rotation angle of the crankshaft. The origin of this axis is confused with the top dead center of fresh air intake.

As shown in this Figure 2, the exhaust valve begins to open at an angle OE located substantially around the bottom dead center of relaxation and closes at an angle FE. In the particular case shown in Figure 2, the angle FE is located after the top dead center.

The inlet valve begins to open at an angle OA and closes at an angle FA.

Here, this graph is represented in the particular case where a valve crossing exists. Indeed, the angle OA precedes the angle FE, which indicates that during a period of time of a few degrees, the intake and exhaust valves are simultaneously open.

FIG. 3 represents in more detail a possible architecture for the unit 60 for estimating the mass Ma and the total filling rate_tot.

For this purpose, the unit 60 implements an estimator 80 of a temperature T _ECH of the burnt gases, an estimator 82 of a pressure P _ECH of the gases, an estimator 84 of a temperature T _ADM of the air charge admitted inside the chamber 18 via the conduit 20, and an estimator 86 of a pressure P _ADM of the fresh air admitted inside the chamber 18.

These estimators 80, 82, 84 and 86 are connected to an estimator 88 of the mass Ma and the total fill fill_tot. This estimator 88 is also connected to a motor control block 90. This block 90 makes it possible in particular to control the various actuators, injectors and ignition devices of the engine according to the estimates of the mass Ma and the total fill fill_tot. For example, the block 90 is able to adjust the quantity of fuel injected and to advance the ignition timing of the fresh air / fuel mixture injected into the chamber 18 or to adjust the opening of a butterfly valve to adjust the amount of fresh air admitted into the room 18. The estimator 88 comprises a module 92 for estimating a mass Mb of burnt gas contained in the chamber 18 at the end of the exhaust of the flue gases, an estimator 94 of a mass Mbal of gas swept from the admission to the exhaust at the crossing of valves, an estimator 96 of the temperature Tb of the flue gases, an estimator 98 of the mass Ma of fresh air admitted into the chamber 18, and an estimator 100 of the total filling repl_tot.

The module 92 has a submodule 102 for estimating a mass Mb_resi of residual burnt gas contained in the chamber 18 at the end of the exhaust, and a submodule 104 for estimating a mass Mb_reasp of burnt gases sucked off at the crossing of the valves inside the chamber 18.

These modules 92 to 100 will be described in more detail with reference to FIG. 4.

The unit 60 is typically made from a programmable computer capable of executing instructions stored in an information storage means. Here, for this purpose, the unit 60 is connected to a memory 106 containing the various instructions and data necessary for the execution of the method of FIG. 4. In particular, the various maps used to implement the method of FIG. 4 are recorded in this memory 106. These maps are for example constructed experimentally so as to minimize errors between the estimated values and the real values.

The operation of the unit 60 of the vehicle 2 will now be described in more detail with regard to the method of Figure 4 in the particular case of the engine described with reference to Figure 1.

Before going into the details of the method of estimating the mass Ma and the total filling fill_tot, the general principle of this method is first described.

The general principle is based on a mass balance on an engine cycle of the gas entering and leaving the chamber 18. This mass balance is decomposed into several calculations that take place throughout the engine cycle.

At first, at the end of the exhaust, the mass Mb of flue gases in the chamber 18 is estimated. In a second step, at the end of the admission, the total mass Mtot of gas contained inside the chamber 18 is estimated. From these two estimates, and because the total mass of gas is preserved on a motor cycle, the mass Ma of air contained inside the chamber 18 during a motor cycle can be obtained by subtraction of the mass Mb to the mass Mtot.

More precisely, according to the mass balance of the gases admitted and discharged during an engine cycle, the mass Ma is given by the following relation: where Mtot is the total mass of gas in chamber 18 at the end of admission, and Mb is the total mass of flue gases in chamber 18 at the end of the exhaust.

In the particular case where a portion of the burned gases are re-aspirated during the crossing of the valves, the estimate of the mass Mb is decomposed into an estimate of the mass Mb_resi of residual burnt gases not removed via the leads 40 at the end of the exhaust and mass Mb_reasp of flue gas re-aspirated during the crossing of valves.

The mass of burned gas Mb is then defined by the following relation: Mb = Mb_resi + Mb_reasp

or :

Mb_resi is the mass of residual burned gas that could not be evacuated during the exhaust, and

- Mb_reasp is the mass of burned gas re-sucked at the crossing of valves.

In the particular case of a supercharged engine with crossover valves, it is also sought to estimate the total fill fill_tot fresh air supercharged. Total fill repl_tot is the total amount of fresh air admitted through the intake opening during an engine cycle. In the case of a turbocharged supercharged engine, a portion of the fresh air admitted through the intake opening is immediately exhausted by the exhaust (Mbal). Thus, the total filling fill_tot is, as a first approximation, given by the following relation: Mbal replace _ early = replace _ cyl + MB

or :

- fill_tot is the total filling in total fresh air,

- fill_cyl is the fresh air filling of chamber 18,

Mbal is the mass of gases swept from the intake to the exhaust during the crossing of valves, and

Mo is an air reference mass under normal conditions of temperature and pressure.

Fresh air filling fill_cyl is defined by the following relationship:

My replacement _ cyl =

Mo where Ma is the air mass contained in chamber 18 at the end of admission, and Mo is the reference mass.

Here, the normal conditions of temperature and pressure correspond to a temperature of 298.15 K, at a pressure of 1013 mbar, and a volume equal to the volume of the unit cubic capacity.

The quantities fill_tot, fill_cyl and the ratio Mbal / Mo are dimensionless quantities.

Generally, the Mbal mass exists only in the case of supercharged engines. However, the description of the process which follows is made in the most complete case, that is to say the case where the estimates of the Mb_reasp and Mbal masses are both carried out. Indeed, the skilled person can easily simplify the process that follows to adapt it only to the case of atmospheric engines or only in the case of supercharged engines.

The process starts with a step 120 of estimation of the mass Mb_resi of burnt gas contained in the chamber 18 at the end of the exhaust.

In step 120, the submodule 102 estimates the mass Mb_resi using the following relation: _{Λ / fU} . * cyl FE ^ * cyl FE V ^ ECff * ^ ECH / ^X ^ cyl FE

Mb resi = - ^ - - = - -

^{1 Λ λ} ECH ' ^{Λ λ} ECH where:

- P _C yi_FE is the pressure inside chamber 18,

- P _ECH is the exhaust gas exhaust pressure,

- T _ECH is the temperature of the flue gases evacuated via the duct 40,

- A _ECH is a correction coefficient for correcting the pressure P _ECH to a pressure close to P _cy ι_ _FE, whose value is given by a mapping function of the angle PA and the engine speed, and

- Vcyi FE is the geometric volume of the chamber 18 at the end of the exhaust that is to say for the angle FE.

The volume V _cy ι_ _FE is given by the following relation:

Vcyi FE (FE) = - + - {[+ TO - COs (FE) - ^ A ² Sm ² (FE))

where: λ is the rod / crank ratio, Cu is the cubic cylinder capacity of the cylinder 6, and ε is the compression ratio of the engine.

The ratio λ and the rate ξ are known characteristics of a motor. It is simply recalled here that the ratio λ is the ratio between the length of the rod 14 divided by the half-length of the crank 18.

In the above relation and in the following relationships, the pressures P _ECH and PADM and the temperatures TECH and T _A DM are the pressures and temperatures estimated by the estimators 80, 82, 84 and 86 from physical magnitudes. measured in the engine.

Then, during a step 122, the sub-module 104 estimates the Mb_reasp mass of flue gases re-aspired during the crossing of valves. Here, this estimate is given by the following relation: , "Mb reasp

Mb reasp = =

^" K

where Mb_reasp is the flow rate of re-aspirated burned gases expressed in kg / h, and K is a coefficient making it possible to pass from the flow rate to an admitted mass per engine cycle in the chamber 18.

For example, the coefficient K is given by the following relation:

" _{Λ T number of} cylinder _rr .

K = Nx - x60

Nbre_revolutioncycle

where N is the engine speed, "Cylinder_number" is the engine cylinder number, "Nbre_revolutioncycle" is the number of crankshaft revolution during a motor cycle, and "60" is used to convert the N engine speed given in a revolution per minute in number of revolutions per hour.

For example, for a four-stroke engine equipped with four cylinders, the coefficient K is equal to K = N × 2 × 60.

The flow of burned gas re-aspirated Mb _reasp is calculated from the law of Barrier Saint Venant corrected in the following manner during the crossing of valves

Mb _ reasp = x POND

or :

- P _ECH is the exhaust gas exhaust pressure,

- P _ADM is the admission pressure of the air admitted through the conduit 20,

- TECH is the temperature of the flue gases,

Sbase is a predetermined map that gives a first corrective value as a function of the difference between the angles FE and OA and the engine speed,

Scor is a predetermined map which gives a second corrective value as a function of the difference between the angles FE and OA and the engine speed, - POND is a predetermined mapping that gives a third corrective value depending on the position of the valve crossing and the engine speed.

The position of the valve crossing is given by the following relation (FE + OA) / 2.

[73] (P _ADM / P _ECH ) is defined by the following relation:

where γ is the ratio of the heat capacity at constant pressure of the flue gases to the heat capacity at constant volume of the flue gases. For example, this ratio is equal to 1, 4.

The equation above distinguishes the case of a subsonic flow of a sonic flow.

_O (P _ADM / P _ECH ) is defined by the following relation:

Then, during a step 124, the module 94 estimates the total mass Mbal_tot of gas swept between the intake and the exhaust during the crossing of valves.

The mass Mbal_tot is obtained using the following relation:

Mbal _ early

Early Mbal = K or :

- Mbal _tot is the flow of gas swept from the intake to the exhaust during the valve crossing expressed in kg / h, and

K is the same coefficient as previously defined for passing from the flow rate to an admitted mass per engine cycle in chamber 18.

The flow Mbal _tot is estimated from the law of Barrier Saint Venant corrected in the following way to take into account crossover valves:

or :

- PECH, and PADM have already been defined previously,

- T _ADM is the temperature of the air admitted to the chamber 18

S is a predetermined map making it possible to obtain a corrective value as a function of the difference between the angles FE and OA and of the engine speed, and

- POND is a predetermined map to obtain a corrective value depending on the position of the valve crossing and the engine speed.

The ratio Γ (P _E CH / PADM) has already been defined above.

The position of the crossing of valves is equal to the following value: (FE + OA) / 2.

Then, during a step 126, the module 96 estimates the temperature Tb of the flue gases. For this, this temperature Tb is obtained by a calculation of enthalpy mixture between the residual gases and the re-aspirated flue gases. For example, the temperature Tb is obtained from the following relation:

_ ,, Mb reasp x cpb reasp xTb reasp + Mb resixcpb resixTb resi

I b =

Mb _ reasp x cpb _ reasp + Mb _ resi x cpb _ resi

or : Mb_resi is the mass of residual burned gas previously estimated,

- Mb_reasp is the mass of burned gases re-aspirated at the crossing of valves,

- cpb_resi is the mass heat capacity at constant pressure of the residual burnt gases,

- cpb_reasp is the mass heat capacity at constant pressure of the re-aspirated flue gas,

Tb_reasp is the temperature of the flue gases that have been sucked off during the valve crossover, and

Tb_resi is the residual flue gas temperature obtained from an adiabatic expansion calculation.

For simplicity, for example, the capacities cpb_resi and cpb_reasp are equal.

The temperature Tb_reasp is taken equal to the temperature TECH. The temperature Tb_resi is calculated from the following relation:

where all the variables have already been defined previously.

Then, during a step 128, the module 98 estimates the mass Ma by solving the following system of equations:

or :

PADM, Mb, Ma have already been defined previously,

Vcyi FA is the geometric volume of the chamber 18 calculated at the angle FA,

A _ADM is a correction coefficient, r is a constant equal to the ratio R / M where R is the universal constant of perfect gases and M is the molar mass in kg. mol ^"1 of the mixed gases,

Tmégege is the temperature of the mixture of fresh air and flue gases contained in chamber 18, and cpa and cpb are the constant pressure mass capacities, respectively, of fresh air and flue gases, and

Ta and Tb are the temperatures, respectively, of fresh air and flue gases. The volume V _cy ι_ _FA is calculated using the following relation:

VC _≠ _FA (FA) = - + - (l + λ - COS (FA) - J% - sin ² (FA))

The correction coefficient A _ADM is obtained using the following relation:

A - A Ak * (A - A

^ ¹ ^ ¹ ADM ADM ATMO ^{1 τ} ^ ATMO TURBO ^Λ V ¹ ADM TURBO ^ ¹ ADM AT TMMOO). or :

AADM_ATMO is a corrective value obtained from a predetermined cartography as a function of the angle FA and the engine speed,

AADM_TURBO is a corrective value obtained from a predetermined cartography according to the angel FA and the engine speed,

The coefficient kATMO_TURBO is a corrective coefficient given by the following relation:

¹ ATMO TURBO = max 0; min or :

PATMO is the atmospheric pressure,

Po is the reference pressure which is here equal to 1013 mbar, fA (N, FA) is a corrective value obtained from a predetermined mapping as a function of the engine speed and the angle FA, and fB (N) is a corrective value obtained from a predetermined mapping according to the regime engine.

The relationship defining the temperature T _me iangθ is obtained by a calculation of enthalpy mixture between the mass of burnt gas and the fresh air mass contained in the chamber 18.

The system of equations described above is an equation system with three unknowns and three equations. The resolution of this system makes it possible to obtain estimates of the mass Ma, of the temperature T _mé ι _angθ and of the total mass Mtot.

More specifically, the estimate of the mass Ma is given by the following relation in the particular case where cpb and cpa are equal:

Optionally, during step 128, the estimate of the mass Ma obtained after solving the system of equations is corrected according to the inverse of the temperature Ta of the fresh air. For example, the mass Ma is corrected using the following relation:

Ma = f [^) My

Ta ¹

where f (1 / Ta) is a correction coefficient whose value is obtained from a prerecorded cartography giving the value of this correction coefficient as a function of the inverse of the temperature Ta.

Finally, during a step 130, the module 100 estimates the total filling repl_tot fresh air. This total filling, for example, is obtained by means of the following relation: a = - xf ^ ^{ADM XP} ^) * V ^C _≠ _ ^FA _ _ma φ _Mb _ _Mbal _ _to ή _χTb ) _{+ m} in {0; Mb -Mbal_tot] Ta {rj where all the variables of this relation have already been defined previously, Max (...) and Min (...) are respectively the functions returning the maximum and the minimum, and | ... | is the absolute value.

To obtain this last relationship, it was considered that the gas swept from the intake to the exhaust during the valve crossing first completely filled the volume of the chamber 18 before passing directly from the intake to the exhaust. Thus, as long as the mass Mbal_tot of swept gas is less than the mass Mb of flue gases, it is considered that there is no sweeping. Conversely, as soon as the mass Mbal_tot is greater than the mass Mb of burnt gases, it is considered that there is more than a gas sweep between the intake and the exhaust. The Mbal mass defined at the beginning of this description corresponds only to the last term of the relation above.

[0090] Many other embodiments are possible. For example, if the engine is not a supercharged engine but simply an atmospheric engine, then, the formulas that have been previously described can be simplified since there is no gas flow from the intake to the exhaust . In other words, the mass Mbal_tot is zero.

What has been described above can also be applied to a motor without a camshaft dephaser at the intake or the exhaust.

Finally, what has been described above can also be adapted to the case where there is no cross valve. In this case, the mass Mb_reasp and the mass Mbal_tot are zero, which simplifies the previous relations.

Claims

1. Method for estimating the mass Ma of fresh air admitted inside a combustion chamber of a cylinder of an engine during an engine cycle, characterized in that this method comprises the estimation (128) of a total mass Mtot of gas contained in the combustion chamber at the end of the intake of fresh air, the estimate (120, 124) of a mass Mb of burnt gases contained in the chamber at the end of the exhaust of the flue gases, and the estimate (128) of the mass Ma of fresh air from the difference between the total mass Mtot and the estimated mass Mb of flue gases.

2. Method according to claim 1, wherein the estimate of the mass Mb of burnt gas comprises the estimate (120) of a Mb_resi mass of residual burnt gases contained in the combustion chamber at the end of the exhaust of gas burned, and estimating (122) a mass Mb_reasp of burnt gases re-aspirated inside the combustion chamber during the crossover valves.

3. Method according to claim 2, wherein the estimate (120) of the mass Mb_resi is obtained from a pressure P _ECH flue gases, an internal volume of the combustion chamber at the end of the Exhaust of flue gases, a T _ECH temperature of the burnt gases and a correction coefficient A _ECH of the pressure P _ECH whose value is a function of an end of exhaust angle and the engine speed.

4. Method according to any one of the preceding claims, wherein the estimate (128) of the total mass Mtot is obtained from an admission pressure P _ADM of the air, a volume of the combustion chamber. at the end of the admission, a temperature T _me iangθ of the mixture of fresh air and flue gas contained in the combustion chamber at the end of the intake of fresh air, and a correction coefficient A _ADM whose value is obtained from a pre-recorded cartography according to an intake end angle FA and the engine speed.

5. The method as claimed in claim 1, in which the estimate (128) of the mass Ma of fresh air is a solution of the following system of equations:

or :

_ADM is a correction factor whose value depends on the engine speed and the end of intake angle, - P _ADM is the air intake pressure,

V _c yi _FA is the geometric volume of the combustion chamber calculated at the end angle of admission,

Tmégege is the temperature of the mixture of fresh air and flue gases contained in the combustion chamber, r is a constant equal to the following ratio R / M where R is the universal constant of perfect gases and M is the molar mass in kg. mol ^"1 of the mixed gases, cpa and cpb are the constant-pressure mass heat capacities, respectively, of the fresh air and the flue gases, and

Ta and Tb are the temperatures, respectively, of fresh air and flue gases.

6. A method for estimating a total fill fill fresh air supercharged a combustion chamber of a cylinder of an engine during an engine cycle, characterized in that this method comprises the estimation (128) a mass Ma of fresh air admitted inside the combustion chamber by a process according to any one of the preceding claims, the estimate (124) of a mass Mbal_tot of gas swept from the intake to the exhaust at the crossing of the valves, and the estimate (130) of the total filling repl_tot in fresh air supercharged from the fresh air mass Ma and the estimated mass Mbal_tot of estimated flushed gases.

The method of claim 6, wherein estimating (130) the total fill is a solution of the following equation system:

or :

Mo is an air reference mass under normal conditions of temperature and pressure

Mbal_tot is the total mass of swept gases (air and flue gas) during the valve crossing,

Mbal is the mass of gas swept (air) between the intake and the exhaust during the crossing of valves,

| ... | is the absolute value.

8. Information recording medium (106), characterized in that it comprises instructions for the execution of a method according to any one of the preceding claims, when these instructions are executed by an electronic computer.

9. Estimator of a mass Ma of fresh air admitted inside a combustion chamber of a cylinder of an engine during an engine cycle, characterized in that this estimator comprises a module (98) estimating a total mass Mtot of gas contained in the combustion chamber at the end of admission of fresh air, a module (92) for estimating a mass Mb of burnt gases contained in the combustion chamber at the end of the flue gas exhaust, and a module (98) for estimating the mass Ma of fresh air from the difference between the total mass Mtot and the mass Mb of estimated flue gases.

10. Vehicle characterized in that it comprises an estimator (88) according to claim 9.