FR2879252A1 - MOTOR CONTROL METHOD FOR OPTIMIZING THE REGENERATION OF A PARTICLE FILTER - Google Patents

Abstract

The invention proposes a method for controlling a vehicle engine, the engine comprising a particle filter (40), characterized in that it comprises a step of determining a difference between an average gas temperature measured at the input The method further comprises a step of correcting a mean late fuel injection (D0) flow rate in a combustion chamber (11) of a motor block (10) which depends on of said deviation in order to compensate for it.According to a mode of the invention, it is thus possible to correct a dispersion with respect to a given specification of at least one element (30) of the engine, this dispersion being related to at least one one of the following aspects: - wear of the element (30), - manufacture of the element. In particular, it is very interesting to combine the method of the invention with a regeneration process of the particulate filter (40).

Description

2879252 1

  The present invention relates to a control method of a combustion engine comprising in particular an engine block and a particulate filter.

  An application of such a method is particularly advantageous in diesel type engines when regenerating the particulate filter.

  It is recalled that these engines emit in their exhaust polluting soot that we also called particles.

  And we know that an installation of a particulate filter (FAP for Particulate Filter) in the exhaust line, downstream of the combustion chambers of the engine block, can limit these emissions into the atmosphere.

  Such a filter effectively retains the particles of the exhaust gas within it.

  However, a known problem related to the use of such a filter is that it fills with particles as the operation of the engine block and it ends up being clogged by them.

  This then creates a strong counter-pressure to the exhaust of the engine, gases having difficulty escaping, and thus decreases its performance.

  In order to overcome this disadvantage, it is known to use a method in which combustion of the particles contained in the particulate filter is carried out.

  Such a process is commonly referred to as the regeneration of a particulate filter and is carried out periodically, ie as soon as the amount of particles accumulated in the filter becomes too large.

  This type of process essentially consists in increasing, during a so-called regeneration phase, the temperature of the exhaust gas in the particulate filter so as to reach the combustion temperature of the particles to be burned.

  To do this, a delayed injection of fuel into the combustion chambers of the engine block is carried out.

  More precisely, diesel is injected after a top dead center (PMI-I), during a relaxation phase, which has the effect of increasing the temperature of the exhaust gases.

  More precisely, this injection takes place at a crank angle of about sixty degrees.

  It will be noted here that in the following text will be designated such an injection delayed by the term post-injection.

  It is also known that such post-injection can be supplemented with at least one injection of gas oil long after the top dead center.

  Such an additional injection will be designated later in the text by late post-injection.

  And more particularly, it will correspond to a fuel injection between about one hundred and ten and one hundred and twenty degrees crankshaft angle.

  In this case, the excess fuel will not burn in the combustion chamber, but in a catalytic part provided in addition to the particulate filter.

  The hydrocarbons and carbon monoxides resulting from the late injections oxidize at the catalytic sites, which advantageously leads to the release of heat, hence an increase in the temperature of the exhaust gas.

  As an indication, it should be noted that said catalytic portion may consist of an oxidation catalyst installed upstream of the particulate filter in the exhaust line, or else of a catalytic material (for example a platinum) disposed within the latter. (FAP).

  Although having already rendered many services, such a method of regeneration of the particle filter has limitations.

  In particular, a limitation concerns a temperature dispersion at the inlet of the particulate filter.

  This dispersion can be explained as follows.

  Said catalytic portion of oxidation produces an exotherm which depends in particular on the amounts of reducing agents that are, for example, hydrocarbons and carbon monoxides resulting from late post-injections.

  Therefore, the thermal level at the inlet of the filter (FAP) may be a function of one hand of these amounts of reducing agents sent to said catalytic portion and secondly of a heat conversion rate of the latter.

  However, it is known that for the same fuel flow control, particularly with regard to the late post-injection, the mass of fuel actually injected into the combustion chamber can vary from a few milligrams from one engine to another.

  There is therefore a first dispersion on the amount of fuel actually injected into the combustion chamber.

  Furthermore, it is known that said catalytic portion may itself possess a dispersive oxidation power, that is to say a heat-dissipative conversion rate.

  It is therefore understood that these two sources of dispersion, taken here by way of non-limiting example, lead to that of the temperature at the inlet of the filter, which can disadvantageously lead to a loss of efficiency of the regeneration process.

  An object of the present invention is therefore to overcome to a certain extent these disadvantages and to provide a method that allows an efficient and robust regeneration in terms of dispersions.

  For this purpose, the present invention proposes a method of controlling a vehicle engine, the engine comprising a particle filter, characterized in that it comprises a step of determining a difference between an average gas temperature measured in filter input and a set temperature.

  Preferred but non-limiting aspects of the process according to the invention are the following: said method further comprises a step of correcting a mean flow rate (OD) for late post-injection of fuel into a combustion chamber of a block motor that depends on said gap to compensate for it; Increasing or decreasing the rate of late post-fuel injection into the combustion chamber, respectively, if said difference is negative or positive; 2879252 5 E before activating the step of determining the deviation and then correction of the average flow (OD), it is determined that at least one predetermined condition is fulfilled; The step of determining the deviation and the step of correcting the average current flow (OD) are interrupted if the one or one of the predetermined conditions is not respected; The latest late post-injection mean flow rate (DO) value determined at the end of the last correction step is used when the gap determination step and the average flow rate correction step (DO) is not active It is determined whether a temperature of a gas input to the particulate filter is within a predetermined temperature range; It is determined whether at least one of a speed, a motor speed, and an engine load is within a predetermined value range; It is further determined whether for a predefined duration the magnitude does not vary beyond and within a predetermined percentage of its measured value at the beginning of the gap determining step, so that can consider this magnitude as being stable; The step of determining the deviation and the late post-injection mean flow rate (OD) correction step make it possible to correct a dispersion with respect to a given specification of at least one element of the engine, this dispersion being related to at least one of the following: - wear of the element, manufacture of the element; The step of determining the deviation and the step of correcting the mean post-injection mean flow rate (OD) make it possible to correct at least one of the following dispersions with respect to a given specification: dispersion of an oxidation power of a catalytic part in cooperation with the particulate filter, - dispersion on a quantity of fuel injected into a combustion chamber of an engine block in the engine, dispersion linked to a turbo-compressor, dispersion bound at an air flow meter, dispersion linked to a boost pressure sensor in an intake manifold.

  The present invention also provides a vehicle engine, comprising a particle filter, characterized in that it comprises means capable of determining a difference between an average gas temperature measured at the inlet of the particulate filter and a set temperature.

  A preferred but non-limiting aspect of this engine is that it further comprises means capable of correcting a mean flow (DO) for late post-injection of fuel into a combustion chamber which depends on said deviation.

  Thus, the invention advantageously makes it possible to obtain regeneration of the effective and robust particulate filter, and moreover in a simple and inexpensive way.

  Furthermore, it will be noted that the method makes it possible to compensate for average temperature differences at the inlet of the particulate filter that may come from a large number of dispersions. 10

  2879252 7 They may concern different elements of an engine and come from wear problems as well as manufacturing problems (dispersion from one element to another).

  Other aspects, objects and advantages of the invention will appear better on reading the following description of the invention, with reference to the appended drawings, in which: FIG. 1 schematically represents an engine according to the invention, FIG. 2 illustrates graphically, for a so-called nominal motor, an observable difference between an input temperature measurement of the particulate filter and a target temperature during a regeneration, FIG. 3 graphically illustrates, and a so-called cold engine, a difference observable between a temperature measurement at the inlet of the particulate filter and a target temperature during a regeneration.

  Referring now to Figure 1, there is shown an engine comprising a motor unit 10, the exhaust gas 12 passes successively through a turbocharger 20, a catalyst 30 and a particulate filter 40.

  Temperature sensors 50, among others, make it possible to measure temperatures 55 at the inlet of the particulate filter 40.

  These temperatures are supplied to a management unit 60 able to process them and generate appropriate control signals 65 to fuel injectors 70.

  Thus, the control signal 65 is representative, in particular, of a certain quantity of fuel to be injected in real time in each combustion chamber 11.

  And this signal depends on the temperatures 55 measured at the inlet of the particulate filter.

  For example, when the temperature of the exhaust gas measured at the inlet of the filter 40 is lower, respectively higher, than a set temperature, the management unit 60 controls an increase, respectively a decrease, of the quantity of fuel post-injected late to raise, respectively lower, the temperature of said gases and bring them as close as possible to the set value.

  By way of illustration, FIG. 2 shows such a regulation when it is said to be functional.

  It can be seen that the post-injection flow control signal 65 evolves between two bounded quantities 101 and 102, which corresponds to normal operation.

  Indeed, the basic setting of the late post-injection flow leads to a temperature at the inlet of the filter relatively close to the target temperature, so that the late post-injection flow control remains relatively limited and oscillates around an average value. DO.

  It will be noted here that according to the invention such a situation corresponds to a nominal motor operation and that, in this case, said dispersion compensation strategy is not really useful.

  However, it also happens that due to too large dispersions, said control signal 65 does not oscillate around the average value DO or at least between the two aforementioned terminals.

  Such a situation is illustrated in Figure 3 where it can be seen that the signal 65 is glued to one of the terminals (the terminal 101 here).

  In this case, the regulation is no longer functional (such a situation corresponds to a cold engine operation).

  Indeed, the basic setting of late post-injection flow rate is no longer sufficient to provide the quantity ideally requested, thus saturating the control system.

  According to the present invention, such a control method is advantageously completed by a motor control method which makes it possible to compensate for temperature variations measured at the input of the filter.

  Such compensation is implemented by determining a difference between a measured average temperature and a set temperature.

  This difference then makes it possible to correct the average flow rate DO of late post-injection of fuel in each combustion chamber, by playing on the control signal 65.

  Specifically, the management unit calculates a positive or negative amount of late post-injection flow to be added to the basic setting OD.

  And this additional quantity is determined so that the control signal 65 always oscillates between the two aforementioned terminals.

  In order to determine the difference between the average temperature and the set temperature, the management unit uses a set of temperature measurements at the input of the filter.

  Then, it estimates said additional amount as a function of the average temperature at the input of the filter.

  Thus, such a method offers the advantage of guaranteeing good regeneration efficiency of the particulate filter, regardless of the temperature dispersions, for example linked to the dispersion of the conversion rate of the catalyst.

  According to a variant of the invention, the compensation of the dispersions is implemented during the regeneration phase of the particulate filter but only in the case where one is in the presence of favorable rolling conditions.

  Thus, it is possible to condition the activation of the step of determining the difference between the mean temperature at the input of the filter (40) and the set temperature by means of a preliminary test step.

  In this respect, according to the invention, favorable running conditions are understood to mean the combined achievement of the following criteria: the temperature measured at the inlet of the particulate filter is within a range of predefined values; parameters such as the speed of the vehicle; the engine speed and the engine load are within predefined ranges and vary in a limited way in the range in question for a predetermined period of time.

  Note that according to a preferred embodiment of the invention, the speed must be greater than 50km / h and the speed of the engine block (10) between 1500 and 3000 rev / min.

  In addition, the variation of said parameters must preferably be less than ± 20% for at least 200 seconds.

  Thus, for example, if at the beginning of a regeneration cycle of the filter is rolled at 100km / h, the compensation step according to the invention can be activated.

  2879252 11 But it is also necessary that for 200 seconds at least, the vehicle maintains a steady speed, that is to say between 80 and 120km / h.

  Of course, it will also be necessary that all other criteria of running is favorable.

  It will also be noted that, in the case where the rolling conditions are not favorable, even if the compensation step is not activated, the regeneration method of the current particle filter (40) uses the last settings of the previous compensation step.

  For example, it uses the last corrected value of average flow rate OD of late post-injection.

  In this way, at least some of the temperature variations at the input of the filter (40) are at least partially offset.

  According to another variant, the management unit continuously implements this test step.

  Thus, even if the compensation is active, the management unit continuously monitors the driving conditions and, in the event that one of them becomes unfavorable, deactivates.

  Of course, the present invention is not limited to the embodiment described above and shown in the drawings.

  In particular, it can be envisaged that the favorable driving conditions include other parameters (for example the gearbox ratio, etc.).

  Moreover, it will be understood by those skilled in the art that, without departing from the concept of the invention, it generally makes it possible to overcome any source of dispersion that would lead to that of average temperature difference. at the inlet of the particulate filter.

  Thus, it will be recalled here that the process according to the present invention is not limited to solving the problems of dispersion of the oxidation power of the catalyst or of the late post-injection flow of a motor. 'other.

  By way of nonlimiting example, the method is capable of compensating a dispersion linked to the turbo-compressor (20), to a flow-meter of air and / or to a supercharging sensor of one of the intake manifolds (11). .

Claims (2)

13 Claims   1. A method of controlling a vehicle engine, the engine comprising a particle filter (40), characterized in that it comprises a step of determining a difference between an average gas temperature measured at the input of the filter and a set temperature.   2. Method according to claim 1, characterized in that it further comprises a step of correction of a mean flow rate (OD) for late post-injection of fuel into a combustion chamber (11) of an engine block ( 10) which depends on said deviation to compensate for it.   3. Method according to claim 2, characterized in that one increases, respectively decreases, the late post-injection rate of fuel in the combustion chamber (11) if said deviation is negative, respectively positive.   4. Method according to one of claims 2 to 3, characterized in that, before activating the step of determining the difference and then correction of the average flow (OD), it is determined that at least one predetermined condition is fulfilled.   5. Method according to claim 4, characterized in that the step of determining the deviation and the step of correction of the average flow rate (OD) in progress are interrupted if the one or one of the predetermined conditions does not exist. is not respected.   6. Method according to one of claims 4 to 5, characterized in that the last late post-injection mean flow rate (OD) value determined at the end of the last correction step is used when the step of determining the deviation and the step of correction of the average flow (OD) is not active.   7. Method according to one of claims 4 to 6, characterized in that it is determined whether a temperature of a gas inlet of the particulate filter (40) is in a predetermined temperature range.   8. Method according to one of claims 4 to 7, characterized in that it is determined whether at least one of a speed, a motor speed and a motor load, is in a predetermined range of value.   9. The method as claimed in claim 8, characterized in that it is furthermore determined whether, during a predefined duration, the quantity does not vary beyond and below a predetermined percentage of its value measured at the beginning of the step. determining the deviation so that this magnitude can be considered stable.   A method for correcting a dispersion with respect to a given specification of at least one element (30) of an engine, said dispersion being related to at least one of the following aspects: - wear of the element (30) , - manufacture of the element, characterized in that it is in accordance with any one of the preceding claims.   11. A method for correcting at least one of the following dispersions with respect to a given specification: dispersion of an oxidation power of a catalytic part (30) in cooperation with the particulate filter (40), - dispersion on a quantity of fuel injected into a combustion chamber (11) of an engine block (10) in the engine, dispersion linked to a turbo-compressor (20), dispersion linked to an air flow-meter, - dispersion linked a boost pressure sensor in an intake manifold, characterized in that it is according to any one of claims 1 to 9.   12. Vehicle engine, comprising a particulate filter (40), characterized in that it comprises means (50; 60; 70) capable of determining a difference between an average gas temperature measured at the inlet of the particulate filter ( 40) and a set temperature.   13. Motor according to claim 12, characterized in that it further comprises means adapted to correct a mean flow rate (OD) of late post-fuel injection in a combustion chamber (11) which depends on said deviation.