MOTOR VEHICLE COMPRISING AN AMMONIA LEAKAGE CATALYST CONTROL MEANS EVALUATING ITS LOAD, METHOD AND PROGRAM BASED ON SUCH A VEHICLE

Abstract

The invention relates to a motor vehicle comprising an exhaust line which comprises an ammonia leak catalyst, as well as:- temperature, O2, NOx, and total nitrogen sensors;- purging and enriching means for carrying out an ammonia purge phase (PP) out of the ammonia leak catalyst, and an ammonia enrichment phase (PE) in said catalyst;- a means for estimating the storage of ammonia in the ammonia leak catalyst, from the data of the total nitrogen sensor and the NOx sensor. The invention also relates to a method and a program based on such a vehicle. Figure 1

Description

Title of the invention: MOTOR VEHICLE COMPRISING A MEANS FOR CONTROLLING A LEAKAGE CATALYST AMMONIA VEHICLE EVALUATING ITS CHARGE, METHOD AND PROGRAM BASED ON SUCH A VEHICLE

[0001] The invention relates to the field of post-treatment control systems in a gasoline-powered motor vehicle, and more particularly the management of the ammonia slip catalyst.

[0002] The ammonia leak catalyst aims to store ammonia and convert it in the presence of oxygen. To do this, the ammonia leak catalyst must be in a specific temperature window (around 250°C - 450°C). Above 450°C, the ammonia stored in said catalyst could be desorbed without being oxidized.

[0003] It may be required to have a strategy to detect that the storage capacity of the ammonia leak catalyst is damaged for an indication in maintenance to replace the part or for diagnostics for example.

[0004] An objective of the present invention is to remedy the defects of the prior art, and in particular to propose a solution for accurately evaluating the charge of the ammonia leak catalyst, to determine whether it is still capable of storing ammonia.

[0005] To achieve this objective, the invention proposes a motor vehicle comprising an exhaust line which comprises an ammonia leak catalyst, as well as: - a temperature sensor; - at least one O2 sensor; - at least one NOx sensor; - at least one total nitrogen sensor; - a purging means for carrying out at least one cycle of an ammonia purging phase from the ammonia leak catalyst; - an enrichment means for carrying out at least one cycle of an ammonia enrichment phase in the ammonia leak catalyst after the purge phase; the end of the purge phase being determined by a peak of nitrogen oxide; the end of the enrichment phase being determined by an ammonia peak; and - a means of estimating the storage of ammonia in the ammonia leak catalyst, from the data of the total nitrogen sensor and the NOx sensor.

[0006] Advantageously, the invention provides a control strategy aimed at evaluating the quantity of ammonia stored in the ammonia leak catalyst, as well as the state of health of the ammonia leak catalyst.

[0007] Thus, the invention makes it possible to have an evaluation of the catalyst load and to optimize the continuous conversion of ammonia, thus avoiding ammonia leakage and ammonia desorption linked to high temperatures.

[0008] Preferably, the means for estimating the ammonia storage determines the ammonia storage by an integral of the ammonia mass flow rate.

[0009] This makes it possible to obtain an accurate value of the amount of ammonia stored in the ammonia leak catalyst.

[0010] Preferably, the motor vehicle further comprises a means for evaluating the state of health of the ammonia leak catalyst.

[0011] This makes it possible to determine when it is necessary to change this catalyst or to compare catalysts at different stages of use.

[0012] Preferably, the health status of the ammonia leak catalyst is determined using a Boolean value from ammonia storage data.

[0013] This makes it possible to obtain an accurate value of the health status of the ammonia leak catalyst.

[0014] Preferably, the motor vehicle comprises: - a coolant; - a transmission gear; - an engine; and / or - a brake pedal, and it further comprises at least one cycle interruption means among: - a catalyst temperature above a first threshold; - a coolant temperature below a second threshold; - an engagement of the transmission gear; - engine shutdown; - a push of the brake pedal.

[0015] This allows the cycles to be carried out under optimal conditions, particularly temperature.

[0016] The invention further relates to a method for controlling an ammonia leak catalyst of a motor vehicle according to the invention, characterized in that it comprises the following steps: - a purge step for carrying out at least one cycle of an ammonia purge phase; - an enrichment step to carry out at least one cycle of an ammonia enrichment phase after the purge phase; the end of the purge phase being determined by a peak of nitrogen oxide; the end of the enrichment phase being determined by an ammonia peak; and - a step of estimating the ammonia storage from the sensor data total nitrogen and NOx sensor.

[0017] Preferably, in the step of estimating the ammonia storage, the ammonia storage is determined by an integral of the ammonia mass flow rate.

[0018] Preferably, the control method further comprises a step of evaluating the state of health of the ammonia leak catalyst.

[0019] Preferably, the control method further comprises at least one cycle interruption step if one of the following conditions is encountered: - a catalyst temperature above a first threshold; - a coolant temperature below a second threshold; - an engagement of the transmission gear; - engine shutdown; - a push of the brake pedal.

[0020] Another object of the invention 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.

[0021] 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 the different phases and cycles in the context of the control of the ammonia leak catalyst of a vehicle according to the invention; and - [Fig.2] schematically illustrates an exhaust line suitable for implementing the invention.

[0022] The ASC ammonia leak catalyst is a passive element of the exhaust line, placed at the end of the exhaust line, after the catalysts, before the exhaust silencer.

[0023] The strategy for detecting a damaged ASC ammonia leak catalyst storage capacity is based on an intrusive RI richness scheme of successive lean and rich phases to empty and refill the ASC ammonia leak catalyst. The procedure is monitored by observing the linear O2 sensor upstream of a CCC close-coupled catalyst, the binary O2 sensor downstream of the GFP gasoline particulate filter, the binary O2 sensor downstream of the floor catalyst if present (not mandatory), and the NOx sensor downstream of the ASC ammonia leak catalyst.

[0024] RI represents the richness at the level of the closely coupled catalyst CCC. R2 represents the richness at the level of the NOx sensor

[0025] This procedure will be described later, and could preferably be carried out as part of a workshop maintenance procedure because it only lasts a few minutes and: - requires a stable operating point of the internal combustion engine; - may be interrupted under normal driving conditions, requiring the procedure to be restarted; - has an impact on emissions.

[0026] First, the procedure starts with a stabilized engine operating point to increase the overall exhaust line temperature. This phase lasts until the activation conditions are reached (exhaust line temperature, minimum exhaust mass flow target, sensors ready).

[0027] When the ammonia leak catalyst temperature estimate exceeds a minimum threshold (around 350°C), the intrusive richness pattern starts with a lean mixture request (lambda about 1.08). We can talk about a PP purge phase cycle. This has the effect of converting the ammonia already stored in the catalyst by oxidation (with FA ammonium leak). The oxidation process can be confirmed in parallel when the voltage value of the O2 sensor downstream of the floor catalyst decreases (around 250mV, i.e. oxygen is present at the catalyst inlet). The lean phase is maintained until we observe a quantity of NOx at the NOx sensor downstream of the ASC catalyst, which means that there is no more ammonia to convert in the catalyst.

[0028] The estimated temperature in the catalyst must always be above a threshold (around 350°C) to ensure that the ammonia will be correctly stored in the ASC catalyst during the next phase; if this is not the case, it is possible to request a lambda 1 phase with a modified combustion advance to slightly increase the temperature of the ASC catalyst without adding ammonia.

[0029] Then, the first rich phase is requested (lambda approximately 0.95). We can speak of a PE enrichment phase cycle. This has the effect of causing the production of ammonia by the tightly coupled catalyst and its storage SA by the ASC catalyst. The ammonia storage value of the ASC catalyst is calculated during this phase as the integral of the ammonia mass flow rate at the catalyst inlet, starting when the voltage of the O2 sensor downstream of the tightly coupled catalyst exceeds a high threshold (approximately 750mV), and ending when: - the richness measured by the NOx sensor downstream of the ASC catalyst actually becomes rich and, - a maximum amount of ammonia is detected by the NOx sensor downstream of the ASC catalyst, meaning that the catalyst can no longer store ammonia. It has reached its maximum storage capacity.

[0030] The estimated temperature in the ASC catalyst must always be between thresholds (around 300°C to 450°C) to ensure that the ammonia will be oxidized in the next phase and no thermal desorption can occur; if this is not the case, It is possible to request a lambda 1 phase with a modified combustion advance to slightly increase the catalyst temperature or without storage capacity modification to lower the ASC catalyst temperature.

[0031] Then, the second lean phase is requested (lambda approximately 1.08). As with the first, this has the effect of converting the ammonia stored in the catalyst by oxidation (FA). The goal is to empty the ASC catalyst so that it is in good condition to store ammonia in the next driving cycles. This phase ends when: - the richness measured by the NOx sensor downstream of the ASC catalyst actually becomes lean, meaning that oxygen is present downstream of the catalyst, and - a maximum amount of NOx is detected by the NOx sensor downstream of the ASC catalyst, meaning that the catalyst is almost empty of ammonia.

[0032] Then the procedure ends, the intrusive richness request is released. Regulation to lambda one can be carried out before switching off the internal combustion engine.

[0033] The maximum storage capacity value of the catalyst is stored in the so-called NVRAM memory and can be read in the maintenance tool. The value is compared to a threshold, and a boolean is produced to indicate whether the catalyst is in good condition or not and must be replaced.

[0034] Several interruption conditions are monitored throughout the procedure, with the effect of interrupting it as soon as at least one condition is met: - commitment of transmission speed; - computer temperature too high (around 600°C); - coolant temperature too high (around 110°C); - switching off the internal combustion engine; - pressing the brake pedal; - pressing the clutch pedal; - pressing the accelerator pedal.

[0035] This strategy can be realized with a measurement of the catalyst temperature instead of a temperature estimation. It can also be realized by using the catalyst storage output value of a physical catalyst model instead of the ammonia mass flow rate at the catalyst inlet. (This solution is included in the model and can be chosen with a calibratable value).

[0036] The invention further relates to a program for implementing a method as described above. The program can be loaded into the memory of a controller of the motor vehicle, for example in an exhaust line controller.

Claims

Claims

1. A motor vehicle comprising an exhaust line which comprises an ammonia leak catalyst (ASC), as well as: - a temperature sensor; - at least one O2 sensor; - at least one NOx sensor; - at least one total nitrogen sensor; - a purging means for carrying out at least one cycle of an ammonia purge phase (PP) out of the ammonia leak catalyst (ASC); - an enrichment means for carrying out at least one cycle of an ammonia enrichment phase (PE) in the ammonia leak catalyst (ASC) after the purging phase (PP); the end of the purging phase being determined by a nitrogen oxide peak; the end of the enrichment phase being determined by an ammonia peak; and - a means of estimating ammonia storage in the ammonia leak catalyst (ASC), from data from the total nitrogen sensor and the NOx sensor.

2. Motor vehicle according to claim 1, characterized in that the means for estimating the ammonia storage determines the ammonia storage by an integral of the ammonia mass flow rate.

3. Motor vehicle according to any one of claims 1 to 2, characterized in that it further comprises means for evaluating the state of health of the ammonia leak catalyst (ASC).

4. A motor vehicle according to any one of claims 2 to 3, characterized in that the health status of the ammonia leak catalyst (ASC) is determined by means of a Boolean value from ammonia storage data.

5. Motor vehicle according to any one of claims 1 to 4, comprising: - a coolant; - a transmission gear; - an engine; and / or - a brake pedal, characterized in that it further comprises at least one cycle interruption means among: - a catalyst temperature above a first threshold; - a coolant temperature below a second threshold; - an engagement of the transmission gear; - an engine shutdown; - a push of the brake pedal.

6. Method for controlling an ammonia leak catalyst (ASC) of a motor vehicle according to any one of claims 1 to 5, characterized in that it comprises the following steps: - a purging step for carrying out at least one cycle of an ammonia purging phase (PP); - an enrichment step for carrying out at least one cycle of an ammonia enrichment phase (PE) after the purging phase (PP); the end of the purging phase being determined by a nitrogen oxide peak; the end of the enrichment phase being determined by an ammonia peak; and - a step of estimating the ammonia storage from the data of the total nitrogen sensor and the NOx sensor.

7. Control method according to claim 6, characterized in that in the step of estimating the ammonia storage, the ammonia storage is determined by an integral of the ammonia mass flow rate.

8. Control method according to any one of claims 6 to 7, characterized in that it further comprises a step of evaluating the state of health of the ammonia leak catalyst (ASC).

9. Control method according to any one of claims 6 to 8, characterized in that it further comprises at least one cycle interruption step if one of the following conditions is encountered: - a catalyst temperature above a first threshold; - a coolant temperature below a second threshold; - an engagement of the transmission gear; - a shutdown of the engine; - a push of the brake pedal.

10. 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.

Images