METHOD FOR DETECTING ERRONEOUS PRESSURE DIFFERENCE MEASUREMENTS ACROSS THE TERMINALS OF AN INTERNAL COMBUSTION ENGINE PARTICULATE FILTER

Abstract

The invention relates to a method for detecting erroneous pressure difference measurements at the terminals of a particulate filter (16) located on an exhaust line (12) of an internal combustion engine (10), comprising: - a step of measuring the loading of the particulate filter (16) as a function of pressure difference measurements at the terminals of a particulate filter (16), - a step of measuring the filling time of the particulate filter (16) to go from one loading threshold to another, - a step of comparing the measured filling time with a reference filling time, and - a step of detecting erroneous pressure difference measurements in the case where the measured filling time is less than the reference filling time. Figure 1

Description

Title of the invention: METHOD FOR DETECTING ERRONEOUS PRESSURE DIFFERENCE MEASUREMENTS AT TERMINALS OF A HEAT ENGINE PARTICLE FILTER

[0001] The present invention relates to a method for detecting erroneous measurements of pressure difference at terminals of a particulate filter arranged on an exhaust line of a heat engine. The invention finds a particularly advantageous application, in the automotive field, with gasoline heat engines equipped with a particulate filter associated with a differential pressure sensor.

[0002] During the combustion of a mixture of air and fuel in a heat engine, solid or liquid particles consisting essentially of carbon-based soot and / or oil droplets may be emitted. These particles typically have a size of between a few nanometers and one micrometer. To trap them, it is advantageous to provide particle filters, usually consisting of a mineral matrix, of the ceramic type, with a honeycomb structure, defining channels arranged substantially parallel to the general direction of flow of the exhaust gases in the filter, and alternately closed on the side of the gas inlet face of the filter and on the side of the gas outlet face of the filter, as described in document EP2426326.

[0003] The exhaust line is also provided with a differential pressure measuring sensor to measure the pressure difference between an upstream tapping and a downstream tapping of the particulate filter from which it is possible to deduce a mass of accumulated soot. For this purpose, a map is used establishing a correlation, as a function of the admitted air flow rate, between the pressure difference measurement and the mass of soot in the particulate filter.

[0004] The regeneration of the particulate filter is controlled when the latter is sufficiently loaded with particles. To this end, the temperature in the exhaust line is increased, which causes the combustion of soot in the particulate filter. At the end of the regeneration, the particulate filter is freed from the soot it contained and a new loading cycle begins.

[0005] In order to detect erroneous measurements of the differential pressure of the differential pressure measuring sensor, a strategy called TuFrz, for "tubes freezing" according to the English terminology, is capable of detecting cases of freezing in the pipes connected to the differential pressure measuring sensor. This strategy operates below 0°C ambient temperature. However, above 0°C, unexplained cases of erroneous differential pressure measurements have been observed which are not due to freezing and which lead to an erroneous detection of the loading threshold. Reaching a significant loading threshold, in particular a clogging threshold, results in actions to reconfigure the thermal engine in degraded mode (torque limitation) or an alert to the driver, for example by the illumination of a warning light, asking him to go to the garage to carry out an after-sales regeneration of the particulate filter, whereas it is probably a false detection of the loading threshold. Indeed, studies have shown that the majority of cases of clogged particulate filters reported by the vehicle's computer are false detections linked to erroneous measurements of differential pressure at the terminals of the particulate filter.

[0006] The invention aims to effectively remedy the aforementioned drawbacks by proposing a method for detecting erroneous measurements of pressure difference at terminals of a particle filter arranged on an exhaust line of a heat engine comprising: - a step of measuring a loading of the particle filter as a function of pressure difference measurements at terminals of a particle filter, - a step of measuring the duration of filling of the particle filter to move from one loading threshold to another loading threshold, - a step of comparing the measured filling time with a reference filling time, and - a step of detecting erroneous pressure difference measurements in the case where the measured filling time is less than the reference filling time.

[0007] According to an implementation of the invention, the method further comprises a step of inhibiting a diagnosis of operation of the particle filter and reconfigurations of the thermal engine and / or alerts to a driver associated with the filling thresholds.

[0008] According to one implementation of the invention, said method comprises a step of rehabilitating the diagnosis of operation of the particle filter implemented when at least one rehabilitation condition among the following conditions is verified: - a regeneration of the particle filter has just been completed, - a minimum number of points corresponding to a pair [pressure difference; exhaust gas flow] was obtained to carry out a learning of a filling of the particle filter, - a safety delay since detection of erroneous pressure difference measurements at the terminals of the particle filter is greater than a predetermined time threshold.

[0009] According to one implementation of the invention, the loading thresholds are chosen from a first loading threshold corresponding to an overloaded particle filter, a second loading threshold corresponding to an overloaded particle filter, and a third loading threshold corresponding to a clogged particle filter.

[0010] According to one implementation of the invention, the reference filling time is obtained under the most severe real driving conditions possible, maximizing a filling speed of the particle filter.

[0011] The invention also relates to a computer comprising a memory storing software instructions for implementing a method as previously defined.

[0012] The invention further relates to a motor vehicle comprising a computer as defined above.

[0013] According to one embodiment of the invention, said motor vehicle comprises an exhaust line on which a particulate filter and a differential pressure sensor are installed at the terminals of the particulate filter.

[0014] According to one embodiment of the invention, a three-way catalyst is installed on the exhaust line.

[0015] According to one embodiment of the invention, said motor vehicle comprises a gasoline thermal engine.

[0016] The invention will be better understood upon reading the following description and examining the accompanying figures. These figures are given only for illustrative purposes but in no way limit the invention.

[0017] [Fig-1] [Fig.l] is a schematic representation of an exhaust line of a thermal engine comprising a particle filter and a computer allowing the implementation of the method according to the invention;

[0018] [Fig.2] [Fig.2] is a graphical representation of an evolution of a mass of soot estimated from a measurement of differential pressure at terminals of a particle filter as a function of a driving duration respectively for severe driving conditions and erroneous measurements of differential pressure;

[0019] [Fig.3] [Fig.3] is a functional representation of software modules of a computer implementing the method according to the invention for detecting erroneous measurements of pressure difference at terminals of a particle filter arranged on an exhaust line of a heat engine.

[0020] [Fig.l] shows a heat engine 10 intended in particular to equip a motor vehicle. The heat engine 10 is connected to an exhaust line 12 for the evacuation of the burnt gases produced by the operation of the heat engine 10.

[0021] The exhaust line 12 comprises a member 14 for depolluting gaseous pollutants, for example an oxidation catalyst or a three-way catalyst. The three-way catalyst 14 makes it possible in particular to reduce nitrogen oxides to nitrogen and carbon dioxide, to oxidize carbon monoxides to carbon dioxide, and unburned hydrocarbons to carbon dioxide and water.

[0022] The exhaust line 12 further comprises a particulate filter 16 for filtering soot particles in the exhaust gases of the heat engine 10. The particulate filter 16 is suitable for filtering soot particles originating from the combustion of the fuel.

[0023] In the particulate filter 16, the exhaust gases pass through the material making up the particulate filter. Thus, when the particulate filter 16 is formed of channels, each of these channels comprises a blocked end, so that the exhaust gases flowing in the particulate filter 16 pass from channel to channel, passing through the walls of the different channels of the particulate filter 16 to exit the particulate filter 16. The particulate filter 16 may be based on a porous ceramic matrix, for example cordierite, mullite, aluminum titanate or silicon carbide. If necessary, the pollution control member 14 and the particulate filter 16 may be installed inside the same casing 17.

[0024] The exhaust line 12 is also provided with a differential pressure measurement sensor 18 between the upstream and downstream of the particulate filter 16 from which it is possible to deduce a mass of accumulated soot. For this purpose, the sensor 18 is connected upstream and downstream of the particulate filter 16. In addition, a map makes it possible to establish a correlation, as a function of the flow rate of admitted air, between the differential pressure measurement and the mass of soot in the particulate filter 16. The differential pressure sensor 18 may be a single-membrane or double-membrane sensor.

[0025] A computer 20, for example the engine computer or another dedicated or multifunction computer, makes it possible to carry out a diagnosis of the operation of the differential pressure sensor 18. The computer 20 comprises a memory storing software instructions for implementing a method for detecting erroneous measurements of the pressure difference at the terminals of the particle filter.

[0026] The various functional modules M1-M4 of the computer allowing the implementation of the method according to the invention are described below, with reference to [Fig. 3].

[0027] The module M1 is capable of measuring a loading of the particle filter 16 as a function of pressure difference measurements at the terminals of a particle filter 16. For this purpose, the module M1 uses a map establishing a correlation, as a function of the flow rate of admitted air, between the pressure difference measurement and the mass of soot in the particle filter 16.

[0028] The module M1 is capable of detecting different loading thresholds of the particle filter 16. As can be seen in [Fig.2], a first loading threshold SI corresponds to a particle filter 16 overloaded by a mass of soot, for example of the order of 5 g. When the threshold SI is detected, the computer 20 promotes the supply of oxygen into the particle filter 16 for its regeneration.

[0029] A second loading threshold S2 corresponds to a particle filter 16 overloaded by a mass of soot, for example of the order of 10g. When the threshold S2 is detected, the computer 20 controls the heat engine 10 so as to heat the particle filter 16 and supply it with oxygen.

[0030] A third loading threshold S3 corresponds to a filter clogged by a mass of soot, for example up to 15g. When the threshold S3 is detected, the computer 20 initiates actions to reconfigure the thermal engine 10 in degraded mode (torque limitation) or an alert to the driver, for example by lighting a warning light. This is the threshold to be avoided in the event of an erroneous measurement because the driver must go to the garage to carry out an after-sales regeneration.

[0031] The module M2 measures a filling time Tmes of the particulate filter 16 to move from one loading threshold to another loading threshold. The module M2 compares the measured filling time Tmes with a reference filling time Tref. The reference filling time Tref is obtained under the most severe real driving conditions possible, maximizing a filling speed of the particulate filter 16. The real driving conditions maximizing a filling speed of the particulate filter 16 can be obtained at low temperature, for example at -20 degrees Celsius, short consecutive driving of the plug type, and the use of a low volatility fuel of the very low PVR type (for "Raid Vapor Pressure" according to English terminology).

[0032] In [Fig.2], the curve Cl in broken lines is representative of a mass of soot Ms as a function of time t corresponds to a maximum loading speed for a particle filter 16 operating under severe driving conditions. The 5 grams of soot necessary to pass from threshold SI to threshold S2 can be obtained under severe driving conditions within a reference duration Tref of 5 hours, which can represent approximately 75 kilometers traveled by the vehicle.

[0033] The solid line curve C2 was obtained from the pressure difference measurement returned by the sensor 18. It emerges that it only took 2 min or 3 km for the mass of soot Ms in the particle filter 16 to increase by 5 grams and therefore for the threshold SI to pass to the threshold S2. In this case, the measured filling time Tmes of the particle filter 16 is less than the reference filling time Tref.

[0034] The module M2 then detects that the pressure difference measurements are erroneous and will send an implausibility boolean Bimp of the differential pressure measurement to a module M3.

[0035] In the case where erroneous pressure difference measurements are detected by the module M2, the module M3 which receives the Boolean Bimp inhibits an operating diagnosis of the particle filter 16 as well as reconfigurations of the thermal engine 10 and / or driver alerts associated with the filling thresholds SI, S2, S3.

[0036] A module M4 is capable of rehabilitating the operating diagnosis of the particle filter 16 when at least one rehabilitation condition among the following conditions is verified: - a regeneration Regen of the particle filter 16 has just been completed, - a minimum number of points corresponding to a pair [pressure difference dP; exhaust gas flow rate dV] was obtained to carry out a learning of a filling of the particle filter 16, - a safety time delay Temp since a detection of erroneous measurements of pressure difference at the terminals of the particle filter 16 is greater than a predetermined time threshold.

[0037] The module M4 then sends a Boolean Brehab to the module M3 to rehabilitate the operating diagnosis of the particle filter 16.

Claims

Claims

1. Method for detecting erroneous measurements of pressure difference at terminals of a particulate filter (16) arranged on an exhaust line (12) of a heat engine (10) characterized in that it comprises: - a step of measuring a loading of the particulate filter (16) as a function of measurements of pressure difference at terminals of a particulate filter (16), - a step of measuring a filling time of the particulate filter (16) to pass from one loading threshold to another loading threshold, - a step of comparing the measured filling time (Tmes) with a reference filling time (Tref), and - a step of detecting erroneous measurements of pressure difference in the case where the measured filling time (Tmes) is less than the reference filling time (Tref).

2. Method according to claim 1, characterized in that it further comprises a step of inhibiting a diagnosis of operation of the particle filter (16) and reconfigurations of the thermal engine (10) and / or alerts to a driver associated with the filling thresholds (SI, S2, S3).

3. Method according to claim 2, characterized in that it comprises a step of rehabilitation of the operating diagnosis of the particle filter (16) implemented when at least one rehabilitation condition among the following conditions is verified: - a regeneration of the particle filter (16) has just ended, - a minimum number of points corresponding to a pair [pressure difference (dP); exhaust gas flow rate (dV)] has been obtained to carry out a learning of a filling of the particle filter (16), - a safety delay since a detection of erroneous measurements of pressure difference at the terminals of the particle filter (16) is greater than a predetermined time threshold.

4. Method according to any one of claims 1 to 3, characterized in that the loading thresholds are chosen from a first loading threshold (S1) corresponding to an overloaded particle filter (16), a second loading threshold (S2) corresponding to an overloaded particle filter (16), and a third loading threshold (S3) corresponding to a clogged particle filter (16).

5. Method according to any one of claims 1 to 4, characterized in that the reference filling time (Tref) is obtained under the most severe real driving conditions possible, maximizing a filling speed of the particle filter (16).

6. Computer (20) comprising a memory storing software instructions for implementing a method defined according to any one of the preceding claims.

7. Motor vehicle comprising a computer (20) defined according to the preceding claim.

8. Motor vehicle according to claim 7, characterized in that it comprises an exhaust line (12) on which is installed a particulate filter (16) and a differential pressure sensor (18) at the terminals of the particulate filter (16).

9. Vehicle according to claim 8, characterized in that a three-way catalyst (14) is installed on the exhaust line (12).

10. Motor vehicle according to any one of claims 7 to 9, characterized in that it comprises a gasoline thermal engine (10).

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