DE102017205343A1 - Method and control device for determining soot loading of a particulate filter - Google Patents

Abstract

The invention relates to a method for determining a soot load of a particulate filter, which is used in an exhaust aftertreatment system of an internal combustion engine in a motor vehicle, wherein an oxygen content in the exhaust gas upstream and downstream of the particulate filter with a first lambda probe and a second lambda probe is detected.
According to the invention, it is provided that a first oxygen absorption capacity of the particle filter is determined during regeneration of the particle filter, that a second oxygen absorption capacity of the particle filter is determined without regeneration of the particle filter and that the difference between the first and second oxygen absorption capacity, the soot loading of the particulate filter is determined.
The inventive method can be determined without additional facilities and thus cost the loading of a particulate filter, which is installed in the exhaust passage of an internal combustion engine.

Description

State of the art

The invention relates to a method for determining a soot load of a particulate filter, which is used in an exhaust aftertreatment system of an internal combustion engine in a motor vehicle, wherein an oxygen content in the exhaust gas upstream and downstream of the particulate filter with a first lambda probe and a second lambda probe is detected.

The invention further relates to a control device for determining a soot load of a particulate filter in an exhaust aftertreatment system of an internal combustion engine in a motor vehicle, wherein a first lambda probe before the particulate filter and a second lambda probe are arranged thereafter.

An exhaust aftertreatment system of a self-igniting internal combustion engine (diesel engine) usually contains a particle filter for filtering soot particles from the exhaust gas. Due to the accumulation of the soot particles, the exhaust back pressure increases and the particle filter must be regenerated. For this purpose, it is heated to a sufficiently high temperature and oxygen-containing (lean) exhaust gas is supplied.

An exhaust aftertreatment system of a spark-ignited internal combustion engine (gasoline engine) usually consists of a first lambda probe, a three-way catalytic converter and a second lambda probe in the flow direction of the exhaust gas downstream of the internal combustion engine. If necessary, after this another three-way catalyst and optionally a further lambda probe may be arranged. Due to increasingly stringent emission requirements, a gasoline-fueled internal combustion engine may also be provided with a particle filter (Gasoline Particle Filter GPF) in the exhaust gas duct. This can be provided as a separate component before or after the three-way catalyst. Alternatively, a coated particle filter with catalyst properties (coated gasoline particle filter cGPF) may be provided.

For optimal use of the particulate filter, it is advantageous to know its loading with soot particles. This is usually determined by a model from the operating parameters of the internal combustion engine. Alternatively, the differential pressure in the exhaust duct above the particulate filter can be determined. However, this differential pressure determination is only of limited suitability because of the low exhaust gas volumetric flow rate and thus the low exhaust gas back pressure, which are operated with gasoline. Furthermore, the pressure measurement requires additional sensors, resulting in additional costs.

The font DE 10 2011106 933 A1 relates to a method for testing a, in particular used in a gasoline engine, particulate filter for operability, wherein the particulate filter also fulfills the function of a three-way catalyst due to a corresponding coating. The functionality of the catalytic coating is tested and concluded on the ability to function for the separation of particles. In this case, in a jump from fat to lean, the air-fuel ratio is measured and the air ratio determined after the jump. In the case of an undamaged particulate filter, due to the oxygen storage capacity of the coating, the air ratio of unity sets for a certain period of time, and a higher air ratio in case of damage due to leakage. From the extent of deviation from one, one can conclude the extent of damage of the particulate filter.

In contrast to the present application, it is not stated to quantify the oxygen uptake capacity with and without Rußabbrand and to conclude from this on the carbon black loading. Rather, by the in the DE 10 2011106 933 A1 specified method in particular a mechanical damage of the particulate filter.

In Scripture DE 10 2013 218 900 A1 a method for diagnosing a arranged in an exhaust passage of an internal combustion engine particulate filter is specified, wherein upstream of the particulate filter, a catalyst is arranged. The oxygen content of the exhaust gas is determined by means of exhaust gas probes. To diagnose the functionality of the particulate filter, the penetration of fresh air after switching off the internal combustion engine is detected and evaluated via one or more exhaust pipes in the exhaust duct. The oxygen storage capacity of the catalyst is not detected and evaluated in the process.

It is an object of the invention to provide a method which allows an accurate and cost-effective determination of a loading of a particulate filter in the exhaust passage of a spark-ignited internal combustion engine.

It is a further object of the invention to provide a control device suitable for carrying out the method.

Disclosure of the invention

The object of the invention relating to the method is achieved in that a first oxygen absorption capacity of the particle filter during a regeneration of the particulate filter is determined that a second oxygen scavenging ability is determined without regeneration of the particulate filter and that the difference in the first and second oxygen scavenging ability, the soot load of the particulate filter is determined. If the oxygen absorption capacity is determined once with Rußabbrand during a regeneration of the particulate filter and once without Rußabbrand, the difference of the two values of oxygen absorption capacity is just consumed by Rußabbrand oxygen mass. This is a measure of the amount of soot burned and thus of the charge before the regeneration of the particulate filter. The internal combustion engine can be designed as a self-igniting (diesel engine) or spark-ignited (gasoline engine) internal combustion engine.

In a development of the method it is provided that in the exhaust aftertreatment system after the first lambda probe and before the particulate filter, a three-way catalyst is provided that the first oxygen absorption capacity of the combination of three-way catalyst and particulate filter is determined during regeneration of the particulate filter that the second oxygen scavenging capability of the combination is determined without regeneration of the particulate filter and that the soot loading of the particulate filter is determined from the difference in the first and second oxygen scavenging capacities. To determine an oxygen storage capacity of a three-way catalytic converter, it is initially charged with rich exhaust gas in order to empty it of oxygen. In a second process step, the three-way catalyst is charged with lean exhaust gas to fill it with oxygen. The first lambda probe in front of the three-way catalyst is generally designed as a broadband lambda probe and is used to determine the oxygen input into the three-way catalyst in the second process step. The second lambda probe behind the three-way catalyst is used to detect a passage of rich exhaust gas mixture or oxygen in lean exhaust gas mixture to complete the respective process step. The oxygen mass introduced into the three-way catalyst until oxygen passes is referred to as its oxygen storage capability. Carrying out such a determination of the oxygen storage capacity in a combination of three-way catalyst and particulate filter, it is referred to here as "oxygen uptake", since it is the oxygen storage capacity of the three-way catalyst and the oxygen consumption by burning of soot in the particulate filter. If the oxygen absorption capacity is determined once with Rußabbrand during a regeneration of the particulate filter and once without Rußabbrand, the difference of the two values of oxygen absorption capacity is just consumed by Rußabbrand oxygen mass. This is a measure of the amount of soot burned and thus of the charge before the regeneration of the particulate filter. If further lambda probes are provided in the exhaust aftertreatment system, they can also be used to determine the oxygen uptake capacity, whenever one lambda probe is arranged before and another after the particulate filter or the combination of three-way catalyst and particulate filter.

In a variant of the method, in a first process step, the first oxygen absorption capacity is determined at such a high temperature of the particulate filter and / or the three-way catalyst, so that in the first process step regeneration of the particulate filter with Rußabbrand expires and it is in a shortly thereafter second process step, the second oxygen scavenging capacity of the combination of three-way catalyst and particulate filter determined. Thus, in the second step, the oxygen absorption capacity of the particulate filter or the combination of three-way catalyst and particulate filter is determined. In this case, the second method step can be carried out at a similarly high temperature of the three-way catalyst and / or the particle filter as the first method step, since now no Rußabbrand takes place. It can be selected in the second process step, a lower temperature. In any case, the sum of the oxygen uptake capacity of the three-way catalyst (if present) and the oxygen consumption during Rußabbrand is determined in the first process step. In the second process step, only the oxygen uptake capacity of the three-way catalyst is determined. The difference between the first and second oxygen absorption capacity can thus be determined as the oxygen consumption during soot combustion. This depends on the burned soot loading of the particulate filter, which can thus be determined. In this process variant, it makes sense that the process steps follow each other so briefly that in the meantime, no significant amount of soot can deposit in the particulate filter.

A further variant of the method provides that, in a first method step, the second oxygen absorption capacity is determined at such a low temperature of the particulate filter and / or the three-way catalyst that no regeneration of the particulate filter with Rußabbrand runs and that in a second step, the first oxygen Absorbency at such a high temperature of the particulate filter and / or the three-way catalyst is determined that a regeneration of the particulate filter with Rußabbrand runs. In this variant as well, the difference between the first and second oxygen absorption capacity results in the oxygen consumption during soot combustion.

The accuracy of the method can be improved by determining influences of an exhaust gas mass flow and / or a temperature dependence of the oxygen uptake capacity and / or a temperature of the exhaust gas rising by the soot burn-off or of components in the exhaust gas duct when determining the first and second oxygen absorption capacity be taken into account.

In one embodiment of the method it is provided that the soot loading of the particulate filter is used to correct a model for soot loading of the particulate filter. The model can be used to make a prediction of the current soot load without having to check it in any case with a follow-up test with regeneration with soot burn-off. However, the model can be checked and adjusted at any time during operation.

The object of the invention relating to the control device is achieved by providing in the control device a program sequence or circuit for determining a first oxygen absorption capacity of the particle filter during a regeneration of the particle filter and a second oxygen absorption capacity without regeneration of the particle filter and from the difference the first and second oxygen scavenging capacity is provided a determination of the soot loading of the particulate filter. The control device can be realized in a particularly cost-effective manner since, apart from the lambda probes provided in the exhaust duct, no further devices, such as, for example, pressure sensors or differential pressure sensors, are required.

In one embodiment of the control device it is provided that after the first lambda probe and before the particulate filter, a three-way catalyst is provided that the program sequence or circuit for determining an oxygen absorption capacity of the three-way catalyst is provided by exposure to lean and rich exhaust gas, in the control device, a further program sequence or circuit for determining a first oxygen absorption capacity of the combination of three-way catalyst and particle filter during a regeneration of the particulate filter and a second oxygen absorption capacity of the combination without regeneration of the particulate filter is provided and that of the difference of the first and second oxygen scavenging ability, a determination of the soot loading of the particulate filter is provided. In particular, in spark-ignited internal combustion engines with low exhaust gas flow rate at which a differential pressure measurement on the particulate filter is inaccurate due to the low exhaust backpressure, a determination of the soot load of the particulate filter with high accuracy is possible.

• 1 in einer schematischen Darstellung das technische Umfeld, in der das erfindungsgemäße Verfahren angewendet werden kann.

The invention will be explained in more detail below with reference to an embodiment shown in the figure. It shows:

• 1 in a schematic representation of the technical environment in which the inventive method can be applied.

1 schematically shows the technical environment in which the method according to the invention can be applied. An internal combustion engine 10 , which is designed as externally ignited gasoline engine (gasoline engine), gets combustion air via an air supply 11 fed. In this case, the air mass of the combustion air by means of an air mass meter 12 in the air supply 11 be determined. The supplied air mass serves to determine the amount of fuel to be metered at a lambda value to be preselected. Furthermore, exhaust gas parameters, in particular an exhaust gas mass flow and, derived therefrom, an exhaust gas mass are determined with the aid of the air mass. The exhaust gas of the internal combustion engine 10 is via an exhaust duct 15 dissipated, in which a three-way catalyst 16 and a particulate filter 17 (Gasoline Particle Filter GPF) are arranged. Furthermore, in the exhaust passage 15, a first lambda probe 14 in front of the three-way catalyst 16 and a second lambda probe 18 after the particle filter 17 arranged, the signals of which are supplied to a control device 20. The first lambda probe 14 is generally designed as a broadband lambda probe. The second lambda probe is generally designed as a jump lambda probe. The control device 20 continues to be the signal of the mass air flow sensor 12 fed. Based on the calculated air mass and the signals of the lambda probes 14 . 17 is in the controller 20 The fuel mass determined over a fuel dosage 13 the internal combustion engine 10 is supplied. The control device 20 contains for this purpose a pilot control and a control device for regulating the composition of the air-fuel mixture based on the signals of the lambda probes 14 . 18 , Instead of the three-way catalyst 16 and the particulate filter 17 For example, a coated particulate filter with three-way catalyst properties may also be used. These components are also referred to as "coated gasoline particle filters (cGPF)".

To determine the loading of the particulate filter 17 becomes the oxygen uptake capacity of the combination of three-way catalyst 16 and particle filters 17 once with regeneration of the particulate filter 17 and once without regeneration of the particulate filter 17 certainly. Here, a known method for determining the oxygen storage ability of a three-way catalyst 16 used, in which the three-way catalyst 16 is first charged with rich exhaust gas to empty it of oxygen. In a second process step, the three-way catalyst 16 with lean Exhaust gas applied to fill it with oxygen. The first lambda probe 14 before the three-way catalyst 16 is used to determine the oxygen input, the second lambda probe 18 behind the particle filter 17 is used to detect passage of oxygen to stop filling. The oxygen mass introduced into the three-way catalyst 16 until oxygen passes is referred to as its oxygen storage capability. Performing such a determination of the oxygen storage capacity on a combination of the three-way catalyst 16 and the particulate filter 17 (then referred to as oxygen uptake) once with Rußabbrand and once without Rußabbrand in the particle filter 17 by, the difference of the two values of the oxygen absorption capacity is just the oxygen mass consumed by the Rußabbrand. This is a measure of the amount of soot burned and thus of the charge before the regeneration of the particulate filter 17 ,

1. 1. Zunächst die Sauerstoff-Aufnahmefähigkeit bei einer so niedrigen Temperatur des Dreiwege-Katalysators 16 und/oder des Partikelfilters 17 durchgeführt wird, dass kein Rußabbrand zu erwarten ist. In einem zweiten Schritt wird die Sauerstoff-Aufnahmefähigkeit bei einer so hohen Temperatur des Dreiwege-Katalysators 16 und/oder des Partikelfilters 17 durchgeführt, dass Rußabbrand zu erwarten ist.
2. 2. In einem ersten Schritt die Sauerstoff-Aufnahmefähigkeit bei einer so hohen Temperatur des Dreiwege-Katalysators 16 und/oder des Partikelfilters 17 durchgeführt wird, dass Rußabbrand zu erwarten ist. In dem zweiten Schritt kann die Sauerstoff-Aufnahmefähigkeit bei einer ähnlich hohen Temperatur des Dreiwege-Katalysators 16 und/oder des Partikelfilters 17 durchgeführt werden, da kein Rußabbrand mehr stattfinden kann. Sinnvollerweise sollten diese Messungen so kurz aufeinander erfolgen, dass in der Zwischenzeit kein nennenswerter neuer Ruß in den Partikelfilter eingetragen werden kann.

The two levels of oxygen uptake can be determined by:

1. 1. First, the oxygen-absorbing capacity at such a low temperature of the three-way catalyst 16 and / or the particulate filter 17 is carried out that no Rußabbrand is expected. In a second step, the oxygen uptake becomes so high at the temperature of the three-way catalyst 16 and / or the particulate filter 17 carried out that Rußabbrand is expected.
2. 2. In a first step, the oxygen uptake at such a high temperature of the three-way catalyst 16 and / or the particulate filter 17 is carried out that Rußabbrand is expected. In the second step, the oxygen uptake capability may be at a similarly high temperature of the three-way catalyst 16 and / or the particulate filter 17 be carried out because no Rußabbrand can take place. It makes sense to make these measurements so close to each other that in the meantime no significant new soot can be introduced into the particulate filter.

In the measurements, overlapping effects such as a dependence of the oxygen absorption capacity on the exhaust gas mass flow, an exhaust gas temperature and an increase in the temperatures of the exhaust gas and particulate filter 17 considered in Rußabbrand to improve the accuracy of the method for determining the soot loading of the particulate filter.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102011106933 A1 [0006, 0007]
• DE 102013218900 A1 [0008]

Claims (8)

A method for determining a soot load of a particulate filter (17) which is used in an exhaust aftertreatment system of an internal combustion engine (10) in a motor vehicle, wherein an oxygen content in the exhaust upstream and downstream of the particulate filter (17) with a first lambda probe (14) and a second lambda probe (18) is detected, characterized in that a first oxygen absorption capacity of the particulate filter (17) during regeneration of the particulate filter (17) is determined that a second oxygen scavenging ability without regeneration of the particulate filter (17) is determined and that from Difference of the first and second oxygen absorption capacity soot loading of the particulate filter (17) is determined. Method according to Claim 1 , characterized in that in the exhaust aftertreatment system after the first lambda probe (14) and before the particulate filter (17) a three-way catalyst (16) is provided, that the first oxygen absorption capacity of the combination of three-way catalyst (16) and particulate filter ( 17) during regeneration of the particulate filter (17), it is determined that the second oxygen scavenging capability of the combination is determined without regeneration of the particulate filter (17), and that the difference in the first and second oxygen scavenging capacities determines the soot loading of the particulate filter (17) becomes. Method according to Claim 1 or 2 , characterized in that in a first process step, the first oxygen absorption capacity at such a high temperature of the particulate filter (17) and / or the three-way catalyst (16) is determined that in the first process step, a regeneration of the particulate filter (17) Rußabbrand expires and that in a second step shortly after the second oxygen uptake capacity of the particulate filter (17) or the combination of three-way catalyst (16) and particulate filter (17) is determined. Method according to one of Claims 1 to 3 , characterized in that in a first method step, the second oxygen absorption capacity at such a low temperature of the particulate filter (17) and / or the three-way catalyst (16) is determined that no regeneration of the particulate filter (17) proceeds with Rußabbrand and that in a second step, the first oxygen absorption capacity at such a high temperature of the particulate filter (17) or the combination of three-way catalyst (16) and particulate filter (17) is determined that a regeneration of the particulate filter (17) proceeds with Rußabbrand. Method according to one of Claims 1 to 4 , characterized in that in the determination of the first and second oxygen absorption capacity influences of an exhaust gas mass flow and / or a temperature dependence of the oxygen absorption capacity and / or increasing by the Rußabbrand temperature of the exhaust gas or components are considered in the exhaust duct. Method according to one of Claims 1 to 5 characterized in that the soot loading of the particulate filter (17) is used to correct a model for soot loading of the particulate filter (17). Control device (20) for determining a soot load of a particulate filter (17) in an exhaust aftertreatment system of an internal combustion engine (10) in a motor vehicle, wherein a first lambda probe (14) before the particulate filter (17) and a second lambda probe (18) are arranged thereafter, characterized characterized in that a program sequence or circuit for determining a first oxygen absorption capacity of the particulate filter (17) during regeneration of the particulate filter (17) and a second oxygen scavenging capacity without regeneration of the particulate filter (17) is provided in the control device (20) and that a determination of the soot loading of the particulate filter (17) is provided from the difference of the first and second oxygen absorption capacity. Control device (20) after Claim 7 , characterized in that after the first lambda probe (14) and before the particulate filter (17) a three-way catalyst (16) is provided, that the program sequence or circuit for determining an oxygen absorption capacity of the three-way catalyst (16) by applying lean and with rich exhaust gas is provided that in the control device (20) another program sequence or circuit for determining a first oxygen absorption capacity of the combination of three-way catalyst (16) and particulate filter (17) during regeneration of the particulate filter (17) and a second oxygen-absorbing capacity of the combination without regeneration of the particulate filter (17) is provided and that from the difference of the first and second oxygen absorption capacity, a determination of the soot loading of the particulate filter (17) is provided.

Images