EXHAUST GAS LINE OF A STOICHOMETRIC COMBUSTION GASOLINE VEHICLE ENGINE

Abstract

The exhaust gas line (LDE1) is designed for a stoichiometric combustion (MT) gasoline internal combustion engine and comprises a three-way catalytic converter (TWC), a gas particulate filter (GPF), and a silencer (ESIL) mounted in cascade between an exhaust gas inlet and outlet of the line. According to the invention, the exhaust gas line also includes a soot sensor (CS) mounted downstream of the silencer. Figure 3

Description

Title of the invention: EXHAUST GAS LINE OF A VEHICLE THERMAL ENGINE OF THE GASOLINE TYPE WITH STOECHIOMETRIC COMBUSTION

[0001] The present invention relates generally to the detection of the state of degradation of a particulate filter in an exhaust gas line of a stoichiometric combustion gasoline thermal engine. More particularly, the invention relates to an exhaust gas line of a stoichiometric combustion gasoline type vehicle thermal engine.

[0002] A modern vehicle with a thermal engine is equipped with an anti-pollution device which is integrated into its exhaust gas line. In addition to one or more catalysts which transform the toxic components of the exhaust gases, such as carbon monoxide (CO), unburned hydrocarbons, and nitrogen oxides (NOx), into less toxic components, such as carbon dioxide (CO2), and water, this anti-pollution device also includes a particulate filter, catalyzed or not, which traps the carbon particles resulting from combustion in the cylinders of the thermal engine.

[0003] The particle filter is necessary to comply with anti-pollution standards for vehicles, in particular the European regulations known as “Euroôd”, “Euro6d-temp”, “Euroôe” and the future “Euro7” standard which regulates carbon particle emissions in number and mass.

[0004] In [Fig.l], statistical distributions, in number (curve Cn) and in mass (curve Cv), of a population of carbon particles of 10 to 1000 nm in diameter emitted by an internal combustion engine are shown for illustrative purposes. The vast majority of particles emitted in number are very small and represent only a very low mass, conversely very few very large particles represent the majority of the mass emitted.

[0005] The particulate filter, generally cylindrical in shape, comprises a ceramic body having a multitude of porous parallel channels of small diameters. The exhaust gases pass through these parallel channels and the carbon particles present in the gases are trapped in the porous ceramic of the channels. The filter must be regenerated periodically to remove the accumulated particles and reduce the pressure drop in the exhaust gas line. The regeneration of the filter is obtained by raising its temperature, typically between 500°C and 650°C, which allows the accumulated carbon particles to be burned.

[0006] The need for regeneration of the particulate filter can be detected by measuring of the pressure drop due to the filter, by measuring with sensors a differential pressure between the inlet and outlet of the filter. The need for filter regeneration can also be estimated based on the number of kilometers traveled and the vehicle's operating conditions. A model embedded in the engine control computer can be used to estimate the need for regeneration as well as its duration.

[0007] Filter regeneration generally occurs without the driver's knowledge. It is triggered automatically by the engine control computer, depending on the load of the thermal engine, taking advantage in particular of occurrences of oxygen present upstream of the filter during fuel injection cuts when the driver lifts his foot.

[0008] For various reasons, the particulate filter may suffer damage, such as cracking, leading to an impaired filtering function and non-compliant emission of carbon particles. Too high a temperature gradient inside the filter, for example during a regeneration, can seriously damage the filter by causing cracking. The filter may also be damaged due to faulty engine control, producing an upstream temperature that is too high in the exhaust gas line. An overall temperature that is too high, generally above 1000°C, can lead to the destruction of the filter, or of its catalytic coating, known as "catalytic washcoat" in English, when the latter is impregnated. An overload of carbon particles in the filter, due for example to a previous regeneration interrupted by the driver, can also lead to cracking of the filter during a subsequent regeneration.Willful damage by malicious individuals also occurs.

[0009] To cover the phenomena of filter degradation, the aforementioned European regulations impose two thresholds, namely, a particle mass emission threshold of 4.5 (mg / km) and a particle number emission threshold of 6e 11 (nb / km), which must not be exceeded by carbon particle emissions. In addition, the Euro7 regulation currently being developed proposes on-board monitoring in vehicles, known as "OBM" for "On-Board Monitoring" in English, of emissions on each journey of the vehicle, to cover the risk of mass emissions.

[0010] For diesel vehicles, a robust solution is known using a soot sensor to measure the quantity of carbon particles accumulated in the particulate filter, known as a "DPF" for "Diesel Particulate Filter" in English. The soot sensor is mounted in the exhaust line, generally downstream of the "DPF" filter and upstream of the silencer in all known architectures. Document FR3018544A1 describes an architecture of the type indicated above.

[0011] A soot sensor CS mounted in an exhaust pipe CE equipped with a “DPF” filter (not shown) is shown schematically in [Fig. 2]. The soot sensor CS is here a resistive type sensor. The detection principle implemented in this sensor is based on an accumulation of carbon particles PC between the branches of two comb-shaped electrodes El and E2. The electrodes El, E2, are formed on a sensitive element ES exposed to the flow of carbon particles. The accumulation of particles between the electrodes El and E2, polarized by a measurement voltage Vm, allows the conduction of a measurement current. The measurement current delivered by the sensor CS is used to quantify the emission of particles downstream of the “DPF” filter. The sensor CS is regenerated periodically to eliminate the accumulation of particles when they reach a certain level and is reset.

[0012] The soot sensor allows a robust measurement as long as the temperature to which it is subjected remains below approximately 600°C. Indeed, above 600°C, the soot accumulated on the sensitive element ES of the sensor CS burns and the accumulation of particles necessary for the conduction of the measurement current becomes impossible. In a diesel vehicle, the temperature in the exhaust gas line does not exceed 600°C, under normal operating conditions, and detection by soot sensor of the emission level of particles downstream of the “DPF” filter is therefore an operational solution.

[0013] In the state of the art, the detection by soot sensor of the level of emission of particles downstream of the particulate filter of a gasoline vehicle, called "GPF" filter for "Gasoline Particulate Filter" in English, is not used. Indeed, in the exhaust gas line of a gasoline vehicle, the temperatures under normal operating conditions very frequently exceed 600°C at the known mounting location of the soot sensor.

[0014] In a gasoline vehicle, the currently available “GPF” filter diagnostic solution allows coverage of the risk of mass over-emission of carbon particles by indirect measurement only. The measurement of the pressure drop between the inlet and the outlet of the “GPF” filter, with pressure sensors, is used to detect, via a large drop in back pressure, a significant cracking of the “GPF” filter through which a mass emission of particles is produced. This method using pressure sensors does not allow robust detection of fine cracks in the “GPF” filter, because the latter do not cause a sufficiently large drop in back pressure for a reliable measurement. As a result, a direct measurement of the quantity of particles emitted, as required for the on-board monitoring “OBM” of the “Euro7” standard, is not possible with this method.Similarly, it is not possible with this method to detect, as required by the "Euro7" standard, levels of over-emissions of . particles weaker than those currently detected by on-board monitoring known as “OBD”, for “On-Board Diagnostic” in English, of the “Euroôd” standard.

[0015] The present invention aims to provide an exhaust gas line having a new architecture for a stoichiometric combustion vehicle gasoline thermal engine, so as to provide a solution to the aforementioned drawbacks of the prior art.

[0016] According to a first aspect, the invention relates to an exhaust gas line of a stoichiometric combustion gasoline vehicle thermal engine comprising a three-way catalyst, a particulate filter and a silencer which are mounted in cascade between an inlet and an outlet of the exhaust gases of the line. According to the invention, the exhaust gas line also comprises a soot sensor which is mounted downstream of the silencer.

[0017] According to a particular feature, the exhaust gas line also comprises another three-way catalyst which is mounted between the particulate filter and the silencer.

[0018] According to another particular characteristic, the exhaust gas line also comprises an ammonia leak catalyst which is mounted between the particulate filter and the silencer.

[0019] According to yet another particular characteristic, the exhaust gas line also comprises another three-way catalyst followed by an ammonia leak catalyst which are mounted between the particulate filter and the silencer.

[0020] According to yet another particular characteristic, the particulate filter is a catalyzed particulate filter.

[0021] According to yet another particular characteristic, the soot sensor is a resistive type soot sensor.

[0022] The invention also relates to an assembly of a gasoline-type thermal engine with stoichiometric combustion and an exhaust gas line as briefly described above. According to a particular characteristic of this assembly, the thermal engine is of the turbocharged type.

[0023] The invention also relates to a motor vehicle comprising an assembly as indicated above.

[0024] Other advantages and characteristics of the present invention will appear more clearly on reading the detailed description below of several particular embodiments of the invention, with reference to the appended drawings, in which:

[0025] [Fig-1] shows statistical distribution curves, in number and in mass, of a population of carbon particles emitted by an internal combustion engine.

[0026] [Fig.2] is a sectional view schematically showing the mounting of a resistive type soot sensor in an exhaust pipe of a thermal engine of the type Diesel.

[0027] [Fig.3] is a simplified diagram of a first architecture of a gas line exhaust according to the invention for a gasoline thermal engine of a vehicle with stoichiometric combustion.

[0028] [Fig.4] is a simplified diagram of a second architecture of a gas line exhaust according to the invention for a gasoline thermal engine of a vehicle with stoichiometric combustion.

[0029] [Fig.5] is a simplified diagram of a third architecture of a gas line exhaust according to the invention for a gasoline thermal engine of a vehicle with stoichiometric combustion.

[0030] [Fig.6] is a simplified diagram of a fourth architecture of a gas line exhaust according to the invention for a gasoline thermal engine of a vehicle with stoichiometric combustion.

[0031] [Fig.7] is a simplified diagram of a fifth architecture of a gas line exhaust according to the invention for a gasoline thermal engine of a vehicle with stoichiometric combustion.

[0032] [Fig.8] is a simplified diagram of a sixth architecture of a gas line exhaust according to the invention for a gasoline thermal engine of a vehicle with stoichiometric combustion.

[0033] [Fig.9] is a simplified diagram of a seventh architecture of a gas line exhaust according to the invention for a gasoline thermal engine of a vehicle with stoichiometric combustion.

[0034] [Fig. 10] is a simplified diagram of an eighth architecture of an exhaust gas line according to the invention for a stoichiometric combustion vehicle gasoline thermal engine.

[0035] Generally speaking, the invention is based on the integration of a soot sensor in an exhaust gas line of a gasoline thermal engine of a vehicle with stoichiometric combustion, so as to obtain a direct measurement of carbon particle emissions. A soot sensor of the type used in the exhaust gas lines of diesel thermal engines can be integrated into an exhaust gas line according to the invention. Unlike an exhaust gas line of a diesel thermal engine in which the soot sensor is mounted upstream of the silencer, generally downstream of the particulate filter "DPF", in the present invention, the soot sensor is mounted downstream of the silencer. The mounting of the soot sensor at the location recommended by the invention results from the observation by the inventive entity of the fact that the temperature of the gases in an exhaust line of a gasoline thermal engine drops below 600°C downstream of the silencer.The silencer has a large exchange surface with the ambient air, so that the exhaust gases . the through undergo a significant drop in temperature. The temperature of the exhaust gases at the outlet of the muffler is compatible with normal operation of the soot sensor.

[0036] The invention can easily be implemented in different architectures of an exhaust gas line of a gasoline thermal engine of a stoichiometric combustion vehicle.

[0037] In the architecture shown schematically in [Fig. 3], the exhaust gas line LGE1 equips a gasoline thermal engine MT equipped with a turbocharger TC for air supercharging. The exhaust gas line LGE1 comprises in particular a three-way catalyst TWC, a gasoline particulate filter “GPF”, marked GPF, an ESIL silencer, a soot sensor CS and other known sensors and components not shown, such as the NOx sensor and the oxygen sensor (lambda probe). The three-way catalyst TWC and the particulate filter GPF are mounted in cascade, with the catalyst TWC as close as possible to the exhaust gas outlet of the turbocharger TC, and are part of an exhaust line subassembly called “under-turbocharger assembly” EsT. The ESIL silencer and a soot sensor CS are part of another exhaust line subassembly called “under-body assembly” EsC. As can be seen in [Fig.3], in accordance with the invention, the soot sensor CS is mounted downstream of the ESIL silencer, here in a portion of exhaust pipe CE between the outlet of the ESIL silencer and an exhaust outlet cannula CN.

[0038] In the architecture shown schematically in [Fig. 4], the exhaust gas line LGE2 differs essentially from the line LGE1 of [Fig. 3] by the fact that it comprises, in the assembly under turbocharger EsT, a catalyzed gasoline particulate filter, marked GPFc, in place of the particulate filter GPF. As visible in [Fig. 4], in accordance with the invention, the soot sensor CS is mounted downstream of the silencer ESIL, as described above with reference to [Fig. 3].

[0039] In the architecture shown schematically in [Fig. 5], the exhaust gas line LGE3 differs essentially from the line LGE1 of [Fig. 3] by the fact that it comprises, in the underbody assembly EsC, another three-way catalyst TWC2 mounted upstream of the silencer ESIL. As visible in [Fig. 5], in accordance with the invention, the soot sensor CS is mounted downstream of the silencer ESIL, as described above with reference to [Fig. 3].

[0040] In the architecture shown schematically in [Fig. 6], the exhaust gas line LGE4 differs essentially from the line LGE3 of [Fig. 5] by the fact that it comprises, in the assembly under turbocharger EsT, a catalyzed gasoline particulate filter, marked GPFc, in place of the particulate filter GPF. As visible in [Fig. 6], in accordance with the invention, the soot sensor CS is mounted in downstream of the ESIL silencer, as described above with reference to [Fig.3].

[0041] In the architecture shown schematically in [Fig. 7], the exhaust gas line LGE5 differs essentially from the line LGE1 of [Fig. 3] by the fact that it comprises, in the underbody assembly EsC, an ammonia leak catalyst, marked ASC, which is mounted upstream of the silencer ESIL. As visible in [Fig. 7], in accordance with the invention, the soot sensor CS is mounted downstream of the silencer ESIL, as described above with reference to [Fig. 3].

[0042] In the architecture shown schematically in [Fig. 8], the LGE6 exhaust gas line differs essentially from the LGE5 line of [Fig. 7] by the fact that it comprises, in the assembly under the EsT turbocharger, a catalyzed gasoline particulate filter, marked GPFc, in place of the GPF particulate filter. As visible in [Fig. 8], in accordance with the invention, the CS soot sensor is mounted downstream of the ESIL silencer, as described above with reference to [Fig. 3].

[0043] In the architecture shown schematically in [Fig. 9], the exhaust gas line LGE7 differs essentially from the line LGE1 of [Fig. 3] by the fact that it comprises, in the underbody assembly EsC, another three-way catalyst TWC2 followed by an ammonia leak catalyst ASC which are mounted upstream of the silencer ESIL. As visible in [Fig. 9], in accordance with the invention, the soot sensor CS is mounted downstream of the silencer ESIL, as described above with reference to [Fig. 3].

[0044] In the architecture shown schematically in [Fig. 10], the exhaust gas line LGE8 differs essentially from the line LGE7 of [Fig. 9] by the fact that it comprises, in the assembly under turbocharger EsT, a catalyzed gasoline particulate filter, marked GPFc, in place of the particulate filter GPF. As visible in [Fig. 10], in accordance with the invention, the soot sensor CS is mounted downstream of the silencer ESIL, as described above with reference to [Fig. 3].

[0045] In the embodiments LGE1 to LGE8 described above, it is considered that the soot sensor is mounted in a portion of exhaust pipe downstream of the silencer. It will be noted that in other embodiments the soot sensor may be integrated into the silencer, at the gas outlet thereof. In addition, the soot sensor usable in the invention is not limited to the resistive type soot sensor. Other types of soot sensors may be integrated into an exhaust gas line according to the invention.

[0046] The invention is not limited to the particular embodiments which have been described here by way of example. Those skilled in the art, depending on the applications of the invention, will be able to make various modifications and variants falling within the scope of protection of the invention.

Claims

Claims

1. Exhaust gas line of a stoichiometric combustion (MT) gasoline vehicle thermal engine comprising a three-way catalyst (TWC), a particulate filter (GPF) and a silencer (ESIL) which are mounted in cascade between an inlet and an outlet of the exhaust gases of said line, characterized in that it also comprises a soot sensor (CS) which is mounted downstream of said silencer (ESIL).

2. Exhaust gas line according to claim 1, characterized in that it also comprises another three-way catalyst (TWC2) which is mounted between said particulate filter (GPF) and said silencer (ESIL).

3. Exhaust gas line according to claim 1, characterized in that it also comprises an ammonia leak catalyst (ASC) which is mounted between said particulate filter (GPF) and said silencer (ESIL).

4. Exhaust gas line according to claim 1, characterized in that it also comprises another three-way catalyst (TWC2) followed by an ammonia leak catalyst (ASC) which are mounted between said particulate filter (GPF) and said silencer (ESIL).

5. Exhaust gas line according to any one of claims 1 to 4, characterized in that said particulate filter is a catalyzed particulate filter (GPFc).

6. Exhaust gas line according to any one of claims 1 to 5, characterized in that said soot sensor (CS) is a resistive type soot sensor.

7. Assembly of a stoichiometric combustion gasoline type thermal engine (MT) and an exhaust gas line, characterized in that said exhaust gas line is an exhaust gas line (LDE1 to LDE8) according to any one of claims 1 to 6.

8. Assembly according to claim 7, characterized in that said thermal engine is of the turbocharged type.

9. Motor vehicle characterized in that it comprises an assembly according to claim 7 or 8.

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