MOTOR VEHICLE COMPRISING A MEANS FOR CONTROLLING AN AMMONIA LEAKAGE CATALYST AS A FUNCTION OF ITS LOAD AND TEMPERATURE, METHOD AND PROGRAM BASED ON SUCH A VEHICLE

Abstract

The invention relates to a motor vehicle comprising a means for controlling an ammonia leak catalyst according to modes depending on its ammonia load (Q) and its temperature, namely control, among: - a mode without control strategy (0), at low load (Q); - a heating mode (2), at intermediate load (Q) and low temperature (T), where a heating request is made for the catalyst according to a given torque application. This makes it possible to control the load and the temperature of the catalyst and to put it in a good temperature and oxygen quantity range, limiting the ammonia leak phenomenon. 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 OF AMMONIA DEPENDING ON ITS CHARGE AND TEMPERATURE, 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] In the prior art, the ammonia leak catalyst is a passive part of the exhaust line. It is not proposed to manage its load. As a result, an ammonia leak may occur, i.e. the catalyst is no longer able to store ammonia.

[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. If not, this results in an interruption of ammonia conversion and a desorption of the ammonia.

[0005] To achieve this objective, the invention provides a motor vehicle comprising an engine; wheels; an engine acceleration control; an exhaust line equipped with an ammonia leak catalyst; a temperature estimation means estimating the temperature of the catalyst; a load estimation means estimating the ammonia load of the catalyst; a history estimation means estimating whether the ammonia load increases or decreases; and a means for controlling the catalyst according to control modes among: - a mode without control strategy if the catalyst has a load lower than a first load threshold; or if the catalyst has a load higher than the first load threshold and lower than a second load threshold, and has a temperature lower than a first temperature threshold; - a heating mode if the catalyst has a load greater than the second load threshold and less than a third load threshold, and has a temperature lower than the first temperature threshold; or if the catalyst has a load greater than the third load threshold, and has a temperature lower than the first temperature threshold, and higher than a second temperature threshold, wherein a heating means makes a heating request of the catalyst as a function of a given application of torque.

[0006] Advantageously, the invention provides a control strategy aimed at activating preventive actions to bring the ammonia leak catalyst into good conditions for converting ammonia, namely a good temperature range and a good oxygen contribution.

[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] Having active management of the catalyst load allows for having a catalyst in good temperature and oxygen conditions to convert ammonia adequately.

[0009] Preferably, the heating means increases the temperature of the catalyst to a value between 250°C and 450°C, and for a catalyst heating demand, a minimum torque demand is calculated as a function of: - an engine speed; - engine coolant temperature; - a temperature upstream of the catalyst; - the ammonia charge of the catalyst.

[0010] Preferably, the catalyst control means has additional control modes, namely: - an opportunistic purge mode if the catalyst has a load greater than the first load threshold and less than the second load threshold, and has a temperature greater than the first temperature threshold, wherein an opportunistic purge means effects a coupling of the engine to the wheels and a drive request if the throttle control is released; - a drive and purge mode active if the catalyst has a load greater than the second load threshold, and has a temperature greater than the first temperature threshold, in which a drive means performs a coupling of the engine to the wheels with an injection cut-off.

[0011] The dragging demand is a demand to drive (or "dragging" in English) the gasoline engine (or ICE engine) by the road. This allows oxygen to be supplied to the catalyst so that it can cover the conversion of ammonia.

[0012] Preferably, the catalyst control means has an additional control mode, namely an inhibition mode if the catalyst has a load greater than the third load threshold, and has a temperature lower than the second temperature threshold, wherein an inhibiting means inhibits the production of ammonia upon engine start-up.

[0013] This makes it possible to limit the quantity of ammonia produced by the catalysts, and consequently the phenomenon of ammonia leakage.

[0014] Preferably, the load estimation means is based on a physical model of the balance between absorption and desorption of ammonia from the catalyst, as well as on oxidation-reduction reactions of ammonia and nitrogen oxides.

[0015] This allows for an accurate determination of the amount of ammonia in the catalyst.

[0016] The invention further relates to a method for controlling a catalyst of a motor vehicle according to the invention, characterized in that it comprises the following steps: - a step without control strategy if the catalyst has a load lower than a first load threshold; or if the catalyst has a load higher than the first load threshold and lower than a second load threshold, and has a temperature lower than a first temperature threshold; - a heating step if the catalyst has a load greater than the second load threshold and less than a third load threshold, and has a temperature lower than the first temperature threshold; or if the catalyst has a load greater than the third load threshold, and has a temperature lower than the first temperature threshold, and higher than a second temperature threshold, in which a catalyst heating request is made as a function of a given torque application.

[0017] Preferably, in the heating step, the temperature of the catalyst is increased to a value between 250°C and 450°C, and for a catalyst heating request, a minimum torque request is calculated as a function of: - an engine speed; - engine coolant temperature; - a temperature upstream of the catalyst; - the ammonia charge of the catalyst.

[0018] Preferably, the control method further comprises the following steps: - an opportunistic purge step if the catalyst has a load greater than the first load threshold and less than the second load threshold, and has a temperature greater than the first temperature threshold, in which a coupling of the engine to the wheels is carried out and a request is made engine drive on road if the throttle control is released; - a drive and purge step active if the catalyst has a load greater than the second load threshold, and has a temperature greater than the first temperature threshold, in which the engine is coupled to the wheels with an injection cut-off.

[0019] Preferably, the control method further comprises an inhibition step if the catalyst has a load greater than the third load threshold, and has a temperature lower than the second temperature threshold, in which the production of ammonia is inhibited when the engine is started.

[0020] Preferably, the load estimation step is based on a physical model of the equilibrium between absorption and desorption of ammonia from the catalyst, as well as on oxidation-reduction reactions of ammonia and nitrogen oxides.

[0021] 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.

[0022] The invention will be further detailed by the description of non-limiting embodiments, and on the basis of the appended [Fig.l] illustrating the different control strategies as a function of the temperature and the catalyst load within the framework of the invention.

[0023] The 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 muffler. The storage and conversion of ammonia by the catalyst can be managed with a specific strategy for managing the powertrain of the internal combustion engine and its coupling to the wheels.

[0024] The strategy is based on 5 different modes which will be described below, and the demand for a specific mode is based on the estimation of the catalyst temperature, the estimation of the catalyst ammonia loading and the catalyst history, i.e. whether the loading is increasing or decreasing. The estimation of the current ammonia storage is based on a physical model of equilibrium between ammonia adsorption / desorption, NOx / NH3 oxidation-reduction reactions.

[0025] This makes it possible to determine 5 different modes of action: - normal mode 0: in this mode, no strategy is required; - the mode of opportunistic purge levers 1: for example a drive request (or “dragging” in English) is made if possible: the engine is coupled to the wheels, and opportunistic drive is implemented when the foot is released; - heating mode 2: a request for heating of the leak catalyst ammonia can be performed with minimal application of torque; - active drive and purge mode 3: in this mode, the engine is coupled to the wheels with an injection cut-off; - Inhibition mode 4: this is a protection mode to prevent ammonia production when restarting the engine in the event that the catalyst is almost full, but not hot enough for the ammonia to be converted.

[0026] Normal mode 0 is determined if the catalyst has a low load below a first load threshold A; or if the catalyst has a load above the first load threshold A and below a second load threshold B, and has a temperature below a first temperature threshold T1.

[0027] Opportunistic lever mode 1 is determined if the catalyst has a load greater than the first load threshold A and less than a second load threshold B, and has a temperature greater than the first temperature threshold TL

[0028] Heating mode 2 is determined if the catalyst has a load greater than the second load threshold B and less than a third load threshold B1, and has a temperature less than the first temperature threshold T1; or if the catalyst has a load greater than the third load threshold B1, and has a temperature less than the first temperature threshold T1, and greater than a second temperature threshold T2.

[0029] The active drive and purge mode 3 is determined if the catalyst has a load greater than the second load threshold B, and has a temperature greater than the temperature threshold T.

[0030] Inhibition mode 4 is determined if the catalyst has a charge greater than the third charge threshold B1, and has a temperature lower than the second temperature threshold T2.

[0031] The purpose of heating the catalyst is to increase its internal temperature to a value above 250°C so that it can convert the stored ammonia in the presence of oxygen. For a catalyst heating demand, a minimum torque demand is calculated based on: - Engine speed; - Engine coolant temperature; - The temperature upstream of the catalyst; - The ammonia charge of the catalyst.

[0032] The dragging request aims to supply oxygen to the catalyst so that it can cover the ammonia conversion, because the catalyst is already hot enough to do so. Dragging is a mode where the internal combustion engine is requested to be coupled to the wheels, with an injection cut-off so that oxygen can be supplied to the exhaust line in large quantities and mass flow. In addition, supplying oxygen to a catalyst that is already hot avoids the massive catalyst ammonia release event that occurs when the catalyst temperature rises too high.

[0033] The protection mode aims to limit the amount of ammonia produced by the catalysts, to ensure that a catalyst that is already almost full and not hot enough to accommodate the ammonia conversion would not be further loaded, thus avoiding ammonia leakage events (massive amount of ammonia seen at the catalyst outlet as a result of the catalyst's inability to load more ammonia.

[0034] 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 engine; wheels; an engine acceleration control; an exhaust line equipped with an ammonia leak catalyst; a temperature estimation means estimating the temperature (T) of the catalyst; a load estimation means estimating the ammonia load (Q) of the catalyst; a history estimation means estimating whether the ammonia load (Q) increases or decreases; and a means for controlling the catalyst according to control modes among: - a mode without control strategy (0) if the catalyst has a load (Q) lower than a first load threshold (A); or if the catalyst has a load (Q) higher than the first load threshold (A) and lower than a second load threshold (B), and has a temperature (T) lower than a first temperature threshold (Tl);- a heating mode (2) if the catalyst has a load (Q) greater than the second load threshold (B) and less than a third load threshold (Bl), and has a temperature (T) less than the first temperature threshold (Tl); or if the catalyst has a load (Q) greater than the third load threshold (Bl), and has a temperature (T) less than the first temperature threshold (Tl), and greater than a second temperature threshold (T2), in which a heating means makes a heating request of the catalyst according to a given torque application.;

2. Motor vehicle according to claim 1, characterized in that the heating means increases the temperature of the catalyst to a value between 250°C and 450°C, and in that for a catalyst heating request, a minimum torque request is calculated as a function of: - an engine speed; - an engine coolant temperature; - a temperature upstream of the catalyst; - the ammonia charge of the catalyst.

3. Motor vehicle according to any one of claims 1 to 2, characterized in that the catalyst control means has additional control modes, namely: - an opportunistic purge mode (1) if the catalyst has a load (Q) greater than the first load threshold (A) and less than the second threshold load (B), and has a temperature (T) above the first temperature threshold (Tl), in which an opportunistic purge means performs a coupling of the engine to the wheels and a drive request if the acceleration control is released; - a drive and active purge mode (3) if the catalyst has a load (Q) above the second load threshold (B), and has a temperature (T) above the first temperature threshold (Tl), in which a drive means performs a coupling of the engine to the wheels with an injection cut-off.

4. Motor vehicle according to any one of claims 1 to 3, characterized in that the catalyst control means has an additional control mode, namely an inhibition mode (4) if the catalyst has a load greater than the third load threshold (B1), and has a temperature lower than the second temperature threshold (T2), in which an inhibition means inhibits the production of ammonia when the engine is started.

5. Motor vehicle according to any one of claims 1 to 4, characterized in that the load estimation means is based on a physical model of the balance between absorption and desorption of ammonia from the catalyst, as well as on oxidation-reduction reactions of ammonia and nitrogen oxides.

6. Method for controlling a catalyst of a motor vehicle according to any one of claims 1 to 5, characterized in that it comprises the following steps: - a step without control strategy (0) if the catalyst has a load (Q) lower than a first load threshold (A); or if the catalyst has a load (Q) higher than the first load threshold (A) and lower than a second load threshold (B), and has a temperature (T) lower than a first temperature threshold (Tl); - a heating step (2) if the catalyst has a load (Q) higher than the second load threshold (B) and lower than a third load threshold (Bl), and has a temperature (T) lower than the first temperature threshold (Tl);or if the catalyst has a load (Q) greater than the third load threshold (Bl), and has a temperature (T) less than the first temperature threshold (Tl), and greater than a second temperature threshold (T2), in which a request for heating of the catalyst is made; function of a given torque application.

7. Control method according to claim 6, characterized in that in the heating step, the temperature of the catalyst is increased to a value between 250°C and 450°C, and for a catalyst heating request, a minimum torque request is calculated as a function of: - an engine speed; - an engine coolant temperature; - a temperature upstream of the catalyst; - the ammonia charge of the catalyst.

8. Control method according to any one of claims 6 to 7, characterized in that it further comprises the following steps: - an opportunistic purging step if the catalyst has a load (Q) greater than the first load threshold (A) and less than the second load threshold (B), and has a temperature (T) greater than the first temperature threshold (Tl), in which a coupling of the engine to the wheels and a request for engine drive on the road are carried out if the acceleration control is released; - an active driving and purging step if the catalyst has a load (Q) greater than the second load threshold (B), and has a temperature (T) greater than the first temperature threshold (Tl), in which a coupling of the engine to the wheels is carried out with an injection cut-off.

9. Control method according to any one of claims 6 to 8, characterized in that it further comprises an inhibition step (4) if the catalyst has a load greater than the third load threshold (B1), and has a temperature lower than the second temperature threshold (T2), in which the production of ammonia is inhibited when the engine is started.

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.

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