FR2923544A1 - Supercharged diesel internal combustion engine for motor vehicle, has control unit with calculating unit that calculates setpoint position values of valve and flaps from setpoint values of air flow and gas rates in engine - Google Patents

Abstract

The engine (1) has a low pressure exhaust gas recirculation loop (17) connecting an exhaust pipe/line (14) with an air intake pipe, and an electronic control unit (24) receiving values of operating parameters e.g. air flow rate, of the engine and controlling different units such as actuators, of the engine. The unit (24) has a calculating unit that calculates setpoint position values of a controlled recirculation valve (18) and controlled intake and exhaust flaps (22, 19) from setpoint values of a rate of entered air flow and a rate of recycled exhaust gas in the engine. An independent claim is also included for a method for controlling an air flow rate and a recycled exhaust gas rate in a supercharged diesel internal combustion engine.

Description

APPLICATION FOR PATENT B07 / 0674FR AxC / cal

Société Anonyme known as: RENAULT sas Internal combustion engine of the supercharged diesel type and method of controlling the air flow and the rate of the exhaust gas recycled in such an engine Invention of: BUIS Emmanuel GUINOIS Arnaud Internal combustion engine of the diesel type The present invention relates to internal combustion engines of the supercharged diesel type used in motor vehicles and comprising a particulate filter mounted in the supercharged diesel engine and the method of controlling the air flow and the rate of recycled exhaust gas in such an engine. exhaust pipe and a partial recirculation loop of low pressure exhaust gas. In a more general manner, the invention relates to the control of the engine, that is to say the management of all the sensors and actuators for optimizing the operation of the engine. The set of control control laws, which is generally in the form of software strategies and characterization parameters representing the calibration of the engine, are stored in a computer generally called electronic control unit (ECU). Standards limiting the amount of pollutants produced in the vehicle exhaust and, in particular, the various nitrogen oxides (NO, NO2, N2O, generically noted, NOx) and soot particles, are increasingly severe. To meet these standards on new vehicles it is necessary to change the design of the latter and more particularly that of the engines. For this purpose, it is possible to integrate a recirculation loop connecting the exhaust manifold to the plenum of the intake manifold. Through this loop, a portion of the exhaust gases (known as EGR for Exhaust Gas Recirculation) is reintroduced on admission. As a result, the mixture of gases admitted to the engine is composed of fresh air from the supercharger and exhaust gas from the exhaust manifold. A recirculation valve (called EGR valve) can be inserted into this loop to regulate the amount of exhaust gas recycled to the engine intake. The recycled exhaust gas being inert with respect to combustion, this partial recirculation has the effect of reducing the maximum combustion temperature and reducing the excess oxygen compared to a diesel engine of the same type without such a recirculation loop. The formation of nitrogen oxides during combustion is favored by a high temperature and oxygen level. The formation of unburnt soot particles is, in turn, favored by a low oxygen level. The partial recirculation of exhaust gas therefore has the direct consequence of reducing the quantity of nitrogen oxides and of increasing the quantity of soot particles formed during combustion. To compensate for this increase in unburned soot particles, it is possible to install, between the turbine of the turbocharger and the exhaust silencer, a device for trapping particles, called particle filter, which may, for example, comprise a set of micro-channel traversed by the exhaust gases loaded with particles. Once the filter is saturated with soot particles, it is necessary to empty it by burning the particles by a suitable rise in temperature. This phase is called the regeneration phase. The regeneration can be achieved either by a device integrated in the filter, or by means of specific engine settings which have the effect of increasing the temperature of the exhaust gas passing through the particulate filter during the regeneration phase.

The exhaust gas recirculation at the engine intake mentioned above, however, does not allow to reduce the amount of pollutants produced in the exhaust in a manner sufficient to meet future standards. In order to improve the treatment of gases discharged into the atmosphere, it has therefore been imagined to cool the mixture of gases admitted to the engine by means of an air / water heat exchanger placed in the exhaust gas recirculation loop. The reduction in the temperature of the gases admitted to the engine makes it possible to introduce a larger mass of recycled exhaust gases, since the filling of the engine increases with the decrease in the temperature of the admitted mixture. As a result, the amount of nitrogen oxides emitted decreases, both because of the decrease in temperature and because of the increase in the amount of recycled exhaust gas.

Another possibility is to provide on the engine a low pressure exhaust gas recirculation loop. In this case, the exhaust gases recycled to the intake are taken between the particulate filter and the silencer mounted in the exhaust line. These exhaust gases are then reintroduced upstream of the supercharger so that the mixture of air and recycled exhaust gas passes through the charge air cooler which is in the form of a heat exchanger mounted between compressor and intake manifold. Since the efficiency of the charge air cooler is high and the exhaust gases downstream of the particulate filter have much lower temperatures than at the output of the engine, such a system makes it possible to obtain temperatures gas mixture admitted into the engine even lower than in the case of a conventional recirculation loop with a cooler. As a result, it is possible to further reduce the amount of nitrogen oxides produced in the exhaust by lowering the temperature and increasing the amount of the recycled exhaust gas. In addition, the exhaust gases reintroduced into the engine contain very little soot particles since they passed through the particulate filter before being reintroduced into the engine, contrary to what was the case with a recirculation loop. a conventional type in which the recycled exhaust gases are not filtered and lead to clogging of the recirculation loop, the intake manifold and the engine.

The reduction in the amount of nitrogen oxides produced, however, leads, as previously mentioned, to an increase in the amount of unburnt soot particles in the exhaust gas. These soot particles saturate the particulate filter more quickly. It is therefore necessary, for a given operating point, to determine a compromise between the quantity of nitrogen oxides and the amount of soot particles by acting appropriately on the exhaust gas rate and on the mixture admitted in engine. US patent application 2004/0006978 describes a supercharged diesel type internal combustion engine equipped with a low pressure exhaust gas recirculation loop. The tapping of the recirculation loop is located between the particulate filter and the muffler mounted in the exhaust line. The return is between the air filter and the compressor. The exhaust gas recirculation loop includes a controlled valve that regulates the recycled exhaust gas (EGR) rate. The recycled exhaust gas is introduced into a vacuum created by a venturi mounted in the intake pipe upstream of the supercharger. As a result, the pressure difference that the recirculation valve can detect is related to the operating point of the engine. Indeed, for example, for a running point at low speed, the depression created by the venturi is very low. Consequently, the maximum flow rate of the recycled exhaust gases for this operating point remains limited and is related to the pressure difference between the upstream and the downstream of the venturi. The patent application US 2005/0045407 as well as US Patent 5,806,308 propose to remove the venturi and replace it with an exhaust flap. I1 thus becomes possible to create a pressure difference across the recirculation valve, independent of the operating point of the engine. French patent application FR-A-2 894 623 (Renault) relates to a method for controlling the air flow rate on a direct injection supercharged engine which provides for management of the function of an EGR recirculation valve and a 'a flap in the exhaust.

In all these engines, it is necessary to provide a particulate filter in the exhaust line to capture the soot that could foul the intake line and mounted organs such as the compressor and the engine. charge air cooler. The particulate filter is also needed to minimize the amount of soot particles in the exhaust gas released into the atmosphere. As mentioned above, it is necessary to periodically regenerate the particulate filter, for example by increasing the temperature of the exhaust gas during the regeneration phases. During these regeneration phases, however, an increase in the quantity of nitrogen oxides released into the atmosphere is observed.

The object of the present invention is to solve these difficulties and to improve the control strategies of the air flow admitted into the engine and the recirculation rate of the recycled exhaust gases in the case of a supercharged diesel engine equipped with a partial recirculation loop of the exhaust gas at low pressure.

In one embodiment, a supercharged diesel type internal combustion engine comprises: a particulate filter and a controlled exhaust flap, mounted in the exhaust duct; a partial recirculation loop of low pressure exhaust gas including a controlled recirculation valve, said loop connecting the exhaust pipe, downstream of the particulate filter with the air supply pipe, upstream of the compressor of overeating; a controlled intake flap, mounted in the intake duct of the gas mixture in the engine, upstream of the intake manifold; and an electronic control unit capable of receiving engine operating parameter values and controlling different engine components. The electronic control unit comprises means for calculating position reference values of the recirculation valve, the exhaust flap and the intake flap from set values of the air flow rate admitted into the engine and the amount of exhaust gas recycled into the engine. The electronic control unit may comprise a first regulator for determining the position setpoint values of the recirculation valve and the exhaust flap and a second regulator, associated with a prepositioning device, for determining the value of position indicator of the intake flap. In a preferred embodiment, the electronic control unit comprises first calculation means capable of estimating a set value of the pressure at the intake flap and a set value of the flow rate of the gases flowing through the flap. admission as well as second calculation means capable of estimating the effective flow rate of the gases passing through the intake flap.

The first calculation means can receive, as input, the set values of the air flow rate admitted into the engine and the rate of exhaust gases recycled to the engine in order to calculate the set value of the flow rate of the gases admitted to the engine to the engine. from stored equations corresponding to an inverted model of the intake manifold. The first calculation means can also calculate the setpoint value of the pressure in the intake manifold of the engine, at the inlet flap. The second calculation means are capable of determining the value of the flow rate of the gases passing through the intake flap from stored equations corresponding to a model of the flow rate of the gases admitted into the engine. The second regulator and the prepositioning device can receive on their respective inlet, a value of the effective passage section of the intake flap, estimated from the flow rate of the gases passing through the intake flap and a set value of the section. effective passage of the intake flap, estimated from the setpoint values of the pressure in the intake manifold at the intake flap and the flow rate of the gas flowing through the intake flap. The first regulator may, preferably, receive as input a set value of a parameter related to the admission of the gases into the engine and a measured value of the said parameter, so as to determine the values of the position setpoint of the valve. recirculation and the exhaust flap, for a regulation of said parameter. This parameter related to the admission of gases into the engine may be the flow of recycled exhaust gas, the rate of recycled exhaust gas or the air flow admitted into the engine. In another aspect, there is provided a method of controlling the air flow and the rate of exhaust gas recycled in a supercharged diesel type internal combustion engine. The engine comprises: a particulate filter and a controlled exhaust flap, mounted in the exhaust duct; a partial recirculation loop of low pressure exhaust gas including a controlled recirculation valve, said loop connecting the exhaust pipe, downstream of the particulate filter with the air supply pipe, upstream of the compressor of overeating; a controlled intake flap, mounted in the intake duct of the mixture of gases in the engine, upstream of the intake manifold. According to the control method, a parameter related to the admission of gases into the engine is regulated by acting on the recirculation valve and on the exhaust flap. In addition, the intake air flow in the engine is regulated by acting on the intake flap. The aforementioned parameter may be the flow rate of the recycled exhaust gas, the rate of the recycled exhaust gas or the flow of air admitted into the engine. Generally, the difference between the setpoint and the measurement of the flow rate of the recycled exhaust gas is brought to the inlet of the airflow control, which emits a position setpoint signal. Several cases are then possible, depending on the set point of the exhaust gas recycled rate. Normally, the flow regulation of the recycled exhaust gas is made by the recirculation loop acting on the recirculation valve and the exhaust flap while simultaneously acting on the intake flap to control the filling of the motor.

However, in some cases, the flow of air admitted into the engine is regulated by acting solely on the recirculation valve and on the exhaust flap, the intake flap being kept in the open position and a saturation is applied to the calculation of the set point of the flow rate of the recycled exhaust gas. In other cases, the air flow admitted into the engine is regulated by acting solely on the intake flap, the exhaust flap being kept in the open position and the recirculation valve being kept in the closed position.

It is thus possible to control the intake air flow rate in the engine and the rate of the recycled exhaust gases so as to minimize NOx nitrogen oxide emissions, even during the regeneration phases of the particulate filter. . The present invention will be better understood on studying an exemplary embodiment and implementation illustrated by the accompanying drawings in which: • Figure 1 schematically illustrates a supercharged diesel-type internal combustion engine according to the present invention; and FIG. 2 shows the main calculation and regulation elements that make it possible to implement the strategy for regulating the air flow rate and the recycled exhaust gas content according to the invention. As illustrated in FIG. 1, the diesel-type internal combustion engine referenced 1 as a whole comprises four cylinders 2 receiving, via an intake manifold 3, a mixture of recycled air and exhaust gas and The engine 1 is associated with a turbocharger 5 comprising a compressor 6 and a turbine 7 mounted on a common shaft 8. The fresh air, symbolized by the arrow 9, passes through all the exhaust pipes. first an air filter 10, then a flow meter 11 before being fed through line 12 to the inlet of the compressor 6. The exhaust gases from the exhaust manifold 4 are fed through line 13 to the inlet of the turbine 7, in which they relax, rotating the turbine 7 which itself drives the compressor 6. The exhaust pipe 14 is connected to the outlet of the turbine 7. Thus the gases of exhaust from the turbine 7 cross all of ab ord a particulate filter 15, then a silent device 16 before being released into the atmosphere. It is also possible to have in the exhaust line 14 other devices such as catalyst devices. A partial recirculation loop of low pressure EGR exhaust gas is constituted by a bypass line 17 which is stitched in the exhaust line 14 downstream of the particulate filter 15 and which brings back a part of the exhaust gas having through the particulate filter 15 in the pipe 12 upstream of the compressor 6. A controlled recirculation valve 18 is mounted in the recirculation loop 17. In addition, an exhaust flap 19, which can be controlled, is mounted in the exhaust line 14, downstream of the stitching of the recirculation loop 17. The mixture of the fresh air from the air filter 10 and the recycled exhaust gas from the recirculation loop 17 is compressed by the compressor 6 and exits from it through line 20 at high temperature. A heat exchanger 21 is a supercharger cooler capable of lowering the temperature of this compressed mixture. A controlled intake flap 22 is mounted in the intake duct 23 which connects the exchanger 21 to the intake manifold 3. An electronic control unit (ECU) referenced 24 receives various operating parameters of the engine and is capable of act on different actuators to control the operation of the engine. In particular, FIG. 1 shows different sensors and actuators. The flow rate of air admitted into the Qair engine is measured by the flowmeter 11 and brought via the connection 25 to the input of the electronic control unit 24. A pressure sensor 26 measures the pressure of the gases admitted to the engine in upstream of the admission flap 22. The measured value of this pressure denoted Pboost is brought via line 27 to the input of the electronic control unit 24. A temperature sensor 28 measures the temperature of the gas mixture upstream of the flap 22. The value of the measured temperature noted Tboost is brought through the connection 29 to the input of the electronic control unit 24. A pressure sensor 30 measures the pressure Peol in the intake manifold 3, c that is to say downstream of the admission flap 22. The measured value is brought via the connection 31 to the input of the electronic control unit 24. In the example illustrated, a temperature sensor 30a measures the Teol temperature in the intake manifold The electronic control unit 24 is capable of emitting signals to change the position of the EGR recirculation valve 18, the measured value being fed through the connection 31a to the input of the electronic control unit. by the connection 32, the exhaust flap 19 by the connection 33 and the intake flap 22 by the connection 34. We will now describe more precisely one embodiment of the calculation and control means included in the electronic control unit 24 and for defining the position setpoint values for the EGR 18, the exhaust flap 19 and the intake flap 22. For this purpose, reference is made to FIG. An overview of the Qair airflow control software strategy and the EGR recycled exhaust rate noted 'tegr. The objective of the strategy is to monitor a recycled airflow and exhaust rate by acting on the three actuators EGR 18, the exhaust flap 19 and the flap. admission 22. It should be noted, for the record, that the recycled exhaust gas rate 'Legr represents the proportion of the recycled exhaust gas with respect to the total flow rate of the gases admitted to the engine. Therefore, we have: tiegr Qegr equation 1 egr + Vair and = tegr egr Qair = Qmot ù Qair equation 2 1ùtegr in which Qmot is the total flow of gases admitted to the engine and Qair is the airflow admitted as measured by the flowmeter 11.

In the present description, the abbreviations

following:

Qmot_dyn: flow of the gases admitted into the engine at the intake flap 22,

Pboost: boost pressure upstream of the intake flap 22 as measured by the sensor 26,

Tboost: supercharging temperature upstream of the intake flap 22 as measured by the sensor 28,

Pcol: pressure in the intake manifold 3 downstream of the intake flap as measured by the sensor 30,

Tcol: temperature in the intake manifold 3 downstream of the intake flap as measured by the sensor 30a,

R: perfect gas constant,

Seff: effective passage section of the admission flap 22 (in m2), Kr: filling coefficient,

rivol: filling performance,

Nmot: rotational speed of the motor 1,

Vcyl: engine displacement 1

Vcol: volume of the intake manifold 3.

The suffix _cons is added when it is a setpoint value.

The set of air flow setpoints Qair cons and recycled exhaust gas rates ERG Tegrcons are defined in blocks 35 and 35a and fed to the input of first calculation means 36 included in the electronic control unit. 24 (Figure 1) and corresponding to a

Inverted model of the intake manifold 3. These setpoints are converted by the first calculating means 36 into a recycled exhaust gas flow rate setpoint Qegrcons which appears on the outlet 37, a setpoint value of the pressure in the intake manifold 3, Pcol cons appears on the output 38 and a set value of the flow of gases admitted into the engine at the intake flap 22, Qmot_dyn_cons appearing on the output 39. Second computing means 40 comprise a dynamic model of the flow of gases admitted into the engine Qmot included in the electronic control unit 24 (Figure 1). The calculation means 40 are capable of determining an estimated value of the effective flow rate of the gases passing through the intake flap Qmotdyn from input parameters comprising the pressure Pcol in the intake manifold 3, the pressure Pboost and the temperature Tboost upstream of the admission flap 22, these values being measured respectively by the sensors 26 and 28 (Figure 1). The dynamic model of the second calculation means 40 also receives as input the value of the fill factor Kr. This fill factor Kr is also brought to the input of the first calculation means 36. The estimated value of the engine flow at the flap Qmotdyn admission appears at the output 41 of the second calculation means 40. The set value of the flow rate of the gases admitted into the engine Qmot_dyn_cons as well as the estimated value Qmotdyn are transformed in the calculation blocks 42 and 43 respectively in order to take consider the physical phenomena in the intake circuit. Blocks 42 and 43 comprise an inverted model based on the Barré Saint Venant formula which makes it possible to determine, at the output 44 of the calculation block 42, a set value for the effective cross section of the admission flap 22 noted by Seff. cons. In the same way, at the output 45 of the calculation block 43, an estimated value of this passage cross section Seff appears. The calculation block 42 receives on its inputs, besides the set point value of the pressure in the intake manifold Pcol cons and the set value of the flow rate of the gases admitted into the engine at the inlet flap Qmot_dyn_cons, the pressure and the booster temperature Pboost and Tboost. The calculation block 43 receives, meanwhile at its inputs, in addition to the estimated value of the flow of gases admitted into the engine at the intake damper Qmotdyn, the value of the pressure in the intake manifold Peol and the temperature and boost pressure Pboost and Tboost. The effective cross section setpoint Seff cons determines a pre-positioning command symbolized by the block 46 which is associated with a regulator 47 which is, in the example illustrated, an integral proportional regulator with a coefficient of proportionality Kp and a coefficient The controller 47 receives on its input 48 the error signal determined by the comparator 48a, which is the difference between the set value of the cross section Seff calculated by the block 42 and the estimated value from of the block 43. The output of the adder 49 which receives both the output signal of the regulator 47 and the pre-positioning signal from the device 46, provides the position reference value for the admission flap 22.

The reference value of the flow rate of the recycled exhaust gases Qegr cops appearing on the output 37 of the first calculation means 36 is compared in the comparator 50 with an estimated value of the flow rate of the recycled exhaust gas Qegr determined in a calculation block 51 which includes a stored model and which receives on its inputs, the air flow Qair values of the pressure and boost temperature Pboost and Tboost and the filling factor Kr. The result of this comparison constitutes the signal of error brought to the input of a regulator 52, which is of the integral proportional type in the example illustrated, with a proportionality constant Kp and an integration constant K. The controller translates this difference into a position reference value which appears on the output 53 of an adder 53a. This setpoint value is sent to a setpoint separator 54 which translates the setpoint value from the regulator 52 into two separate setpoints, one for the position of the recirculation valve 18 and the other for the exhaust flap. The setpoint separator 54 comprises two saturation blocks respectively referenced 55 and 56. The first block 55 receives the setpoint value coming from the regulator 52 as well as a saturation threshold via the connection 57. The saturation block 55 transmits on its output 58, the position command signal for the EGR recirculating valve 18. The setpoint value from the regulator 52 is, moreover, brought by the connection 59 to an adder 60 which compares this value with the saturation threshold coming from the connection 57. The result of the comparison is brought to the input of the second saturation block 56 which emits at its output 61 a position command signal for the exhaust flap 19. Thanks to this In this arrangement, when the position setpoint from the regulator 52 is smaller than the position of the EGR 18 which corresponds to the saturation threshold, it is the EGR 18 recirculation valve which regulates the air flow from the position reference value appearing on the output 58. On the contrary, when the position setpoint from the regulator 52 is greater than this saturation position, it is the exhaust flap 19 which regulates the air flow, the recirculation valve 18 remaining frozen in its saturation position. The strategy adopted for regulating the admission flap 22 consists in prepositioning the position setpoint of the intake flap 22 from a reversal of a model of the flow rate of the gases passing through the intake flap, a model stored in the block. 42, based on the Barré Saint Venant (BSV) formula using setpoint values of the motor flow and the pressure in the manifold. In addition, the regulator 47 is linearized by the use of an inverted Saint Venant Barré model stored in the block 43, this time applied to the measured or estimated value of the gas flow admitted to the engine. The formula of Barré Saint Venant adapted to the intake flap 22 in the illustrated case of a motor comprising a partial recirculation circuit of the exhaust gas EGR at low pressure is the following: n _S P (P `Gmot_dyn ù boost BSV boost equation 3 eff VR.Tboost BSV The BSV function, which groups together several terms of the Barré Saint Venant formula, depends on the pressure ratio between the downstream and the upstream of the organ in question, and varies between 0 and around 0.7. depending on the value of this pressure ratio, we will now specify the different formulas used in the calculation means 36 and 40 and corresponding to the models stored in the blocks 42 and 43. Inverted model of the intake manifold To determine the value setpoint of the flow rate of the gases admitted to the engine, brought back to the level of the intake flap Qmot_dyn_aons, it starts from the setpoint values of the air flow rate Qair cons from the block 35 and the recycled exhaust gas content Te from 35a. The equations for defining the ratio of recycled exhaust gas, for maintaining the mass in the intake manifold and for filling the engine are then used. One obtains: equation 4 = Vcol dtegr_cons Qair cons Vcol 1 dQair cons + Qair cons dyn cons Kr dt (1utegrons) Kr (1tegrons) dt 1tetegrons with Kr = 120

To determine the set value of the flow cross section of the intake flap 22, it is also necessary to know the corresponding reference value of the pressure in the intake manifold. This setpoint value is obtained from the engine filling equation and assuming a perfect gas: col col 1 1 1 1 1 1 1 1 1 1 La La La La La La La La La La La La La La La La La La Recycled exhaust Qegr_cons is determined simply from the definition of the recycled exhaust rate:

~ egr_cons ~ egr_cons = air cons equation 6 1 egrcons' IvolNmotVcyi Dynamic model of the flow of gases admitted to the engine The flow of gases admitted into the engine at the intake flap 22, which is called the "dynamic engine flow "and which is noted Qmot_dyn, can be obtained in the calculation means 40 from the filling of the motor and the conservation equation of the mass in the intake manifold: i Qmot_dyn = VCO PCOl + Kr PCOl equation 7 R In the example illustrated in FIG. 1, it has been planned to measure the temperature of the gases in the intake manifold Taol by means of a sensor 30a. It is also possible to replace this measure with an estimate assuming perfect gases: Qmotdyn = VC` d 1 Pol + Kr 1 P, 017 equation 8 R dt Tboost 7 R Tboost Pboost Pboost Y Inverted Saint Venant model The use of the Barré Saint Venant formula makes it possible to determine the set value of the effective cross section through the admission flap 22 from the setpoint of the flow rate of the gases admitted to the engine at the inlet flap Qmot_dyn_cons and of the set value of the pressure in the admission manifold Pool cons previously calculated and obtained in the calculating means 36. We have in fact:. jRTboost Pboost BSV Seffcons = Qmotdyncons equation 9 (1 col cons In the same way, in the calculation block 43, it is estimated through the admission flap 22 current cross section effective by means of the formula: jRTboost Seff = Qmotdyn / P Boost boost BSV Pcol equation 10 Regulator 52 The regulator 52 is of the typ e PI in the illustrated example, as previously indicated. The regulation is calibrated according to the two parameters Kp and K; which respectively represent the proportional gain and the integral gain and which make it possible to calibrate the compromise overrun / response time of the regulation. The flow control dynamics of the exhaust gas recycled with the recirculation valve 18 being different from the regulation dynamics with the exhaust flap 19, the gains Kp and K; preferably have two sets of values. A first set of values corresponds to the flow control of the recycled exhaust gases EGR by the recirculation valve 18. Another set corresponds to the control of the flow rate of the exhaust gases recycled by the exhaust flap 19.

The estimation of the flow rate of the recycled exhaust gas Qegr is made in the block 51 from the airflow Qair measured by the flowmeter 11 and the filling of the engine by the formula: Qegr Q. ,, ùQair = Kr 1 Pcotl ùQair equation 11 R 1 boost P boost y The coordination between the two regulators 52 and 47 causes several different situations depending on the case. In the nominal case, the regulation of the flow rate of the recycled exhaust gases is done by the low pressure circuit by means of the combination of the recirculation valve 18 and the exhaust flap 19, while the filling of the engine is regulated by intake flap 22.

In another case, it only regulates the flow of the exhaust gas recycled by the low pressure circuit and it does not act on the intake flap which is kept in the open position. In order for the admission flap to be kept in the open position, the set point value of the flow cross section Seff cons must be maximum. This setpoint is defined by the preceding equation 9.

For this value to be maximum, the Pboost I Pcol cons ratio must be close to 1. Under these conditions, a set value for the recycled exhaust gas rate satisfies the condition: \ Qair cons egr_cons I 1 equation 13 so that the error signal which is brought to the input of the regulator 52 depends solely on the set point value of the air flow rate and the value measured for the air flow rate, since there is Thus, in this situation it is possible to force the opening of the admission flap 22 by means of the set point value of the flow rate of the inlet flap 22. In this case, the regulation of the flow of the recycled exhaust gases EGR is done only by the low-pressure circuit by means of the recirculation valve 18 and the exhaust flap 19. that the air flow admitted into the engine is well regulated To risk a penalty due to an uncertainty in the value of the filling of the engine, a saturation is preferably applied to the calculation of the value of the setpoint of the flow rate of the recycled exhaust gases in the following way: Qegrcons ù Qegr = air ù Qair Cons) Equation In another situation, the regulation of the air flow is, on the contrary, only by the intake flap 22 and there is no recirculation of the exhaust gas. In this case, the rate of recycled exhaust gas is zero and we have: R Qair cons Tboost Pcol cons Pboost ~ Gmot In this case, we actually Qegr_cons = Qmot ù Qair cons equation 12 K Pboost air cons Qmot equation In this situation, two actuators are able to act on a single control variable. It is therefore necessary to inhibit the air regulation by the low pressure circuit as soon as the value of the set point of the recycled exhaust gas is zero. This causes a complete opening of the exhaust flap 19 and a complete closure of the recirculation valve 18 mounted in the low pressure circuit. The regulation of the air flow is done, in this case, only by the admission flap 22. The error value which is brought to the input of the regulator 52 is equal to: Qmotùdyncons `Gmot_dyn BSV P BSboost BSV Pboost \, P \, COI / col / In order to limit as much as possible a drift related to the estimation of the filling of the engine, it is preferable, in this case, to replace the calculation of the estimated value of the flow rate of the admitted gases in the motor at the inlet flap 22 Qmotdyn, which is determined by the calculation means 40 from the temperature and pressure measurements, by a measurement directly made by the flowmeter by returning it to the level of the intake flap 22 by the formula: `Gmot_dyn = Qair_dyn =` Gain R LCat Tboost / where Vadm represents the volume between the flowmeter 11 and the intake flap 22. It can thus be seen that it is possible to manage the two actuators of the recirculation circuit of the gases low pressure exhaust constituted by ar the recirculation valve 18 and the exhaust flap 19 and the inlet flap 22, in a manner appropriate to the case. In a more precise way, when the set point value of the recycled exhaust gas meets the condition: S -s = .NIR loost eff cons efff Pboost equation 18 25 Vadm d Pb ° ost equation 19 Qmot the gases of d recycled exhaust are allowed in the engine. The setpoints are the Qair airflow and the recycled exhaust rate 'tegr. The regulation is made on the flow rate of the recycled exhaust gases Qegr for the low pressure circuit and the regulation is made on the flow rate of gases admitted into the engine Qmot for the intake flap 22. Qmot the exhaust gases are recycled at the intake of the engine, but the intake flap is kept in the open position. The set point is the air intake rate Qair and the regulation is done on the flowrate of the recycled exhaust gases Qegr for the low pressure recirculation circuit with the setpoint value: Qegr cons = Qmot ù Qair_cons equation 22 Finally, when the nominal value of the recycled exhaust gas ratio is equal to zero, the exhaust gases are no longer recycled to the intake and only the filling of the engine is regulated by a regulation of the position of the engine. intake flap 22. The set point is the air intake flow rate Qair and the regulation is done on the intake air flow rate Qair for the intake flap 22 with: Qmot ù Qair The present invention thus makes it possible to control The air flow rate and the rate of exhaust gas recycled in an engine as described are satisfactorily met, even during the regeneration phases of the particulate filter by limiting the maximum emissions of pollutants. In the present description, the regulation of the flow rate of the recycled exhaust gases has been essentially concentrated by means of the regulator 52 associated with the setpoint separator 54, so as to obtain position reference values for the recirculation valve. 18 In the event that the target value of the recycled exhaust gas content satisfies the condition: ti) Qair-cons equation 21 egr cons and the flap of 19. Alternatively, the flow rate of the recycled exhaust gas Qegr could be regulated, but on the other hand the recycled exhaust gas content, in which case the error signal at the inlet of the regulator 52 would be the difference between a set point of the recycled exhaust rate and a measured value. It would also be possible to regulate the air flow Qair, in which case the error signal at the input of the regulator 52 would be the difference between a set value of the air flow rate and a measured value for the air flow rate.

Claims (12)

A supercharged diesel type internal combustion engine comprising: a particulate filter (15) and a controlled exhaust flap (19) mounted in the exhaust line; a low pressure partial exhaust gas recirculation loop (17) including a controlled recirculation valve (18), said loop connecting the exhaust pipe, downstream of the particulate filter (15) with the inlet pipe of air, upstream of the supercharger (6); a controlled intake flap (22) mounted in the intake duct of the gas mixture in the engine, upstream of the intake manifold (3); and an electronic control unit (24) capable of receiving engine operating parameter values and controlling different engine components; characterized in that the electronic control unit comprises means for calculating position setpoints of the recirculation valve, the exhaust flap and the intake flap from airflow setpoint values. admitted into the engine and the rate of the exhaust gases recycled into the engine. 2. Motor according to the preceding claim wherein the electronic control unit comprises a first regulator (52) for determining the position set point values of the recirculation valve and the exhaust flap and a second regulator (47), associated with a prepositioning device (46) for determining the position setpoint value of the intake flap. 3. Motor according to one of the preceding claims wherein the electronic control unit comprises first calculation means (36) capable of estimating a set value of the pressure at the inlet flap and a set value. the flow rate of gases passing through the intake flap and the second calculation means (40) capable of estimating the effective flow rate of the gases flowing through the intake flap (22). 4. Motor according to claim 3 wherein the first calculation means (36) receive as input the set values of the intake air flow into the engine and the rate of exhaust gas recycled into the engine to calculate the value. of the flow rate of the gases passing through the intake flap (22) and the setpoint value of the pressure in the intake manifold of the engine, from stored equations corresponding to an inverted model of the intake manifold. 5. Motor according to claim 3 wherein the second calculation means (40) are capable of determining the value of the flow rate of the gas passing through the intake flap (22) from stored equations corresponding to a model of the gas flow rate. admitted into the engine. 6. Motor according to claim 3 wherein the second regulator (47) and the prepositioning device (46) receive on their respective inlet, a value of the effective passage cross section of the intake flap estimated from the flow of gas through the admission flap and a set value of the intake passage effective passage cross section estimated from the set values of the intake manifold pressure and the flow rate of the gases flowing through the intake flap. 7. Motor according to one of claims 2 to 6 wherein the first regulator (52) receives as input, a set value of a parameter related to the admission of gases into the engine and a measured value of said parameter, of to determine the position setpoint values of the recirculation valve (18) and the exhaust flap (19) for regulation of said parameter 8. Motor according to claim 7 wherein the parameter related to the admission of gases into the engine is selected from the flow rate of the recycled exhaust gas, the rate of recycled exhaust gas and the air flow admitted into the engine. engine. 9. A method of controlling the air flow and the rate of recycled exhaust gas in a supercharged diesel type internal combustion engine comprising: a particulate filter (15) and a controlled exhaust flap (19), mounted in the exhaust pipe; a partial recirculation loop of low pressure exhaust gas including a controlled recirculation valve (18), said loop connecting the exhaust pipe, downstream of the particulate filter with the air supply pipe, upstream of the supercharger (6); a controlled intake flap (22), mounted in the intake duct of the gas mixture in the engine, upstream of the intake manifold, characterized in that a parameter related to the admission of the gases is regulated in the engine by acting on the recirculation valve (18) and on the exhaust flap (19) and that the air flow admitted into the engine is regulated by acting on the intake flap (22) . 10. The method of claim 9 wherein said parameter is selected from the flow rate of recycled exhaust gas, the rate of recycled exhaust gas and the air flow admitted into the engine. 11. The method of claim 9 wherein regulates the air flow admitted into the engine by acting only on the recirculation valve and on the exhaust flap, the intake flap being held in the open position and applies a saturation when calculating the set point value of the recycled exhaust flow. 12. The method of claim 9 wherein regulates the flow of air admitted into the engine by acting only on the intake flap, the exhaust flap being held in the open position and the recirculation valve being held in the closed position. .