EP2399015B1 - Method for estimating total filling of a combustion chamber of an engine - Google Patents

Description

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

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 corresponds to two piston round trips between the two extreme positions of its stroke, i.e. the top dead center (TDC) and the point low death (PMB).

The exhaust of burnt 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.

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 this engine. This amount of air is itself proportional to the density of this air. Therefore, in case of high power demand, it is expected to increase this amount of air by means of compression of the air before it is admitted into this combustion chamber. This operation is more commonly called supercharging and can be carried out by a supercharging device such as a turbocharger or a driven compressor such as a screw compressor.

In order to further increase this quantity of air admitted into the cylinder, provision may be made for carrying out an admission mode with a sweeping of the residual burnt gases. This sweep evacuates the burnt gases present in the combustion chamber to replace them with supercharged air.

As explained in the patent US 4,217,866 , this sweeping 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 of rotation of the crankshaft. Typically, this occurs at the end of the exhaust of the burnt gases and at the start of the intake of fresh air. Concretely, the fact that the air pressure at the open intake valve is higher than the pressure at the exhaust valve creates an air flow which passes directly from the intake to the exhaust causing part of the residual burnt gases present in the combustion chamber to pass. This period during which the intake and exhaust valves are simultaneously open is called "valve crossing".

In the case of naturally aspirated engines, that is to say engines without supercharging, a valve crossing may also be provided. In this case, during the valve crossing, burnt gases are drawn into the combustion chamber. It is said that the burnt gases are re-aspirated. This feature is known by the acronym IGR (Internal Gas Recirculation) or Internal Exhaust Gas Recirculation.

Methods for estimating the flow rate of fresh air admitted inside a combustion chamber of a cylinder of an engine are known, for example from the document DE10254475B3 corresponding to the preamble of claim 1. However, these methods are imprecise and do not really make it possible to obtain an estimate of the quantity of fresh air admitted into each combustion chamber. However, this estimate is important for correctly controlling the engine. For example, this estimate is useful for determining the amount of fuel to inject or for adjusting the ignition advance.

The invention aims to remedy this drawback by proposing a more precise method making it possible to estimate the mass of fresh air admitted inside a combustion chamber.

• l'estimation d'une masse Ma d'air frais admis à l'intérieur de la chambre de combustion d'un cylindre d'un moteur lors d'un cycle moteur mis en œuvre par un calculateur électronique,
• l'estimation d'une masse totale Mtot de gaz contenue dans la chambre de combustion à la fin de l'admission de l'air frais, l'estimation d'une masse Mb de gaz brûlés contenue dans la chambre de combustion à la fin de l'échappement des gaz brûlés, et l'estimation de la masse Ma d'air frais à partir de la différence entre la masse totale Mtot et la masse Mb de gaz brûlés estimées,

dans lequel l'estimation de la masse totale Mtot est obtenue à partir d'une pression admission P_ADM de l'air , d'un volume de la chambre de combustion à la fin de l'admission, d'une température T_mélange du mélange d'air frais et de gaz brûlés contenu dans la chambre de combustion à la fin de l'admission d'air frais, et d'un coefficient correcteur A_ADM dont la valeur est obtenue à partir d'une cartographie préenregistrée en fonction d'un angle FA de fin d'admission et du régime moteur, l'estimation du remplissage total étant une solution du système d'équation suivant : $$\{\begin{array}{l}\mathit{rempl}\_\mathit{tot}=\frac{\mathit{Ma}}{\mathit{Mo}}+\frac{\mathit{Mbal}}{\mathit{Mo}}\\ \frac{\mathit{Ma}}{\mathit{Mo}}=\frac{\mathit{Mtot}}{\mathit{Mo}}-\max \left(0;\frac{\mathit{Mb}}{\mathit{Mo}}-\frac{\mathit{Mbal}\_\mathit{tot}}{\mathit{Mo}}\right)\\ \frac{\mathit{Mbal}}{\mathit{Mo}}=\left|\min \left(0;\frac{\mathit{Mb}}{\mathit{Mo}}-\frac{\mathit{Mbal}\_\mathit{tot}}{\mathit{Mo}}\right)\right|\end{array}$$

où :

• Mtot est la masse totale de gaz contenue dans la chambre de combustion à la fin de l'admission de l'air frais définie précédemment,
• Mo est une masse de référence d'air dans les conditions normales de températures et de pression
• Mb est une masse de gaz brûlés contenue dans la chambre de combustion à la fin de l'échappement des gaz brûlés
• Mbal_tot est la masse totale de gaz balayé (air ou gaz brûlé) pendant le croisement de soupapes,
• Mbal est la masse de gaz balayé (air) entre l'admission et l'échappement pendant le croisement de soupapes,
• Max(...) et Min(...) sont respectivement les fonctions retournant le maximum et le minimum, et
• |...| est la valeur absolue.

caractérisé en ce que ce procédé comprend :

• l'estimation d'une masse Mbal_tot de gaz balayés de l'admission vers l'échappement lors du croisement de soupapes,
• l'estimation du remplissage total rempl_tot en air frais suralimenté à partir de la masse d'air frais Ma et de la masse Mbal_tot de gaz balayés estimées.
• la commande de différents actionneurs, injecteurs et dispositifs d'allumage du moteur en fonction des estimations de la masse Ma et du remplissage total rempl_tot.

It therefore relates to a method for estimating a total filling filled with fresh supercharged air from a combustion chamber of an engine cylinder during an engine cycle, comprising

• the estimation of a mass Ma of fresh air admitted inside the combustion chamber of a cylinder of an engine during an engine cycle implemented by an electronic computer,
• the estimation of a total mass Mtot of gas contained in the combustion chamber at the end of the intake of fresh air, the estimation of a mass Mb of burnt gases contained in the combustion chamber at the end the exhaust of the burnt gases, and the estimation of the mass Ma of fresh air from the difference between the total mass Mtot and the mass Mb of estimated burnt gases,

in which the estimate of the total mass Mtot is obtained from an intake pressure P _ADM of the air, a volume of the combustion chamber at the end of the intake, a temperature T _mixture of the mixture of fresh air and burnt gases 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 map as a function of '' an angle of FA end of intake and engine speed, the estimation of the total filling being a solution of the following equation system: $$\{\begin{array}{l}\mathit{repl}\_\mathit{early}=\frac{\mathit{My}}{\mathit{MB}}+\frac{\mathit{Mbal}}{\mathit{MB}}\\ \frac{\mathit{My}}{\mathit{MB}}=\frac{\mathit{M\; tot}}{\mathit{MB}}-\max \left(0;\frac{\mathit{Mb}}{\mathit{MB}}-\frac{\mathit{Mbal}\_\mathit{early}}{\mathit{MB}}\right)\\ \frac{\mathit{Mbal}}{\mathit{MB}}=\left|\min \left(0;\frac{\mathit{Mb}}{\mathit{MB}}-\frac{\mathit{Mbal}\_\mathit{early}}{\mathit{MB}}\right)\right|\end{array}$$

or :

• Mtot is the total mass of gas contained in the combustion chamber at the end of the intake of fresh air defined above,
• Mo is a reference mass of air 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 burnt gases
• Mbal_tot is the total mass of gas swept (air or gas burned) during the crossing of valves,
• Mbal is the mass of swept gas (air) between the intake and the exhaust during the valve crossing,
• Max (...) and Min (...) are respectively the functions returning the maximum and the minimum, and
• | ... | is the absolute value.

characterized in that this process comprises:

• the estimation of a mass Mbal_tot of gases swept from the intake to the exhaust during the crossing of valves,
• the estimate of the total filling repl_tot in supercharged fresh air from the mass of fresh air Ma and the mass Mbal_tot of estimated swept gases.
• the control of various actuators, injectors and ignition devices of the engine according to the estimates of the mass Ma and of the total filling repl_tot.

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. Consequently, this method of estimating the mass Ma is more precise. The above process is more precise because the mass of gas swept towards the exhaust is taken into account when crossing the valves.

The embodiments of this method of estimating the mass Ma can include one or more of the characteristics corresponding to the variants described below.

In a variant, the estimation of the mass Mb of burnt gases comprises the estimation of a mass Mb_resi of residual burnt gases contained in the combustion chamber at the end of the exhaust of the burnt gases, and the estimation of 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 precise estimate of the mass Mb since the residual mass of burnt gases and the mass of burnt gases re-aspirated during a crossing 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, from an interior volume of the combustion chamber at the end of the exhaust of the burnt gases, from a temperature T _ECH of the burnt gases and a correction coefficient A _ECH of the pressure P _ECH whose value is function of an exhaust end angle and 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 the need to measure the pressure or the temperature inside the combustion chamber. combustion.

où:

• Mb_reasp est le débit de gaz brûlés ré-aspirés,
• P_ECH est la pression échappement des gaz brûlés,
• P_ADM est la pression admission de l'air,
• T_ECH est la température des gaz brulés,
• r est une constante égale au rapport suivant R/M où R est la constante universelle des gaz parfaits et M est la masse molaire en kg.mol^-1 des gaz brûlés,
• Sbase est une valeur corrective fonction du régime moteur et de la différence entre des angles FE et OA, respectivement, de fermeture d'échappement et d'ouverture d'admission et,
• Scor est une valeur corrective fonction de la différence entre les angles FE et OA et du régime moteur,
• POND est une valeur corrective fonction du régime moteur et d'une position du croisement de soupapes donné par la relation suivante (FE + OA) / 2,
  • Γ(P_ADM/P_ECH) est défini par la relation suivante :

$$\mathrm{Si}\frac{P_{\mathit{ADM}}}{P_{\mathit{ECH}}}>{\left(\frac{2}{\gamma +1}\right)}^{\frac{\gamma }{\gamma -1}}\Rightarrow \mathrm{\Gamma }\left(\frac{P_{\mathit{ADM}}}{P_{\mathit{ECH}}}\right)=\sqrt{\frac{2\times \gamma }{\gamma -1}\times \left[{\left(\frac{P_{\mathit{ADM}}}{P_{\mathit{ECH}}}\right)}^{\frac{2}{\gamma }}-{\left(\frac{P_{\mathit{ADM}}}{P_{\mathit{ECH}}}\right)}^{\frac{\gamma +1}{\gamma }}\right]}$$

$$\mathrm{Si}\frac{P_{\mathit{ADM}}}{P_{\mathit{ECH}}}<{\left(\frac{2}{\gamma +1}\right)}^{\frac{\gamma }{\gamma -1}}\Rightarrow \mathrm{\Gamma }\left(\frac{P_{\mathit{ADM}}}{P_{\mathit{ECH}}}\right)=\sqrt{\gamma \times {\left(\frac{2}{\gamma +1}\right)}^{\frac{\gamma +1}{\gamma -1}}}$$

où γ est le rapport de la capacité calorifique à pression constante des gaz brulés sur la capacité calorifique à volume constant des gaz brulés,

• Γ₀(P_ADM/P_ECH) est défini par la relation suivante : $${\mathrm{\Gamma }}_0\left(\frac{P_{\mathit{ADM}}}{P_{\mathit{ECH}}}\right)=\sqrt{\gamma \times {\left(\frac{2}{\gamma +1}\right)}^{\frac{\gamma +1}{\gamma -1}}}$$
  

In a variant which makes it possible to increase the precision of the estimate by taking account of the crossing of the valves, the estimate of the mass Mb_reasp is obtained using the following relation: $$\stackrel{·}{\mathit{Mb}\_\mathit{reasp}}=\frac{P_{\mathit{ECH}}}{\sqrt{r\times T_{\mathit{ECH}}}}\times \left[\mathit{\$\; base}+\mathit{Scor}\times \left(\mathrm{\Gamma }\left(\frac{P_{\mathit{ADM}}}{P_{\mathit{ECH}}}\right)-{\mathrm{\Gamma }}_0\left(\frac{P_{\mathit{ADM}}}{P_{\mathit{ECH}}}\right)\right)\right]\times \mathit{POND}$$

or:

• Mb_reasp is the flow of re-aspirated burnt gases,
• P _ECH is the exhaust pressure of the burnt gases,
• P _ADM is the air intake pressure,
• T _ECH is the temperature of the burnt gases,
• r is a constant equal to the following ratio R / M where R is the universal constant of the ideal gases and M is the molar mass in kg.mol ^-1 of the burnt gases,
• Sbase is a corrective value depending on the engine speed and the difference between the FE and OA angles, respectively, of exhaust closure and intake opening and,
• Scor is a corrective value depending on 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 _ADM / P _ECH ) is defined by the following relation:

$$\mathrm{Yes}\frac{P_{\mathit{ADM}}}{P_{\mathit{ECH}}}>{\left(\frac{2}{\gamma +1}\right)}^{\frac{\gamma }{\gamma -1}}\Rightarrow \mathrm{\Gamma }\left(\frac{P_{\mathit{ADM}}}{P_{\mathit{ECH}}}\right)=\sqrt{\frac{2\times \gamma }{\gamma -1}\times \left[{\left(\frac{P_{\mathit{ADM}}}{P_{\mathit{ECH}}}\right)}^{\frac{2}{\gamma }}-{\left(\frac{P_{\mathit{ADM}}}{P_{\mathit{ECH}}}\right)}^{\frac{\gamma +1}{\gamma }}\right]}$$

$$\mathrm{Yes}\frac{P_{\mathit{ADM}}}{P_{\mathit{ECH}}}<{\left(\frac{2}{\gamma +1}\right)}^{\frac{\gamma }{\gamma -1}}\Rightarrow \mathrm{\Gamma }\left(\frac{P_{\mathit{ADM}}}{P_{\mathit{ECH}}}\right)=\sqrt{\gamma \times {\left(\frac{2}{\gamma +1}\right)}^{\frac{\gamma +1}{\gamma -1}}}$$

where γ is the ratio of the heat capacity at constant pressure of the burnt gases to the heat capacity at constant volume of the burnt gases,

• Γ ₀ (P _ADM / P _ECH ) is defined by the following relation: $${\mathrm{\Gamma }}_0\left(\frac{P_{\mathit{ADM}}}{P_{\mathit{ECH}}}\right)=\sqrt{\gamma \times {\left(\frac{2}{\gamma +1}\right)}^{\frac{\gamma +1}{\gamma -1}}}$$
  

The use of a solution of the above equation makes it possible to increase the accuracy since it is taken into account that the admitted air mass fills the volume of the combustion chamber until it there are no more burnt gases in it.

• la figure 1 est une illustration schématique d'un véhicule dans lequel la masse Ma et le remplissage total rempl_totsont estimés ;
• la figure 2 est un graphe illustrant schématiquement des déplacements des soupapes d'échappement et d'admission lors d'un cycle moteur,
• la figure 3 est une illustration plus détaillée de l'architecture d'un calculateur électronique implémentant un estimateur de la masse Ma et du remplissage total rempl_tot, et
• la figure 4 est un organigramme d'un procédé d'estimation de la masse Ma et du remplissage total rempl_tot dans le véhicule de la figure 1.

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

• the figure 1 is a schematic illustration of a vehicle in which the mass Ma and the total filling repl_tot are estimated;
• the figure 2 is a graph schematically illustrating movements of the exhaust and intake valves during an engine cycle,
• the figure 3 is a more detailed illustration of the architecture of an electronic computer implementing an estimator of the mass Ma and of the total filling repl_tot, and
• the figure 4 is a flowchart of a method for estimating the mass Ma and the total filling repl_tot in the vehicle of the figure 1 .

The figure 1 schematically represents a vehicle 2 equipped with an internal combustion engine. For example, vehicle 2 is a motor vehicle such as a car.

The engine of vehicle 2 is equipped with several cylinders. However, to simplify the illustration, only one cylinder 6 of this combustion engine is shown in the figure 1 . Inside the cylinder 6, a piston 8 is mounted movable 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 rotates, via a mechanism not shown, the drive wheels of the vehicle 2 such that the wheel 16.

The cylinder 6 defines a combustion chamber 18 delimited 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 via an intake opening. An intake valve 24 is movable between a closed position in which it closes the fresh air opening in an airtight manner, and an open position in which the fresh air can be admitted inside the chamber 18 via the admission 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 line 20 to inject fuel into the fresh air admitted inside the chamber 18. Thus, the fresh air / fuel mixture begins to occur at inside the intake air duct.

The duct 20 is fluidly connected to a compressor 30 of a turbocharger 32 capable of compressing the fresh air admitted inside the chamber 18. The fresh air thus compressed is called fresh supercharged air.

A spark plug 34 capable of igniting the fresh air / fuel mixture opens into chamber 18. This spark plug is controlled by an ignition device 36.

An exhaust duct 40 also opens into the interior of the chamber 18 via an exhaust opening. This exhaust opening can be closed by a valve 44 which can be moved 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 makes it possible in particular to relax the exhaust gases before sending them to an exhaust line 50.

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

The unit 60 is also connected to numerous 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 the number of revolutions per minute made by the motor drive shaft.

The figure 2 represents, in the form of a graph, the movements of the valves 24 and 44 relative to the movements of the piston 8 during an engine cycle. On this graph, an axis 70 of the abscissas represents the displacement of the piston 8 between its top dead center and its bottom dead center noted, respectively, TDC and TDC on this graph. The ordinate axis represents the amplitude of movement 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 fully 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 angle of rotation of the crankshaft. The origin of this axis is confused with the top dead center of fresh air intake.

As depicted on this figure 2 , the exhaust valve begins to open at an angle OE located substantially around the bottom dead center of expansion and closes at an angle FE. In the particular case represented on the figure 2 , the FE angle is located after the top intake neutral point.

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 a few degrees, the intake and exhaust valves are simultaneously open.

The figure 3 represents in more detail a possible architecture for the unit 60 for estimating the mass Ma and the total filling repl_tot.

To this end, 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 fresh air admitted to 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 of the total filling repl_tot. This estimator 88 is also connected to a block 90 of engine controls. This block 90 makes it possible in particular to control the various actuators, injectors and ignition devices of the engine as a function of the estimates of the mass Ma and of the total filling repl_tot. For example, the block 90 is capable of adjusting the quantity of fuel injected and of advancing the instant of ignition of the fresh air / fuel mixture injected into the chamber 18 or of adjusting the opening of a butterfly valve making it possible to adjust the quantity of fresh air admitted inside the chamber 18.

The estimator 88 comprises a module 92 for estimating a mass Mb of burnt gases contained in the chamber 18 at the end of the exhaust of the burnt gases, an estimator 94 of a mass Mbal of gases swept from the intake towards the exhaust when the valves cross, an estimator 96 of the temperature Tb of the burnt 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 presents a sub-module 102 for estimating a mass Mb_resi of residual burnt gases contained in the chamber 18 at the end of the exhaust, and a sub-module 104 for estimating a mass Mb_reasp of burnt exhaust gases when the valves cross inside the chamber 18.

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

The unit 60 is typically produced from a programmable computer capable of executing instructions recorded 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 process of the figure 4 . In particular, the different maps used to implement the process of figure 4 are stored in this memory 106. These maps are for example constructed experimentally so as to minimize the 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 the figure 4 in the particular case of the engine described opposite the figure 1 .

Before going into the details of the method for estimating the mass Ma and the total filling repl_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 gases entering and leaving the chamber 18. This mass balance is broken down into several calculations which take place throughout the engine cycle.

First, at the end of the exhaust, the mass Mb of gas burned 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 over an engine cycle, the mass Ma of air contained inside the chamber 18 during an engine cycle can be obtained by subtracting the mass Mb to mass Mtot.

où Mtot est la masse totale de gaz dans la chambre 18 à la fin de l'admission, et Mb est la masse totale de gaz brûlés dans la chambre 18 à la fin de l'échappement.More precisely, according to the balance of the masses of the gases admitted and discharged during an engine cycle, the mass Ma is given by the following relationship: $$\mathit{My}=\mathit{M\; tot}-\mathit{Mb}$$

where Mtot is the total mass of gas in chamber 18 at the end of the intake, and Mb is the total mass of gas burned in chamber 18 at the end of the exhaust.

In the particular case where a part of the burnt gases are re-aspirated during the crossing of valves, the estimate of the mass Mb is broken down into an estimate of the mass Mb_resi of residual burnt gases not discharged by through the conduit 40 at the end of the exhaust and the mass Mb_reasp of burnt gas re-aspirated during the crossing of valves.

où :

• Mb_resi est la masse de gaz brûlé résiduelle qui n'a pas pu être évacuée lors de l'échappement, et
• Mb_reasp est la masse de gaz brûlés ré-aspirée lors du croisement de soupapes.

The mass of burnt gases Mb is then defined by the following relation: $$\mathit{Mb}=\mathit{Mb}\_\mathit{resi}+\mathit{Mb}\_\mathit{reasp}$$

or :

• Mb_resi is the mass of residual burnt gas which could not be evacuated during the exhaust, and
• Mb_reasp is the mass of burnt gas re-aspirated during the crossing of valves.

où :

• rempl_tot est le remplissage total en air frais total,
• rempl_cyl est le remplissage en air frais de la chambre 18,
• Mbal est la masse des gaz balayés de l'admission vers l'échappement pendant le croisement de soupapes, et
• Mo est une masse de référence d'air dans les conditions normales de températures et de pression.

In the particular case of a supercharged engine with valve crossing, one also seeks to estimate the total filling repl_tot in supercharged fresh air. Total filling repl_tot is the total quantity of fresh air admitted through the intake opening during an engine cycle. In the case of a supercharged engine with valve crossing, part of the fresh air admitted via the intake opening is immediately exhausted by the exhaust (Mbal). Thus, the total filling repl_tot is, as a first approximation, given by the following relation: $$\mathit{repl}\_\mathit{early}=\mathit{repl}\_\mathit{cyl}+\frac{\mathit{Mbal}}{\mathit{MB}}$$

or :

• repl_tot is the total filling with total fresh air,
• repl_cyl is the fresh air filling of chamber 18,
• Mbal is the mass of gases swept from the intake to the exhaust during valve crossing, and
• Mo is a reference mass of air under normal conditions of temperature and pressure.

où Ma est la masse d'air contenu dans la chambre 18 à la fin de l'admission, et Mo est la masse de référence.The fresh air filling repl_cyl is defined by the following relation: $$\mathit{repl}\_\mathit{cyl}=\frac{\mathit{My}}{\mathit{MB}}$$

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

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

The quantities repl_tot, repl_cyl and the Mbal / Mo ratio are dimensionless quantities.

Generally, the mass Mbal 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 masses Mb_reasp and Mbal are both carried out. Indeed, a person skilled in the art can easily simplify the following process to adapt it only to the case of naturally aspirated engines or only to the case of supercharged engines.

The method begins with a step 120 of estimating the mass Mb_resi of burnt gas contained in the chamber 18 at the end of the exhaust.

où :

• P_{cyl_FE} est la pression à l'intérieur de la chambre 18,
• P_ECH est la pression échappement des gaz brûlés,
• T_ECH est la température des gaz brûlés évacués par l'intermédiaire du conduit 40,
• r est une constante égale au rapport suivant R/M où R est la constante universelle des gaz parfaits et M est la masse molaire en kg.mol^-1 des gaz brûlés,
• A_ECH est un coefficient correcteur permettant de corriger la pression P_ECH pour obtenir une pression proche de P_{cyl_FE}, dont la valeur est donnée par une cartographie en fonction de l'angle FE et du régime moteur, et
• V_{cyl_FE} est le volume géométrique de la chambre 18 à la fin de l'échappement c'est-à-dire pour l'angle FE.

During step 120, the sub-module 102 estimates the mass Mb_resi using the following relation: $$\mathit{Mb}\_\mathit{resi}=\frac{P_{\mathit{cyl}\_\mathit{FE}}\times V_{\mathit{cyl}\_\mathit{FE}}}{r\times T_{\mathit{ECH}}}=\frac{\left({\mathrm{AT}}_{\mathit{ECH}}\times P_{\mathit{ECH}}\right)\times V_{\mathit{cyl}\_\mathit{FE}}}{r\times T_{\mathit{ECH}}}$$

or :

• P _{cyl_FE} is the pressure inside the chamber 18,
• P _ECH is the exhaust pressure of the burnt gases,
• T _ECH is the temperature of the burnt gases discharged via the conduit 40,
• r is a constant equal to the following ratio R / M where R is the universal constant of the ideal gases and M is the molar mass in kg.mol ^-1 of the burnt gases,
• A _ECH is a correction coefficient making it possible to correct the pressure P _ECH to obtain a pressure close to P _{cyl_FE} , the value of which is given by a map as a function of the angle FE and of the engine speed, and
• V _{cyl_FE} is the geometric volume of the chamber 18 at the end of the exhaust, that is to say for the angle FE.

où :λ est le rapport bielle/manivelle, Cu est la cylindrée unitaire du cylindre 6, et ε est le taux de compression du moteur.The volume V _{cyl_FE} is given by the following relation: $$V_{\mathit{cyl}\_\mathit{FE}}\left(\mathit{FE}\right)=\frac{\mathit{Cu}}{\epsilon -1}+\frac{\mathit{Cu}}{2}\left(1+\lambda -\cos \left(\mathit{FE}\right)-\sqrt{{\lambda }^2-{\sin }^2\left(\mathit{FE}\right)}\right)$$

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

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

In the relationship above and in the following relationships, the pressures P _ECH and P _ADM and the temperatures T _ECH and T _ADM are the pressures and temperatures estimated by the estimators 80, 82, 84 and 86 from physical quantities measured in engine.

où $\stackrel{·}{\mathit{Mb}\_\mathit{reasp}}$

est le débit de gaz brûlés ré-aspirés exprimé en kg/h, et K est un coefficient permettant de passer du débit à une masse admise par cycle moteur dans la chambre 18.Then, during a step 122, the sub-module 104 estimates the mass Mb_reasp of burnt gases re-aspirated during the crossing of valves. Here, this estimate is given by the following relation: $$\mathit{Mb}\_\mathit{reasp}=\frac{\stackrel{·}{\mathit{Mb}\_\mathit{reasp}}}{K}$$

or $\stackrel{·}{\mathit{Mb}\_\mathit{reasp}}$

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

où N est le régime moteur, « Nbre_cylindre » est le nombre de cylindre du moteur, « Nbre_revolutioncycle » est le nombre de révolution du vilebrequin lors d'un cycle du moteur, et « 60 » permet de convertir le régime moteur N donné en tour par minute en nombre de tours par heure.For example, the coefficient K is given by the following relation: $$K=\mathrm{NOT}\times \frac{\mathit{No.}\_\mathit{cylinder}}{\mathit{No.}\_\mathit{revolutio}\underset{\_}{\mathrm{not}}\mathit{cycle}}\times 60$$

where N is the engine speed, "Nbre_cylindre" is the number of cylinder of the engine, "Nbre_revolutioncycle" is the number of revolution of the crankshaft during a cycle of engine, and “60” converts the engine speed N given in revolutions per minute to the number of revolutions per hour.

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

est calculé à partir de la loi de Barré Saint Venant corrigée de la façon suivante pendant le croisement de soupapes $$\stackrel{·}{\mathit{Mb}\_\mathit{reasp}}=\frac{P_{\mathit{ECH}}}{\sqrt{r\times T_{\mathit{ECH}}}}\times \left[\mathit{Sbase}+\mathit{Scor}\times \left(\mathrm{\Gamma }\left(\frac{P_{\mathit{ADM}}}{P_{\mathit{ECH}}}\right)-{\mathrm{\Gamma }}_0\left(\frac{P_{\mathit{ADM}}}{P_{\mathit{ECH}}}\right)\right)\right]\times \mathit{POND}$$

où :

• P_ECH est la pression échappement des gaz brûlés,
• P_ADM est la pression admission de l'air admis par l'intermédiaire du conduit 20,
• T_ECH est la température des gaz brulés,
• Sbase est une cartographie prédéterminée qui donne une première valeur corrective en fonction de la différence entre les angles FE et OA et du régime moteur,
• Scor est une cartographie prédéterminée qui donne une seconde valeur corrective en fonction de la différence entre les angles FE et OA et du régime moteur,
• POND est une cartographie prédéterminée qui donne une troisième valeur corrective en fonction de la position du croisement de soupapes et du régime moteur.

The flow of re-aspirated burnt gases $\stackrel{·}{\mathit{Mb}\_\mathit{reasp}}$

is calculated from the law of Barré Saint Venant corrected as follows during the crossing of valves $$\stackrel{·}{\mathit{Mb}\_\mathit{reasp}}=\frac{P_{\mathit{ECH}}}{\sqrt{r\times T_{\mathit{ECH}}}}\times \left[\mathit{\$\; base}+\mathit{Scor}\times \left(\mathrm{\Gamma }\left(\frac{P_{\mathit{ADM}}}{P_{\mathit{ECH}}}\right)-{\mathrm{\Gamma }}_0\left(\frac{P_{\mathit{ADM}}}{P_{\mathit{ECH}}}\right)\right)\right]\times \mathit{POND}$$

or :

• P _ECH is the exhaust pressure of the burnt gases,
• P _ADM is the inlet pressure of the air admitted via the conduit 20,
• T _ECH is the temperature of the burnt gases,
• Sbase is a predetermined map which gives a first corrective value according to the difference between the angles FE and OA and the engine speed,
• Scor is a predetermined map which gives a second corrective value depending on the difference between the FE and OA angles and the engine speed,
• POND is a predetermined map which 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.

$$\mathrm{Si}\frac{P_{\mathit{ADM}}}{P_{\mathit{ECH}}}<{\left(\frac{2}{\gamma +1}\right)}^{\frac{\gamma }{\gamma -1}}\Rightarrow \mathrm{\Gamma }\left(\frac{P_{\mathit{ADM}}}{P_{\mathit{ECH}}}\right)=\sqrt{\gamma \times {\left(\frac{2}{\gamma +1}\right)}^{\frac{\gamma +1}{\gamma -1}}}$$

où γ est le rapport de la capacité calorifique à pression constante des gaz brulés sur la capacité calorifique à volume constant des gaz brulés. Par exemple, ce rapport est égal à 1,4.Γ (P _ADM / P _ECH ) is defined by the following relation: $$\mathrm{Yes}\frac{P_{\mathit{ADM}}}{P_{\mathit{ECH}}}>{\left(\frac{2}{\gamma +1}\right)}^{\frac{\gamma }{\gamma -1}}\Rightarrow \mathrm{\Gamma }\left(\frac{P_{\mathit{ADM}}}{P_{\mathit{ECH}}}\right)=\sqrt{\frac{2\times \gamma }{\gamma -1}\times \left[{\left(\frac{P_{\mathit{ADM}}}{P_{\mathit{ECH}}}\right)}^{\frac{2}{\gamma }}-{\left(\frac{P_{\mathit{ADM}}}{P_{\mathit{ECH}}}\right)}^{\frac{\gamma +1}{\gamma }}\right]}$$

$$\mathrm{Yes}\frac{P_{\mathit{ADM}}}{P_{\mathit{ECH}}}<{\left(\frac{2}{\gamma +1}\right)}^{\frac{\gamma }{\gamma -1}}\Rightarrow \mathrm{\Gamma }\left(\frac{P_{\mathit{ADM}}}{P_{\mathit{ECH}}}\right)=\sqrt{\gamma \times {\left(\frac{2}{\gamma +1}\right)}^{\frac{\gamma +1}{\gamma -1}}}$$

where γ is the ratio of the heat capacity at constant pressure of the burnt gases to the heat capacity at constant volume of the burnt gases. For example, this ratio is 1.4.

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

Γ ₀ (P _ADM / P _ECH ) is defined by the following relation: $${\mathrm{\Gamma }}_0\left(\frac{P_{\mathit{ADM}}}{P_{\mathit{ECH}}}\right)=\sqrt{\gamma \times {\left(\frac{2}{\gamma +1}\right)}^{\frac{\gamma +1}{\gamma -1}}}$$

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.

où :

• $\stackrel{·}{\mathit{Mbal}\_\mathit{tot}}$
  
  est le débit de gaz balayés de l'admission vers l'échappement pendant le croisement de soupapes exprimé en kg/h, et
• K est le même coefficient que précédemment défini pour passer du débit à une masse admise par cycle moteur dans la chambre 18.

The mass Mbal_tot is obtained using the following relation: $$\mathit{Mbal}\_\mathit{early}=\frac{\stackrel{·}{\mathit{Mbal}\_\mathit{early}}}{K}$$

or :

• $\stackrel{·}{\mathit{Mbal}\_\mathit{early}}$
  
  is the gas flow swept from the intake to the exhaust during valve crossing expressed in kg / h, and
• K is the same coefficient as previously defined for passing from the flow rate to a mass admitted per engine cycle in the chamber 18.

est estimé à partir de la loi de Barré Saint Venant corrigée de la façon suivante pour tenir compte des croisements de soupapes : $$\stackrel{·}{\mathit{Mbal}\_\mathit{tot}}=\frac{P_{\mathit{ADM}}\times S}{\sqrt{r\times T_{\mathit{ADM}}}}\times \mathrm{\Gamma }\left(\frac{P_{\mathit{ECH}}}{P_{\mathit{ADM}}}\right)\times \mathit{POND}$$

où :

• P_ECH, et P_ADM ont déjà été définis précédemment,
• T_ADM est la température de l'air admis dans la chambre 18
• S est une cartographie prédéterminée permettant d'obtenir une valeur corrective en fonction de la différence entre les angles FE et OA et du régime moteur, et
• POND est une cartographie prédéterminée permettant d'obtenir une valeur corrective en fonction de la position du croisement de soupapes et du régime moteur.

The flow $\stackrel{·}{\mathit{Mbal}\_\mathit{early}}$

is estimated from Barré Saint Venant's law corrected as follows to take account of valve crossings: $$\stackrel{·}{\mathit{Mbal}\_\mathit{early}}=\frac{P_{\mathit{ADM}}\times S}{\sqrt{r\times T_{\mathit{ADM}}}}\times \mathrm{\Gamma }\left(\frac{P_{\mathit{ECH}}}{P_{\mathit{ADM}}}\right)\times \mathit{POND}$$

or :

• P _ECH , and P _ADM have already been defined previously,
• T _ADM is the temperature of the air admitted into the room 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 making it possible to obtain a corrective value depending on the position of the valve crossing and the engine speed.

The ratio Γ (P _ECH / P _ADM ) has already been defined above.

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

où :

• - - Mb_resi est la masse de gaz brûlés résiduels précédemment estimée,
• - - Mb_reasp est la masse de gaz brûlés ré-aspirés lors du croisement de soupapes,
• - - cpb_resi est la capacité calorifique massique à pression constante des gaz brûlés résiduels,
• - - cpb_reasp est la capacité calorifique massique à pression constante des gaz brûlés réaspirés,
• - - Tb_reasp est la température des gaz brûlés réaspirés lors du croisement de soupape, et
• - - Tb_resi est la température des gaz brûlés résiduels obtenue à partir d'un calcul de détente adiabatique.

Then, during a step 126, the module 96 estimates the temperature Tb of the burnt gases. For this, this temperature Tb is obtained by calculating an enthalpy mixture between the residual gases and the burnt gases re-aspirated. For example, the temperature Tb is obtained from the following relation: $$\mathit{Tb}=\frac{\mathit{Mb}\_\mathit{reasp}\times \mathit{cPB}\_\mathit{reasp}\times \mathit{Tb}\_\mathit{reasp}+\mathit{Mb}\_\mathit{resi}\times \mathit{cPB}\_\mathit{resi}\times \mathit{Tb}\_\mathit{resi}}{\mathit{Mb}\_\mathit{reasp}\times \mathit{cPB}\_\mathit{reasp}+\mathit{Mb}\_\mathit{resi}\times \mathit{cPB}\_\mathit{resi}}$$

or :

• - - Mb_resi is the mass of residual burnt gas previously estimated,
• - - Mb_reasp is the mass of burnt gas re-aspirated during the crossing of valves,
• - - cpb_resi is the specific heat capacity at constant pressure of the residual burnt gases,
• - - cpb_reasp is the specific heat capacity at constant pressure of the re-aspirated burnt gases,
• - - Tb_reasp is the temperature of the burnt gases re-aspirated during the valve crossing, and
• - - Tb_resi is the temperature of the residual burnt gases obtained from an adiabatic expansion calculation.

To simplify, for example, the capacities cpb_resi and cpb_reasp are taken equal.

The temperature Tb_reasp is taken equal to the temperature TECH.

où toutes les variables ont déjà précédemment été définies.The temperature Tb_resi is calculated from the following relation: $$\mathit{Tb}\_\mathit{resi}=T_{\mathit{ECH}}\times \left[\frac{1}{\gamma }+\left(\frac{\gamma -1}{\gamma }\right)\times \frac{P_{\mathit{ADM}}}{P_{\mathit{ECH}}}\right]$$

where all the variables have already been previously defined.

où :

• P_ADM, Mb, Ma ont déjà été définis précédemment,
• V_{cyl_FA} est le volume géométrique de la chambre 18 calculé à l'angle FA,
• A_ADM est un coefficient correcteur,
• r est une constante égale au rapport suivant R/M où R est la constante universelle des gaz parfaits et M est la masse molaire en kg.mol^-1 des gaz mélangés,
• T_mélange est la température du mélange d'air frais et de gaz brûlés contenu dans la chambre 18, et
• cpa et cpb sont les capacités calorifiques massiques à pression constante, respectivement, de l'air frais et des gaz brulés, et
• Ta et Tb sont les températures, respectivement, de l'air frais et des gaz brulés. Le volume V_{cyl_FA} est calculé à l'aide de la relation suivante : $$V_{\mathit{cyl}\_\mathit{FA}}\left(\mathit{FA}\right)=\frac{\mathit{Cu}}{\epsilon -1}+\frac{\mathit{Cu}}{2}\left(1+\lambda -\cos \left(\mathit{FA}\right)-\sqrt{{\lambda }^2-{\sin }^2\left(\mathit{FA}\right)}\right)$$
  

Then, during a step 128, the module 98 estimates the mass Ma by solving the following system of equations: $$\{\begin{array}{l}\mathit{My}=\mathit{M\; tot}-\mathit{Mb}\\ \mathit{M\; tot}=\frac{\left({\mathrm{AT}}_{\mathit{ADM}}\times P_{\mathit{ADM}}\right)\times V_{\mathit{cyl}\_\mathit{FA}}}{\left(r\times T_{\mathit{mixed}}\right)}\\ T_{\mathit{mixed}}=\frac{\mathit{My}\times \mathit{cpa}\times \mathit{Your}+\mathit{Mb}\times \mathit{cPB}\times \mathit{Tb}}{\mathit{My}\times \mathit{cpa}+\mathit{Mb}\times \mathit{cPB}}\end{array}$$

or :

• P _ADM , Mb, Ma have already been defined previously,
• V _{cyl_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 following ratio R / M where R is the universal constant of the ideal gases and M is the molar mass in kg.mol ^-1 of the mixed gases,
• T _mixture is the temperature of the mixture of fresh air and burnt gases contained in the chamber 18, and
• cpa and cpb are the mass heat capacities at constant pressure, respectively, of fresh air and burnt gases, and
• Ta and Tb are the temperatures of fresh air and burnt gases, respectively. The volume V _{cyl_FA} is calculated using the following relation: $$V_{\mathit{cyl}\_\mathit{FA}}\left(\mathit{FA}\right)=\frac{\mathit{Cu}}{\epsilon -1}+\frac{\mathit{Cu}}{2}\left(1+\lambda -\cos \left(\mathit{FA}\right)-\sqrt{{\lambda }^2-{\sin }^2\left(\mathit{FA}\right)}\right)$$
  

où :

• AADM_ATMO est une valeur corrective obtenue à partir d'une cartographie prédéterminée en fonction de l'angle FA et du régime moteur,
• AADM_TURBO est une valeur corrective obtenue à partir d'une cartographie prédéterminée en fonction de l'ange FA et du régime moteur,
• Le coefficient kATMO_TURBO est un coefficient correcteur donné par la relation suivante : $$k_{\mathit{ATMO}\_\mathit{TURBO}}=\max \left(0;\min \left(1,\frac{P_{\mathit{ADM}}-f_A\left(N,\mathit{FA}\right)\times \frac{P_{\mathit{ATMO}}}{\mathit{Po}}}{f_B\left(N\right)\times \frac{P_{\mathit{ATMO}}}{\mathit{Po}}}\right)\right)$$
  
  où :
  • PATMO est la pression atmosphérique,
  • Po est la pression de référence qui est ici égale à 1013 mbar,
  • fA(N, FA) est une valeur corrective obtenue à partir d'une cartographie prédéterminée en fonction du régime moteur et de l'angle FA, et
  • fB(N) est valeur corrective obtenue à partir d'une cartographie prédéterminée en fonction du régime moteur.

The correction coefficient A _ADM is obtained using the following relation: $${\mathrm{AT}}_{\mathit{ADM}}={\mathrm{AT}}_{\mathit{ADM}\_\mathit{SFX}}+k_{\mathit{SFX}\_\mathit{TURBO}}\times \left({\mathrm{AT}}_{\mathit{ADM}\_\mathit{TURBO}}-{\mathrm{AT}}_{\mathit{ADM}\_\mathit{SFX}}\right)$$

or :

• AADM_ATMO is a corrective value obtained from a predetermined map according to the angle FA and the engine speed,
• AADM_TURBO is a corrective value obtained from a predetermined map according to the angel FA and the engine speed,
• The coefficient kATMO_TURBO is a correction coefficient given by the following relation: $$k_{\mathit{SFX}\_\mathit{TURBO}}=\max \left(0;\min \left(1,\frac{P_{\mathit{ADM}}-f_{\mathrm{AT}}\left(\mathrm{NOT},\mathit{FA}\right)\times \frac{P_{\mathit{SFX}}}{\mathit{Po}}}{f_B\left(\mathrm{NOT}\right)\times \frac{P_{\mathit{SFX}}}{\mathit{Po}}}\right)\right)$$
  
  or :
  • PATMO is 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 map as a function of the engine speed and the angle FA, and
  • fB (N) is corrective value obtained from a predetermined map as a function of the engine speed.

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

The system of equations described above is a system of equations 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 _mixture and of the total mass Mtot.

More precisely, the estimate of the mass Ma is given by the following relation in the particular case where cpb and cpa are equal: $$\mathit{My}=\frac{1}{\mathit{Your}}\times \left(\frac{\left({\mathrm{AT}}_{\mathit{ADM}}\times P_{\mathrm{AT}\mathit{DM}}\right)\times V_{\mathit{cyl}\_\mathit{FA}}}{r}-\mathit{Mb}\times \mathit{Tb}\right)$$

où f (1/Ta) est un coefficient correcteur dont la valeur est obtenue à partir d'une cartographie préenregistrée donnant la valeur de ce coefficient correcteur en fonction de l'inverse de la température Ta.Optionally, during step 128, the estimate of the mass Ma obtained after solving the system of equations is corrected as a function of the inverse of the temperature Ta of the fresh air. For example, the mass Ma is corrected using the following relation: $$\mathit{My}=f\left(\frac{1}{\mathit{Your}}\right)\mathit{My}$$

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

où l'ensemble des variables de cette relation ont déjà été définis précédemment, Max(...) et Min(...) sont respectivement les fonctions retournant le maximum et le minimum, et |...| est la valeur absolue.Finally, during a step 130, the module 100 estimates the total filling repl_tot in fresh air. This total filling repl_tot is for example obtained using the following relation: $$\mathit{My}=\frac{1}{\mathit{Your}}\times \left(\frac{\left({\mathrm{AT}}_{\mathit{ADM}}\times P_{\mathrm{AT}\mathit{DM}}\right)\times V_{\mathit{cyl}\_\mathit{FA}}}{r}-\max \left(0;\mathit{Mb}-\mathit{Mbal}\_\mathit{early}\right)\times \mathit{Tb}\right)+\left|\min \left(0;\mathit{Mb}-\mathit{Mbal}\_\mathit{early}\right)\right|$$

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

What has been described above can also be applied to an engine devoid of camshaft phase shifter on intake or exhaust.

Claims (4)

1. A method for estimating a total filling rempl_tot with supercharged fresh air of a combustion chamber of an engine cylinder during an engine cycle, including:

   - the estimation (128) of a mass Ma of fresh air taken into the interior of the combustion chamber of an engine cylinder during an engine cycle, implemented by an electronic computer,

   - 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 estimation (120, 124) of a mass Mb of burnt gases contained in the combustion chamber at the end of the exhaust of the burnt gases, and the estimation (128) of the mass Ma of fresh air from the different between the total mass Mtot and the mass Mb of estimated burnt gases, in which the estimation (128) of the total mass Mtot is obtained from an intake pressure P_ADM of the air, a volume of the combustion chamber at the end of the intake, a temperature T_mélange of the mixture of fresh air and of burnt gases contained in the combustion chamber at the end of the intake of fresh air, and a correction coefficient A_ADM, the value of which is obtained from a prerecorded cartograpnhy as a function of an angle FA of end of intake and of the engine speed, the estimation of the mass of air Ma of fresh air being a solution of the following system of equations: $$\{\begin{array}{l}\mathit{Mtot}=\frac{\left(A_{\mathit{ADM}}\times P_{\mathit{ADM}}\right)\times V_{\mathit{cyl}\_\mathit{FA}}}{\left(r\times T_{\mathit{melange}}\right)}\\ \mathit{Ma}=\mathit{Mtot}-\mathit{Mb}\\ T_{\mathit{mélange}}=\frac{\mathit{Ma}\times \mathit{cpa}\times \mathit{Ta}+\mathit{Mb}\times \mathit{cpb}\times \mathit{Tb}}{\mathit{Ma}\times \mathit{cpa}+\mathit{Mb}\times \mathit{cpb}}\end{array}$$

   

   where:

   - A_ADM is the correction coefficient, the value of which is a function of the engine speed and of the end of intake angle,

   - P_ADM is the air intake pressure,

   - V_{cyl_FA} is the geometric volume of the combustion chamber calculated at the end of intake angle,

   - T_mélange is the temperature of the mixture of fresh air and of burnt gases contained in the combustion chamber,

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

   - cpa and cpb are the specific heat capacities at constant pressure, respectively, of the fresh air and of the burnt gases, and

   - Ta and Tb are the temperatures, respectively, of the fresh air and of the burnt gases,

   characterized in that this method includes:

   - the estimation (124) of a mass Mbal_tot of swept gases from intake to exhaust on valve overlap,

   - the estimation (130) of the total filling rempl_tot of supercharged fresh air from the mass of fresh air Ma and the mass Mbal_tot of estimated swept gases,

   - the control of different actuators, injectors and ignition devices of the engine as a function of the estimations of the mass Ma and of the total filling rempl_tot.
2. The method according to Claim 1, in which the estimation of the mass Mb of burnt gases includes the estimation (120) of a mass Mb_resi of residual burnt gases contained in the combustion chamber at the end of the exhaust of the burnt gases, and the estimation (122) of a mass Mb-reasp of reaspirated burnt gases in the interior of the combustion chamber during the valve overlap.
3. The method according to Claim 2, in which the estimation (120) of the mass Mb_resi is obtained from a pressure P_ECH of the burnt gases, an interior volume of the combustion chamber at the end of the exhaust of the burnt gases, a temperature T_ECH of the burnt gases and a correction coefficient A_ECH of the pressure P_ECH, the value of which is a function of an angle of end of exhaust and of engine speed.
4. The method according to one of the preceding claims, in which the estimation (130) of the total filling is a solution of the following equation system: $$\{\begin{array}{l}\mathit{rempl}\_\mathit{tot}=\frac{\mathit{Ma}}{\mathit{Mo}}+\frac{\mathit{Mbal}}{\mathit{Mo}}\\ \frac{\mathit{Ma}}{\mathit{Mo}}=\frac{\mathit{Mtot}}{\mathit{Mo}}-\max \left(0;\frac{\mathit{Mb}}{\mathit{Mo}}-\frac{\mathit{Mbal}\_\mathit{tot}}{\mathit{Mo}}\right)\\ \frac{\mathit{Mbal}}{\mathit{Mo}}=\left|\min \left(0;\frac{\mathit{Mb}}{\mathit{Mo}}-\frac{\mathit{Mbal}\_\mathit{tot}}{\mathit{Mo}}\right)\right|\end{array}$$

   

   where:

   - Mtot is the total mass of gas contained in the combustion chamber at the end of intake of fresh air previously defined,

   - Mo is a reference mass of air in the normal temperature and pressure conditions,

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

   - Mbal_tot is the total mass of swept gases (air and burnt gas) during the valve overlap,

   - Mbal is the mass of swept gas (air) between intake and exhaust during the valve overlap,

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

   - |...| is the absolute value.

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