MOTOR VEHICLE INCLUDING A MEANS FOR CONTROLLING AN AMMONIA LEAK CATALYST, EVALUATING ITS CHARGE, METHOD AND PROGRAM BASED ON SUCH A VEHICLE
A vehicle system with sensors and control strategies addresses the challenge of evaluating ammonia slip catalyst charge and health, ensuring efficient ammonia storage and preventing leakage by monitoring nitrogen oxide and ammonia peaks under optimal temperature conditions.
Patent Information
- Application Number
- FR2024001699
- Authority / Receiving Office
- FR · FR
- Patent Type
- Patents
- Current Assignee / Owner
- Filing Date
- 2024-02-21
- Publication Date
- 2026-01-02
- Estimated Expiration
- 2044-02-21
AI Technical Summary
Existing systems fail to accurately evaluate the charge and health status of ammonia slip catalysts, leading to potential ammonia leakage and desorption due to high temperatures.
A motor vehicle system comprising sensors, purging and enrichment means, and control strategies to determine ammonia storage and catalyst health by monitoring nitrogen oxide and ammonia peaks, with temperature management for optimal conditions.
Enables precise evaluation of ammonia storage and catalyst health, optimizing ammonia conversion and preventing leakage, allowing timely replacement or comparison of catalysts.
Smart Images
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Abstract
Description
Title of the invention: MOTOR VEHICLE COMPRISING A MEANS FOR CONTROLLING A CATALYST LEAK AMMONIA EVALUATING ITS LOAD, PROCESS AND PROGRAM BASED ON SUCH A VEHICLE
[0001] The invention relates to the field of control systems after treatment in a motor vehicle with a gasoline engine, and more particularly the management of the ammonia slip catalyst (or "Ammonia slip catalyst" in English).
[0002] The ammonia leak catalyst is designed to store ammonia and convert it in the presence of oxygen. To achieve this, the ammonia leak catalyst must be within a specific temperature range (around 250°C - 450°C). Above 450°C, the ammonia stored in the catalyst could be desorbed without being oxidized.
[0003] It may be necessary 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 the precise evaluation of the charge of the ammonia leak catalyst, in order to determine if it is still able to store ammonia.
[0005] To achieve this objective, the invention proposes a motor vehicle comprising an exhaust line which includes 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 to carry out at least one cycle of a phase purging of ammonia out of the ammonia leak catalyst; - an enrichment means to carry out at least one cycle of an ammonia enrichment phase in the ammonia leak catalyst after the purge phase; the end of the purging 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 ammonia storage in the ammonia leak catalyst, from the data of the total nitrogen sensor and the NOx sensor.
[0006] Advantageously, the invention proposes 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 charge and to optimize the continuous conversion of ammonia, thereby avoiding ammonia leakage and ammonia desorption related to high temperatures.
[0008] Preferably, the means for estimating ammonia storage determines ammonia storage by an integral of the mass flow rate of ammonia.
[0009] This allows us to obtain a precise value of the quantity of ammonia stored in the ammonia leak catalyst.
[0010] Preferably, the motor vehicle further includes a means for assessing the health status 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 by means of a boolean value from ammonia storage data.
[0013] This allows us to obtain a precise 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 includes at least one means of cycle interruption 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 on the brake pedal.
[0015] This allows the cycles to be carried out under optimal conditions, particularly in terms of temperature.
[0016] The invention further relates to a method for controlling an ammonia leak catalyst in a motor vehicle according to the invention, characterized in that it comprises the following steps: - a purging step to complete at least one cycle of an ammonia purging phase; - an enrichment step to carry out at least one cycle of an ammonia enrichment phase after the purging phase; the end of the purging 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 ammonia storage from sensor data of total nitrogen and the NOx sensor.
[0017] Preferably, in the ammonia storage estimation step, the ammonia storage is determined by an integral of the ammonia mass flow rate.
[0018] Preferably, the control method further includes a step of evaluating the health status of the ammonia leak catalyst.
[0019] Preferably, the control method further includes at least one cycle interruption step if one of the following conditions is met: - 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 on 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 process according to the invention, when said program is running on a computer.
[0021] The invention will be further detailed by describing non-limiting embodiments, and based on the accompanying figures illustrating variants of the invention, in which: - [Fig. 1] schematically illustrates the different phases and cycles involved in controlling the ammonia leakage 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 ammonia leakage catalyst (ASC) storage capacity is based on an intrusive richness index (RI) scheme of successive lean and rich phases to empty and refill the ASC. The procedure is monitored by observing the linear O2 sensor upstream of a close-coupled catalyst (CCC), the binary O2 sensor downstream of the gasoline particulate filter (GFP), the binary O2 sensor downstream of the floor catalyst if present (not mandatory), and the NOx sensor downstream of the ASC.
[0024] RI represents the air-fuel ratio at the CCC close-coupled catalyst. R2 represents the air-fuel ratio at the NOx sensor.
[0025] This procedure will be described later, and could preferably be carried out as part of a workshop maintenance procedure since it only takes a few minutes and: - requires a stable operating point of the internal combustion engine; - can be interrupted under normal driving conditions, requiring the procedure to be restarted; - has an impact on emissions.
[0026] First, the procedure begins with a stabilized engine operating point to increase the overall temperature of the exhaust line. This phase lasts until the activation conditions are met (exhaust line temperature, minimum exhaust mass flow target, sensors ready).
[0027] When the estimated temperature of the ammonia leak catalyst exceeds a minimum threshold (around 350°C), the intrusive enrichment scheme begins with a lean mixture demand (lambda approximately 1.08). This can be described as a PP purge phase cycle. This has the effect of converting the ammonia already stored in the catalyst by oxidation (with an ammonium leak FA). 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 a quantity of NOx is observed 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 properly 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 the addition of ammonia.
[0029] Next, the first rich phase is requested (lambda approximately 0.95). This can be referred to as the enrichment phase cycle (PE). This results in the production of ammonia by the tight-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 tight-coupled catalyst exceeds a high threshold (approximately 750 mV), and ending when: - the fuel mixture measured by the NOx sensor downstream of the ASC catalyst effectively 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 certain thresholds (around 300°C to 450°C) to ensure that the ammonia will be oxidized in the next phase and that no thermal desorption can occur; if this is not the case, It is possible to request a lambda phase 1 with a modified combustion advance to slightly increase the catalyst temperature or without modification of storage capacity to lower the ASC catalyst temperature.
[0031] Next, the second lean phase is requested (lambda approximately 1.08). As with the first, this converts the ammonia stored in the catalyst by oxidation (FA). The aim is to empty the ASC catalyst so that it is in good condition to store ammonia in subsequent driving cycles. This phase ends when: - the richness measured by the NOx sensor downstream of the ASC catalyst effectively 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] Next, the procedure ends, and the intrusive richness request is released. Lambda one regulation can be performed 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 by the maintenance tool. The value is compared to a threshold, and a boolean value is generated to indicate whether the catalyst is in good condition or not and needs to 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: - engagement of the transmission speed; - computer temperature too high (around 600°C); - coolant temperature too high (around 110°C); - shutdown of the internal combustion engine; - pressing the brake pedal; - depressing the clutch pedal; - pressing the accelerator pedal.
[0035] This strategy can be implemented by measuring the catalyst temperature instead of estimating it. It can also be implemented by using the catalyst storage output value from 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 selected with a calibrable 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 motor vehicle controller, for example, an exhaust system controller.
Claims
Demands
1. A motor vehicle comprising an exhaust system which includes an ammonia leakage catalyst (ASC), and: - 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 leakage catalyst (ASC); - an enrichment means for carrying out at least one cycle of an ammonia enrichment phase (PE) in the ammonia leakage catalyst (ASC) after the purge phase (PP); the end of the purge 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 the ammonia storage in the ammonia leak catalyst (ASC), from the data of the total nitrogen sensor and the NOx sensor.
2. Motor vehicle according to claim 1, characterized in that the means for estimating ammonia storage determines the ammonia storage by an integral of the mass flow rate of ammonia.
3. Motor vehicle according to any one of claims 1 to 2, characterized in that it further comprises a means for assessing the health status of the ammonia leakage catalyst (ASC).
4. 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 means of cycle interruption 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. A method for controlling an ammonia leakage 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 to carry out at least one cycle of an ammonia purging phase (PP); - an enrichment step to carry 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 for 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 mass flow rate of ammonia.
8. A control method according to any one of claims 6 to 7, characterized in that it further comprises a step of evaluating the health status of the ammonia leak catalyst (ASC).
9. A 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 met: - 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.
10. Computer program comprising program code instructions for performing the steps of the control process according to any one of claims 6 to 9, when said program is running on a computer.