EP1647692A1 - Air inlet control method for an internal combustion engine and automotive vehicle for applying this method - Google Patents

Abstract

The method involves estimating total mass of gas admitted in combustion chambers of an internal combustion engine. A fresh air flow is measured, and total mass of estimated gas and the measured fresh air flow are provided as input values in a regulator that controls an inlet of the engine. The total mass of input gas is obtained from individual estimation of total mass of input gas in each combustion chamber of the engine. An independent claim is also included for a motor vehicle having an internal combustion engine provided with an input gas collector and a storage and calculation unit for implementing an air intake system control method.

Description

The invention relates to a method of regulating an intake system of an internal combustion engine, and to a motor vehicle comprising an internal combustion engine and means implementing this method.

To obtain optimal operation of an internal combustion engine, several parameters are used, for example the quantity of air admitted into the combustion chamber or chambers of the engine. Indeed, the air mass admitted, per operating cycle, in each of the combustion chambers determines the emissions and the torque supplied by the engine. For this purpose, it is generally used a filling map possibly associated with a boost pressure sensor in the presence of a turbocharger or a compressor. Moreover, in many engines, fresh air is added to a percentage of the engine exhaust gases that are recirculated or recirculated to the inlet of the combustion chamber or chambers to limit the emissions of toxic gases. However, the demands for fresh air and the recirculated gas requirements vary during the operation of the engine, especially according to the engine speed and load, it is necessary to know at any time the fresh air mass sucked by the engine so to be able to regulate the air intake device and recirculated gas.

In the context of the present invention, the term "admitted gases" denotes indifferently fresh air alone and fresh air mixed with a recirculated portion of the exhaust gas, whatever their volume ratio, intended to be admitted. in one or more combustion chambers of an internal combustion engine.

This designation also goes along with the object of the invention according to which the gas admission system is regulated on the basis of an estimate of the total mass of the gases admitted to the chambers of gas. combustion of an internal combustion engine, unable to directly measure the mass of recirculated gas.

The motors to which the present invention is more particularly applicable are compression ignition engines. However, the invention can also be applied to spark ignition engines.

Methods of estimating the air mass admitted into a combustion chamber of an internal combustion engine are known. Thus, for example, the document FR-A-2,835,281 describes a method of estimating the air mass admitted into a combustion chamber from measurements of the pressure in the cylinders of the engine. The estimate is based on a polytropic model and the air mass is estimated by a formula of the type M = A x ΔP + B, where the coefficients A and B are mapped as a function of the engine speed. The coefficient A is also corrected according to the temperature of the intake air. This estimation method only applies to engines that do not have an exhaust gas recirculation system.

Another method of estimating the mass of air is known from EP-A-0 522 908. This method is based, like that described in the document cited above, on a polytropic model and on an M-type formula. = A x ΔP + B where A and B are a function of the angular positions of the crankshaft of the engine as well as the pressure in the combustion chambers, the volume in the combustion chambers at the indicated angular positions of the crankshaft and other parameters. This estimation method applies only to spark ignition engines without exhaust gas recirculation.

US-A-005245969 discloses a method for controlling the injection and ignition timing parameters in an internal combustion engine from the evaluation of the filling on the basis of the signal of a pressure sensor of the combustion chamber. This method ignores an air flow meter and therefore does not seem applicable to a supercharged engine and provided with an exhaust gas recirculation device.

US-A-006167755 discloses a method for estimating the air load admitted into an internal combustion engine. The estimate is made from the pressure measurement in a combustion chamber at two predetermined angular positions of the crankshaft. This process seems unsuited to the operation of a supercharged engine and provided with an exhaust gas recirculation device.

Yet another method of estimating the air mass admitted is known from US-A-005359975. The air mass is estimated based on the indications of a flow meter and is limited to applications to a non-supercharged spark ignition engine.

All the methods for estimating the fresh air mass admitted into a combustion chamber mentioned above are therefore based in particular on the information from an air flow meter and on a measurement of the pressure. However, these processes have some disadvantages because of which these known methods can not be applied primarily to a supercharged compression ignition engine and provided with an exhaust gas recirculation device.

Indeed, when the total mass of air admitted is estimated using the pressure measured in the intake manifold of the combustion engine, the air mass actually admitted into the combustion chambers may vary with respect to this estimated value as a function of load losses between the intake manifold and the combustion chambers. These load losses may vary from one type of engine to another due to manufacturing tolerances, and may vary over the life of the engine. motor due to clogging of the combustion chambers and the resulting change in volumetric efficiency of the engine.

When the air flow is measured at the inlet of the air supply system, the information provided by this flowmeter is likely to be shifted in time with respect to the quantities present in the combustion chambers. This offset is due to the transport time of an air mass considered between the inlet of the supply system and the combustion chamber. In addition, there are air compression effects through the complete intake system.

The object of the invention is to provide a method, and means for its implementation, to overcome the disadvantages of known methods.

The method of the invention, as well as the means for its implementation, must be applicable to any type of internal combustion engine and more particularly to a compression ignition engine, supercharged and with recirculation of exhaust gas.

The object of the invention is achieved with a method of regulating an intake system of an internal combustion engine, which comprises a step of estimating the total mass of gas admitted into combustion chambers of the engine according to an estimation method set out below, a fresh air flow measurement step and a step of introducing the estimated total gas mass and the fresh air flow rate measured as input values in a regulator intended for regulate the intake system.

The object of the invention is also achieved with a motor vehicle comprising an internal combustion engine provided with an intake gas manifold, intake valves intended to allow the passage of the intake gases to combustion chambers. the engine as well as pistons for varying the pressure of the gases in the combustion chambers of the engine, the position of the pistons being determined using means measuring the angular position of a crankshaft to which the pistons are connected, as well as means for measuring the pressure of the gases in at least one combustion chamber of the engine, means for measuring the flow of fresh air, storage means , modeling or calculation of a value of gas flow admitted into a combustion chamber as a function of a pressure variation in the combustion chamber, and storage and calculation means connected to the pressure measuring means in the at least one combustion chamber, the means for measuring the flow of fresh air and the means for measuring the angular position of the crankshaft, the storage and calculation means being shaped to implement the regulation method stated herein. before.

• déterminer, c'est-à-dire mesurer, cartographier ou modéliser, une série de valeurs de débit de gaz admis dans une chambre de combustion en fonction d'une variation de pression dans la chambre de combustion,
• mesurer au moins une valeur de pression dans au moins une chambre de combustion du moteur et calculer la ou les variations de pression par rapport à une pression de référence,
• estimer la masse totale de gaz admise dans l'ensemble des chambres de combustion du moteur à partir de la (ou des) variation(s) de pression calculée(s) et sur la base de la série de valeurs de débit de gaz déterminée.

The method for estimating the total mass of gas admitted into combustion chambers of an internal combustion engine, which is used for regulating an intake system of an internal combustion engine according to the control method stated above, includes at least the following steps:

• determining, that is to say, measuring, mapping or modeling, a series of values of gas flow admitted to a combustion chamber as a function of a pressure variation in the combustion chamber,
• measuring at least one pressure value in at least one combustion chamber of the engine and calculating the pressure variation or variations relative to a reference pressure,
• estimating the total mass of gas admitted to all the combustion chambers of the engine from the calculated pressure variation (s) and on the basis of the series of determined gas flow values.

• obtenir la masse totale de gaz admise dans l'ensemble des chambres de combustion du moteur à partir des estimations individuelles de la masse totale de gaz admise dans chacune des chambres de combustion du moteur ;
• obtenir la masse totale de gaz admise dans l'ensemble des chambres de combustion du moteur à partir d'une estimation de la masse totale de gaz admise dans une seule chambre de combustion du moteur ;
• mesurer la température des gaz admis dans les chambres de combustion du moteur et corriger la masse totale de gaz admise en fonction des variations de la température des gaz admis ;
• estimer la température des gaz admis dans les chambres de combustion du moteur à partir des paramètres du moteur et d'un modèle d'échanges thermiques, et à corriger la masse totale de gaz admise en fonction des variations de la température des gaz admis ;
• recaler les moyens de mesure du débit d'air frais, cet étape étant effectuée lorsque le taux de gaz d'échappement recirculés est zéro.

These steps can be completed by one or more of the following steps:

• obtain the total mass of gas admitted into all the combustion chambers of the engine from individual estimates of the total mass of gas allowed in each of the combustion chambers of the engine;
• obtaining the total mass of gas admitted into all the combustion chambers of the engine from an estimate of the total mass of gas admitted into a single combustion chamber of the engine;
• measuring the temperature of the gases admitted to the combustion chambers of the engine and correcting the total mass of admitted gas as a function of the variations in the temperature of the admitted gases;
• estimating the temperature of the gases admitted to the combustion chambers of the engine from the engine parameters and a heat exchange model, and correcting the total mass of admitted gas as a function of the variations in the temperature of the admitted gases;
• recalibrate the means for measuring the flow of fresh air, this step being performed when the recirculated exhaust gas rate is zero.

Other features and advantages of the present invention will become apparent from the following description of a method for regulating an intake system of an internal combustion engine and its implementation in a motor vehicle.

• la figure 1 représente un diagramme sur la base duquel la masse totale de gaz peut être déterminée, c'est-à-dire mesurée, cartographiée ou modélisée.
• la figure 2 montre un schéma d'un agencement de moyens permettant la mise en oeuvre du procédé de l'invention.

The description is made with reference to the drawings in which:

• FIG. 1 represents a diagram on the basis of which the total mass of gas can be determined, that is to say measured, mapped or modeled.
• Figure 2 shows a diagram of an arrangement of means for carrying out the method of the invention.

The present invention is based on an estimation of the total flow rate of the gases admitted into combustion chambers of an internal combustion engine, that is to say on an estimate of the total flow rate of the admitted gases, that these gases are solely of fresh air or a mixture of air fresh with a percentage of recirculated exhaust gas. To achieve this, the method of the invention relies on an estimation based on parameters of the operation of the engine, which are determined during the development of the engine, that is to say that are measured, mapped or modeled.

Estimating the total flow rate of gases admitted to the combustion chambers of the engine requires the presence of at least one pressure sensor in at least one of the combustion chambers of the internal combustion engine. This estimation also requires the presence of means for measuring the angular position of a crankshaft to which pistons of the combustion chambers are attached. Indeed, in order to be able to estimate the total gas flow rate with the greatest possible accuracy, the pressure in a given combustion chamber is measured after the closure of the exhaust valve and before the start of the combustion. at least two different angular positions of the crankshaft, which corresponds to at least two different positions of the piston in the combustion chamber and hence to at least two different volumes of the combustion chamber. For this purpose, a linear relationship is used linking the total flow rate of the gases and n pressure variations in a given combustion chamber, measured between a reference angular position and n angular positions considered in the intake and output phases. / or compression of the combustion chamber. n is of course greater than or equal to 1.

FIG. 1 illustrates, in the form of two graphs, a pressure profile in a given combustion chamber, measured during the compression phase (left graph) and the linear relationship linking the total gas flow rate and the sum of variations in pressure in the combustion chamber considered according to the angular positions of the crankshaft. The different angular positions are referenced α _MES for a position of measure from n possible positions, MES ranging from 1 to n, and α _ref for the reference position.

qui permet de calculer le débit de gaz et dans laquelle
Δ Pi = Pcyli - Pcyl_ref , avec Pcyli et Pcyl_ref comme pressions du cylindre considéré respectivement à l'angle α_i et à l'angle α_ref ;
A : pente de régression et
B : ordonnée à l'origine que le coefficient A est calculé suivant l'équation $$\mathrm{A}=\frac{\mathrm{V}{\alpha }_{\mathrm{ref}}}{\mathrm{R}\times \mathrm{T}{\alpha }_{\mathrm{ref}}}\times \left(\frac{1}{1/{\rho }_1^{\gamma }+1/{\rho }_2^{\gamma }+\dots +1/{\rho }_{\mathrm{n}}^{\gamma }-\mathrm{n}}\right)$$

avec ${\rho }_1={}^{\mathrm{V\hspace{1em}\alpha }1}{/}_{{\mathit{V\hspace{1em}\alpha }}_{\mathit{ref}}},\mathrm{.....},{\rho }_{\mathrm{n}}={}^{\mathrm{V\hspace{1em}\alpha n}}{/}_{{\mathrm{V\hspace{1em}\alpha }}_{\mathrm{ref}}}$

et
γ : coefficient polytropique
V_αref : volume de chambre de combustion à la position angulaire α_ref
T_αref : température des gaz admis dans la chambre de combustion à la position angulaire α_ref du vilebrequin et
B = Masse de résiduels.Taking into account the ideal gas equation and the isentropic compression hypothesis, we can prove in the equation $$Q_{\mathrm{gas}}=\mathrm{AT}\times {\displaystyle \underset{\mathrm{i}=1}{\overset{\mathrm{not}}{\Sigma }}\mathrm{\Delta }\mathrm{P}\mathrm{i}}+\mathrm{B},$$

which allows to calculate the gas flow and in which
Δ Pi = Pcyli - Pcyl _ref , with Pcyli and Pcyl _ref as pressures of the cylinder considered respectively at the angle α _i and the angle α _ref ;
A: regression slope and
B: originally ordered that the coefficient A is calculated according to the equation $$\mathrm{AT}=\frac{\mathrm{V}{\alpha }_{\mathrm{ref}}}{\mathrm{R}\times \mathrm{T}{\alpha }_{\mathrm{ref}}}\times \left(\frac{1}{1/{\rho }_1^{\gamma }+1/{\rho }_{\mathrm{two}}^{\gamma }+...+1/{\rho }_{\mathrm{not}}^{\gamma }-\mathrm{not}}\right)$$

with ${\rho }_1={}^{\mathrm{V\; \alpha }1}{/}_{{\mathit{V\; \alpha }}_{\mathit{ref}}},\mathrm{.....},{\rho }_{\mathrm{not}}={}^{\mathrm{V\; \alpha n}}{/}_{{\mathrm{V\; \alpha }}_{\mathrm{ref}}}$

and
γ: polytropic coefficient
V _αref : combustion chamber volume at the angular position α _ref
T _αref : temperature of the gases admitted into the combustion chamber at the angular position α _ref of the crankshaft and
B = Mass of residuals.

The difficulty in determining the regression slope, that is to say the coefficient A, lies in the fact that this coefficient depends on the temperature of the gases admitted to the combustion chamber. And, as noted above, the temperature of the gases admitted depends strongly on the changes in the rate (or percentage) of recirculated exhaust gas.

Advantageously, the coefficient A is calculated according to the relation A = A ₀ / T _coll , where A ₀ is a constant calibrated according to the results obtained by specific tests for each configuration of an internal combustion engine and where T _coll is the temperature in the intake manifold after mixing makes fresh air and recirculated exhaust gas. The temperature in the intake manifold can be measured by a specific sensor. But it can also be estimated on the basis of an engine exhaust temperature map from the other operating parameters of the engine and a heat exchange model in a cooler in which the recirculated exhaust gas passes. The decision for one or other of the ways to determine the temperature of the intake manifold, ie the decision to use a measured manifold temperature or for the use of a estimated collector temperature, is taken depending on the type of engine, all the instruments and sensors that can be implemented and the risk of drift or dispersion of the various sensors and the characteristics of the components of the intake system.

Thus, the total mass of gas admitted into combustion chambers of an internal combustion engine is estimated by firstly predetermining a series of gas flow values admitted to a combustion chamber as a function of a pressure variation in a combustion chamber. the combustion chamber, by measuring one or more pressure values in one or more combustion chambers of the engine and then calculating the pressure variation (s) relative to a reference pressure, and then estimating the total mass of admitted gas in all of the combustion chambers of the engine from the calculated pressure change (s) and on the basis of the set of predetermined gas flow values.

The total mass of admitted gas thus estimated is advantageously corrected taking into account the temperature of the gases admitted, whether this temperature is measured or estimated as described above.

During the operation of an internal combustion engine, in particular a compression ignition engine, the gas intake system is regulated, when it comprises a turbocharger for supercharging the combustion chambers, by acting on the engine. turbocharger and a valve for varying the percentage of recirculated exhaust gas, and, in some engines, a metering butterfly for passing a portion of the intake gas in an exchanger to change their temperature. The intake system regulating means receive as input the flow rate of fresh air measured by the flowmeter and the total flow rate of the admitted gases, estimated according to the method of the invention described above. This method is advantageous because the fresh air flow rate and the total gas flow rate are known with good accuracy. It is therefore more advantageous to determine the rate of recirculated exhaust gas, and also more precise, than to want to estimate the rate of recirculated exhaust gas from a measurement of the boost pressure and the air flow rate. because this first method is sensitive to dispersions and fouling of the various ducts through which the intake air passes, which can not only modify the volumetric efficiency of the engine, but also the ratio between the boost pressure and the mass actually admitted into the combustion chambers.

It is thus that one regulates the admission system of an internal combustion engine by estimating the total mass of gas admitted into the combustion chambers of the engine according to the method described above and by measuring the flow of fresh air and introducing these values as an input value into a regulator intended to regulate the intake system.

In order to ensure that the fresh air flow meter does not drift or, at least, that any drift from this flowmeter does not falsify the estimates of the fresh air mass admitted to the engine's combustion chambers, proceeds, in predetermined intervals, regular or irregular, to a reset of the fresh air flowmeter. This adjustment is preferably performed when the operating conditions of the engine that the rate of recirculated exhaust gas admitted is zero. These conditions are fulfilled, for example, when the engine is running at full load, during deceleration and during prolonged idling. For this purpose, the engine is advantageously provided with means for detecting conditions that are favorable for resetting the air flow meter.

In the event that such operating conditions, favorable to the resetting of the flowmeter, could not be met with sufficient frequency, it is possible to conform the control and regulating means of the intake system so as to trigger conditions recaling at regular intervals, when the forced presence of these registration conditions do not affect the operation of the engine.

To reach different points on the linearization curve of the flowmeter, the flow of air admitted into the combustion chambers can be reduced temporarily when it does not degrade the motor operation (for example in deceleration), by means of an active winnowing on admission and without exhaust gas recirculation.

FIG. 2 represents, in a block diagram of general operation, the regulation obtained by means of the regulation method described above.

On this synoptic are found the various means contributing to the implementation of the method of the invention. And it is more particularly seen that the input values of the intake system regulating means arise on the one hand from the fresh air flow meter whose measurement values are introduced into mapping means to correct the values of the flow meter, the result being sent as data representing the flow of fresh air, by means of internal combustion engine intake system regulations. On the other hand, the input values originate in the pressure sensor or sensors of which one or more or all combustion chambers of the internal combustion engine are provided. The sensor signal, or the signals of the sensors, are introduced into a means for calculating and estimating the total mass of admitted gas, means which are also introduced with data representing the engine speed, the angular positions of the crankshaft, the permissible gas temperature and the temperature of the engine cooling water and, if necessary, further data. The calculation and estimation means send signals on the one hand to the regulating means of the intake system and, on the other hand, to means for resetting the flowmeter in order to carry out a resetting of the flowmeter under the conditions described above and to correct the mapping of the flowmeter, so that the corrections that these mapping means provide to the data from the fresh air flowmeter are correctly updated.

In addition to the data representing the corrected fresh air flow rate and the total flow rate of the admitted gases, or the total mass of admitted gas, the admission system regulating means receive data representing the engine load, the fresh air intake temperature, the engine cooling water temperature and, where appropriate, other control parameters.

On the basis of the different input values, the regulating means calculate and send instructions to the means intended to act on the turbocharger, setpoint signals intended to act on the means intended to vary the rate of the recirculated exhaust gases, setpoint signals to the means for varying the flow rate of the intake air and, where appropriate, other setpoint signals, to additional means for acting on elements necessary to ensure the optimal operation of the combustion engine internal.

Claims (7)

A method of regulating an intake system of an internal combustion engine comprising a step of measuring the flow of fresh air, characterized in that it comprises
a step of estimating the total mass of gas admitted into combustion chambers of the engine, this estimation being obtained by determining, that is to say by measuring, by mapping or modeling, a series of flow rate values of gas admitted into a combustion chamber as a function of a pressure variation in the combustion chamber, by measuring at least one pressure value in at least one combustion chamber of the engine by calculating the pressure variation or variations with respect to a reference pressure, and estimating the total mass of gas admitted to all the combustion chambers of the engine from the calculated variation (s) of pressure (s) and on the basis of the series of values determined gas flow rate, and
a step of introducing the estimated total mass of gas and the fresh air flow measured as input values in a regulator for regulating the intake system. Process according to Claim 1, characterized in that the total mass of gas admitted into all the combustion chambers of the engine is obtained from the individual estimates of the total mass of gas allowed in each of the combustion chambers of the engine. Method according to claim 1 or 2,
characterized in that the total mass of gas admitted into all of the combustion chambers of the engine is obtained from an estimate of the total mass of gas admitted into a single combustion chamber of the engine. Process according to one of Claims 1 to 3, characterized by a step consisting in measuring the temperature of the gases admitted into the combustion chambers of the engine and in correcting the total mass of admitted gas as a function of the variations in the temperature of the admitted gases. Process according to any one of claims 1 to 3, characterized by a step of estimating the temperature of the gases admitted to the combustion chambers of the engine from the engine parameters and a heat exchange model, and to correct the total mass of gas admitted as a function of variations in the temperature of the gases admitted. A method according to any one of claims 1 to 5, characterized by a step of resetting the means for measuring the flow of fresh air, this step being performed when the recirculated exhaust gas rate is zero. Motor vehicle comprising an internal combustion engine provided with an intake gas manifold, the intake gases comprising at least fresh air, intake valves intended to allow the passage of the intake gases to combustion chambers of the engine, pistons for varying the pressure of the gases in the combustion chambers of the engine, the position of the pistons being determined using means measuring the angular position of a crankshaft to which the pistons are connected, of means for measuring the pressure of the gases in at least one combustion chamber of the engine and means for measuring the flow of fresh air, characterized in that it further comprises means for storing a series of flow values of gas admitted to a combustion chamber as a function of a pressure variation in the combustion chamber, and storage and calculation means connected to the gas pressure measuring means, to the flow measurement means t fresh air and means for measuring the angular position of the crankshaft, the storage and calculation means being shaped to implement the control method according to claim 1.

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