FR3107555A1 - PARTICULATE FILTER REGENERATION STOP OPTIMIZATION - Google Patents

Abstract

The subject of the invention is a method for controlling the regeneration of a particulate filter (6.2) of an exhaust line (6) of a combustion engine (4), comprising the following steps: starting the regeneration ; regeneration by fuel injection at the end of combustion engine cycles so as to cause an exothermic reaction in the exhaust line upstream of the particulate filter (6.2) and burn the soot particles accumulated in said particulate filter (6.2) ; stop regeneration; the stage is executed when the first of the following two conditions is met: the amount of fuel injected during the stage reaches a maximum value; and a calculated regeneration efficiency during the step reaches a predetermined minimum value. Figure 1

Description

PARTICULATE FILTER REGENERATION STOP OPTIMIZATION

The invention relates to the field of motor vehicles with internal combustion engines, more particularly to the regeneration of motor vehicle particulate filters.

Motor vehicles with a combustion engine, in particular fuel of the diesel type but also fuel of the gasoline type with direct injection, are commonly equipped, in the exhaust line of the combustion engine, with a particulate filter. These engines in fact emit soot particles essentially composed of carbon and typically having a size of between 10 nm and 1 μm. These particles are harmful to health and must be filtered.

A particulate filter is conventionally made of an extruded sintered ceramic honeycomb. The honeycomb channels are blocked alternately at the inlet and at the outlet of the filter in order to force the passage of gases through the porous walls to collect the particles. The capture of particles in the filter is obtained by filtration. The accumulation of particles leads to the formation of a layer of soot on the walls which, initially, improves the efficiency of filtration, but, in a second step, gradually increases the pressure drop imposed in the line. exhaust. Cleaning or regeneration of the particle filter then becomes essential on a recurring basis.

Regeneration is based on the combustion of soot by raising the temperature of the exhaust gases at the filter inlet. The fuel injection system in the combustion engine is controlled to carry out a post-injection, that is to say at the end of each cycle of the combustion engine, so that the fuel thus post-injected does not is not burnt in the engine but in the exhaust line in order to significantly raise the temperature of the exhaust gases and activate the oxidation of the soot accumulated in the particulate filter. In some vehicles, it is planned to add an additive to the fuel which has the effect of lowering the combustion temperature of the soot particles. A catalyst material can also be provided on the structure of the filter.

Post-fuel injection has the disadvantage of increased fuel consumption. The effectiveness of regeneration depends significantly on the type of driving, driving on national roads at constant speed is more favorable than driving in town, because it allows higher temperatures to be reached. Post-fuel injection also has the disadvantage of fuel dilution in the engine lubricating oil. Indeed, part of the fuel post-injected into the combustion chambers condenses on the liners and passes through the segmentation of the pistons in the lubricating oil.

The published patent document US9,551,258B2 provides optimization of motor vehicle particle filter regeneration by determining a profile of the driver and of the type of route taken, in particular by means of the GPS satellite location system and by determining, on the basis of of these profiles, an optimal period to regenerate the particulate filter. Such an approach is interesting but has the drawback that in the event of a change in driving style and/or type of route in relation to the determined profile, regeneration may prove to be inefficient and lead to an increase in fuel consumption. and/or excessive fuel-in-oil dilution.

The aim of the invention is to overcome at least one of the drawbacks of the aforementioned state of the art. More particularly, the aim of the invention is to optimize the particulate filter regeneration operations, in particular when the driving profile undergoes a change.

The subject of the invention is a method for controlling the regeneration of a particulate filter of an exhaust line of a combustion engine, comprising the following steps: (a) starting the regeneration; (b) regeneration by fuel injection at the end of cycles of the combustion engine so as to cause an exothermic reaction in the exhaust line upstream of the particulate filter and burn the soot particles accumulated in said particulate filter; (c) termination of regeneration; remarkable in that step (c) is executed when the first of the following two conditions is fulfilled: the quantity of fuel injected during step (b) reaches a maximum value; and a calculated regeneration efficiency during step (b) reaches a predetermined minimum value.

According to an advantageous mode of the invention, the maximum value of fuel injected is between 10 and 20 grams.

According to an advantageous embodiment of the invention, the maximum regeneration efficiency value is between 50 and 70%.

According to an advantageous embodiment of the invention, in step (b) the quantity of fuel injected at the end of each cycle of the combustion engine is a function of the intake air flow of the combustion engine.

According to an advantageous embodiment of the invention, in step (b) the quantity of fuel injected at the end of each cycle of the combustion engine is also a function of an average intake air flow rate of the combustion engine over a slippery period.

According to an advantageous mode of the invention, the sliding period is between 60s and 600s (s=seconds).

According to an advantageous embodiment of the invention, the calculated regeneration efficiency during step (b) is a ratio between a quantity of soot particles burned during step (b) and a quantity of soot particles accumulated before the step (b).

According to an advantageous embodiment of the invention, the quantity of soot particles accumulated before step (b) is a quantity of soot particles accumulated between two successive steps (b).

According to an advantageous embodiment of the invention, step (c) is exempt from consideration of a driving profile of the motor vehicle.

The invention also relates to a motor vehicle comprising a combustion engine; a combustion engine exhaust line, with a particulate filter; and a combustion engine control unit; remarkable in that the control unit is configured to execute the method according to the invention.

The measures of the invention are interesting in that they make it possible to optimize the fuel consumption to carry out the regeneration of the particulate filter and to limit the dilution of fuel in the oil of the combustion engine. Indeed, by stopping regeneration as soon as the first of the two conditions is fulfilled, a limitation of regeneration on a quantitative basis and a limitation on an efficiency basis are put in competition. This means that an inefficient regeneration will be limited in the amount of fuel injected, and a more efficient regeneration will be limited to keep only the best part. In other words, observing these two conditions makes it possible to minimize the ratio between the quantity of fuel injected and the quantity of soot particles evacuated from the particulate filter.

is a schematic representation of a motor vehicle with a combustion engine and an exhaust line, in accordance with the invention;

is a graph illustrating the evolution of the quantities of fuel injected and the quantities of soot particles burned on a route of the main road type and a route of the urban type, and the conditions for stopping the regeneration, according to the invention.

detailed description

Figure 1 schematically illustrates a motor vehicle 2 comprising a combustion engine 4, an exhaust line 6 of the gases produced by the combustion engine 4, and a control unit 8 of the combustion engine 4.

The combustion engine 4 comprises several cylinders 4.1 and a fuel injector 4.2 for each cylinder. The fuel can be of the gasoil (diesel), gasoline or other type. The injectors are supplied with fuel under pressure, advantageously by a common rail (supply not shown) and are electrically controlled by the control unit 8. The combustion engine 4 also comprises an exhaust manifold 4.3 and optionally a turbocharger 4.4 of intake air (whose pipes are not shown). The outlet of the turbine of the turbocharger 4.4 is connected in an aeraulic way to the exhaust line 6. This comprises one or more catalysts 6.1 for the reduction of nitrogen oxides into dinitrogen and carbon dioxide, for the oxidation of monoxides carbon into carbon dioxides and/or oxidation of unburned hydrocarbons (HC) into carbon dioxides and water, depending on the type of fuel and the configuration of the combustion engine and the exhaust line. These catalysts are in themselves well known to those skilled in the art. The exhaust line 6 also includes a particulate filter 6.2 located downstream of the catalyst(s) 6.1. The particulate filter 6.2 consists of an extruded honeycomb substrate, in particular of sintered ceramic. The honeycomb channels can be blocked alternately at the inlet and at the outlet of the filter in order to force the passage of gases through the porous walls to collect the particles of soot, that is to say unburnt carbon. The capture of particles in the filter is obtained by filtration.

During the operation of the combustion engine, soot particles gradually accumulate on the substrate and gradually increase its pressure drop. It is therefore necessary to remove these soot particles regularly by regeneration consisting in causing the combustion of these soot particles by increasing the temperature in the filter in question. This temperature increase is achieved by injecting fuel at the end of the combustion engine's operating cycles, that is to say during the burnt gas expulsion phases, so as to cause an exothermic reaction in the exhaust line. The resulting increase in temperature allows the particulate filter to cause soot particles to burn, producing carbon dioxide gas. The soot particles are thus removed from the particulate filter substrate. The principle of regeneration which has just been described is in itself well known to those skilled in the art.

Regeneration of the particulate filter 6.2 is started automatically when there is a need for regeneration and when the motor vehicle is moving with the combustion engine running. The need for regeneration can be determined in several ways, in particular by modeling accumulated soot particles and/or by direct or indirect measurement of the pressure drop at the level of the particulate filter.

The performance of the regeneration depends on the type of journey made with the vehicle, i.e. a journey on a national road where the combustion engine is under essentially constant load is more favorable than an urban journey where the combustion engine is at variable expenses.

The invention provides, during each regeneration, to observe two conditions and to stop the regeneration as soon as one of the two conditions is fulfilled. The two conditions are, on the one hand, the amount of fuel injected during regeneration reaching a maximum value and, on the other hand, the regeneration efficiency calculated during regeneration reaching a minimum value.

FIG. 2 is a graph illustrating these two conditions for two types of route, namely a route of the national road type and an route of the urban type.

The horizontal axis corresponds to time t expressed in seconds (s) and the vertical axis corresponds to a mass m expressed in grams (g). The curves in continuous lines correspond to a course of the national road type and the curves in broken lines correspond to a course of the urban type. The two horizontal lines in centerlines correspond to the two conditions mentioned above.

Curve 10 corresponds to the mass of fuel injected into the exhaust line during regeneration. The fuel injection rate is essentially a function of the combustion engine intake air rate. Since the load level of the combustion engine is likely to vary, an average of intake air flow over a given period, in this case preceding each injection, can be used to determine a driving profile of the driver . Such a period is then said to be sliding.

Curve 12 corresponds to a reduction in mass of soot particles in the particulate filter, resulting from regeneration by fuel injection according to curve 10. This reduction in mass of soot particles in the particulate filter is determined by calculation by means of modeling taking into account various parameters, such as in particular the temperature prevailing in the particulate filter. The initial load of soot particles is 17g and it can be observed that this load gradually decreases over time as the fuel is injected into the exhaust line following curve 10.

The condition that the quantity of fuel injected during regeneration reaches a maximum value is represented by the horizontal line 14. In this case the maximum value is 15g. It can be between 10g and 20g. The other condition that the regeneration efficiency calculated during regeneration reaches a minimum value is represented by the horizontal line 16. In this case, the minimum efficiency value is 10g (=17g-7g) of soot particles burned for an initial charge of 17g, or 59%. It can be between 50% and 70%.

By considering curves 10 and 12 relating to the route of the national road type, it is observed that the condition that the regeneration efficiency calculated during regeneration reaches a minimum value, illustrated by the horizontal line 16, is fulfilled before the other condition, namely that the quantity of fuel injected during regeneration reaches a maximum value, and represented by the horizontal line 14. It can be observed that the meeting point of the curve 12 of reduction in mass of soot particles with the horizontal line 16 of minimum level of efficiency, corresponds to a mass of injected fuel of the order of 10g. An injected mass of 10g of fuel thus made it possible to evacuate 10g of soot particles, i.e. a ratio of 1. If regeneration is extended to the end of the cycle, the quantity of fuel injected would be around 14g and the quantity of soot particles evacuated would be around 11g, ie a ratio of 1.27. However, it is clear that an optimization consists in reducing this ratio.

The urban type route is represented by curves 18 and 20 in broken lines. Curve 18 corresponds to the mass of fuel injected into the exhaust line during regeneration and curve 20 corresponds to a reduction in the mass of soot particles in the particulate filter, resulting from regeneration by the injection of fuel following curve 18. By considering these curves 18 and 20, it is observed that the condition that the quantity of fuel injected during regeneration reaches a maximum value is fulfilled before the other condition, namely that the regeneration efficiency calculated during regeneration reaches a minimum value. It can be observed that the meeting point of the curve 18 of mass of fuel injected with the horizontal line 14 of maximum value of fuel injected corresponds to a mass of soot particles evacuated of the order of 9 g. An injected mass of 15g of fuel thus made it possible to evacuate 9g of soot particles, i.e. a ratio of 1.7. If regeneration is extended to the end of the cycle, the quantity of fuel injected would be around 20g and the quantity of soot particles evacuated would be around 11g, i.e. a ratio of 1.82.

It can be seen that stopping regeneration according to the two conditions described above makes it possible to optimize the fuel injected and to limit the dilution in the lubricating oil of the combustion engine, and this for any type of route. In other words, the approach described above is also robust in that it tolerates changes in the type of path during regeneration without penalizing the optimization.

Claims (10)

Method for controlling the regeneration of a particulate filter (6.2) of an exhaust line (6) of a combustion engine (4), comprising the following steps:
(a) start of regeneration;
(b) regeneration by fuel injection at the end of cycles of the combustion engine so as to cause an exothermic reaction in the exhaust line (6) upstream of the particulate filter (6.2) and burn the soot particles accumulated in said particle filter;
(c) termination of regeneration;
characterized in that
step (c) is executed when the first of the following two conditions is met:
- the amount of fuel injected during step (b) reaches a maximum value; And
- a calculated regeneration efficiency during step (b) reaches a predetermined minimum value. Method according to Claim 1, characterized in that the maximum value of fuel injected is between 10 and 20 grams. Method according to one of Claims 1 and 2, characterized in that the maximum regeneration efficiency value is between 50 and 70% of soot particles burned. Method according to one of Claims 1 to 3, characterized in that in step (b) the quantity of fuel injected at the end of each cycle of the combustion engine is a function of the intake air flow rate of the engine at combustion. Method according to Claim 4, characterized in that in step (b) the quantity of fuel injected at the end of each cycle of the combustion engine is also a function of an average intake air flow rate of the engine at combustion over a sliding period. Method according to Claim 5, characterized in that the sliding period is between 60s and 600s. Method according to one of Claims 1 to 6, characterized in that the calculated regeneration efficiency during step (b) is a ratio between a quantity of soot particles burned during step (b) and a quantity of soot particles accumulated before step (b). Process according to Claim 7, characterized in that the quantity of soot particles accumulated before step (b) is a quantity of soot particles accumulated between two successive steps (b). Method according to one of Claims 1 to 8, characterized in that step (c) does not take into account a driving profile of the motor vehicle. Motor vehicle (2) comprising a combustion engine (4); an exhaust line (6) of the combustion engine (4), with a particulate filter (6.2); and a control unit (8) of the combustion engine (4); characterized in that the control unit (8) is configured to execute the method according to one of claims 1 to 9.