EP1916404A1 - Method of estimating characteristic parameters of a heat engine and of controlling thermal flux applied to components of this engine - Google Patents

Abstract

The method involves estimating determined parameters e.g. value of mass of fuel, injected in a combustion chamber of each of cylinders (1a-1d), value of mass of air mixture and exhaust gas recirculation at an intake pipe (310) of a thermal engine (3), and temperature of the mixture, and magnitude of combustion phasing in a combustion cycle. Thermal flux applied to a component e.g. piston or actuator, of the thermal engine is controlled in a closed loop, from the derived magnitude of the estimated characteristic parameters.

Description

The invention relates to a method for estimating the parameters characterizing the operation of a heat engine and controlling heat flows applied to components of this engine.

It relates to the thermal resistance of the components of such an engine directly subjected to combustion flows. These components include piston, cylinder head and cylinder

More particularly, the method according to the invention makes it possible to directly control, in a closed loop and in real time, the thermal flux levels applied to these motor components.

In the context of the invention, the term "engine" applies equally to all types of combustion engines, whether of gasoline or diesel type. For simplicity, in what follows, the generic term "engine" will be used.

First of all, it is useful to recall the main data characterizing the generation of heat flows from combustion.

Figure 1 at the end of the present description illustrates very schematically an example of configuration of a cylinder block 1 of a heat engine. The main components comprise a cylinder proper 11, a cylinder head 10 and a piston 12 in linear movement back and forth within the walls of the cylinder 11. The space between the upper wall of the piston 12 and the lower wall of the cylinder head 10 defines the combustion chamber 13, a place of intense heating due to the combustion of the gas mixture injected into this chamber. This results in significant heat transfer to the walls of the cylinder head 10, the cylinder 11 and to the piston 12. To limit the heating of these components, the four-stroke engines are provided with "water jackets", 100 and 110 respectively, the water circulating in enclosures created in the walls of the cylinder head 10 and the cylinder 11.

$$F{T}_{\mathit{culasse}}=K\times S_{\mathit{culasse}}\left(T_{\mathit{gaz\; combustion}}-T_{\mathit{paroi\; culasse}}\right)$$

$$F{T}_{\mathit{cylindre}}=K\times S_{\mathit{cylindre}}\left(T_{\mathit{gaz\; combustion}}-T_{\mathit{paroi\; cylindre}}\right)$$

relations dans lesquelles FT_piston, FT_culasse, FT_cylindre représentent les flux thermiques respectifs sur le piston, la culasse et le cylindre. De même, T_paroi piston, T_{paroi culasse}, T_{paroi cylindre} représentent les températures (en °C) respectives des parois de ces composants et S_piston, S_culasse, S_cylindre, leurs surfaces (en m²) d'exposition aux flux thermiques. Enfin, T_{gaz combustion} est la température des gaz (en °C) lors de la combustion, c'est-à-dire la température régnant dans la chambre de combustion 13.As is well known, the heat fluxes on the various components of the engine, namely the piston 12, the cylinder head 10 and the cylinder 11, expressed in Watts, obey the following relationships: $$F{T}_{\mathit{piston}}=K\times S_{\mathit{piston}}\left(T_{\mathit{combustion\; gas}}-T_{\mathit{piston\; wall}}\right)$$

$$F{T}_{\mathit{cylinder\; head}}=K\times S_{\mathit{cylinder\; head}}\left(T_{\mathit{combustion\; gas}}-T_{\mathit{cylinder\; wall}}\right)$$

$$F{T}_{\mathit{cylinder}}=K\times S_{\mathit{cylinder}}\left(T_{\mathit{combustion\; gas}}-T_{\mathit{cylinder\; wall}}\right)$$

relations in which FT _piston , FT _{cylinder head} , FT _cylinder represent the respective heat flows on the piston, the cylinder head and the cylinder. Similarly, T piston _wall , T _{cylinder wall} , T _{cylinder wall} represent the respective temperatures (in ° C) of the walls of these components and S _piston , S _{cylinder head} , S _cylinder , their surfaces (in m ² ) exposure to the flow thermal. Finally, the _{combustion gas} is the temperature of the gases (in ° C) during combustion, that is to say the temperature prevailing in the combustion chamber 13.

The coefficient K is obtained by empirical correlations generally used during combustion analyzes for the calculation of heat flux. The correlation most often used is the so-called "Woschni" correlation which makes it possible to fix this coefficient K.

In a manner also known, heat fluxes are generally calculated using combustion analysis software which determines the temperatures of the combustion gases as well as the wall temperatures as functions of predetermined motor parameters (air mass, fuel mass, etc.)

It is therefore possible to map the thermal flows according to the operating point of a given engine (speed / torque), during the development phase of this engine.

The parameters influencing the thermal flows are multiple.

• la masse ou le débit de carburant injecté ;
• la masse ou le débit d'air utilisé;
• la température du mélange air + EGR (air + "EGR", pour "Exhaust Gas Recirculation", ou recyclage des gaz d'échappement) en entrée du moteur ; et
• l'angle de début d'injection ou d'allumage pour les moteurs à essence, qui se traduit fonctionnellement par une valeur dite de "phasage de combustion" dans le cycle (début de combustion ou angle correspondant à x % de carburant brûlé).

As just recalled, the heat fluxes are a function of the engine operating point. It is therefore possible to estimate and identify them according to the following main engine parameters:

• the mass or flow of fuel injected;
• the mass or flow of air used;
• the temperature of the air + EGR mixture (air + "EGR", for "Exhaust Gas Recirculation", or exhaust gas recirculation) at the engine inlet; and
• the injection or ignition start angle for gasoline engines, which is functionally translated into a so-called "combustion phase" value in the cycle (start of combustion or angle corresponding to x% of fuel burned).

The flow on each component of the engine, piston 12, cylinder head 10 and cylinder 11, then obeys the following relation (4), in which relation f () is a function of several parameters and T _{mixture air + EGR} the temperature of the injected air: $$\mathit{Thermal\; Flow}=f\left(\mathit{fuel\; mass}\mathit{air\; mass}{T}_{\mathit{air\; mixture}+\mathit{EGR}}\mathit{Burning\; angle}\right)$$

This relationship can be linear (which is usually true at full load), or higher.

relation dans laquelle A, B, C, D et E sont des coefficients dépendant des caractéristiques propres à un moteur donné.For a linear relation, the preceding expression takes the following form: $$\mathit{Thermal\; Flow}=\mathrm{AT}\times \left(\mathit{fuel\; mass}\right)+B\times \left(\mathit{air\; mass}\right)+\mathrm{VS}\times T_{\mathit{air\; mixture}+\mathit{EGR}}+D\times \left(\mathit{Burning\; angle}\right)+E$$

in which A, B, C, D and E are coefficients depending on the characteristics of a given engine.

During the development of an engine, the absolute flows can be calculated in a given repository by using a combustion analysis tool, and the parameters of the previous linear relation identified.

In practical terms, for each point of charge, a thermal flux is therefore associated with different values of the parameters "fuel mass", "air mass", "air mixture temperature + EGR admitted", etc.

The different input parameters above can be system data (calculator instructions for the fuel mass, the injection advance, etc.).

However, the methods used in the known art for estimating heat fluxes have several drawbacks.

In particular, the main disadvantage encountered when using this input data is that the system parameters do not reflect the actual values.

In particular, it is well known that fuel injectors have dispersions with regard to their operating characteristics, even when they are new, and drift over time, with drift amplitudes of significant values. It follows that the actual quantities of fuel injected actually correspond to different values of the required system quantities.

A similar phenomenon is observed with regard to the air flow, as a consequence of the dispersions and drifts of the components of the air loop (turbocharger, air flow meter, etc.), of a temperature sensor, or of the sensor regime (for determining the start of injection or ignition),

To overcome these malfunctions, it is customary in the known art to adopt significant development margins to avoid any risk of destruction of the engine after dispersions and drifts of the first-order components for heat flows. This leads most often to cost increases, in any case to operational operations lacking precision.

The object of the invention is to provide a method of estimating determined physical parameters, characteristic of the operation of a heat engine, and of controlling the thermal flows to which the components of this heat engine are subjected, aiming at overcoming the disadvantages of the processes and devices of the known art, some of which have just been recalled

• une phase d'estimation de paramètres physiques déterminés, caractéristiques du fonctionnement d'un moteur thermique ;
• et une phase de contrôle des flux thermiques sur des composants déterminés de ce moteur, notamment le ou les cylindres, la culasse et le piston de chaque cylindre;

The process according to the invention comprises two main phases:

• a phase of estimation of determined physical parameters characteristic of the operation of a heat engine;
• and a heat flow control phase on specific components of this engine, including the cylinder or cylinders, the cylinder head and the piston of each cylinder;

According to a first important characteristic of the invention, the estimation of determined physical parameters associated with an engine thermal is performed in real time, in particular with regard to the fuel flow, the air flow, the combustion phase, etc., as a function of the cylinder pressure, the associated thermal flows as a function of identified constants being calculated during the development of this engine, that is to say during a preliminary or initial phase, for example experimentally.

It can be noted as of now that the temperature of the injected air + EGR mixture can be measured or estimated by a predetermined specific model. If the "measurement" option is selected, this measurement can be done in the intake manifold for example, taking into account the "EGR" mentioned above.

According to a second important characteristic of the invention, unlike the methods of the prior art, a direct, closed-loop and real-time control of the thermal flux levels applied to the engine components is carried out.

The estimation of the parameters and the flow control having the characteristics recalled above can be obtained by measuring the pressure prevailing in all or some of the cylinders, and by adopting a control strategy, using this cylinder pressure parameter, which will be specified. and detailed below.

Such a measurement can be made simply by using one or more standard pressure sensor implanted in one or more rolls. Current motors of such sensors are already present, and the pressure measurement necessary to perform the control step according to the invention does not entail a significant additional cost and complexity.

The invention thus has many advantages, in particular the method of the invention makes it possible to reduce the development margins during the development of the engines with respect to the thermal flows, and to control the flow levels during critical life situations. for the motor components. It allows a good behavior over time of these components.

• un première phase consistant en l'estimation des paramètres déterminés, ces paramètres étant la valeur de la masse de carburant injecté dans la chambre de combustion de chacun des cylindres, la valeur de la masse du mélange air+ EGR en entrée du moteur thermique, la température du mélange et une grandeur dite de "phasage de combustion" dans un cycle de combustion ; et
• une deuxième phase consistant dans le contrôle en boucle fermée et en temps réel du flux thermique appliqué à au moins un des composants du moteur thermique, à partir d'une grandeur dérivée d'au moins un des paramètres caractéristiques estimés, dite "actionneur"

The main object of the invention is therefore a method for estimating specific parameters characterizing the operation of a heat engine comprising at least one cylinder and controlling the heat flows applied to components of the heat engine, the heat engine comprising means for reinject as input a given percentage of the mass of exhaust gas ejected to achieve a recycling of these gases called "EGR", characterized in that it comprises, at least,

• a first phase consisting in estimating the determined parameters, these parameters being the value of the mass of fuel injected into the combustion chamber of each of the cylinders, the value of the mass of the air + EGR mixture at the inlet of the engine, the temperature mixture and a so-called "combustion phasing" quantity in a combustion cycle; and
• a second phase consisting in the closed-loop control and in real time of the heat flux applied to at least one of the components of the heat engine, from a quantity derived from at least one of the estimated characteristic parameters, called "actuator"

• la figure 1 illustre schématiquement un exemple de configuration d'un bloc cylindre montrant les principaux composants exposés aux flux thermique dus à la combustion des gaz ;
• la figure 2 illustre schématiquement un exemple de configuration de moteur thermique et d'un dispositif associé pour la mise en oeuvre du procédé selon un mode de réalisation préféré de l'invention;
• les figures 3A et 3B sont des graphes illustrant un profil de pression dans une chambre de combustion mesuré pendant la phase de compression et la relation linéaire liant le débit total de gaz et la somme de variations de pression dans cette chambre de combustion ; et
• la figure 4 illustre schématiquement, à titre d'exemple, le contrôle du flux thermique sur un piston en pleine charge

The invention will now be described in more detail with reference to the accompanying drawings, in which:

• Figure 1 schematically illustrates an example configuration of a cylinder block showing the main components exposed to heat flow due to the combustion of gases;
• FIG. 2 schematically illustrates an example of a thermal engine configuration and of an associated device for implementing the method according to a preferred embodiment of the invention;
• FIGS. 3A and 3B are graphs illustrating a pressure profile in a combustion chamber measured during the compression phase and the linear relationship linking the total gas flow rate and the sum of pressure variations in this combustion chamber; and
• FIG. 4 schematically illustrates, by way of example, the control of the heat flow on a fully loaded piston.

We will first describe the configuration of a motor and a device for implementing the method according to the invention.

Figure 2 very schematically illustrates such a configuration. Only the essential organs necessary for a good understanding of the invention have been represented.

The motor 3 includes an engine block 30 itself comprising, in the example of Figure 2, four cylinders 1a to 1d, similar to the cylinder 1 already described with reference to Figure 1. In the engine inlet block 30, fresh air is fed to the cylinders, 1a to 1d, via an intake duct 310, to an inlet manifold 31 and the individual conduits 311. at the output of the engine block 30, the exhaust gas is expelled by an exhaust line 300.

In addition to various conventional members (muffler, etc., not shown), there is disposed on this exhaust line 300 a stitching member of the EGR consists of a valve 33 for diverting to the inlet distributor 31 via a conduit 330, a variable percentage of the exhaust gas. It therefore turns out that, in fact, the intake distributor 31 delivers an air / exhaust mixture at the inlet of the engine 3by the intake duct 310.

According to an important characteristic of invention there is provided one or more pressure sensors 34 for measuring the pressure in the combustion chambers of the cylinders 1 a to 1 d, at least one sensor being necessary in the specific context of the invention . This or these sensors 34 may be integrated in the cylinder head or in the glow plugs. The sensors 34 measure the pressure in the combustion chamber of all or part of the cylinders 1a through 1d. The output signals of sensors 34 are transmitted to an electronic control unit or "ECU" (for "Electronic Control Unit" according to the English terminology commonly used).

It may advantageously be a digital computer with a registered program. Such calculators are generally present on recent engines, which does not entail significant additional cost. The necessary modifications essentially boil down to an adaptation of the resident programs and / or the addition of software modules specific to the method of the invention.

A temperature sensor 35 is also provided on the intake distributor 31. The measured signals are also transmitted to the computer 32.

The motor 3 also comprises a body 40 comprising a common supply rail (not shown) adapted to feed the engine cylinders, 1a to 1d, in multiple injections of fuel such as a pilot injection followed by a main injection.

Provision is also made for means 36 for acquiring the crankshaft angle of each cylinder and means 37 for acquiring the operating point of the engine, in particular the rotational speed of the engine, the engine torque demanded by the driver and the pressure in the engine. the common feeding ramp.

The output signals of these devices (temperature sensor 35, pressure sensor (s) 34, crank angle acquisition means 36 and operating point 37) are transmitted to the computer 32.

According to these signals and other standard signals, the computer 32 generates control signals, in a conventional manner per se, and transmits control signals making it possible to drive specific members of the motor 3 (injectors not shown, valve 33, member 40, etc.), especially those necessary for carrying out the process of the invention.

The computer 32 is particularly suitable for controlling the fuel injection parameters in each cylinder, in particular the feed angle, the flow rate and the duration of the fuel injection into the cylinder, as is known per se. in the state of the art.

More specifically, the piloting of the fuel injection is carried out from a first predetermined law for controlling the injection of fuel into the cylinders, 1 a to 1 d , and a second predetermined law for controlling the fuel injection. intake of the air / exhaust mixture at the inlet 31/310 of the engine 3.

The computer 32 is arranged to correct the first control law of the injection in order to obtain throughout the life of the vehicle nominal emission levels of pollutants and combustion noise despite the presence of drifts in the operation in the motor and fast transients of it.

To do this, the motor 3 comprises a body 38 comprising computing means 380 receiving the output signals or sensor (s) 34 measuring the pressure in at least one of the engine cylinders, 1a to 1d, and the crank angle acquisition member 36. These calculation means 380 are adapted to determine, as a function of the acquired pressures and angles, a quantity relative to the phasing of the combustion of the fuel in each cylinder, 1 a to 1 d , and for each cycle of this cylinder. These calculation means 380 also make it possible to determine the release of heat caused by the combustion of the fuel injected into the cylinder for the current cycle from relations which will be explained below.

The member 38 further comprises calculation means 381 which receive the output signals of the calculation means 380 and are adapted to the calculation, as a function of the release of heat delivered by the calculation means 380, a crankshaft angle CAx corresponding to a predetermined fraction X of the total amount of fuel burned in the cylinder for the current cycle, as will be detailed hereinafter in the description of the process.

The motor 3 also comprises means 39 which receive the output signals of the calculation means 381 and are adapted to correct the control of the injection as a function of the crankshaft angle CAx determined. These means 39 comprise in particular mapping means (not shown) which receive the output signals from the operating acquisition device 37 of the engine 3 and which are arranged to deliver, as a function of the operating point acquired from the engine 3, an instruction for the crankshaft angle CAx from a predetermined mapping of angles.

The method of the invention will now be described.

As has been pointed out in the preamble of the present description, the method according to the invention comprises two main phases: a phase of estimation of determined physical parameters characteristic of the operation of a heat engine and a phase of control of heat flows. on specific components of this engine, including the cylinder or cylinders, the cylinder head and the piston of each cylinder.

As will be specified below, the first phase may be preceded by an initial or preliminary phase performed at the time of engine design, the first and second phases comprising taking place in real time.

We will now detail the first phase and the main steps involved in estimating specific physical parameters characteristic of the operation of a given engine.

To fix ideas, it will be assumed in the following that the engine comprises four cylinders, it being understood that this number can be any (1, 4 or 6 cylinders, for example). It will also be assumed that this is a diesel engine, it being understood that the process according to the invention applies equally to gasoline engines and diesel engines, as has been recalled. To fix ideas, we will refer again, in what follows, to the configuration described with reference to Figure 2.

• calcul de la masse de carburant injecté dans les cylindres
• calcul de la masse d'air entrant dans les cylindres ;
• calcul du phasage de combustion ; et
• mesure de la température du mélange air + EGR en entrée du moteur.

The main steps necessary to obtain an estimate of physical parameters characterizing the operation of a given engine are as follows:

• calculation of the mass of fuel injected into the cylinders
• calculation of the air mass entering the cylinders;
• calculation of the combustion phase; and
• measurement of the air + EGR mixture temperature at the engine inlet.

These steps will now be detailed.

The first step consists in calculating the fuel mass injected from the cylinder pressure signal.

The calculation of the mass of fuel can be carried out according to the process described in the patent European EP 1 429 009 B1 in the name of Peugeot Citroën Automobiles SA and Delphi Technologies Inc., entitled "Diesel engine equipped with a fuel injection rate control device".

In this patent, it was demonstrated that it is possible, by measuring the pressure in the combustion chamber of a cylinder, 1a to 1d, to determine elemental exotherms at a given time.

From these data, the determination of the quantity of fuel injected during the so-called main injection, and therefore of the fuel mass, can be carried out by evaluating the average heat clearance DQ over an interval centered with respect to this injection. main,

The heat evolution measurements are obtained from measurements of the pressure prevailing in the combustion chamber of a cylinder, 1a to 1d, for example by means of one or more sensor (s) 34 integrated pressure (s) in the cylinder head or in the glow plug of a diesel engine.

For a more detailed description of the method for calculating the mass of fuel injected from the cylinder pressure signal, reference may be made to the patent European EP 1 429 009 B1 supra.

relation dans laquelle :

• dQ/dα est exprimé en Joules par ° ;
• P et V sont la pression et le volume dans le cylindre, respectivement;
• α est l'angle vilebrequin en °;
• k est le coefficient polytropique fixé à 1,34

More specifically, in the context of the present invention, the calculation of the injected fuel mass is based on the calculation of a simplified heat release obeying the relation below: $$\frac{dQ}{d\alpha }=\frac{1}{k-1}\times \left(v\times \frac{dP}{d\alpha }+k\times P\times \frac{dV}{d\alpha }\right)$$

relationship in which:

• dQ / dα is expressed in Joules per °;
• P and V are the pressure and the volume in the cylinder, respectively;
• α is the crankshaft angle in °;
• k is the polytropic coefficient set at 1.34

relation dans laquelle :

• m_carburant est la masse de carburant (en kg) ;
• dQ est exprimé en joules ; et
• PCI est exprimé kg/joules,

The injected fuel mass is deduced by integration of the heat release on the combustion window and multiplication by the fuel heat potential (PCI): $$m_{\mathit{fuel}}=\mathit{PCI}\mathrm{.}\int dQ$$

relationship in which:

• m _fuel is the mass of fuel (in kg);
• dQ is expressed in joules; and
• PCI is expressed kg / joules,

relation dans laquelle I ₁ et I ₂ correspondent à l'intégrale de dQ sur deux fenêtres différentes (fenêtre de compression et de combustion), et A et B deux constantes équivalentes à la prise en compte du PCI, et calibrées en développement,A variant of the calculation of the fuel mass is also described in the aforementioned European patent. In this variant, a calibration of various coefficients is taken into account during engine development: $$m_{\mathrm{fuel}}=\mathrm{AT}\left(I_1+\mathrm{AT}\times I_2\right)+B$$

relation in which I ₁ and I ₂ correspond to the integral of dQ on two different windows (compression and combustion window), and A and B two constants equivalent to the taking into account of the PCI, and calibrated in development,

The second step consists in calculating the mass of air entering the cylinders, 1 a to 1 d , via the intake duct 310, again from the cylinder pressure signal.

This calculation can be carried out according to the process described in the patent applications, in the name of Peugeot Citroën Automobiles SA, FR 2 876 739 A1 and FR 2 878 575 A1 , both entitled "Method of regulating an intake system of an internal combustion engine and a motor vehicle implementing this method".

In many engines, a percentage of the engine exhaust gases that are recirculated to the inlet of the combustion chamber or chambers is added to the fresh air admitted to limit the emissions of toxic gases. This percentage of gas is commonly called "EGR" (from the Anglo-Saxon "Exaust Gas Recirculation"). As a result, the term "air mass" means the parameter [fresh air + "EGR"]. When the engine 3 comprises several cylinders, 1 a to 1 d, an air intake distributor is usually provided (Figure 2: 31). The above percentage is obtained by controlling the valve 33.

The estimate of the air mass entering the cylinders, 1 a to 1 d, is based on a polytropic model.

For a more detailed description of the method for calculating the mass of fuel injected from the cylinder pressure signal, reference may be made to the patent European EP 1 429 009 B1 supra.

FIGS. 3A and 3B, appended hereto, illustrate, in the form of two graphs, a pressure profile in a given combustion chamber (for example FIG. 1:13) measured during the compression phase (FIG. 3A) and FIG. linear relationship between the total gas flow rate and the sum of pressure variations in the combustion chamber considered according to the angular positions of the crankshaft (for example Figure 1: 12).

The ordinate axis of the graph of FIG. 3A represents the cylinder pressure in bars (10 ⁵ Pa) and the abscissa axis the crankshaft angle (° VII).

The ordinate axis of the graph of FIG. 3B represents the total flow (in Kg) and the abscissa axis the sum of pressure variations also in bars.

To fix the ideas, it is represented on the graph of Figure 3A different angular positions, α _REF , α ₁ , α ₂ , ..., α _n , for measurement positions among n possible. These positions are between zero and the "top dead center" ( TDC ), with α _REF representing the reference angular position and Δ P _i representing the pressure variations with respect to the measured pressure for α _REF .

The graph of FIG. 3B clearly shows a linear relationship linking the flow rate to ΣΔP _i , with i : 1 to n.

relation dans laquelle les coefficients A' et B' sont cartographiés en fonction du régime moteur. Cette cartographie peut être enregistrée dans des moyens de mémoires habituellement associés au calculateur 32.More precisely, the air mass is estimated by a formula of the type satisfying the following relation: $$m_{\mathit{air}}=\mathit{AT}\times \mathrm{\Delta }{P}_{\mathit{cyl}}+\mathit{B\text{'}}$$

relation in which the coefficients A ' and B' are mapped as a function of the engine speed. This mapping can be recorded in memory means usually associated with the computer 32.

relation dans laquelle A₀ est une constante calibrée en fonction d'essais réalisés en phase de conception spécifiques à chaque configuration moteur (phase initiale précitée) et T mélange air + EGR la température dans le collecteur admission après mélange de l'air et de l'EGR.The coefficient A 'is corrected as a function of the temperature of the intake air which can be measured by the sensor 35 positioned in the above-mentioned distributor 31. This estimate, which requires the presence of at least one pressure sensor 34 in one of the rolls, 1 a to 1 d, is based on a linear relationship linking the flow rate as has been shown with reference to FIGS. 3A and 3B. The difficulty of evaluating the regression slope (coefficient A ') lies in its dependence on the temperature of the gases in a cylinder (for a chosen reference angle), which itself strongly depends on the variations of the EGR rate. in a diesel engine. The following next relationship is used: $$\mathit{AT}=\frac{{\mathrm{AT}}_0}{T_{\mathit{charge}}}$$

relation in which A ₀ is a constant calibrated according to tests carried out in the design phase specific to each engine configuration (initial phase mentioned above) and T air + EGR mixture the temperature in the intake manifold after mixing air and fuel. EGR.

The third step is the calculation of the combustion phasing.

relation dans laquelle :

• P est la pression dite de cylindre dans la chambre ;
• V est le volume de la chambre ;
• α est l'angle vilebrequin; et
• k est le coefficient polytropique fixé à 1,34.

The phasing calculation is performed by the calculation means 380 from the heat generation, more precisely the phasing is again calculated from the following simplified heat generation: $$\frac{dQ}{d\alpha }=\frac{1}{k-1}\times \left(v\times \frac{dP}{d\alpha }+k\times P\times \frac{dV}{d\alpha }\right)$$

relationship in which:

• P is the so-called cylinder pressure in the chamber;
• V is the volume of the chamber;
• α is the crankshaft angle; and
• k is the polytropic coefficient set at 1.34.

The combustion phase corresponds to the crankshaft angle for which X% of fuel has been burned (with X between 0 and 100).

• CA₅ (Angle pour lequel 5% de carburant a été brûlé- représentatif de l'angle de début de combustion);
• CA ₂₅ (Angle pour lequel 25% de carburant a été brûlé) ;
• CA ₅₀ (Angle pour lequel 50% de carburant a été brûlé) ;
• CA₇₅ (Angle pour lequel 75% de carburant a été brûlé) ; et
• CA₉₀ (Angle pour lequel 90% de carburant a été brûlé - représentatif de l'angle de fin de combustion)

As an example, for example, the following CA _x phasings are traditionally used:

• CA ₅ (Angle for which 5% fuel was burned-representative of the start angle of combustion);
• CA ₂₅ (Angle for which 25% fuel was burned);
• CA ₅₀ (Angle for which 50% fuel has been burned);
• CA ₇₅ (Angle for which 75% fuel was burned); and
• CA ₉₀ (Angle for which 90% of fuel has been burned - representative of the end of combustion angle)

The burned fraction (cumulative energy release) is obtained by integration of the previous heat release, and obeys the following relation: $$\mathit{BKW}\left(\mathit{angle}\right)={\displaystyle \underset{k=1}{\overset{\mathit{angle}}{\Sigma }}}\mathit{dQ}\left(k\right)$$

The phasing CA _x corresponds to the angle at which the BKW normalized by the total mass burned (integration over the entire combustion cycle) equals X %

Finally, the fourth step consists of measuring the temperature of the air + EGR malfunction at the engine inlet.

As recalled previously for the calculation of the mass of air, the temperature of the air + EGR mixture can be measured using a temperature sensor 35 positioned in the inlet distributor 31 downstream of the EGR quilting. .

However, depending on the instrumentation specific to a given engine, this temperature can also be modeled or mapped as a function of the operating point of this engine (initial phase mentioned above). In the latter case, this mapping can, as before, be recorded in memory means usually associated with the computer 32.

We will now describe the second main phase of the method according to the invention, namely the control phase of thermal flows on specific components of this engine, including the cylinder or cylinders, the cylinder head and the piston of each cylinder.

The control of the thermal flows is based on the estimation of the aforementioned thermal flows, the estimation being a function of the four physical parameters acquired or measured during the stages of the first phase and characteristics of a given heat engine, namely the mass or the air flow, mass or fuel flow, combustion phasing and charge temperature.

In what follows, reference will again be made to the motor configuration and the device described with reference to FIG.

According to an important characteristic, the method according to the invention makes it possible, according to a flow setpoint mapping for each operating point of the engine, to control the closed-loop, real-time and cycle-to-cycle flux levels, also using one or more cylinder pressure sensors 34.

The aforementioned mapping is determined during the initial tuning of a given engine 3 (initial phase mentioned above).

• chaque paramètre pris à lui seul : quantité d'air, quantité de carburant, ou phasage de combustion ou température de la charge ;
• un couplage d'au moins deux paramètres : par exemple quantité d'air et quantité de carburant, ou quantité de carburant et phasage de combustion, etc., ou tout autre combinaison de tout ou partie des quatre paramètres.

The actuator or the means of action to modify the thermal flows can be either:

• each parameter taken alone: amount of air, quantity of fuel, or combustion phase or temperature of the charge;
• a coupling of at least two parameters: for example quantity of air and quantity of fuel, or quantity of fuel and combustion phasing, etc., or any other combination of all or part of the four parameters.

It should be noted, however, that the most important parameters are fuel quantity and combustion timing.

It should also be noted that, as part of the partial load thermal flow control, the "fuel quantity" actuator can not be used, since the partial load operation is set by the amount of fuel. On the other hand, an action on the ignition advance, the air flow and / or the temperature can be used to control the heat flow.

With regard to the "fuel mass" parameter, which can be derived from the "fuel flow", or quantity per unit of time, the instructions can be adapted by changing the injection time in the case of a diesel engine or the ignition advance in the case of a gasoline engine.

With regard to the parameter "air mass", which can be derived from the "air flow", or quantity per unit of time, the set points can be adapted by changing the air boost pressure the position of the throttle valve. EGR valve 33, that is the fraction of the recycled exhaust gas. It is understood again that "air" "[air + EGR].

With regard to the parameter "combustion phasing", it is possible to adapt the setpoints by modifying the fuel injection advance (diesel engine) or the ignition advance (gasoline engine).

With regard to the parameter the temperature of the load, it is possible to adapt the setpoints by modifying the temperature by a so-called "proportional bypass" system for example.

For example, the decrease in heat flow on a piston can be achieved by reducing the amount of fuel and a "sub-calibration of the injection". Such operation is obtained by a later combustion, itself obtained by a delayed injection into the combustion cycle.

Still in the context of the thermal flow control on a piston, and by way of non-exhaustive example, we will now describe zero-rated the main stages of this control by reference to block diagram 2 of Figure 4.

Reference is also made to the engine configuration depicted in Figure 2. In order to fix ideas, it is assumed that the engine 3 has four cylinders, 1a to 1d, and it is equipped with four pressure sensors cylinder 34, and a temperature sensor 35 of the load in the distributor 31.

The controlled heat flow is here the heat flow on each piston (for example Figure 1: 12) and the actuator is, for example, the amount of fuel, hereinafter referred to as Qcarb .

Because of the nature of the actuator implemented, as has been indicated, the heat flow control can be achieved here only on the full load.

The regulator is a regulator of type known as "PID" (for proportional action - integral - derivative) classic used generically for the control of the engines.

• cartographie d'un paramètre "régime/charge des flux thermiques" sur chaque piston ;
• paramètre "Offsets" de quantité de carburant ;
• cartographie des paramètres "quantités de carburant nominales (Qcarb)" ; et
• paramètre "tolérance maximale sur l'erreur de consigne de flux thermique", que l'on notera ε _L .

The input data, stored in memory means associated with the computer 32, are as follows:

• mapping of a parameter "speed / load of heat flows" on each piston;
• "Offsets" parameter of fuel quantity;
• mapping of nominal fuel quantity (Qcarb) parameters; and
• parameter "maximum tolerance on the thermal flow setpoint error", which will be noted ε _L.

• le régime moteur en tr/mn; et
• la charge du moteur, c'est-à-dire le couple exprimé en Nm et la puissance en kW

The "speed / load" parameter depends on the operating points of the engine 3. Each operating point is characterized in particular by:

• the engine speed in rpm; and
• the motor load, that is to say the torque expressed in Nm and the power in kW

It is therefore possible to construct a two-dimensional mapping of the heat flux levels for each operating point of the engine 3.

The parameter called "Offset" corresponds to the pitch of the variation of the quantity of fuel necessary to modify the thermal flows. As non-limiting example, this step is typically of the order 0.2 mg per shot. This quantity is determined during an initial phase of development depending on the engine and the sensitivities of the heat flows to this parameter.

Referring again to block diagram 2 of FIG. 4, block 20 calculates heat flow to the piston (for example, FIG. 1: 12). It receives the results of the calculations made by the blocks 26 and 27 described below (links 260 and 270).

The results of these calculations (link 200) are transmitted to block 21 which calculates the error on the following heat flow: $$\epsilon =\mathit{FT\; calculated}-\mathit{FT\; deposit}\left("\mathit{FT}"\mathrm{meaning}"\mathrm{Thermal\; Flow}"\right)$$

If ε> ε _L , the result is transmitted to block 23 to be recorded (link 210), otherwise, if ε <ε _L , the result is transmitted to block 24 to be recorded (link 211).

In the second case, since the calculated error ε is smaller than the set error ε _L , the result is transmitted to block 26 (link 240) for applying the nominal quantity of fuel Qcarb. Indeed, since the heat flow control actuator is this parameter, there is no need to change it. The output of the block 26 is, as previously indicated looped (link 260) on the block 20 for calculating heat flow to the piston.

et applique cette nouvelle valeur. En d'autres termes, cette nouvelle valeur est transmise à des moyens de commande de la carburation (injecteurs, etc., non représentés) par le calculateur 32.When the calculated error ε is greater than the set error ε _L , corrective action must be taken. The output of the block 23 is transmitted (link 230) to the calculation block 25. This performs a control calculation consisting of the determination of the offset of Qcarb to minimize the error ε. The result is transmitted (link 250) to the calculation block 27. The latter determines a new value of Qcarb satisfying the following relation: $$\mathit{Qcarb}\mathit{=}\mathit{Qcarb\; nominal}\mathit{+}\mathit{Qcarb\; Offset}$$

and apply this new value. In other words, this new value is transmitted to the carburizing control means (injectors, etc., not shown) by the computer 32.

The output of the block 27 is looped back, as previously indicated (link 270) on the heat flow calculation block 20 to the piston.

The necessary calculations and data storage are advantageously carried out using a digital computer 32, of the registered program type or any similar device. As has been indicated, such calculators are commonly used in modern engine design. It is therefore sufficient to adapt the recorded program to implement the subroutines and / or routines specific to the method of the invention. This adaptation, in itself, is within the reach of the skilled person and does not imply any increase in complexity or significant additional cost.

However, the calculations and operations associated above could equally well be performed by dedicated electronic circuits without departing from the scope of the invention.

In this significant but not exhaustive example, it is clear that the invention achieves the goals it has set for itself.

Indeed, the method according to the invention makes it possible to directly control, in a closed loop and in real time, the heat flux levels applied to the components of the engine.

More generically, it is possible to summarize the heat flow control phase on engine components as indicated below.

• la détermination pendant la phase initiale d'une cartographie de valeurs de consigne de flux thermique pour chaque point de fonctionnement du moteur thermique;
• la détermination pendant la phase initiale d'un paramètre dit "tolérance maximale d'erreur de consigne de flux thermique" ;
• l'enregistrement de ces données dans des moyens de mémoire ;
• le choix d'un ou plusieurs paramètres caractéristique estimés comme actionneur pour agir sur le fonctionnement du moteur thermique et l'enregistrement d'une valeur de consigne de cet actionneur ;
• la détermination des valeurs du flux thermique instantané sur un ou plusieurs composants du moteur thermique ;
• le calcul d'une valeur d'erreur de flux thermique égale à la différence entre la valeur du flux thermique instantané et les valeurs de consigne de flux thermique pour chaque point de fonctionnement du moteur ; et
• la correction de la valeur de consigne de l'actionneur seulement et seulement si la valeur d'erreur est supérieure au paramètre "tolérance maximale d'erreur de consigne", de manière à minimiser la valeur d'erreur de flux thermique, l'enregistrement dans des moyens de mémoire de cette nouvelle valeur de consigne de l'actionneur et son application à des moyens de commande pour modifier le fonctionnement du moteur thermique.

This phase comprises at least the following steps:

• determining during the initial phase a mapping of heat flow setpoint values for each operating point of the heat engine;
• the determination during the initial phase of a parameter called "maximum tolerance of thermal flow setpoint error";
• recording of these data in memory means;
• the choice of one or more characteristic parameters estimated as an actuator for acting on the operation of the heat engine and the recording of a set value of this actuator;
• determining the values of the instantaneous heat flux on one or more components of the heat engine;
• calculating a thermal flux error value equal to the difference between the value of the instantaneous heat flux and the heat flow setpoint values for each operating point of the engine; and
• the correction of the actuator setpoint only and only if the error value is greater than the parameter "maximum error tolerance setpoint", so as to minimize the heat flow error value, the recording in memory means of this new setpoint value of the actuator and its application to control means for modifying the operation of the heat engine.

It should be clear, however, that the invention is not limited to the only examples of embodiments explicitly described, particularly in relation to FIGS. 1 to 4.

As has been specified in particular, the invention applies equally to a diesel engine or a gasoline engine.

Finally, the numerical examples have been provided only to better fix the ideas and can not constitute any limitation of the scope of the invention. They proceed from a technological choice within the reach of the Man of Profession.

Claims (20)

A method for estimating specific parameters characterizing the operation of a heat engine comprising at least one cylinder and controlling the thermal flows applied to components of the heat engine, the heat engine comprising means for injecting a determined percentage of the mass into the input. exhaust gas ejected to achieve a recycling of these gases called "EGR", characterized in that it comprises, at least, - a first phase consisting of the estimation of the determined parameters, these parameters being the value of the fuel mass injected into the combustion chamber (13) of each of the cylinders (1 a - 1 d), the value of the mass of the air + EGR mixture at the inlet (310) of the heat engine (3), the temperature of the mixture and a so-called "combustion phasing" quantity in a combustion cycle a second phase consisting in the closed-loop control and in real time of the heat flux applied to at least one of the components of the heat engine (10, 11, 12), from a quantity derived from at least one of the parameters estimated characteristics, called "actuator and in that it furthermore comprises an initial phase consisting in determining, during the design of the heat engine (3), additional parameters and storing them in memory means, and that the additional parameters comprise at least one cartography two-dimensional heat flux levels for each operating point of the heat engine, representing the speed and the load of this engine, maximum error tolerance on heat flow setpoints (ε _L ), the quantity variation step of fuel, called "offset", necessary to modify the thermal flows, and nominal quantities of fuel. Method according to claim 1, characterized in that , said engine being equipped with at least one sensor (34) measuring the pressure in at least one of the cylinders (1 a - 1 d ), the estimation of the mass of fuel injected comprises the step of determining the elemental heat releases d Q from the following relation: $$\frac{dQ}{d\alpha }=\frac{1}{k-1}\times \left(v\times \frac{dP}{d\alpha }+k\times P\times \frac{dV}{d\alpha }\right)$$

in which dQ / dα is expressed in Joules per °, P and V are the pressure measured by the pressure sensor (34) and the fuel volume in the cylinder (1 a - 1 d ), respectively, α is the angle called "crankshaft" in °, and k is the polytropic coefficient of determined value, and in that the mass of injected fuel is obtained by integration of the release of heat on a combustion window and multiplication by the heating potential PCI of the fuel obeying the following relation: $$m_{\mathit{fuel}}=\mathit{PCI}\mathrm{.}\int dQ$$

in which m is the _fuel mass expressed in kg, d is expressed in joules, and PCI is expressed kg / joules. Process according to Claim 2, characterized in that the determined value of the polytropic coefficient is 1.34. Method according to claim 1, characterized in that said thermal engine being equipped with at least one sensor (34) measuring the pressure in at least one air + EGR mixture the mass of the "charge" at the input of the heat engine ( 3) is based on a polytropic model, comprising a step of measuring a determined number i of pressure variations ΣΔP _i measured by the pressure sensor (34), for i angles α _i called "crankshaft", relative to the pressure measured for a "crank angle" referred to as α _REF , so as to satisfy the following relation: $$m_{\mathit{air}}=\mathit{AT}\times \mathrm{\Delta }{P}_{\mathit{cyl}}+\mathit{B\text{'}}$$

in which A ' and B' are coefficients mapped as a function of the engine speed (3) and determined during the initial phase. Method according to Claim 4, characterized in that the coefficient A ' is corrected as a function of the temperature of the "charge" so as to satisfy the following relation: $$\mathit{AT}=\frac{{\mathrm{AT}}_0}{T_{\mathit{mélangeair}\mathit{+}\mathit{egr}}}$$

relation in which A ₀ is a constant calibrated as a function of tests carried out during the initial phase on the heat engine and T _{air + EGR} mixture the temperature of the air + egr mixture Method according to claim 1, characterized in that , the heat engine being equipped with at least one sensor measuring the pressure (34) in at least one of the cylinders (1 a - 1 d ), the estimation of the combustion phase comprises : a first step of determining the elemental heat releases d Q from the following relation: $$\frac{dQ}{d\alpha }=\frac{1}{k-1}\times \left(v\times \frac{dP}{d\alpha }+k\times P\times \frac{dV}{d\alpha }\right),$$

in which dQ / dα is expressed in Joules per °, P and V are the pressure measured by the pressure sensor (34) and the fuel volume in the cylinder (1 a - 1 d ), respectively, α is the angle called "crankshaft" in °, and k is the polytropic coefficient of determined value; and a second step of determining the fraction FMB (angle) of fuel burned by integrating said heat releases, "angle" being the crankshaft angle for which a percentage of fuel X determined, between 0% and 100%, has burned, said fraction obeying the following relation: $$\mathit{BKW}\left(\mathit{angle}\right)={\displaystyle \underset{k=1}{\overset{\mathit{angle}}{\Sigma }}}\mathit{dQ}\left(k\right),$$

and in that the combustion phasing is obtained by determining the crankshaft angle for which the burned fuel fraction normalized by integration over a complete combustion cycle is equal to the specified percentage. Process according to Claim 6, characterized in that the determined value of the polytropic coefficient is 1.34. Process according to one of Claims 6 or 7, characterized in that CA _x is the combustion phase for which the determined percentage of fuel X has been burned and in that X is chosen from the following values: 5%, 25%, 50%, 75% or 90%. Process according to Claim 1, characterized in that , the heat engine comprising an intake distributor (31) in which the air used at the inlet and said "EGR" are mixed, the temperature estimate of the mixture is obtained by means of measurements temperature provided by a temperature sensor (35) positioned in the intake manifold. Process according to Claim 1, characterized in that the temperature estimate of the mixture is obtained from values, modeled or mapped as a function of the operating point of the heat engine (3), stored in memory means, and in that that these values are determined during the initial phase, Method according to any one of claims 1 to 10, characterized in that the heat flow control phase applied to at least one of the components (10, 11, 12) of the heat engine (3), called "actuator comprises at least the following steps: the determination during the initial phase of a mapping of heat flow setpoint values for each operating point of the heat engine (3); the determination during the initial phase of the parameter "maximum error tolerance of heat flow setpoint" (ε _L ); recording of these parameters in memory means; the choice of at least one of the determined characteristic parameters estimated as an "actuator" value to act on the operation of the thermal engine (3) and the recording of a set value of this "actuator"; determining the instantaneous thermal flux values on at least one component of the heat engine (3); the calculation of a so-called thermal flux error value equal to the difference between the determined value of the instantaneous heat flux and the heat flow setpoint values for each operating point of the heat engine; and the correction of the setpoint value of said "actuator" only and only if the so-called value of heat flow error is greater than the "maximum tolerance on the heat flow setpoint error" parameter, so as to minimize the value of the error, the recording in the memory means of this new setpoint value of said "actuator" and its application to carburizing control members to modify the operation of the heat engine (3). Process according to Claim 11, characterized in that the heat engine is a diesel engine (3). Method according to claim 11, characterized in that the engine is a gasoline engine. A method according to claim 12, characterized in that , at least the parameter "value of the fuel mass injected into the combustion chamber (13) of each of the cylinders (1 a - 1 d ) constitutes said" actuator "and in that that the correction is made by modifying the duration of fuel injection in the cylinders (1 a - 1 d ), Method according to Claim 13, characterized in that at least the combustion phase parameter (13) of each of the cylinders (1 a - 1 d ) constitutes said "actuator" and that the correction is performed by modifying the advance on ignition, Process according to Claim 12 or 13, characterized in that at least the parameter "value of the mass of the air + EGR mixture" constitutes said "actuator" and in that the correction is carried out by modifying the fuel boost pressure or the determined percentage (33,330) of the mass of recycled ejected exhaust gas forming said "EGR". Process according to Claim 12, characterized in that , at least the so-called "combustion phasing" parameter parameter constitutes said "actuator" and that the correction is performed by modifying the fuel injection advance. Process according to Claim 12 or 13, characterized in that at least the so-called "temperature of the mixture" parameter constitutes said "actuator" and in that the correction is performed by modifying this temperature by equipping the heat engine (3) with a so-called "proportional bypass" system Method according to any one of claims 11 to 18, characterized in that said "actuator" is a combination of all or part of the estimated characteristic parameters. Process according to any one of the preceding claims, characterized in that the components of the heat engine consist of an assembly comprising all or part of the following components: pistons (12), cylinder heads (13) and / or cylinders (1 a - 1 d ).

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