RU2484266C2 - Method and device for detection of combustion in particle filter - Google Patents

Abstract

FIELD: engines and pumps.

SUBSTANCE: essence of the invention of the method for combustion detection in particle filter (6) built into a waste gas outlet system of internal combustion engine (1), at that, periodic regeneration of filter (6) is performed with the appropriate devices, which includes the stage of measurement or evaluation of specific combustion parameters in the above filter (6) and processing stage of those parameters for diagnostics of combustion case and its intensity, differing by the fact that those stages are performed during the whole phase of engine (1) operation, and namely during phases controlled with filter (6) regeneration. The invention also refers to the device meant for the method's implementation.

EFFECT: providing effective filtration of the filter owing to monitoring spontaneous particle combustion in the filter.

12 cl, 1 dwg

Description

The present invention claims the priority of French application 0853563, filed on May 30, 2008, the contents of which (text, drawings and claims) in this case are used as a reference.

The invention relates to the field of purification from pollution of internal combustion engines, and in particular, to the control of particle filters, which are equipped with exhaust systems for exhaust gases to capture particles formed during the combustion of fuel in the engine.

The internal combustion engine produces during operation exhaust gases from the combustion of fuel containing a certain amount of certain contaminants. Particles generated during combustion in an engine may, in particular, contain solid carbon particles. In the absence of the ability to adjust the engine so that it emits an acceptable amount of certain contaminants, the exhaust gases must be treated to reduce these contaminants to a lower level of normalized threshold values.

The gas treatment means is typically located in an engine exhaust system. It is, therefore, about the post-processing of gases. This processing means may be formed by one or more elements and may, in particular, comprise a particle filter.

An automotive particle filter allows you to remove solid particles found in the exhaust gases of engines, especially diesel ones, by filtering. Particles accumulating in the filter should be periodically removed by increasing the temperature inside the filter from 450 to 700 ° C in order to ensure their combustion. This operation is often called "regeneration" of the particle filter. Classically, the energy required for regeneration is provided by a controlled increase in temperature of the exhaust gases.

The additional energy classically necessary for the regeneration phase is obtained by increasing the temperature compared to normal engine operation by using late fuel injection after the top dead center of the cycle, or by reducing the combustion efficiency, or also by injecting fuel directly into the exhaust system.

In the case of using late fuel injection, the latter can completely or partially burn out in the engine, causing an increase in the temperature of exhaust gases, or, if it is sufficiently delayed, lead to an increase in the amounts of CO and HC that are oxidized, coming to the oxidation catalyst to generate heat. It is this phenomenon that is usually used in the direct injection of fuel in atomized or vapor form into the exhaust system of the engine.

However, the carbon particles trapped in the filter are combustible, and their spontaneous combustion can be carried out at a temperature exceeding approximately 450 ° C, if an additional additive is used in the filter to ensure regeneration, or, otherwise, 600 ° C, and if fuel is available in sufficient quantity.

Oxygen is usually present in engine exhaust gases, and soot particles can thus be overloaded if soot is heavily contaminated by the filter, resulting in significant release of energy in the filter that could cause it to malfunction (e.g., cracking) or destruction.

Clogging of the filter with soot can, in particular, be observed when a car equipped with a filter carries out mainly urban trips, that is, at low speed and frequent stops. Under these conditions, it is extremely difficult to regenerate the particle filter, since the temperature of the exhaust gases is very far from the temperature of the regeneration of the filter, or they reach a temperature sufficient for regeneration to occur, only in very short time intervals, insufficient to complete this regeneration. Recall that usually the temperature of the exhaust gases of an automobile diesel engine equipped with a turbocharger, measured at the turbine output of the turbocharger, is about 150 ° C, and that approximately 450 ° C is necessary in order to regenerate the filter with the additive.

In addition, if with a large amount of soot in the particle filter, the engine undergoes a long trip with a heavy load, the temperature of the exhaust gases can spontaneously cause soot to ignite in the filter. In addition, under certain conditions, soot combustion, which began before the engine stopped, can continue after it has stopped, and may even start somewhat later than this stop, if the exhaust system is very hot and the filter is no longer cooled by the exhaust stream.

Uncontrolled soot combustion can damage the filter if it occurs at a significant temperature, or if it causes a very rapid increase in temperature in the filter. Such damage is harmful for many reasons. On the one hand, the efficiency of the post-processing system is compromised, and, on the other hand, in accordance with current and future standards and regulations regarding on-board diagnostics (the “built-in diagnostics” function), it is necessary to guarantee the effectiveness of post-processing systems during the service life (usually 160,000 km in accordance with EURO 5) or signal the driver of the car about the malfunction of the post-processing system.

Renault SA patent FR 2814498 describes a means for diagnosing a particle filter malfunction or calculating its load by monitoring the energy used in the filter regeneration process. While various methods are known, monitoring the regeneration of a particle filter is not known in the prior art, there is no known method aimed at monitoring in the case of this type of spontaneous combustion of particles in the filter, as well as filter malfunctions that it can cause.

In addition, the influence of this type of uncontrolled combustion of particles on the soot loading of the filter is not currently taken into account in the models for determining this loading.

An object of the present invention is a method for recognizing combustion and, in particular, uncontrolled combustion, in a particle filter that is integrated in an exhaust system of an internal combustion engine. This recognition and characteristic of the detected combustion allows, thus, diagnosing a filter malfunction or taking into account the effect of this combustion on the soot load of the filter during the entire phase of engine operation. The invention allows to control the filter during all of their phases of use, and not only during its controlled regenerations, as in the prior art.

To this end, the proposed method comprises the step of measuring or evaluating the characteristic parameters of combustion in the filter or the step of processing these parameters to diagnose the case of combustion and determine its intensity, while in the method these steps are carried out during the entire phase of the engine and, in particular, in the process of controlled phases filter regeneration, and in a variant of the method, also in the process of a pre-calculated duration following the engine shutdown.

Preferably, the characteristic parameters considered are respectively the inlet temperature of the particle filter and the outlet temperature of the particle filter.

Evaluation or measurement of these parameters and their processing differ in that they are carried out outside the phases of the controlled regeneration of the filter. In addition, the evaluation or measurement and processing of the considered parameters continues after the engine is stopped.

Thanks to this method, in this case, it can be concluded that particles in the filter (6) of particles are uncontrolled if the temperature at the filter outlet (6) exceeds the temperature of a predetermined threshold at the filter inlet for a predetermined time, although the on-board computer does not control the regeneration.

In accordance with an embodiment of the invention, a temperature gradient in the filter is determined in accordance with a change in temperature at the inlet and outlet of the filter, and in this case, it is concluded that particles in the particle filter (6) are burned if the measured temperature gradient exceeds a previously calculated maximum.

When combustion in the filter is determined, it is also possible to estimate the amount of soot burned during this combustion due to the change in temperature at the inlet and outlet of the filter during this combustion and due to the duration of this combustion.

The proposed method can serve to diagnose damage to the particle filter integrated in the exhaust system of an internal combustion engine. The conclusion about damage to the particle filter is made if the temperature at the outlet of the filter exceeds the temperature at the inlet of the filter by a predetermined amount over a certain period of time.

A conclusion about the damage to the filter is also made if the measured temperature gradient exceeds a predetermined limit.

In a car with an internal combustion engine equipped with an exhaust system containing a particle filter and also containing an “on-board diagnostics” module (built-in diagnostics), information about damage to the particle filter can also be written to the module if damage to the particle filter is determined.

If the vehicle additionally contains, for example in the cab, a light device signaling a defect in the particle filter, then it informs the driver of the malfunction of the particle filter.

The invention also relates to a device for implementing the described method. The device comprises an internal combustion engine equipped with an exhaust system, including a particle filter, means for controlling the regeneration of the filter, means for evaluating the parameters characterizing the combustion of particles in the filter, means for processing these parameters to diagnose the case of combustion, and also to evaluate its intensity, characterized in that that the aforementioned means are periodically turned on during engine operation, and not only during controlled filter regenerations, as is the case at a known level e technique.

Preferably, the device is provided with means for evaluating or measuring the temperature at the inlet of the particle filter and a temperature probe at the outlet of the filter.

The invention is further explained in the following description, which is not restrictive, with reference to a single drawing schematically representing an apparatus for implementing the method in accordance with a preferred embodiment of the invention.

FIG. 1 schematically depicts a complex formed by an internal combustion engine and its main air circuit, that is, its air intake and exhaust system, as well as means for post-processing exhaust gases, and devices necessary for diagnosing a particle filter in accordance with a preferred embodiment of the invention.

The diesel engine 1 is equipped with a boost system using a turbocharger 2. Air enters the engine through the intake pipe 3. The exhaust gases after combustion are carried out through the exhaust pipe 4.

In the example presented here, the exhaust gas is treated with an oxidizing catalyst 5 and a particle filter 6.

The on-board computer 7 (presented in this case as a single complex, but it can be formed of several elements or divided into several boards or electronic units) generates various control commands for the engine, fuel injection algorithms, and also controls the post-processing means and, in particular, monitors particle filter filling. The on-board computer 7 also contains control means for controlling the periodic regeneration of the particle filter 6. The on-board computer 7 also performs the function of the built-in diagnostics 8, which records and records the main malfunctions or defects in the operation of the engine and its periphery, and can, for example, in the event of a malfunction, give an alarm with a light alarm device 9 to an engine operator or a driver of a car equipped with such an engine.

In the embodiment presented here, a temperature probe 10 is integrated in the exhaust pipe 4 between the oxidation catalyst 5 and the particle filter 6. The temperature probe 11 is placed in the exhaust pipe 4 at the outlet of the particle filter 6.

It should be noted that the temperature probe 10 at the inlet of the filter can be easily replaced by a digital model for estimating the temperature at the inlet of the particle filter stored in the on-board computer. This option is of some economic interest at the cost of less accuracy, which remains, however, comparable to that used in a classic car.

The temperature probe 10 at the inlet of the filter 6 and the temperature probe 11 at the output of the filter 6 are connected to the on-board computer 7 via, for example, buses 12 and 13, which, in addition, implements the proposed method. In general, the proposed method consists in comparing the inlet temperature and the outlet temperature of the particle filter 6, as well as determining the change in these temperatures during the use of the engine 1 and for a given duration, for example, one minute after it is stopped. Comparison of temperatures is carried out not only in the process of regeneration of the filter 6, implemented by the on-board computer. The proposed diagnostics by monitoring these two temperatures and their changes allows, on the one hand, to recognize spontaneous combustion in the filter 6 particles and, on the other hand, to diagnose the destruction of the filter 6 caused by a very intense and very fast energy release.

Usually, if the temperature measured by the probe 11 at the filter outlet exceeds the temperature of the probe 10 at the filter inlet by a certain threshold for a certain time, while the on-board computer 7 does not control regeneration (for example, by means of late fuel injection), then in accordance with the algorithm, the conclusion about the uncontrolled combustion of soot in the filter 6. These temperature and time boundaries make it possible to distinguish the case of combustion in the filter 6 from the case of a decrease in the load of the engine 1, which produces less heated exhaust gases, h о, depending on the thermal inertia of the filter, it can temporarily lead to a decrease in the temperature measured by the probe 10, compared with the temperature measured by the probe 11. Thus, it seems clear that the temperature threshold and the duration in question depend on the filter used, as well as on the engine and its operating points selected by the on-board computer.

In addition, monitoring the temperature at the inlet and outlet of the filter 6 allows you to evaluate the temperature gradient in the filter. A significant temperature gradient is a good indicator of uncontrolled combustion in the filter 6.

The determination of such uncontrolled combustion and observation of the temperatures at the inlet and outlet of the particle filter and their change during this spontaneous combustion allow, in addition, to adjust the estimated load level in the filter 6 particles, taking into account the amount of oxidized particles in the process of uncontrolled regeneration.

In addition, in the framework of controlled or uncontrolled regeneration of the particle filter, a comparison of the temperatures at the inlet and at the outlet of the filter 6 allows us to conclude about cases of destruction of the filter. If the temperature measured by probe 11 exceeds the temperature of probe 10 by a certain amount (potentially different from the threshold used to determine uncontrolled combustion) for a certain period (potentially different from the duration used to determine spontaneous combustion), it is concluded that the filter is destroyed .

In addition, if the temperature gradient estimated in the filter 6 exceeds a predetermined maximum, it is concluded that there is a destruction of the filter.

If, in accordance with the algorithm, it is concluded that the filter has been destroyed, then the built-in diagnostics module 8 of the on-board computer 7 gives an alarm. In accordance with the current legislation, in the future, information can be recorded in the memory of a computer 7 or module 8 of the built-in diagnostics, and a light alarm device 9 warns the driver about a defect.

Thus, in the framework of car use and in accordance with existing and future regulations, which, for example, prescribe to observe filter filtration efficiency over 160,000 km in accordance with the European standard EURO 5, it becomes possible to warn the driver that a critical regeneration of the particle filter is determined, controlled or uncontrolled and, in known cases, spontaneously occurred while driving, and that its performance may be impaired.

Claims (12)

1. A method for recognizing combustion in a particle filter (6) integrated in an exhaust system of an internal combustion engine (1), the periodic regeneration of which is carried out by appropriate means, including a step for measuring or evaluating characteristic combustion parameters in said filter (6) and a processing step for these parameters for diagnosing the case of combustion and assessing its intensity, characterized in that the said steps are carried out during the entire phase of the engine (1) and, in particular, during the phases of the controlled p filter regeneration (6). 2. The method according to claim 1, characterized in that the said steps are additionally carried out during a predetermined time following the shutdown of the internal combustion engine (1). 3. The method according to claim 1 or 2, characterized in that said characteristic parameters are the inlet temperature of the particle filter (6) and the outlet temperature of the particle filter (6). 4. The method according to claim 3, characterized in that the conclusion about the combustion of particles in the filter (6) of particles is made in the case when the temperature at the outlet of the filter (6) exceeds a predetermined threshold temperature at a predetermined period of time at the inlet of the filter (6) . 5. The method according to claim 3, characterized in that the temperature gradient in the filter (6) is estimated by the change in temperature at the inlet and outlet of the filter and the conclusion about the combustion of particles in the filter (6) of particles is made when the estimated temperature gradient exceeds a predetermined maximum. 6. The method according to claim 1, characterized in that in the case of determining combustion in the filter, the amount of soot burned during this combustion is evaluated by the change in temperature at the inlet and outlet of the filter (6) during this combustion and by the duration of this combustion. 7. A method for diagnosing a malfunction of a particle filter built into the exhaust system of an internal combustion engine using a combustion recognition method according to one of claims 2 to 4, characterized in that a conclusion about a malfunction of the particle filter (6) is made if the temperature at the output of the filter (6) exceeds the temperature at the input of the filter (6) by a predetermined limit in a given period of time. 8. A method for diagnosing a malfunction of a particle filter built into the exhaust system of an internal combustion engine using a combustion recognition method according to one of claims 2, 3 or 5, characterized in that a conclusion about a malfunction of the particle filter (6) is made in the case when the measured temperature gradient exceeds a predetermined threshold. 9. The method according to claim 7 or 8, characterized in that it is implemented in a car with an internal combustion engine containing a particle filter in the exhaust system and additionally containing an “integrated diagnostics” (OBD) module (8), moreover, into said module ( 8) record information about the malfunction of the particle filter (6), if the malfunction of the particle filter (6) is determined. 10. The method according to claim 7, implemented in a car, containing, in addition, a light device (9) for signaling a filter malfunction (6) of particles, characterized in that the light device (9) is controlled when a filter malfunction (6) is detected . 11. A device comprising an internal combustion engine (1) equipped with an exhaust system containing a particle filter (6), means for evaluating the characteristic parameters of the combustion in the particle filter (6), means for processing these parameters to diagnose a combustion event, and also to evaluate its intensity, characterized in that the said means are involved in the process of the entire phase of the engine, and, in particular, during the phases of controlled filter regenerations (6). 12. The device according to claim 11, characterized in that the means for evaluating the parameters are means for evaluating or measuring the temperature at the inlet of the filter and a temperature probe (11) at the output of the filter.

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