MOTOR VEHICLE COMPRISING AN EXHAUST CONTROL SYSTEM FOR DETERMINING NITROGEN OXIDE EMISSIONS, METHOD AND PROGRAM BASED ON SUCH A VEHICLE

Abstract

The invention relates to a motor vehicle comprising: - an exhaust system defining an upstream / downstream direction, the system including a catalyst receiving ammonia to reduce exhaust gases; and - an exhaust control system, the exhaust control system comprising: - means for determining ammonia flow rate (M1) determining a total ammonia flow rate (dT) downstream of the catalyst, - a correction means (M2) applying a sensitivity factor to the total ammonia flow rate to obtain a corrected ammonia flow rate (dTc); - means for determining nitrogen gas flow rate (M3) determining a nitrogen gas flow rate; - a means for determining nitrogen oxide flow rate (M4) subtracting the corrected ammonia flow rate from the nitrogen gas flow rate, and thus determining the nitrogen oxide flow rate. The invention further relates to a method and a program based on such a vehicle. Figure 2

Description

Title of the invention: MOTOR VEHICLE COMPRISING AN EXHAUST CONTROL SYSTEM DETERMINING NITROGEN OXIDE EMISSIONS, METHOD AND PROGRAM BASED ON SUCH A SYSTEM VEHICLE

[0001] The invention relates to the field of motor vehicle exhaust systems, and more particularly, selective catalytic reduction systems. The invention relates more particularly to an exhaust control system and method based on such a selective catalytic reduction system.

[0002] The applicant has proposed in patent EP3511540B1, an on-board system for determine the ammonia (NH3) desorbed downstream of an SCR catalyst (for "selective catalytic reduction") without using an additional sensor. This estimation is used to improve the control of urea injection and for on-board diagnostics of nitrogen oxides. The subject of the aforementioned patent is applied in the control of diesel vehicles according to the European standard relating to emissions called "Euroôd".

[0003] The new European standard relating to emissions called "Euro7" currently being created, plans to impose, in addition to the diagnosis of nitrogen oxides (Nox), the measurement on each journey of the value of nitrogen oxides emitted, continuously.

[0004] Unfortunately, currently available nitrogen oxide sensors measure both nitrogen oxides and ammonia in the exhaust gases without being able to separate their values. This is called the cross-sensitivity of the nitrogen oxide sensor. This measurement is therefore not directly usable to meet the requirements of the new European standard, which will probably require only a nitrogen oxide value, therefore without the potential ammonia.

[0005] An objective of the present invention is to remedy the defects of the prior art, and in particular to propose a solution for determining a quantity of nitrogen oxides at the exhaust outlet in a precise manner.

[0006] To achieve this objective, the invention proposes a motor vehicle comprising: - an exhaust apparatus defining an upstream downstream direction, the apparatus comprising a catalyst receiving ammonia to reduce exhaust gases; and - an exhaust control system, the exhaust control system comprising: - means for determining the ammonia flow rate determining a total ammonia flow rate downstream of the catalyst, - a correction means applying a sensitivity factor to the total ammonia flow rate, to obtain a corrected ammonia flow rate; - nitrogen gas flow rate determination means determining a nitrogen gas flow rate; - a means for determining the flow rate of nitrogen oxides subtracting the corrected ammonia flow rate from the flow rate of nitrogen gas, and thus determining the flow rate of nitrogen oxides.

[0007] Advantageously, the invention makes it possible to easily determine the flow rates of nitrogen oxides in an on-board manner with precision from ammonia and nitrogen gas flow rate data.

[0008] According to a variant, the motor vehicle further comprises a nitrogen gas sensor downstream of the catalyst, and the nitrogen gas flow rate determining means receive the measurements from the nitrogen gas sensor and an exhaust flow rate value, and determine the nitrogen gas flow rate by means of the measurements from the nitrogen gas sensor and the exhaust flow rate.

[0009] This makes it easy to determine nitrogen gas flow rates accurately.

[0010] According to a variant, the exhaust control system further comprises means for determining nitrogen oxide emissions per distance receiving vehicle speed information to determine mass nitrogen oxide emissions per distance traveled.

[0011] This allows the user to be informed of the quantity of nitrogen oxides emitted per distance traveled, for example in milligrams per kilometer.

[0012] According to a variant, the means for determining the ammonia flow rate comprise: - a modeling means modeling a total ammonia flow rate downstream of the catalyst from at least one parameter representative of the operation of the exhaust apparatus, - a means for determining the desorption flow rate determining an ammonia desorption flow rate downstream of the catalyst from the mass of ammonia stored in the catalyst and the maximum storage capacity of the catalyst, - a saturation flow rate determination means determining an ammonia saturation flow rate downstream of the catalyst from the ammonia flow rate passing through the catalyst, - the total ammonia flow downstream of the catalyst being modeled by adding the desorption flow rate and the saturation flow rate.

[0013] This makes it possible to determine the ammonia flow rate from a model without the need for an ammonia sensor which is complex to manufacture and not widely available.

[0014] Another object of the invention relates to an exhaust control system for a motor vehicle according to the invention, characterized in that it comprises: - means for determining the ammonia flow rate determining the total ammonia flow rate downstream of the catalyst, - a correction means applying a sensitivity factor to the total ammonia flow rate, to obtain a corrected ammonia flow rate; - nitrogen gas flow rate determination means determining a nitrogen gas flow rate; - a means for determining the flow rate of nitrogen oxides by subtracting the corrected ammonia flow rate from the flow rate of nitrogen gas, and thus determining the flow rate of nitrogen oxides.

[0015] The invention also relates to an exhaust control method for a motor vehicle according to the invention, characterized in that it comprises: - ammonia flow rate determination steps determining the total ammonia flow rate downstream of the catalyst, - a correction step applying a sensitivity factor to the total ammonia flow rate, to obtain a corrected ammonia flow rate; - steps of determining nitrogen gas flow rate determining a nitrogen gas flow rate; - a step of determining the flow rate of nitrogen oxides subtracting the corrected ammonia flow rate from the flow rate of nitrogen gas, and thus determining the flow rate of nitrogen oxides.

[0016] According to a variant, the method is implemented with a motor vehicle further comprising a nitrogen gas sensor downstream of the catalyst, and the steps of determining the nitrogen gas flow rate are based on the measurements of the nitrogen gas sensor and an exhaust flow rate value, and determine the nitrogen gas flow rate by means of the measurements of the nitrogen gas sensor and the exhaust flow rate.

[0017] According to a variant, the steps for determining the ammonia flow rate comprise: - a modeling step modeling a total ammonia flow rate downstream of the catalyst from at least one parameter representative of the operation of the exhaust apparatus, - a desorption flow rate determination step determining an ammonia desorption flow rate downstream of the catalyst from the mass of ammonia stored in the catalyst and the maximum storage capacity of the catalyst, - a saturation flow rate determination step determining an ammonia saturation flow rate downstream of the catalyst from the ammonia flow rate passing through the catalyst, - the total ammonia flow downstream of the catalyst being modeled by adding the desorption flow rate and the saturation flow rate.

[0018] According to a variant, the control method further comprises a step of determining nitrogen oxide emissions by distance in which information is received. vehicle speed training to determine mass nitrogen oxide emissions per distance traveled.

[0019] The invention further relates to a computer program comprising program code instructions for executing the steps of the control method according to the invention, when said program operates on a computer.

[0020] The invention will be further detailed by the description of non-limiting embodiments, and on the basis of the appended figures illustrating variants of the invention, in which: - [Fig.l] schematically illustrates a control system according to the prior art comprising means for determining a total ammonia flow rate by modeling; and - [Fig.2] schematically illustrates a control system according to an embodiment of the invention comprising means for determining a flow rate of nitrogen oxides.

[0021] The invention relates to a motor vehicle comprising an exhaust apparatus and an exhaust control system.

[0022] The exhaust apparatus defines an upstream downstream direction from the engine to an exhaust outlet.

[0023] The apparatus comprises a catalyst receiving ammonia to reduce exhaust gases.

[0024] The exhaust control system comprises ammonia flow rate determination means M1 determining the total ammonia flow rate dT downstream of the catalyst. In particular, these are means detailed in the applicant's patent EP3511540B1.

[0025] These means are illustrated in [Fig.l]. They include in particular: - a temperature sensor measuring a Tcat temperature inside the catalyst; - an hourly volumetric velocity sensor measuring an hourly volumetric velocity vvh of the exhaust gases flowing in the exhaust apparatus; - a calculator determining a total flow rate dT of ammonia downstream of the catalyst. Such a calculator can in particular be the engine control calculator, also known as ECU for Engine Control Unit in English.

[0026] The calculator determines and uses the following parameters: - the mass m of ammonia stored in the catalyst, for example from the temperature Tcat measured in the catalyst and the proportion of nitrogen oxides in the exhaust gases; - the desorption rate dD, for example by determining the maximum ammonia storage capacity Cmax of the catalyst, which can itself be determined from the temperature Tcat measured in the catalyst and the hourly volume velocity vvh of the exhaust gases; - a desorption factor Fd modeling the transient effect when the stored mass m reaches the maximum storage capacity Cmax. This makes it possible to model the delay in the desorption of excess ammonia in the catalyst. The calculator can determine the desorption factor Fd from the temperature Tcat measured in the catalyst and the hourly volume velocity vvh of the exhaust gases; - the saturation flow rate dS of ammonia downstream of the catalyst S, for example from the through flow rate dR. For this purpose, the quantity of ammonia leaving the catalyst is measured over a period of time T, also called the integration period. This measured quantity is separated into two parts based on a predetermined factor called a "ratio"; - the saturation capacity Csat of the catalyst, for example from the temperature Tcat measured in the catalyst and the hourly volumetric velocity vvh of the exhaust gases. Preferably, this determination is carried out from maps which may also include an aging factor.

[0027] Furthermore, the computer compares the stored mass m of ammonia in the catalyst to the saturation capacity Csat and thus determines whether the catalyst is saturated. When the stored mass m is greater than or equal to the saturation capacity Csat, the computer is configured to determine the throughflow dR of ammonia in the catalyst from the incoming flow dE of ammonia upstream of the catalyst. The throughflow dR thus corresponds to the flow of ammonia passing through the catalyst.

[0028] The determination of ammonia flow rate can be done as described in the patent and in [Fig.l], or according to another method. The information obtained is used in the invention.

[0029] The invention proposes to obtain the nitrogen oxide information based on the ammonia information, corrected to take into account the cross-sensitivity, and subtracted from a measurement of the SNOX nitrogen oxide sensor to obtain the nitrogen oxide measurements. To this end, the system of the invention comprises a correction means M2 applying a sensitivity factor to the total ammonia flow rate, to obtain a corrected ammonia flow rate dTc.

[0030] According to the invention, the on-board control is improved by adding an additional step to the existing control logic which comprises two additional blocks - apply to the ammonia estimation the cross-sensitivity factor based on a sensitivity table of the nitrogen oxide sensor SNOx to measure ammonia, for example in a non-linear manner; - then subtract the information from the SNOx nitrogen oxide sensor downstream of the system, the estimate of ammonia NH3 corrected in order to obtain a measurement of “isolated” nitrogen oxides at the end of the cannula.

[0031] For this purpose, the system of the invention comprises nitrogen gas flow rate determination means M3 determining a nitrogen gas flow rate. In particular, this is an evaluation based on measurements from the SNOX nitrogen gas sensor of the exhaust flow rate E.

[0032] We can then deduce the continuous measurement information of “isolated” nitrogen oxides required by the new European standard on emissions, using a specific M4 method.

[0033] The emissions can be determined in quantity per distance traveled by means of a specific means M5 using vehicle speed information V. This is in particular a mass per distance traveled, for example in milligrams per kilometer.

[0034] The invention also relates to a method and a control program, for example implemented in an on-board computer or one or more calculators, such as the engine control calculator, also known as ECU for Engine Control Unit in English.

Claims

Claims

1. A motor vehicle comprising: - an exhaust apparatus defining an upstream-downstream direction, the apparatus comprising a catalyst receiving ammonia to reduce exhaust gases; and - an exhaust control system, the exhaust control system comprising: - ammonia flow rate determining means (M1) determining a total ammonia flow rate (dT) downstream of the catalyst, - a correction means (M2) applying a sensitivity factor to the total ammonia flow rate, to obtain a corrected ammonia flow rate (dTc); - nitrogen gas flow rate determining means (M3) determining a nitrogen gas flow rate; - nitrogen oxide flow rate determining means (M4) subtracting the corrected ammonia flow rate from the nitrogen gas flow rate, and thus determining the nitrogen oxide flow rate.

2. Motor vehicle according to claim 1, further comprising a nitrogen gas sensor (SNOX) downstream of the catalyst, characterized in that the nitrogen gas flow rate determining means (M3) receive the measurements from the nitrogen gas sensor (SNOX) and an exhaust flow rate value, and determine the nitrogen gas flow rate by means of the measurements from the nitrogen gas sensor and the exhaust flow rate (E).

3. Motor vehicle according to any one of claims 1 to 2, characterized in that the exhaust control system further comprises means for determining nitrogen oxide emissions (M5) per distance receiving vehicle speed information (V) for determining mass nitrogen oxide emissions per distance traveled.

4. Motor vehicle according to any one of claims 1 to 3, characterized in that the means for determining the ammonia flow rate (Ml) comprise: - a modeling means modeling a total flow rate (dT) of ammonia downstream of the catalyst from at least one parameter (Tcat, vvh) representative of the operation of the exhaust equipment, - a means for determining the desorption flow rate determining a desorption rate (dD) of ammonia downstream of the catalyst from the mass (m) of ammonia stored in the catalyst and the maximum storage capacity (Cmax) of the catalyst, - a means of determining the saturation rate determining a saturation rate (dS) of ammonia downstream of the catalyst from the flow rate (dR) of ammonia passing through the catalyst, - the total flow rate (dT) of ammonia downstream of the catalyst being modeled by adding the desorption rate (dD) and the saturation rate (dR).

5. Exhaust control system for a motor vehicle according to any one of claims 1 to 4, characterized in that it comprises: - ammonia flow rate determining means (M1) determining the total ammonia flow rate (dT) downstream of the catalyst, - correction means (M2) applying a sensitivity factor to the total ammonia flow rate, to obtain a corrected ammonia flow rate (dTc); - nitrogen gas flow rate determining means (M3) determining a nitrogen gas flow rate; - nitrogen oxide flow rate determining means (M4) subtracting the corrected ammonia flow rate from the nitrogen gas flow rate, and thus determining the nitrogen oxide flow rate.

6. Exhaust control method for a motor vehicle according to any one of claims 1 to 4, characterized in that it comprises: - ammonia flow rate determination steps determining the total ammonia flow rate downstream of the catalyst, - a correction step applying a sensitivity factor to the total ammonia flow rate, to obtain a corrected ammonia flow rate; - nitrogen gas flow rate determination steps determining a nitrogen gas flow rate; - a nitrogen oxide flow rate determination step subtracting the corrected ammonia flow rate from the nitrogen gas flow rate, and thus determining the nitrogen oxide flow rate.

7. A control method according to claim 6, with a motor vehicle further comprising a nitrogen gas sensor downstream of the catalyst, characterized in that the steps of determining the nitrogen gas flow rate are based on the measurements of the nitrogen gas sensor and a value of

8.

9.

10. exhaust flow, and determine the nitrogen gas flow using the nitrogen gas sensor measurements and the exhaust flow. Control method according to any one of claims 6 to 7, characterized in that the steps of determining the ammonia flow rate comprise: - a modeling step modeling a total flow rate (dT) of ammonia downstream of the catalyst from at least one parameter (Tcat, vvh) representative of the operation of the exhaust equipment, - a desorption flow rate determination step determining a desorption flow rate (dD) of ammonia downstream of the catalyst from the mass (m) of ammonia stored in the catalyst and the maximum storage capacity (Cmax) of the catalyst, - a saturation flow rate determination step determining a saturation flow rate (dS) of ammonia downstream of the catalyst from the flow rate (dR) of ammonia passing through the catalyst, - the total flow rate (dT) of ammonia downstream of the catalyst being modeled by adding the desorption flow rate (dD) and the saturation flow rate (dS). Control method according to any one of claims 6 to 8, characterized in that it further comprises a step of determining nitrogen oxide emissions (M5) per distance in which vehicle speed information is received to determine nitrogen oxide emissions in mass per distance traveled. A computer program comprising program code instructions for carrying out the steps of the control method according to any one of claims 6 to 9, when said program is running on a computer.

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