EP4234909A1 - Method for controlling richness in a carburized mixture of an internal combustion engine of a motor vehicle - Google Patents

Abstract

This method for controlling the richness of a fuel mixture for an internal combustion engine (10) of an automobile equipped with a variable timing system (50) of the engine valves, comprises the steps of:
- detection of a change in the operating point of the engine;
- calculation of at least one position instruction of said system;
- measurement of a current position of said system;
- predictive calculation of a position of said system;
- estimation of the air flow from said predictive calculation;
- Calculation from the estimate of the air flow, the quantity of fuel to be injected for operation of the engine at richness 1, and opening of the engine's fuel injectors to inject said quantity of fuel.

The predictive calculation of the position of the variable valve timing system (50) corresponds to the position of said system at the instant of opening of the fuel injectors.

Description

Technical area

The present invention relates to the control of an internal combustion engine and more particularly of a controlled ignition engine, during a transient operating phase of the engine.

Prior techniques

During a change in the operating point of an internal combustion engine, such as a change in rotational speed or a change in torque setpoint for example, it is observed that the real richness of the exhaust gases deviates from the wealth setpoint. The richness of a mixture is evaluated relative to a richness of 1, which corresponds to combustion of the fuel under stoichiometric conditions.

This difference in richness is due to a poor estimation of the air flow entering the engine and can lead to an increase in polluting emissions, an increase in engine noise and/or a driving pleasure problem due to jerks.

Conventionally, for an engine mounted on a motor vehicle, the driver of the vehicle determines, by actuating the accelerator pedal, a vehicle acceleration setpoint. From the acceleration setpoint and the engine speed, a computer defines an engine torque setpoint to be obtained in order to reach this acceleration setpoint.

In the case of a spark-ignition engine (running in particular on gasoline), the torque setpoint is translated into a mass air flow setpoint Qair, into an ignition advance value AA which is chosen preferably so as to optimize the combustion efficiency, and in a richness setpoint generally equal to 1, which corresponds to the flow rate of the fuel that must be burned in stoichiometric proportions to obtain the torque while making operate a three-way catalyst of the engine in its catalytic operating range in which it is able to treat unburnt hydrocarbons, carbon monoxide and nitrogen oxides.

It should be noted that in the case of a hybrid engine made up of a heat engine and at least one electric machine, the variations in torque requested from the heat engine are not necessarily correlated only with the accelerator pedal, because the torque is distributed over all the available driving sources.

Furthermore, when the vehicle is equipped with a partial exhaust gas recirculation circuit at the engine inlet, a recirculated gas mass flow setpoint Qegr is also defined which corresponds to the recirculation rate to be applied to comply with the target fuel consumption.

The sum of the air flow Qair and the recirculated gas flow Qegr represents the total gas mass flow Qmot entering the engine, which is generally regulated by adjusting the position of a throttle body in the air intake circuit of the engine, so as to obtain a pressure value Pcol in the engine intake manifold corresponding to the total gas flow rate sought, the recirculated gas flow rate Qegr being obtained by adjusting the position of a valve in the partial recirculation circuit, the desired air flow Qair being obtained indirectly as the difference between the total gas flow Qmot and the recirculated gas flow Qegr.

An engine computer uses an air filling model, which makes it possible to determine the value of the minimum pressure of the intake manifold to meet the engine torque setpoint.

This infill pattern follows the following equation: $${\eta }_{\mathit{appointment}}=\frac{Q_{\mathit{word}}\times 120}{\mathrm{NOT}\times \mathrm{Cylinder}\mathrm{e}e\times \frac{P_{\mathit{collar}}}{T_{\mathit{collar}}\times R}}$$

• η_rdvl désigne le rendement volumétrique ou « remplissage », adimensionnel ;
• Qmot désigne le débit massique total rentrant réellement, en kg/s ;
• N désigne le régime, en tours/min ;
• Cylindrée désigne la cylindrée du moteur, en m³ ;
• Pcol désigne la pression dans le collecteur d'admission, en Pa ;
• Tcol, désigne la température dans le collecteur d'admission, en K ; et
• R désigne la constante massique des gaz parfaits pour l'air égale à environ 287,058 $\raisebox{1ex}{$J$}\!\left/ \!\raisebox{-1ex}{$\mathit{kg}\times K$}\right.$
  
  .

In which :

• η _rdvl designates the volumetric efficiency or “filling”, dimensionless;
• Qmot designates the total mass flow actually entering, in kg/s;
• N designates the speed, in revolutions/min;
• Cylinder designates the cylinder capacity of the engine, in ^m3 ;
• Pcol designates the pressure in the intake manifold, in Pa;
• Tcol, designates the temperature in the intake manifold, in K; And
• R denotes the ideal gas constant for air equal to approximately 287.058 $\raisebox{1ex}{$J$}\!\left/ \!\raisebox{-1ex}{$\mathit{kg}\times K$}\right.$
  
  .

The term “filling” is defined as being equal to the ratio between the mass of air actually sucked in and the mass of air which could have entered by considering only the total volume of the cylinders.

In all cases, the value of the efficiency η _rdvl depends at least on the speed N and the pressure in the intake manifold Pcol.

However, if the engine is also equipped with a variable valve timing system (also called VVT system, from the English acronym for: Variable Valve Timing), in particular at the intake, which is the case with many engines In modern systems, the efficiency η _rdvl also depends on the position of this VVT system at the intake, which determines the instants of opening and closing of the intake valves in the engine's combustion cycle.

It will also be noted that in the case where the engine is additionally equipped with an exhaust VVT system, the efficiency also depends on the position of this exhaust VVT system, which determines the times of opening and closing exhaust valves, although the sensitivity of the efficiency value to the position of the exhaust VVT system is much less than in the case of an intake VVT system.

The volumetric efficiency is mapped by preliminary tests on the bench according to these parameters: engine speed; couple ; and, position of the VVT system on intake, and the map is stored in the memory of the engine computer. It is possible for example not to take into account the position of the VVT system on the exhaust, if the engine has such a system.

Thus, according to the state of the art, when using the vehicle, the computer determines a current value of the speed N, of the pressure in the intake manifold Pcol and of a value of the position of the VVT system at intake, then it uses the mapping to calculate the volumetric efficiency value. The computer also determines a current value of the temperature Tcol in the exhaust manifold. It then uses the filling model to calculate a value of the total gas flow Qmot, then a value of the air flow Qair by subtracting the flow of recirculated gases Qegr from the total gas flow Qmot. The recirculated gas flow Qegr can be determined, for its part, for example in a manner known per se from a Barré Saint Venant equation at the terminals of the valve of the recirculation circuit.

The richness adjustment is generally carried out in a closed loop on a set value. The system measures, for example, the actual richness of the combustion gases leaving the engine using a proportional oxygen sensor located upstream of a three-way catalytic converter in the engine.

The value of the difference in richness between the measured value and the setpoint value is sent as input to a regulator, for example of the PID (proportional, integral, derivative) type, the output value of which is a flow rate correction value of fuel which is added to a fuel flow value calculated for the open-loop servo-control, to correspond to the theoretical fuel flow allowing combustion in stoichiometric proportions.

The richness adjustment is obtained by adjusting the quantity of fuel injected by imposing the duration of opening of the fuel injectors of the engine.

For example, the quantity of fuel is the sum of a first quantity of fuel calculated in open loop from the current air flow at the rate of one gram of fuel for 14.7 grams of air, to correspond to the proportions stoichiometric, and a corrective term used for closed-loop control. THE values of the corrective term are all the smaller as the first calculated quantity is right.

The current airflow used in the calculation of the current airflow estimate is obtained from the filling model of equation 1, which depends in particular on the pressure in the intake manifold and the position of the intake VVT system. However, because of the rapid dynamics of the processes involved, when the order to open the injectors is given by an engine computer, the pressure Pcol in the intake manifold and the position of the VVT system at the intake generally no longer correspond to the values measured and which are used to calculate the volumetric efficiency, then the total gas flow Qmot and the air flow Qair.

Thus the estimate of the current air flow is distorted, and the quantity of fuel to be injected determined by open-loop calculation from the air flow no longer corresponds to the pressure measured in the intake manifold or to the measured position of the VVT system at intake and at the corresponding intake valve opening and closing times. It is then observed that the regulator, which slaves the richness value to a setpoint value (generally equal to 1) must use higher fuel quantity corrective terms to compensate for the air flow calculation error.

It can however be estimated that the variations in the pressure in the intake manifold Pcol are much less dynamic than the variations in the position of the VVT system at the intake and therefore than the corresponding variations in the times of opening and closing of the valves of admission, and that they thus have a lesser influence on the adjustment of the richness. This lesser influence is particularly true for engines operating on asymmetrical Atkinson or Miller cycles, in which there is a tendency to leave the throttle body wide open so as to increase the pressure in the intake manifold to reduce losses by pumping. In both cases, the mass of air admitted to the combustion chamber is adjusted by controlling the intake valves, with delay values of inlet closing (RFA) very offset from bottom dead center (BDC). The main engine air load control actuator is then the variable intake valve timing system in both cases, instead of the throttle body in traditional engines that do not use the one of these cycles.

Disclosure of Invention

In view of the foregoing, the object of the invention is to improve control of the richness of the fuel mixture in the transient phases of engine operation during which the position of a variable valve timing system, and more particularly of a variable intake valve timing system, evolves between the beginning and the end of the transient phases.

The subject of the invention is a method for controlling the richness of a fuel mixture for an internal combustion engine of a motor vehicle equipped with a variable timing system for the engine intake valves.

• détection d'un changement du point de fonctionnement du moteur ;
• calcul d'au moins une consigne de position dudit système de calage variable (50), correspondant à la nouvelle consigne de point de fonctionnement ;
• mesure d'une position courante dudit système de calage variable ;
• calcul prédictif d'une position dudit système de calage variable (50) ;
• estimation du débit d'air à partir dudit calcul prédictif ;
• calcul à partir de l'estimation du débit d'air, de la quantité de carburant à injecter pour un fonctionnement du moteur à richesse 1, et ouverture d'injecteurs de carburant du moteur pour l'injection de ladite quantité de carburant

caractérisé en ce que le calcul prédictif de la position du système de calage variable correspond à la position dudit système à l'instant de début d'ouverture des injecteurs de carburant.This process includes the following steps:

• detection of a change in the operating point of the engine;
• calculation of at least one position setpoint of said variable timing system (50), corresponding to the new operating point setpoint;
• measurement of a current position of said variable wedging system;
• predictive calculation of a position of said variable wedging system (50);
• estimating the air flow from said predictive calculation;
• calculation from the estimate of the air flow, of the quantity of fuel to be injected for operation of the engine at richness 1, and opening of fuel injectors of the engine for the injection of said quantity of fuel

characterized in that the predictive calculation of the position of the variable wedging system corresponds to the position of said system at the time the fuel injectors start to open.

The richness control method is configured to improve the precision of calculation of the quantity of fuel to be injected during transient phases of engine operation.

Advantageously, the predictive calculation of the position of the variable valve timing system of the intake valves at the moment of the start of the opening of the fuel injectors, makes use of a model of response to a setpoint of the valves.

For example, the response model of the variable valve timing system is characterized by a dead time parameter and a maximum speed of movement of the system.

Advantageously, the response model of the variable valve timing system takes into account an anticipation to obtain an anticipated real position with respect to the measured position.

For example, the anticipation is between 30 ms and 70 ms, and is preferably equal to 50 ms.

According to another characteristic, the engine comprises at least one partial exhaust gas recirculation circuit at the intake.

Advantageously, the estimate of the fresh air flow anticipates the variation in EGR flow, by calculating the position of the EGR valve from the EGR flow setpoint and the response time in order to obtain a flow of anticipated EGR in relation to the EGR flow calculated from the position measurement of the EGR valve.

According to another aspect, the subject of the invention is a system for controlling the richness of a fuel mixture for an internal combustion engine of a motor vehicle equipped with a variable timing system for the valves of the engine, in particular a timing system variable at the intake of the intake valves.

The richness control system comprises means for detecting a change in the operating point of the engine, means for calculating at least one position setpoint of the variable valve timing system, means for predicting calculation of a position the variable valve timing system, the means for estimating the air flow and the means for calculating the quantity of fuel to be injected for operation of the engine at richness 1.

Brief description of the drawings

• [Fig 1] illustre, de manière très schématique, un exemple de structure d'un moteur à combustion interne d'un véhicule automobile équipé d'un système de contrôle de richesse selon l'invention ;
• [Fig 2] illustre un organigramme du procédé de contrôle de richesse selon un mode de mise en oeuvre de l'invention ;
• [Fig 3] illustre un exemple de consigne de position, de position réelle et de position réelle anticipée d'un système de calage variable des soupapes d'admission du moteur de la figure 1 selon l'invention ;
• [Fig 4] illustre un schéma de construction d'une trajectoire anticipée d'une position du système de calage variable des soupapes d'admission selon l'invention ; et
• [Fig 5] illustre l'application selon l'invention d'un temps mort réduit lors des changements de direction du système de calage variable des soupapes d'admission.

Other aims, characteristics and advantages of the invention will appear on reading the following description, given solely by way of non-limiting example, and made with reference to the appended drawings in which:

• [ Fig 1 ] very schematically illustrates an example of the structure of an internal combustion engine of a motor vehicle equipped with a richness control system according to the invention;
• [ Fig 2 ] illustrates a flowchart of the richness control method according to one embodiment of the invention;
• [ Fig.3 ] illustrates an example of position setpoint, actual position and anticipated actual position of a variable timing system for the intake valves of the engine of the figure 1 according to the invention;
• [ Fig 4 ] illustrates a construction diagram of an anticipated trajectory of a position of the variable intake valve timing system according to the invention; And
• [ Fig.5 ] illustrates the application according to the invention of reduced dead time during changes of direction of the variable intake valve timing system.

Detailed description of at least one embodiment

In the example shown in the figure 1 , the internal combustion engine 10 is of the spark ignition type (gasoline) and comprises, in a non-limiting manner, three cylinders 12 in line, a fresh air intake manifold 14, an exhaust manifold 16, a system turbo-compression or turbocharger 18, a variable timing system 50 of the intake valves 51 of the engine and possibly also a variable timing system 52 of the exhaust valves 53 of the engine. The Variable Valve Timing System 50 intake valve is equipped with a sensor 54 which makes it possible to know its angular position at all times, which corresponds to determined times of opening and closing of the intake valves 51 in the combustion cycle of the engine (these times being usually measured in crankshaft degrees from a top dead center position). The variable timing system 52 of the exhaust valves, if present, is also equipped with a sensor 55 which allows its angular position to be known at all times, which also corresponds to determined times of opening and closing. exhaust valves 53 in the engine combustion cycle.

The cylinders 12 are supplied with air via the intake manifold 14, or distributor, itself supplied by a pipe 20 provided with an air filter 22 and a compressor 18a of the turbocharger 18 of the engine 10.

The turbocharger 18 essentially comprises a turbine 18b driven by the exhaust gases and the compressor 18a mounted on the same shaft as the turbine 18b and providing compression of the air distributed by the air filter 22 or air box, in the purpose of increasing the quantity (mass flow) of air admitted into the cylinders 12 of the engine 10 for an identical volume flow.

The internal combustion engine 10 comprises an intake circuit Ca and an exhaust circuit Ce.

• le filtre à air 22;
• un débitmètre 26 disposé dans la conduite d'admission 20 en aval du filtre à air 22 pour mesurer la valeur réelle du débit d'air entrant dans le moteur 10 ;
• une vanne d'admission d'air 28 ;
• le compresseur 18a du turbocompresseur 18 ;
• un boîtier papillon 30 ou une vanne d'admission des gaz dans le moteur ;
• un échangeur thermique 32 configuré pour refroidir les gaz d'admission correspondant à un mélange d'air frais et de gaz recirculés après leur compression dans le compresseur 18a ;
• des capteurs de pression et température 33 pour mesurer la pression et la température dans le collecteur d'admission 14 ; et
• le collecteur d'admission 14.

The intake circuit Ca comprises, from upstream to downstream in the direction of air circulation:

• the air filter 22;
• a flow meter 26 disposed in the intake duct 20 downstream of the air filter 22 to measure the actual value of the air flow entering the engine 10;
• an air inlet valve 28;
• the compressor 18a of the turbocharger 18;
• a throttle body 30 or a gas inlet valve in the engine;
• a heat exchanger 32 configured to cool the intake gases corresponding to a mixture of fresh air and recirculated gases after their compression in the compressor 18a;
• pressure and temperature sensors 33 for measuring the pressure and temperature in the intake manifold 14; And
• the intake manifold 14.

The compressor is associated with a bypass circuit equipped with an inlet relief valve 56 which opens in the event of sudden closing of the throttle valve 30, to prevent the compressed air, located between the compressor 18a and the throttle body 30 passes through the compressor 18a and does not damage it when, for example, the driver of the vehicle suddenly lifts his foot from the accelerator pedal.

• le collecteur d'échappement 16 ;
• la turbine 18b du turbocompresseur 18 ; et
• un système de dépollution des gaz de combustion du moteur (non représenté), comprenant notamment un catalyseur trois voies.

The exhaust circuit Ce comprises, from upstream to downstream in the direction of circulation of the burnt gases:

• the exhaust manifold 16;
• the turbine 18b of the turbocharger 18; And
• an engine combustion gas pollution control system (not shown), comprising in particular a three-way catalyst.

As regards the exhaust manifold 16, the latter recovers the exhaust gases resulting from combustion and evacuates the latter to the outside, via a gas exhaust duct 34 opening out at the entry of the turbine 18b of the turbocharger 18 and by an exhaust line 36 mounted downstream of the turbine 18b.

The engine 10 further comprises a circuit 38 for partial recirculation of the exhaust gases at the intake, called the “EGR” circuit (“exhaust gas recirculation” in Anglo-Saxon terms).

The engine 10 need not be equipped with an EGR circuit, without departing from the scope of the invention.

This circuit 38 is here in a non-limiting manner a low pressure exhaust gas recirculation circuit. It is connected to the exhaust line 36, downstream of said turbine 18b, and in particular downstream of the gas pollution control system and returns the exhaust gases to the fresh air supply pipe 20, upstream of the compressor 18a of the turbocharger 18, in particular downstream of the flow meter 26. The flow meter 26 only measures the flow of fresh air alone.

As illustrated, this recirculation circuit 38 comprises, in the direction of circulation of the recycled gases, a cooler 38a, a filter 38b, and a valve 38c configured to regulate the flow rate of the low-pressure exhaust gases. Valve 38c is disposed downstream of cooler 38a and filter 38b and upstream of compressor 18a.

The engine is associated with a fuel circuit comprising, for example, fuel injectors (not referenced) injecting gasoline directly into each cylinder from a fuel tank (not shown).

Furthermore, the engine comprises an electronic control unit 70 configured to control the various elements of the internal combustion engine from data collected by sensors at various locations of the engine.

The electronic control unit 70 comprises a calculation module 72, a measurement module 73 and a control module 74.

We will now describe with reference to the figure 2 a method 60 for controlling the richness in the transient phase of operation of the engine 10.

Such a method is in particular implemented by the computer 70 from the measurements delivered by the various sensors of the engine and by controlling the various elements of the engine.

The method 60 comprises a preliminary step 61 of detecting a change in the operating point of the engine 10, or operating point setpoint, in which the computer 70 detects a new operating point corresponding to a variation in the operating point of the engine 10. An operating point of the engine 10 is characterized by a rotational speed, a load of the engine 10 and an operating temperature, generally corresponding to the temperature of the water in the engine 10. Thus, a change in operating point corresponds to a variation of at least one of these parameters, for example, without limitation, by a relative value of 5%. For example, a change in operating point may come from a sufficient modification of the depression of the accelerator pedal of the vehicle, which modifies the torque setpoint.

During the next step 62, the computer 70 calculates according to the new operating point setpoint detected in step 61, an optimal position setpoint of the variable timing system 50 of the intake valves 51, and possibly in besides the variable timing system 52 of the exhaust valves 53.

This position setpoint of the variable timing system 50 of the intake valves corresponds to the value that the position of the variable timing system 50 of the intake valves will take on this new operating point in stabilized operation, but this position is not not reached instantaneously because there is a time necessary for the movement of the variable timing system of the intake valves from their old position to their new set value.

However, as already mentioned above and in particular with reference to equation (1) of the filling model, the actual or current position of the variable timing system 50 of the intake valves 51 (and to a lesser extent, that of the system variable timing 52 of the exhaust valves 53) has a first-order influence on the air filling of the engine 10 because it determines the moments of opening and closing of the intake valves, which allow the introduction of air in the engine cylinders.

In order to operate at richness 1, the quantity of fuel to be injected depends on the quantity of air actually admitted into the cylinders 12, therefore predominantly on the instant of opening of the intake valves 51 corresponding to the position of the system variable timing 50 of the intake valves 51.

During a change in the operating point of the engine 10, the variation in air flow must be estimated as precisely as possible so that the quantity of fuel injected corresponds to the mass of air enclosed in the cylinders 12 at each engine revolution. .

However, the greater the airflow gradients, the more the airflow calculation is misled when the calculations use information provided by sensors which themselves have intrinsic response times.

Since a non-zero period necessarily elapses, generally between 30 and 70 milliseconds, for example of the order of 50 milliseconds, between the moment when the position of the variable timing system 50 of the intake valves is measured and the moment when the computer actuates the fuel injectors and begins to open them in order to inject the fuel flow, after having calculated the air flow then said fuel flow to be injected in open loop, it is understood that the flow of fuel actually injected risks no longer corresponding to the flow rate that should be injected, because the actual air flow rate no longer corresponds to the air flow rate corresponding to the measured position of the variable timing system.

To improve the accuracy of calculation of the air flow and the fuel flow to be injected during transient phases, the computer 70 does not use, according to the invention, the position of the variable timing system 50 of the intake valves 51 measured by the sensor 54, but it proceeds during the following step 64 to the predictive calculation of the position that the variable timing system 50 of the intake valves 51 will have at the instant of the start of opening of the fuel injectors by the engine computer. Optionally, this step can also include a predictive calculation of the position that a variable timing system 52 of the exhaust valves 53 will have during the opening order of the injectors.

At this stage, the computer 70 uses maps constituting a model 63 of response to a position setpoint of the variable timing system 50 of the intake valves 51 (respectively of the variable timing system 52 of the exhaust valves), preprogrammed and contained in its memory, which allow it to estimate trajectories of the positions of the variable timing system 50.

The estimates of the trajectories of the positions of the variable timing system 50 of the intake valves 51 (and possibly also of the variable timing system 52 of the exhaust valves 53) take place at a time horizon which corresponds to the time between the moment when the position of the variable timing system 50 of the intake valves is measured and the moment when the flow of fuel begins to be injected (i.e. say: the instant of the start of opening of the fuel injectors).

The response model to a setpoint of the variable timing system 50 of the intake valves 51 (and possibly of the variable timing system 52 of the exhaust valves) can be characterized by two parameters, namely a dead time and a maximum speed movement of said wedging system.

The dead time accounts for the period of time during which a variable timing system 50,52 remains in position, and therefore the opening and closing times of the valves are not yet modified, after the establishment of a new setpoint position of this valve by computer 70.

The maximum travel speed corresponds to the maximum angular position variation that a variable valve timing system can follow.

There picture 3 illustrates the actual trajectory 82 of a variable valve timing system, in particular intake valves, subject to a position setpoint 80, and an anticipated trajectory 81 used to estimate the quantity of air admitted into the combustion chamber and the amount of fuel when the fuel injectors open.

There figure 4 illustrates a construction diagram of an anticipated trajectory of a position of a variable valve timing system.

When the position setpoint 83 changes value, it is possible to estimate an anticipated real position 84 of the variable timing system in anticipation 85 with respect to the real position 86.

The dead time 87 between the setpoint 83 and the real position 86 is reduced by the anticipation 85 to the reduced dead time 88 which corresponds to the dead time between the setpoint 83 and the anticipated real position 84.

After taking into account by anticipation 85 the reduced dead time 88, the response model 63 uses for the anticipated actual position 84 the same position gradient as that of setpoint 83, until the value of setpoint 83 is reached. However, in the case where the position gradient of setpoint 83 is greater than the maximum displacement speed of the variable valve timing system, the gradient of the anticipated actual position 84 is limited to this maximum speed.

As illustrated in the figure 5 , the reduced dead time 88 can also be applied during changes of direction of the variable valve timing system (that is to say: passage from a rotation from clockwise to counter-clockwise or vice versa) without there was no stabilization of the position.

During the following step 65, the computer 70 estimates the necessary air flow from the results obtained in step 64 of predictive calculation of the position of the variable timing system 50 of the intake valves (and possibly also of the variable exhaust valve timing system 52).

This air flow is estimated from the relationship: $${\eta }_{\mathit{appointment}}=\frac{Q_{\mathit{word}}\times 120}{\mathrm{NOT}\times \mathrm{Cylinder}\mathrm{e}e\times \frac{P_{\mathit{collar}}}{T_{\mathit{collar}}\times R}}$$

• η_rdvl désigne le rendement volumétrique ou « remplissage », adimensionnel ;
• Qmot désigne le débit massique total rentrant réellement, en kg/s ;
• N désigne le régime, en tours/min ;
• Cylindrée désigne la cylindrée du moteur, en m³ ;
• Pcol désigne la pression dans le collecteur d'admission, en Pa ;
• Tcol, désigne la température dans le collecteur d'admission, en K ; et
• R désigne la constante massique des gaz parfaits pour l'air égale à environ 287,058 $\raisebox{1ex}{$J$}\!\left/ \!\raisebox{-1ex}{$\mathit{kg}\times K$}\right.$
  
  .

In which :

• η _rdvl designates the volumetric efficiency or “filling”, dimensionless;
• Qmot designates the total mass flow actually entering, in kg/s;
• N designates the speed, in revolutions/min;
• Cylinder designates the cylinder capacity of the engine, in ^m3 ;
• Pcol designates the pressure in the intake manifold, in Pa;
• Tcol, designates the temperature in the intake manifold, in K; And
• R denotes the ideal gas constant for air equal to approximately 287.058 $\raisebox{1ex}{$J$}\!\left/ \!\raisebox{-1ex}{$\mathit{kg}\times K$}\right.$
  
  .

The method 60 continues at step 66 with the calculation of the quantity Q of fuel to be injected into the cylinders 12, for an operation of the engine 10 at richness equal to 1, and by the opening of the fuel injectors by the computer in order to inject the calculated fuel flow.

The quantity Q of fuel to be injected is calculated from the estimated air flow, and in particular, in the case where the richness setpoint is equal to 1, the fuel flow is calculated in proportion to 1 g of fuel for 14 .7g of air.

For engines with at least one EGR circuit, it is still possible to anticipate the variation in the EGR flow rate Qegr which enters into the calculation of the fresh air flow rate Qair, by calculating the position of the EGR valve 38c from the EGR flow setpoint and the response time in order to obtain an anticipated EGR flow with respect to the EGR flow calculated from the position of the EGR valve 38c.

Claims (8)

Method for controlling the richness of a fuel mixture for an internal combustion engine of a motor vehicle equipped with a variable timing system (50) of the intake valves (51) of the engine, characterized in that it comprises the steps following: - detection of a change in the operating point of the motor (10); - Calculation of at least one position setpoint of said variable timing system (50) corresponding to the new operating point setpoint; - Measurement of a current position of said variable wedging system; - predictive calculation of a position of said variable wedging system (50) - estimation of the air flow from said predictive calculation; - calculation from the estimate of the air flow, of the quantity of fuel to be injected for operation of the engine (10) at richness 1, and opening of the fuel injectors of the engine for the injection of said quantity of fuel
characterized in that the predictive calculation of the position of the variable timing system corresponds to the position of said system at the instant of start of opening of the fuel injectors. Method according to claim 1, in which the predictive calculation of the position of the variable timing system (50) of the intake valves (51) makes use of a model of response to a position instruction of the system. A method as claimed in claim 2, wherein the response model of the variable valve timing system is characterized by a dead time parameter and a maximum speed of movement of the system. A method according to claim 3, wherein the response model of the variable valve timing system takes feedforward into account to obtain an anticipated actual position relative to a measured position. Process according to Claim 4, in which the anticipation is between 30 and 70 milliseconds, and is preferably equal to 50 ms. Method according to claim 1, in which the engine comprises at least one partial recirculation circuit (38) of the exhaust gases at the intake. Method according to claim 6, in which the estimation of the fresh air flow anticipates the variation in EGR flow, by calculating the position of the EGR valve (38c) from the EGR flow set point and the time response in order to obtain an anticipated EGR flow with respect to the EGR flow calculated from the position measurement of the EGR valve (38c). System for controlling the richness of a fuel mixture for an internal combustion engine of a motor vehicle equipped with a variable timing system of the valves of the engine, characterized in that it comprises means for detecting a change in the point operating mode of the engine (10), means for calculating at least one position setpoint of the variable valve timing system, means for predictive calculation of the position of the variable valve timing system at , means for estimating the air flow and the means for calculating the quantity of fuel to be injected for operation of the engine (10) at richness 1.

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