EP1819915A1

EP1819915A1 - Method and device for stopping a regeneration phase of a particle filter of a motor vehicle diesel engine

Info

Publication number: EP1819915A1
Application number: EP05819422A
Authority: EP
Inventors: Marc Daneau; Nicolas Dauphin; Céline ETCHEVERRY; Adrien Pillot
Original assignee: Renault SAS
Current assignee: Renault SAS
Priority date: 2004-11-29
Filing date: 2005-11-23
Publication date: 2007-08-22
Also published as: JP2008522072A; FR2878566B1; JP4734340B2; KR20070090216A; FR2878566A1; WO2006056718A1

Abstract

The invention relates to a device for stopping a regeneration phase of a particle filter (30) of a motor vehicle diesel engine, comprising means (31, , 34) for evaluating the quantity of soot eliminated since the beginning of the current regeneration phase. The invention is characterised in that it comprises: means (55) for evaluating a value that indicates diesel fuel dilution in the oil that appeared during the current regeneration phase; and means (55) for monitoring the value of the ratio between the dilution indicator value and the quantity of soot eliminated, whereby said monitoring means (55) can identify the fulfilling of a pre-defined criterion (66) relating to changes in said ratio and initiate the stopping of the regeneration phase when said pre-defined criterion (66) has been fulfilled.

Description

Method and device for stopping a regeneration phase of a diesel engine particle filter of a motor vehicle.

The invention relates to diesel engines equipped with a particulate filter, and more specifically to controlling the stopping of a regeneration procedure applied to such a particulate filter.

Diesel engines, by their specific operation, emit (among others) in their exhaust gases soot pollutants that are also called particles

In order to limit the emissions of these particles into the atmosphere, a particulate filter is placed in the exhaust line, downstream of the combustion chambers of the engine. This filter retains the particles that accumulate within it as as the engine is used. This accumulation of particles eventually clogs the filter, creating a strong back pressure to the exhaust of the engine, that is to say, an obstacle to the path of the gases in the exhaust line The diesel engine then sees its performance markedly diminished. In order to recover the engine performance, the particles contained in the particulate filter are burned. This procedure is called the regeneration of the particle filter

The initialization and maintenance of the combustion of particles in the filter is obtained by raising the internal temperature of the particulate filter.

To do this, one typically proceeds to multiple injections, that is to say the addition of at least one injection in addition to the usual diesel injection. For example, a delayed injection is introduced into the combustion chambers of the engine, that is to say that fuel is injected after the top dead center (TDC) of the engine cycle, during the expansion phase. the effect of increasing the exhaust gas temperature and therefore the temperature in the particulate filter The principle of late injections is also known. It is then a question of injecting gas oil longer after the top dead center so that the gas oil does not burn in the combustion chamber, but in a part of the fuel line. According to the nature of the combustion which has eluted therein, this catalytic portion is constituted by, for example, an oxidation catalyst placed upstream of the particulate filter, or by a simple catalytic material (such as platinum) within the particulate filter It is on these catalytic sites that the compounds HC and CO of the late injecti ons oxidize, increasing the temperature of the gases.

This filtering operation is carried out periodically, as soon as the quantity of particles in the filter becomes too great. This regeneration takes place when the motor is running, and this without the user noticing it. In a regeneration procedure, the dilution of the gas oil in the engine lubricating oil is considerably increased.

Thus, the late injections which are made long after the top dead center, project the diesel on a large surface of the cylinder which is uncovered This situation considerably favors the mixing of the oil covering the wall of the cylinder with the diesel fuel injection, causing then the phenomenon of "dilution"

It is the same for delayed injections These delayed injections of diesel are not only carried out after the top dead center but also long in time The jet of diesel injected has, also in this case, the possibility of reaching directly the wall of the cylinder and mix with the oil covering it

When the dilution becomes too great, the oil does not play its role of lubricant correctly and it appears a risk of deterioration of the engine

For this reason, the regeneration procedure should be as short as possible, in order to keep the oil to a minimum, while at the same time regenerating the filter as much as possible. At present, the processes used implement so - called complete regenerations. The regeneration procedure is, in other words, stopped when the particulate filter no longer contains combustible particles. However, it turns out that much more is spent. of energy to consume a given amount of soot when the particle filter is almost empty, only when the particle filter is heavily loaded

In other words, the soot is more easily consumed with a charged filter than with a substantially clean filter. An object of the present invention is to propose a method and a device for regeneration of a particle filter which implement controlled partial regenerations. in order to limit the consumption of gas oil injected into the chambers for regeneration Thus, an associated goal is to control the dilution occasi oned by the regeneration

A more general object of the invention is to provide a method and regeneration means which keep the engine under healthy operating conditions. This object is achieved according to the invention by means of a stop phase of a regeneration phase of a diesel engine particulate filter of a motor vehicle, comprising means for evaluating a quantity of soot removed since the beginning of the current regeneration phase The device comprises means for evaluating a value indicating the dilution of the oil in the oil during the current regeneration phase, as well as means for monitoring the value. a ratio between the diluti on indicator value and the amount of soot removed, said tracking means being able to identify the achievement of a predefined criterion relating to the evolution of this ratio and to initiate the stopping of the regeneration phase at the achievement of this predefined criterion

The dilution value that appears during the current regeneration phase is preferably a cumulative value in the time of each successive value of the dilution that has appeared since the beginning of the regeneration phase until the moment considered.

The means for monitoring the value of the ratio between the dilution and the quantity of soot eliminated are preferably means capable of identifying the achievement of a minimum of the evolution of the value of said ratio over time and able to initiate a stopping the regeneration phase when this minimum is reached

Alternatively, the means for monitoring the value of the ratio between the dilution and the amount of soot removed are means capable of initiating a stop of the regeneration phase at a point of inflection of an evolution of said dilution ratio. mass over time

The means for monitoring the value of the ratio between the dilution and the quantity of soot eliminated advantageously comprise a series of sensors of physical parameters as well as a calculator implementing a mathematical model, which mathematical model gives an evaluation of said ratio by function of parameters acquired in real time by the sensors.

The means for monitoring the value of the ratio between the dilution and the amount of soot removed include, for example, a series of physical parameter sensors arranged near the particle filter and the cylinder.

The mathematical model used typically delivers, in turn, a result in the form of a probability associated with at least one value of said ratio between the dilution and the amount of soot removed.

The invention also proposes a method for stopping a regeneration phase of a diesel engine particulate filter, said method comprising the step of evaluating a quantity of soot eliminated since the beginning of the regeneration phase. in progress method preferably comprises a step of evaluating a value indicative of a dilution of the oil in the oil appeared during the regeneration phase, a step of establishing a ratio between the dilution indicator value appeared and the quantity value it has been eliminated, as well as a step consi stant to identify the achievement of a criterion predefined by this report during its evolution.

Other features, objects and advantages of the invention will appear on reading the detailed description given with reference to the appended figures, in which:

- Figure 1 is a functional view of an engine block equipped with a particle filter and a device according to the invention;

- Figure 2 is a plot showing the evolution of a report used by the device according to the invention. All the members illustrated in Figure 1 is distributed around a cylinder 10 of diesel engine of a motor vehicle. It distinguishes an air intake pipe 1 1 and an exhaust pipe 12 as well as an injection device 13. The exhaust pipe 12 is equipped with a turbo-compressor 20. The driving of exhaust 12 comprises, downstream of the turbine

20a of the turbo-compressor 20, a catalyst 14 and a particulate filter 30. There is also, within the assembly shown, a system placed in juncti on between the driving duct 1 1 and exhaust duct 12 , intended to recycle the exhaust gases around the cylinder 10. This system known under the terminology EGR (Exhaust

Recycle gas) is referenced 40 in FIG.

There is further shown a calculator 55 acting as hostage host of the regeneration phases, and especially stopping thereof. In order to limit and stop a regeneration phase, the computation unit 55 controls an injection valve 14 at the cylinder 10 by which it physically controls the injection or not for the heating of the particulate filter 30. A decision - making method for stopping the regeneration phase by the computer 55 is proposed.

The computer 55 takes a series of physical data at the level of the particle filter 30. Thus, it receives the signals provided by a series of sensors referenced 31, 32, 33, 34 in FIG.

A temperature sensor 31 takes the temperature upstream of the filter 30, a sensor 32 takes the temperature downstream of the filter 30

Pressure sensors 33 and 34 respectively take the upstream and downstream pressures to the filter 30. A flowmeter 35 is also located near the particulate filter.

In addition to the temperature parameters taken at the level of the particle filter 30 and supplied to the input of the computer 55, other parameters are also taken and supplied to the calculator 55 and enter into the calculations made by the computer to make a decision. starting or stopping a regeneration phase transmitted by the connection 50 to the mjecteur 13

The computer 55 also receives the value of the fuel flow during injection in real time. It also has, by integrating the flow rate values, the global volume of gas oil injected since the beginning of the current regeneration phase.

The calculator 55 further comprises two additional inputs 56 and 57 receiving the signals of two corresponding sensors and not shown in FIG. 1. The sensor associated with the input 56 delivers a value of engine speed in real time, the sensor associated with the input 57 delivers for example a temperature value at the cylinder 10.

From the parameters taken and transmitted to the cal culator, the calculator performs a double evaluation. On the one hand, it assesses the dilution of gas oil in the oil as it has appeared until now during the regeneration phase. On the other hand, it assesses the mass of soot burned up to now in the regeneration phase. The dilution indicator value is obtained here using a pre - recorded model establishing, as a function of temperatures and pressures, the typical evolution of the dilution of gas oil in oil over time. It is based on the use of pre - recorded data matching the different values of the parameters mentioned above with the dilution of the gasol in the oil to be expected. This dilution of the gas oil in the oil could be observed during laboratory tests, by physical sampling of the oil diluted in the oil at the inlet of the exhaust, or as a result of a calculation on a physical model. previously done.

The dilutive indicator value therefore corresponds to the dilution present at the moment considered, as evaluated by taking into account the evolution of the conditions of solicitation of the multiple injection actually implemented at the moment considered and the previous instants of the regeneration phase in progress.

The computation here evaluates the dilution in the form of a cumulative sum of the different dilution values that have appeared over time for the duration already elapsed since the beginning of the regeneration phase. This cumulative sum is established by the computer, for example in the form of an integral over time of each successive dilution value.

This indicator value will be called the "cumulative diluti on since the beginning of the regeneration". In addition to such a model relying directly on the parameters taken, a statistical model is adopted in a variety of ways.

Such a statistical model is established at the design of the vehicle, from experimental records.

At the same time, the calculator performs a second evaluation, always in real time. It is the evaluation of the quantity of soot burned since the beginning of the regeneration Again, this quantity of soot is determined by a physical or statistical model, from the pressure and temperature data taken by the calculator. 55 Thanks to the double evaluation of the cumulative dilution and the mass of soot burned, the calculation 55 determines at any time the ratio

Cumulative dilution (t) / burned soot mass (t) The filter is regenerated only partially There are still soot remaining at the end of the procedure Regeneration procedures are performed more frequently than with the regeneration method At each partial regeneration, the particulate filter is more loaded with soot than at the end of a total regeneration. However, less energy is spent on burning a given quantity of particles with the aid of several regenerations. only in one complete regeneration

In order to better control the regeneration phases by the implementation, the computer 55 carries out a real-time monitoring of the value of the ratio diluti on / mass of burnt soot. The typical evolution of this ratio over the course of time. will show the shape of the plot in Figure 2 The value of this report is noted there r

In addition to an initial burst of the burned mass dilution ratio, this line describes a horizontal plateau 65 followed by a rising phase 70, the slope of which is itself increasing over time, to stabilize in a zone of increase. linear 80

Once the regeneration is complete, that is, once the initial burst 60 has passed, in other words once the particulate filter is warmed up and combustion is initiated, it is decided to stop the process. regeneration procedure in a location of the route described above which proves to be the most suitable

Preferably, it is for this purpose to stop the regeneration procedure at the point where the ratio dilution / mass reaches a minimum, namely here a short vacuum 66 located at the end of the stage 65

The calculator determines for this purpose the slope of the evolution of the report, and this in real time When the slope is canceled, the calculator deduces that the minimum is reached According to a vari ante, the calculator identifies the appearance of a point of inflection which he interprets as revealing the appearance of the minimum expected

The introduction of a cost function in terms of dilution relative to the mass of soot burned, thus reveals a minimum 66 of this function in its evolution over time This minimum 66 is reached at a stage of progress that is susceptible to be adopted as the end of partial regeneration phase. Indeed, this minimum is at a sufficient regeneration progress so that this regeneration, although partial, corresponds to the removal of a satisfactory soot mass.

It follows that little is diluted, by burning a certain quantity of particles given, and this in several partial regenerations. The fact of repeating such optimal partial regenerations multiplies the effect of such an optimal choice on the economy achieved. in terms of dilution

In the case of implementation of a statistical dilution model by the computer 55, the calculator establishes a mass-to-dilution ratio, and implements a decision as to the cessation of the regeneration from the crossing of the a predefined threshold. For example, the calculator monitors the downward crossing of a minimum threshold of the ratio.

The calculator can also determine a minimum ratio 66 of the change in the ratio of dilution to mass, as illustrated in the plot of FIG.

Claims

1-Device for stopping a regeneration phase of a diesel engine particulate filter (30) of a motor vehicle, comprising means (31, ..., 34) for evaluating a quantity of soot eliminated since the beginning of the current regeneration phase, characterized in that it comprises means (55) for evaluating an indicator value for diluting the gas oil in the oil that has appeared during the current regeneration phase, and means (55) for monitoring the value of a ratio between the dilution indicator value and the amount of soot removed, said tracking means (55) being able to identify the achievement of a predefined criterion (66). ) relating to the evolution of this ratio and initiating the stopping of the regeneration phase on reaching this predefined criterion (66).

2-Device according to claim 1, characterized in that the dilution value appeared during the current regeneration phase is a cumulative value in time of each successive value of the dilution appeared since the beginning (60) of the regeneration phase until the moment considered.

3-Device according to claim 1 or claim 2, characterized in that the means (55) for monitoring the value of the ratio between the dilution and the amount of soot removed are means capable of identifying the achievement of a minimum (66) the evolution of the value of said ratio over time and able to initiate a stop of the regeneration phase to reach this minimum. 4-Device according to any one of the preceding claims, characterized in that the tracking means (55) of the value of the ratio between the dilution and the amount of soot removed are means capable of initiating a stop of the regeneration phase in one inflexion point (66) of an evolution of said ratio diluti on to mass over time

5-Device according to any one of the preceding claims, characterized in that the means vi sui (55) of the value of the ratio between the dilution and the amount of soot removed include a series of sensors of physical parameters (31, 34 ) as well as a calculator (55) implementing a mathematical model, which mathematical model delivers an evaluation of said ratio as a function of parameters acquired in real time by the sensors (31, 34)

6-Device according to claim 5, characterized in that the means vi sui (55) of the value of the ratio between the dilution and the amount of sui ee eliminated include a series of sensors (3 1, 34) of physical parameters arranged near the particulate filter (30)

7 - Process for stopping a regeneration phase of a diesel engine particulate filter (30), said method comprising the step of evaluating a quantity of soot removed since the beginning of the regeneration phase in progress , characterized in that it comprises a step of evaluating a value indicative of a dil ution of the gas oil in the oil appeared during the regeneration phase, a step of establishing a ratio between the dilution indicator value appeared and the amount of soot removed, as well as a step of identifying the achievement of a predefined criterion (66) by this ratio during its evolution.