WO2006064145A1

WO2006064145A1 - Device for controlling regeneration of a particulate filter for an internal combustion engine and corresponding method

Info

Publication number: WO2006064145A1
Application number: PCT/FR2005/051040
Authority: WO
Inventors: Marc Daneau; Adrien Pillot
Original assignee: Renault S.A.S
Priority date: 2004-12-14
Filing date: 2005-12-06
Publication date: 2006-06-22
Also published as: FR2879244A1; FR2879244B1

Abstract

The invention concerns a device for regenerating a particulate filter (23) for motor vehicle mounted on an exhaust line (20) of an internal combustion engine (1), comprising first means (25) for measuring the temperature (TSm) at the output of the particulate filter (23). It further comprises means (50) for detecting a particular time during the regeneration phase, first means (52) for estimating a theoretical temperature (TSest) at the output of the particulate filter (23), and second estimating means (63) capable of determining, at said particular time, the volume of residues accumulated in the particulate filter based on the maximum difference (?T) between the estimated temperature (TSest) and the measured temperature (TSm) at the output of the particulate filter.

Description

Device for controlling the regeneration of a particulate filter for an internal combustion engine and method thereof

The present invention generally relates to the regulation of a regeneration phase of a particulate filter by combustion of particles accumulated in the filter, said filter being mounted on the exhaust line of a combustion engine. internal and in particular a diesel engine.

The standards concerning the pollution and consumption of internal combustion engines, including motor vehicles, are becoming more and more severe every day.

Among the known systems for eliminating the particles of substances emitted by internal combustion engines and in particular diesel engines, mention may be made of particulate filters contained in the exhaust lines of the engines. The filters are adapted to remove the soot particles contained in the exhaust gases.

Controlled regeneration devices make it possible to periodically burn the particles trapped in the filters and avoid the matting of the latter. However, the burned particles represent only a part of the particles accumulated in the filter.

Indeed, one can distinguish two categories of particles retained in the filter: combustible particles and incombustible particles.

The combustible particles are mainly due to the incomplete combustion of the fine drops of fuel. They are mainly composed of a carbon core on which unburned hydrocarbons are adsorbed. Regeneration of the particulate filter converts these particles into gaseous species that pass through the filter. These combustible particles burn at temperatures of the order of 550 to 600 ^° C. Such thermal levels are only rarely reached by the exhaust gases of an automotive diesel engine, since for example, in the city, the temperature of the Exhaust gas evolves between 150 and 250 ⁰ C. Hence the need to have appropriate means to raise the temperature of the gases when it is desired to regenerate such a particulate filter. Different systems have been proposed.

The electric resistance heating system including heating grids, allows to bring the exhaust temperature to a value sufficient to cause the combustion of particles in the filter. Other systems propose to increase the temperature of the exhaust gas by injecting an additional quantity of fuel into at least one combustion chamber in the form of a post-injection. A post-injection consists of injecting an additional quantity of fuel, after having injected the quantity of fuel necessary for the conventional operation of the engine. Some of this additional fuel ignites by producing an increase in the temperature of the exhaust gas, the rest of this fuel is converted into partial oxidation products such as carbon monoxide CO and HC hydrocarbons.

Non-combustible particles are mainly derived from engine lubricating oil. They are based on calcium, potassium and zinc. Regeneration does not convert these particles into gaseous species. There is then an accumulation of these particles that are commonly called residues in the filter. These residues occupy space in the filter, and decrease the storage capacity as well as the catalytic conversion efficiency for the catalytic type filters. Thus, from the point of view of controlling the particle filter, the presence of these residues disturbs the recognition of the mass of fuel particles actually stored. The knowledge of this last data is essential for the control of the particle filter since it makes it possible to determine when and under which conditions to trigger the regeneration. Underestimation can lead to destruction of the particulate filter, as combustion is too violent. On the other hand, overestimation results in more frequent regenerations and consequently an increase in fuel consumption as well as a faster degradation of the engine lubricating oil.

The patent application FR-2 829 798 filed by the Applicant, determines the loading into residues of the particulate filter, either from an estimate, or by measuring the pressure difference between upstream and downstream of the particulate filter in the exhaust line, the choice between the two methods being determined by the driving conditions. The pressure drop measured from the differential pressure is then directly connected to the mass of soot contained in the particulate filter. However, due to a specific impregnation of the ceramic material of some particulate filters, the differential pressure between the upstream and the downstream of the vacuum particle filter is almost constant, for a volumetric flow rate of gas. exhaust throughout its life. Thus, the effect of accumulating the residues contained in the filter by measuring the differential pressure of the filter at vi is not measured. On the other hand, this impact is felt when the filter is loaded, causing an increase in the differential pressure and consequently an increase in the regeneration frequencies. The use of the differential pressure for the estimation of residues in the filter, therefore generates significant errors that can lead to damage to the filter.

The invention aims to provide a solution to this problem. The subject of the invention is a device for regulating the regeneration phases of a particle filter so as to avoid damaging it.

The invention also aims to provide means for correcting the value of the differential pressure between the upstream and downstream of the particulate filter taking into account the mass of residues accumulated in the particulate filter.

To this end, the invention proposes a regeneration control device for a particulate filter for a motor vehicle mounted on the exhaust line of an internal combustion engine, comprising a first means for measuring the temperature at the outlet of the particle filter.

According to a general characteristic of the invention, the device further comprises means for detecting a particular moment during the regeneration phase, first means for estimating a theoretical temperature at the outlet of the particulate filter, and second estimation means able to determine, at said particular moment, the mass of residues accumulated in the particle filter from the maximum difference between the estimated temperature and the temperature measured at the outlet of the particulate filter. In other words, the first estimation means generate a theoretical temperature profile in the given combustion conditions. The second estimation means can then determine a difference in temperature equal to the maximum difference between the theoretical temperature and the measured temperature from a predetermined moment in the phase regeneration. Using this difference, it can be deduced using the second estimation means a mass difference that can be attributed to the residues that were not burned during the regeneration phase.

The use of a temperature difference has the advantage of obtaining a very precise measurement, sensitive to the smallest variation of mass of particles.

The second estimation means advantageously comprise means for comparing the estimated temperature and the temperature measured at the outlet of the particulate filter to produce a maximum temperature difference.

Preferably, the second estimation means furthermore comprise an inverse combustion model capable of producing a mass difference of particles present at said particular moment as a function of the maximum temperature difference. According to one embodiment, the flow rate of the air passing through the particle filter and the oxygen content in the particle filter are delivered to the inverse combustion model.

According to one embodiment, the first estimation means advantageously comprise a combustion model capable of estimating the theoretical temperature at the outlet of the particulate filter and the mass of particles burned at each instant during the regeneration phase, as a function of the inlet temperature of the measured particulate filter, the air flow and the oxygen content in the particulate filter.

The device may comprise means for integrating the value of the mass of particles burned at any moment, so as to determine the total mass of particles burned during the regeneration phase.

The device may comprise subtraction means able to calculate at each instant the value of the resulting mass of particles present in the particulate filter during the regeneration phase, said resulting measured value being equal to the difference between the value of the initial mass of particles and the mass of particles burned at each moment. The device may comprise memory means capable of storing, on the one hand, the value of the mass of particles remaining and, on the other hand, the value of the mass of particles burned at said particular moment, the two values having been measured at level of the particulate filter. Preferably, the reverse combustion model receives the resulting mass of particles.

The invention also proposes a regeneration control method of a particulate filter for a motor vehicle mounted on the exhaust line of an internal combustion engine, wherein the temperature at the outlet of the particulate filter is measured. .

According to a general characteristic e of the invention, a particular moment is detected during the regeneration phase, from which a theoretical temperature is estimated at the outlet of the particulate filter so as to be able to determine the mass of residues accumulated in the regeneration phase. particulate filter as a function of the maximum difference between the estimated temperature and the temperature measured at the outlet of the particulate filter.

According to one embodiment, said particular moment corresponds to an injection cutoff during the regeneration phase. According to one embodiment, said particular moment corresponds to the idle return of the engine during the regeneration phase.

Other advantages and features of the invention will be apparent from consideration of the detailed description of a mode of embodiment of the invention in no way limiting, and the accompanying drawings, in which:

FIG 1 shows schematically the main elements of admission and exhaust of internal combustion engine with a particulate filter in the exhaust line;

FIG. 2 illustrates the device for controlling the regeneration of the particulate filter according to the invention; and

FIG. 3 represents the various steps of the control method of the regeneration of the particulate filter according to the invention. As illustrated in FIG. 1, the internal combustion engine 1, shown schematically, comprises a plurality of combustion chambers, such as the combustion chamber 2 illustrated in the figure in the upper part of a cylinder 3 to inside which moves a piston 4. An intake valve 5 allows to control the admission by opening or closing the intake duct

6, in communication with the combustion chamber 2. An exhaust valve 7 allows, for its part, to close or open the passage of the exhaust gas from the combustion chamber 2 to the duct Exhaust 8. The fresh air at atmospheric pressure, whose flow is symbolized by the arrow 9, enters a pipe 10 inside which is mounted a flowmeter 11. The air pressure is increased by a compressor 12 mounted in the pipe 10. The compressor is mounted on a shaft 13 common to a turbine 14, here variable geometry, mounted in the exhaust pipe 8. The exhaust gas passing through the turbine 14 and drive the compressor 12 , so as to increase the pressure of the air admitted into the combustion chamber 2 by the intake duct 6. In the example illustrated, the engine 1 further comprises a partial exhaust feed reinjection system (EGR). For this purpose, a bypass line 15 is stitched on the exhaust pipe 8 upstream of the turbine 14. A control valve 16, called the "EGR valve", controls the amount of exhaust gas which is thus reinjected. by the pipe 17 in the inlet duct 6 after having been suitably mixed in the mixing chamber 18. An adjustable orientation flap 19 is further mounted in the compressed air pipe 10 downstream of the compressor 12 and upstream of the mixing chamber 18.

The exhaust line 20 connects the outlet of the turbine 14 to the atmosphere, the outlet of the exhaust gas being symbolized by the arrow 21. In the exhaust line 20, there is mounted a catalyst device 22 directly in downstream of the turbine 14, and a particulate filter 23 downstream of the catalytic device 22. The particulate filter 23 is of conventional type and comprises means, for example electrostatic, for trapping soot and particles from the engine 1 and conveyed by the exhaust gas in the exhaust line 20. An electronic control unit 24 operates the engine 1 and receives a number of information for this purpose. Various sensors are placed for this purpose in the lines and their signals are fed to the electronic control unit 24. Furthermore, a module 24a of the electronic unit 24 more particularly ensures the operation of the particle filter 23 by a connection 24b.

In FIG. 1, a pressure sensor 25 is shown on the air supply line 10, mounted upstream of the flap 19. A pressure sensor 26 capable of measuring the pressure is also shown. pressure upstream of the turbine 14 and a temperature sensor 27 measuring the temperature upstream of the turbine 14.

The measurement signal of the flow meter 1 1 is fed through the connection 28 to one of the inputs of the electronic control unit 24. In the same way, the signal emitted by the pressure sensor 25 is fed through the connection 29 to the electronic control unit 24. The signals emitted by the sensors 26 and 27 are also fed via the connections 30 and 31 to inputs of the electronic control unit 24. The electronic control unit 24 can control in particular the position of the EGR valve 16 through the connection 32, the position of the movable flap 19 via the connection 33. The electronic control unit also controls the fuel injectors 34 via the connection 35. For the regulation of the particulate filter 23 during In the regeneration phase, the system, as illustrated in FIG. 21, comprises a temperature sensor 36 mounted in the exhaust line 20 at the outlet of the particulate filter 23. The temperature signal e measured by the sensor 36 is fed through the connection 37 to one of the inputs of the electronic control unit 24. The system also comprises a temperature sensor 38 at the input of the particle filter 23. The temperature measured by the sensor 38 is brought by the connection 39 at the input of the electronic unit 24. The system further comprises for regulation during the regeneration phase of the particulate filter 23 a differential pressure sensor 40 mounted on a pipe 41 , parallel to the particulate filter 23. The differential pressure measurement is sent to the input of the electronic unit 24 via a connection 42. FIG. 2 diagrammatically shows the module 24a included in the electronic unit 24, able to control the regeneration phase of the particulate filter 23.

The module 24a comprises a detection means 50 which receives, by a connection 51a, a setpoint Creg indicating the beginning of the regeneration phase. The detection means is capable of generating a set point Cinj when during the regeneration phase, there is an injection cutoff or an idle return of the motor.

Indeed, in injection cutoff, for example when the driver is immobilized in front of the traffic light, the high rate of oxygen, up to 21%, can strongly promote regeneration and thereby cause a rise in temperature. important in the particulate filter.

Similarly, during the idling phases of the engine of the motor vehicle, for example below 800 revolutions / minute, the low airflow greatly reduces the evacuation of the thermal energy released by the combustion of fuel. particles within the filter.

In each case, the rise in temperature is very sensitive to the mass of stored particles. The soot mass can therefore be very accurately evaluated by measuring the value of the temperature.

The setpoint Creg is also delivered to a first estimation means 52 via a connection 51b. The purpose of the estimating means 52 is to estimate an outlet temperature of the particulate filter.

TSis according to predetermined parameters. The estimate is made at the beginning of the regeneration phase.

The parameters delivered by the means 52 comprise the input temperature TEm of the measured particulate filter, delivered to the first estimating means 52 via a connection 53. The means 52 also receives as input via a connection 54 a measurement of revolution of the air flow rate in the particulate filter 23, as well as the oxygen content of the air contained in the particulate filter, this rate being delivered by means 52 via a connection 55. The oxygen level can be measured by a sensor integrated in the particulate filter 23 (not shown), or estimated using an estimator (not shown) able to calculate the oxygen content of the air. Finally, the first means 52 receives as input the initial mass Minit of particles present within the particle filter, by a connection 56. The initial mass Minit of particles can be determined using a stored loading model comprising a set of loading curves that make it possible to know the mass of particles stored from the differential pressure and the evolution of the volume air flow.

The loading model used can be, for example, that described in the patent application FR 2 829 798 filed by the Applicant. The loading model then takes the following form:

ΔT = c.A + B, with:

ΔT: differential pressure between the upstream and downstream of the particulate filter, c: mass of soot stored in the particulate filter, A: volume flow rate of the gas passing through the filter, B: offset of the differential pressure sensor. The first estimation means 52 comprises in particular a combustion model 57 which will estimate at each instant, from the precipitated parameters, the mass of burnt particles Mi and the outlet temperature of the particulate filter TSest.

The mass of particles burned at each instant Mi is delivered, on the one hand, by a connection 58 to a subtraction means 59, which It also receives as input via a connection 60 the value of the initial mass Minit of particles inside the particle filter 23. The function of the subtraction means 59 is to calculate at each instant the resultant value Mr of the mass of particles present in the particulate filter 23 during the regeneration phase.

The mass of particles burned at each instant Mi is also delivered by a connection 61 to an integration means 62, which calculates at each instant the total mass of burned particles Mbt.

The module 24a further comprises a second estimation means 63.

More precisely, the second estimation means 63 comprises a comparison means 65 which receives as input the output temperature TSm measured at the output of the particle filter 23 and delivered by a connection 66. In addition, the means 65 receives by At a connection 67, the estimated output temperature TS is released by the means 51. The comparison means 65 then determines the temperature difference ΔT existing between the estimated temperature TSest and the measured temperature TSm.

The means 63 also comprises an inverse combustion model 68, which receives at input via a connection 69 the temperature difference ΔT calculated by the comparison means 65. In addition, the inverse combustion model 68 receives, via a connection 70, the The flow rate of the air within the particulate filter 23, as well as the connection of the oxygen content present in the air of the particulate filter 23, is changed. In addition, the reverse combustion model 68 receives by a connection 72, the resultant mass M r calculated by the subtractor

59.

Using these various parameters, the inverse combustion model 68 will determine a mass deviation ΔM corresponding to the temperature difference ΔT, from the injection cutoff, the setpoint Cinj being delivered to the model 68 by a connection 68a.

Indeed, at the time of the injection cutoff, the temperature difference ΔT will then be the largest. The mass deviation ΔM is delivered by a connection 73 to a computer 74, which also receives as input via a connection 75 the mass of burnt particles total Mbt. The computer 74 then delivers at output by a connection 76 the actual initial mass Minitre, and by a connection 77 the mass of residues ε present in the particulate filter 23.

FIG. 3 describes the steps of the regeneration method of the particle filter using the device according to the invention.

In a first step 80, upon receipt of the set point Creg indicating the beginning of the regeneration phase, the initial particle mass Minit is determined using a stored loading model as described above. However, this mass Minit does not take into account the mass of residues present in the particulate filter 23; it is therefore different from the actual initial mass of particles. In parallel, during a second step 81, on receipt of the set point Creg indicating the beginning of the regeneration phase, the injection cut-off time or an idle return of the engine is detected, for example, so to deliver a setpoint Cinj.

During a third step 82, the combustion model 57 estimates from the temperature TEm at the inlet of the particulate filter

23, the rate of oxygen and the evolution of air flow, the mass Mi of particles burned at each instant, and the temperature TS is output of the particle filter 23. During a phase 83, the integration means 62 adds at each instant the mass Mi to determine the mass of particles burned since the beginning of the regeneration phase. This value is stored under the name of total mass of burned particles Mbt. Simultaneously, during a phase 84, the subtraction means

59 calculates at each instant the mass Mr of remaining particles in the particle filter 23 by subtracting the mass Mi from the mass of initial particles Minit, this value is stored (not shown) under the name of the resulting mass of particles. At the moment of the injection cutoff, during a phase 85, the mass of burned particles is stored in memory as the mass of particles burned at the moment of the Mbtc cutoff. Similarly, the mass of particles remaining at the moment of the cut is stored in memory under the name of Mrc. From this moment, the evolution of the air flow rate in the particulate filter 23, the oxygen content, the temperature TEm measured at the inlet of the particulate filter 23, as well as the temperature TS is estimated at the outlet of the filter. particles by the combustion model 57, are stored with appropriate sampling. During a step 86, the comparison means 65 measures the difference between the output temperature TSest estimated by the combustion model 57 for the initial mass Minit given, and the measured output temperature TSm by the sensor 25 up to this difference ΔT is maximum. We then stop the storage of the aforementioned parameters.

Indeed, the estimated temperature will be for a mass of particles greater than the real mass, since the device considers the initial mass as being only particles, while part of the partly formed residues. The actual temperature will be lower than the estimated temperature.

During a step 87, from the difference ΔT maximum temperature obtained in step 86, is determined and stored a differential pressure difference between the upstream and downstream of the filter for a given volume flow and, via the aforementioned loading models, we deduce a deviation ΔM between the Mrc mass and the actual mass of particles at the moment of the cut. The real mass Mre of particles is therefore known at the moment of the cutoff by summing Mrc and ΔM. In a phase 88, the mass Mbtc of particulates burned at the moment of cutting is added to the actual mass Mre of particles at the moment of cutting. It is thus possible to determine the actual initial mass and to correct the calibration of the loading model used during the first step 80. In a last phase 89, the initial mass Minit of particles is then subtracted from the mass. in order to determine the error ε on the mass of the residue present in the filter 23 at the initial moment.

By this method, it is possible to measure very precisely the mass difference due to residues which are not burned during the regeneration phase. The influence of this mass of residues on the differential pressure at the terminals of the particle filter can subsequently be known. By knowing exactly the value of the differential pressure, we can then regulate it so as to avoid damage to the filter.

In addition, it is possible to calibrate the loading model at each end of the cycle, so as to take into account the mass of residues generated during the previous cycle. Of course, the invention is not limited to the embodiment which has just been described by way of example.

Claims

1. A regeneration control device of a particulate filter (23) for a motor vehicle mounted on the exhaust line (20) of an internal combustion engine (1), comprising first measuring means (25). the temperature (TSm) at the outlet of the particulate filter (23), characterized in that it further comprises detection means (50) of a particular moment during the regeneration phase, first means estimation (52) of a theoretical temperature (TSest) at the output of the particulate filter (23), and second estimation means (63) able to determine, at said particular moment, the mass of residues accumulated in the particle filter from the maximum deviation (ΔT) between the estimated temperature (TSest) and the measured temperature (TSm) at the outlet of the particulate filter.

2. Device according to any one of the preceding claims, characterized in that the second estimation means (63) comprise means for comparing (65) the estimated temperature (TSest) and the temperature (TSm) measured in output of the particulate filter to develop a maximum temperature difference (ΔT).

3. Device according to any one of the preceding revendi cations, characterized in that the second estimation means (63) further comprise a combustion inverse model (68) adapted to develop a mass deviation (ΔM) of particles present at said particular moment as a function of the maximum temperature difference (ΔT).

4. Device according to claim 3, characterized in that the flow rate of the air passing through the particulate filter (23) and the rate of oxygen within the particle filter (23) are fed to the inverse combustion model (68).

5. Device according to any one of the preceding claims, characterized in that the first estimation means (52) comprise a combustion model (57) capable of estimating the theoretical temperature (TSest) at the outlet of the particulate filter. and the mass of burnt particles (Mi) at each instant during the regeneration phase, as a function of the measured inlet temperature (TEm) of the particulate filter (23), the air flow, and the rate. of oxygen in the particulate filter (23).

6. Device according to claim 5, characterized in that it comprises means for integrating the value of the mass of particles (Mi) burned at each moment, so as to determine the total mass (Mbt) of particles burned. during the regeneration phase.

7. Device according to claim 6, characterized in that it comprises subtraction means (59) capable of calculating at each instant the value of the resulting mass of particles (Mr) present in the particulate filter (23) at during the regeneration phase, said resulting measured value being equal to the difference between the value of the mass of nitinal particles (Minit) and the mass of particles burned at each instant (Mi).

8. Device according to claim 9, characterized in that it comprises storage means able to store, on the one hand the value of the remaining mass of particles (Mrc) and on the other hand the value of the mass. of particulates burned (Mbtc) at said particular moment, both values being measured at the particulate filter (23).

9. Device according to any one of claims 3 to 8, characterized in that the inverse combustion model (68) receives the resulting mass of particles (Mr).

Regeneration control method of a particulate filter (23) for a motor vehicle mounted on the exhaust line (20) of an internal combustion engine (1), where the temperature at the outlet of the engine is measured. particle filter (23), characterized in that a particular moment is detected during the regeneration phase, during the regeneration phase a theoretical temperature (TSest) at the outlet of the particulate filter ( 23) so as to be able to determine, at said particular moment, the mass of residues accumulated in the particle filter as a function of the maximum difference (ΔT) between the estimated temperature (TSest) and the measured temperature (TSm) at the output of the particulate filter (23).

1 1. Device according to claim 10, characterized in that said particular moment corresponds to an injection cut during the regeneration phase.

12. Device according to claim 10, characterized in that said particular moment corresponds to the idle return of the engine during the regeneration phase.