Patent Application
20190390582
This application claims benefit to German Patent Application No. DE 10 2018 114 779.1, filed Jun. 20, 2018, which is hereby incorporated by reference herein.
The invention relates to a method for determining the loading state of a particle filter of a motor vehicle.
Modern motor vehicles are known to have particle filters which, in particular, serve to filter out particles, such as for example fine dust particles and/or soot particles, from an exhaust gas stream of the motor vehicle. In this context, it is already known from practice to determine what is referred to as the loading state of the particle filter in order to perform, in particular, regeneration of the particle filter when the loading state of the particle filter with particles filtered out of the exhaust gas is too large. Hitherto, the precise, reliable and simple determination of the loading state of a particle filter of a motor vehicle presented difficulties.
EP 1 528 229 B1 discloses a method by means of which it is possible to estimate a quantity of particles which are precipitated in a filter for trapping diesel particles. For this purpose, according to EP 1 528 229 B1, a first increased quantity of particles is detected on the basis of a pressure difference across the particle filter. On the basis of an integrated value, obtained by means of integration, a second increased quantity of particles is detected. It is proposed to determine correction data for correcting the integrated value and to correct the integrated value using this correction data. The particle filter is regenerated on the basis of the corrected integrated value or the pressure difference across the filter.
EP 1 529 931 B1 has also disclosed determining a collected quantity of particles in a filter for trapping particles of engine exhaust gas and regenerating the particle filter as a function thereof. For this purpose, a first estimated value of a collected quantity of particles is determined by means of a first estimation means, on the basis of the exhaust gas differential pressure of the particle filter. The collected quantity of particles of the filter is estimated using a second estimation means, on the basis of the engine operating status. A selection unit is configured to select one of the estimation results and to determine the regeneration time of the particle filter as a function thereof.
In an embodiment, the present invention provides a method for determining a loading state of a particle filter of a motor vehicle. The method includes detecting a first differential pressure across the particle filter by a measuring using a differential pressure sensor, determining a second differential pressure across the particle filter by computation using a differential pressure model, and subjecting each of the first differential pressure and the second differential pressure to a filtering process in order to determine a filtered first differential pressure from the first differential pressure and a filtered second differential pressure from the second differential pressure. The method further includes subjecting each of the first filtered differential pressure and the second filtered differential pressure to an integration process in order to determine a first integral of the filtered first differential pressure and a second integral of the filtered second differential pressure, synchronizing the first integral and the second integral with one another to provide synchronized integrals, and determining, as the loading state, a ratio which is dependent on the synchronized integrals.
The present invention will be described in even greater detail below based on the exemplary figures. The invention is not limited to the exemplary embodiments. All features described and/or illustrated herein can be used alone or combined in different combinations in embodiments of the invention. The features and advantages of various embodiments of the present invention will become apparent by reading the following detailed description with reference to the attached drawings which illustrate the following:
Embodiments of the invention to provide novel methods for determining the loading state of a particle filter of a motor vehicle. In a method according to embodiments of the invention for determining the loading state of a particle filter of a motor vehicle, a first differential pressure across the particle filter is detected by measuring technology using a differential pressure sensor. In the method according to embodiments of the invention, furthermore, a second differential pressure across the particle filter is determined by computation using a differential pressure model.
In the method according to embodiments of the invention, the first differential pressure and the second differential pressure are each subjected to a filtering process, in order to determine a filtered first differential pressure and a filtered second differential pressure.
In the method according to embodiments of the invention, the first filtered differential pressure and the second filtered differential pressure are each subjected to an integration process, in order to determine a first integral of the filtered first differential pressure and a second integral of the filtered second differential pressure.
The first integral and the second integral are synchronized with one another in the method according to the invention.
According to the invention, a ratio which is dependent on the integrals which are synchronized with one another is determined as a loading state.
With the present invention, the loading state of a particle filter of a motor vehicle can be determined easily, reliably and precisely. This is based, in particular, on the fact that filtered differential pressures, which are on the one hand measured and on the other hand determined by computation on the basis of a model, are each integrated, wherein the integrals which are determined in the process are synchronized with one another. Ultimately the loading state is determined as a function of the integrals, which are synchronized with one another, of the filtered differential pressures.
Inaccuracies in the determination of the loading state, which arise from a previously unconsidered phase shift between the first differential pressure which is detected by measuring technology and the second differential pressure which is determined by computation can be compensated or eliminated as a result of the filtering of the differential pressures, the integration of the differential pressures and the synchronization of the integrals.
According to one advantageous development, the first integral and the second integral are synchronized with one another in such a way that a delay is impressed on the second integral. As a result, the synchronization can take place particularly advantageously. The delay which is impressed on the second integral is preferably dependent on an operating point, in particular the rotational speed of an internal combustion engine and/or an exhaust gas mass flow of the internal combustion engine. This also serves for the particularly advantageous synchronization of the integrals of the filtered differential pressures.
The first integral is preferably weighted as a function of an operating point, in particular of the rotational speed of an internal combustion engine and/or an exhaust gas mass flow of the internal combustion engine. A ratio between the integrals which are synchronized with one another, specifically a ratio of the weighted first integral and the second integral, on which a delay is impressed, is determined as a loading state. By means of the weighting it is possible to eliminate a measuring error of the differential pressure sensor at low exhaust gas mass flows or exhaust gas volume flows.
According to one advantageous development, the second differential pressure across the particle filter is determined by computation using the differential pressure model in such a way that the second differential pressure, which is dependent on a calculated volume flow upstream of the particle filter, is corrected by means of a temperature-dependent factor. The calculated volume flow upstream of the particle filter is preferably calculated as a function of the static pressure upstream of the particle filter which is corrected as a function of the filtered first differential pressure.
According to one advantageous development of the invention, a static offset of the differential pressure sensor is compensated in such a way that in the event of an engine cold start and when an ignition system is activated a current static offset of the differential pressure sensor is stored, that in the event of an engine warm start and when the ignition system is activated the stored static offset of the differential pressure sensor remains stored, and that the filtering is initialized as a function of the static offset. In this way, the influence of an offset of the differential pressure sensor can advantageously be compensated.
The invention relates to a method for determining the loading state of a particle filter of a motor vehicle.
The particle filter can be a particle filter for a motor vehicle having a spark ignition engine or else a particle filter for a motor vehicle having a diesel engine. Particle filters for a motor vehicle having a spark ignition engine are also referred to as spark-ignition particle filters.
The determination of the loading state of the particle filter is based on two differential pressures. A first differential pressure across the particle filter is detected by measuring technology using a differential pressure sensor. A second differential pressure across the particle filter is determined by computation using a differential pressure model. Both the first differential pressure and the second differential pressure are each subjected to a filtering process, in order to determine a filtered first differential pressure and a filtered second differential pressure. Both filtered differential pressures are respectively subjected to an integration process, in order to determine a first integral of the filtered first differential pressure and a second integral of the filtered second differential pressure. The two integrals are synchronized with one another. A ratio which is dependent on the integrals which are synchronized with one another is determined as a loading state. Further details of the invention are described below with reference to the figures.
A first differential pressure Δp1 is detected by measuring technology using a differential pressure sensor. As stated above, this first differential pressure Δp1 which is detected by measuring technology is subjected to a filtering process, to be precise firstly to a digital low-pass filtering process in a block 10 and subsequently to a digital high-pass filtering process in a block 11, wherein the output variable of the block 11 is a first filtered differential pressure Δp1,F.
The low-pass filtering process in block 10 and the high-pass filtering process in block 11 together make available a bandpass filtering process for the first differential pressure Δp1 which is detected by measuring technology.
As already stated, the determination of the loading state of the particle filter is based not only on the first differential pressure Δp1 which is detected by measuring technology but also on a second differential pressure Δp2 which is determined by computation using a differential pressure model.
This second differential pressure Δp2 is determined by computation in the blocks 12, 13 and 14 which represent the differential pressure model, wherein the second differential pressure Δp2, like the first differential pressure Δp1, is subjected to a filtering process, in order to determine a filtered second differential pressure Δp2,F. The filtering of the second differential pressure Δp2 which is determined by computation is based, like the filtering of the first differential pressure Δp1 which is detected by measuring technology, on a bandpass filtering process which is composed of a digital low-pass filtering process in block 15 and a downstream digital high-pass filtering process in block 16.
A first integral I1 of the filtered first differential pressure Δp1 is determined over time from the first filtered differential pressure Δp1,F in a block 17. In a block 18, a second integral I2 is determined over the time of the filtered second differential pressure Δp2,F.
The synchronization of the two integrals I1 and I2 with one another takes place in a block 19, wherein according to
This delay Δt which is impressed on the second integral I2 is dependent on the operating point of the motor vehicle, in particular on the rotational speed of the internal combustion engine of the motor vehicle and/or on the exhaust gas mass flow {dot over (m)} of the internal combustion engine. The output variable of the block 19 is the second integral I2,S which is synchronized with the first integral I1.
In a block 20, a ratio which corresponds to a loading state B of the particle filter is formed as a function of the two integrals I1 and I2,S which are synchronized with one another. This output variable of the block 20, that is to say the loading state B, can be subjected to a filtering process in a block 21, in order then to make available a filtered loading state BF.
As already stated, the determination of the loading state B or BF of the particle filter is carried out at a second differential pressure Δp2 which is calculated using a differential pressure model.
This differential pressure model for calculating the second differential pressure Δp2 is illustrated in
The second differential pressure Δp2 is preferably determined by computation by means of the following formulas (1) and (2):
where:
The above formula (1) corresponds here to the polynomial of the block 14. The above formula (2) corresponds to the calculation of the volume flow upstream of the particle filter via the blocks 12, 13.
From the above formula (1) it follows that in block 14 the second differential pressure Δp2 is corrected as a function of the temperature-dependent factor X(T). The temperature T is here the temperature of the exhaust gas upstream of the particle filter. This correction factor can be stored in a characteristic curve, a characteristic diagram or a table on the control side.
The determination of the volume flow {dot over (V)} upstream of the particle filter is, according to formula (2), dependent not only on the static pressure pSTAT upstream of the particle filter but, according to the above formula (2), also dependent on the filtered first differential pressure Δp1,F. By this means, ultimately the second differential pressure Δp2 across the particle filter can be advantageously calculated using the differential pressure model.
In the preferred exemplary embodiment shown, the first integral I1 of the filtered first differential pressure Δp1 is weighted in a block 22. The weighting in block 22 is dependent here, in particular, on the operating point of the motor vehicle, preferably on the rotational speed of the internal combustion engine of the motor vehicle and/or on the exhaust gas mass flow {dot over (m)} of the internal combustion engine and/or dependent on the calculated volume flow {dot over (V)} of the exhaust gas upstream of the particle filter.
From
The loading state B in
A plurality of chronological signal profiles are shown plotted against the time tin
The curve profile 28 in
From
Moreover, by selecting corresponding filter values for the blocks 10, 11, 15 and 16 it is also possible to implement a relatively minor phase shift by means of the filtering.
The curve profiles 28 and 29, that is to say the two integrals I1 and I2, are in turn shown at the bottom of
According to one advantageous development of the invention, the loading state B or BF is determined only when the calculated volume flow {dot over (V)} upstream of the particle filter is greater than a limiting value. The curve profile 32 in
As already stated, the blocks 10 and 15 are concerned with the low-pass filtering, and the blocks 11, 16 with the high-pass filtering process of the bandpass filtering process of the respective differential pressure Δp1 and Δp2.
The filter parameters for the high-pass filtering process 11, 16 are kept available in the block 35. The filter parameters for the low-pass filtering process 10, 15 are determined in block 36 in dependence on a characteristic curve, to be precise as a function of the volume flow {dot over (V)} of the exhaust gas upstream of the particle filter which is made available by the block 13.
This volume flow {dot over (V)}, that is to say the output variable of the block 13, is filtered in a block 37, preferably high-pass-filtered, to be precise as a function of a filter constant which is made available by the block 38, wherein the filtered volume flow, that is to say the output variable of the block 37, serves as an input variable for the characteristic diagram or the characteristic curve of the block 36, in order to determine the filter constants for the low-pass filtering processes 10, 15 as a function thereof.
As already stated above, the synchronization of the second integral I2 with the first integral I1 for determining the synchronized second integral I2,S is dependent on the operating state of the motor vehicle, in particular on the rotational speed of the internal combustion engine and/or on the exhaust gas mass flow {dot over (m)} of the internal combustion engine.
In
The arrows or initialization signals 40 are accordingly three corresponding initialization signals, specifically a first initialization signal for the blocks 11, 15, 16, 17, 18, in particular the value “0”, a second initialization signal for the block 21, in particular the value “1”, and an initialization signal for the block 10, which is preferably initialized with the static offset of the differential pressure sensor. The block 41 outputs these initialization signals 40 as output variables.
The initialization of the low-pass filtering process in the block 10 serves to compensate or eliminate the static offset of the differential pressure sensor. In the case of a motor cold start and when an ignition system is activated a current static offset of the differential pressure sensor is stored. If, on the other hand, the ignition process takes place during an engine warm start, the previously stored static offset remains stored. As already stated, when the enable signal 32 is present the initialization is carried out, wherein as described above the low-pass filtering process in the block 10 is initialized with the static offset. The temperature T of the exhaust gas upstream of the particle filter is fed as an input variable to the block 41. Further input variables of the block 41 are an ignition signal Z relating to the activation of the ignition system, the measured first differential pressure Δp1 and the temperature TK which corresponds to the temperature information of the internal combustion engine. Depending on the temperature TK it is possible to decide whether an engine cold start or engine warm start is occurring. The signal Z provides information about the activation of the ignition system. If the ignition system is activated, the static offset of the differential pressure sensor can be determined as a function of the signal Δp1. In order to check whether an engine cold start is occurring, the temperature TK is compared with a threshold value which is made available by the block 42.
The above initialization takes place after the ignition, preferably in a defined sequence. Firstly, the initialization of the block 10 occurs with the static offset of the differential pressure sensor. Subsequently, the initialization of the blocks 11, 15, 16, 17, 18 occurs with the value “0”. Finally, the initialization of the block 21 occurs with the value “1”.
A block 43 in
A block 44 in
A block 46 in
The invention is particularly preferably used to determine the loading state of a spark-ignition particle filter.
While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive. It will be understood that changes and modifications may be made by those of ordinary skill within the scope of the following claims. In particular, the present invention covers further embodiments with any combination of features from different embodiments described above and below.
The terms used in the claims should be construed to have the broadest reasonable interpretation consistent with the foregoing description. For example, the use of the article “a” or “the” in introducing an element should not be interpreted as being exclusive of a plurality of elements. Likewise, the recitation of “or” should be interpreted as being inclusive, such that the recitation of “A or B” is not exclusive of “A and B,” unless it is clear from the context or the foregoing description that only one of A and B is intended. Further, the recitation of “at least one of A, B and C” should be interpreted as one or more of a group of elements consisting of A, B and C, and should not be interpreted as requiring at least one of each of the listed elements A, B and C, regardless of whether A, B and C are related as categories or otherwise. Moreover, the recitation of “A, B and/or C” or “at least one of A, B or C” should be interpreted as including any singular entity from the listed elements, e.g., A, any subset from the listed elements, e.g., A and B, or the entire list of elements A, B and C.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2018 114 779.1 | Jun 2018 | DE | national |
