DE102016202349A1 - Method and device for exhaust aftertreatment of an internal combustion engine - Google Patents

Abstract

The invention relates to a method for treating exhaust gas of an internal combustion engine (10) with an exhaust gas duct (12), a catalytic converter (14) arranged in the exhaust duct (12), a lambda probe (20) arranged in the exhaust duct (12) and heatable by a heating element (16) ) and with a particle filter (18, 26), comprising the following steps: - Determining a loading state of the particulate filter (18, 26), - Determining an exhaust gas temperature in the exhaust passage (12) of the internal combustion engine (10) by measuring the internal resistance RI of the first lambda probe ( 20), - determination of an oxygen content in the exhaust gas by the first lambda probe (20), - initiation of a regeneration of the particulate filter (18, 26), if a corresponding load state is reached, the temperature (TA) in the exhaust duct (12) and the combustion air ratio ( λE) of the internal combustion engine (10) in a for a regeneration of the particulate filter (18, 26) predefined range, - avoiding the Einleitu ng a regeneration by appropriate engine measures, if the temperature (TA) in the exhaust passage (12) and / or the oxygen content in the exhaust gas above certain defined limits, - conditioning of the particulate filter (18, 26) for regeneration by introducing appropriate engine measures when the temperature in the exhaust duct (12) is below a defined threshold. The invention further relates to a device for carrying out such a method.

Description

The invention relates to a method and a device for exhaust aftertreatment of an internal combustion engine according to the preambles of the independent claims.

The continuous tightening of the exhaust emission legislation places high demands on the vehicle manufacturers, which are solved by appropriate measures for the reduction of the engine raw emissions and by a corresponding exhaust aftertreatment. With the introduction of the next legislative level EU6, a limit for a number of particles is prescribed for gasoline engines. This may mean that some models may require the use of an Ottoparticle filter. When driving, such a gasoline particulate filter is loaded with soot. So that the exhaust gas backpressure does not increase too much, this Otto particle filter must be regenerated continuously or periodically. In order to carry out a thermal oxidation of the soot retained in the Otto particle filter with oxygen, a sufficiently high temperature level in conjunction with simultaneously existing oxygen in the exhaust system of the gasoline engine is necessary. Since modern gasoline engines are normally operated without oxygen surplus with a stoichiometric combustion air ratio (λ _E = 1), additional measures are required. These come as measures, for example, a temperature increase by a Zündwinkelverstellung, a temporary lean adjustment of the gasoline engine, the injection of secondary air into the exhaust system or a combination of these measures in question. The regeneration of a particulate filter is for example from DE 10 2013 220 899 A1 known. In this case, a lambda control is provided for the gasoline engine, wherein the combustion air ratio is adjusted for the regeneration of the particulate filter, starting from a stoichiometric combustion air ratio in the direction of a superstoichiometric combustion air ratio, and with the oxygen excess regeneration of the particulate filter is achieved by oxidizing the soot. However, under certain unfavorable operating conditions, namely when a high temperature in the exhaust gas channel and an excess of oxygen prevail at the same time, uncontrolled combustion of the soot on the particle filter and thus damage to the component may occur.

For lambda control of the internal combustion engine lambda probes are used, which can be heated to increase the measurement accuracy by means of a heating element to bring the lambda probe to a predefined temperature. Such a temperature control of a lambda probe can be done for example by means of a temperature sensor in the exhaust duct. However, such a temperature sensor is connected as an additional component with additional costs. Therefore, solutions have already been proposed in the past in which the exhaust gas temperature is determined from a resistance or a change in resistance of the lambda probe.

From the DE 10 2008 011 833 A1 a method is known for controlling a lambda-controlled exhaust system of an internal combustion engine, wherein the exhaust system has at least one catalytic converter and at least one heating element for heating the lambda probe to an operating temperature. It is envisaged that the performance of the heating element is determined and at least one corrected control parameter is used by the heating element control for controlled heating of the heating element.

The invention is based on the object to facilitate a facilitated regeneration of the particulate filter and component damage of components for exhaust aftertreatment, in particular damage to the particulate filter to avoid.

• – Ermittlung eines Beladungszustandes des Partikelfilters,
• – Ermittlung einer Abgastemperatur im Abgaskanal des Verbrennungsmotors durch eine Messung des Innenwiderstandes der Lambdasonde,
• – Ermittlung eines Sauerstoffgehaltes im Abgas durch die Lambdasonde,
• – Einleitung einer Regeneration des Partikelfilters, wenn ein entsprechender Beladungszustand erreicht ist, die Temperatur im Abgaskanal und das Verbrennungsluftverhältnis des Verbrennungsmotors in einem für eine Regeneration des Partikelfilters vordefinierten Bereich liegen,
• – Vermeidung der Einleitung einer Regeneration durch entsprechende motorische Maßnahmen, wenn die Temperatur im Abgaskanal und/oder der Sauerstoffgehalt im Abgas oberhalb bestimmter, definierter Grenzen liegen,
• – Konditionierung des Partikelfilters für eine Regeneration durch Einleitung entsprechender motorischer Maßnahmen, wenn die Temperatur im Abgaskanal unterhalb eines definierten Schwellenwertes liegt.

According to the invention, this object is achieved by a method for exhaust aftertreatment of an internal combustion engine having an exhaust gas channel, a catalyst arranged in the exhaust gas channel, a lambda probe which is arranged in the exhaust gas channel and can be heated by means of a heating element, and which comprises the following steps:

• Determination of a loading state of the particulate filter,
• Determining an exhaust gas temperature in the exhaust passage of the internal combustion engine by measuring the internal resistance of the lambda probe,
• Determination of an oxygen content in the exhaust gas by the lambda probe,
• Initiation of a regeneration of the particulate filter, when a corresponding loading state is reached, the temperature in the exhaust passage and the combustion air ratio of the internal combustion engine are in a predefined for a regeneration of the particulate filter area,
• Avoiding the initiation of regeneration by means of corresponding engine measures, when the temperature in the exhaust gas channel and / or the oxygen content in the exhaust gas are above defined limits,
• - Conditioning of the particulate filter for regeneration by introducing appropriate engine measures when the temperature in the exhaust duct is below a defined threshold.

This can advantageously a combined measurement of the oxygen content in Exhaust duct and the exhaust gas temperature made so that both parameters are determined by means of a component. Thereby, the reliability of the measurement can be improved and thus the process for the regeneration of the particulate filter can be initiated more easily. In addition, by the parallel measurement of oxygen content and temperature increased component protection of components in the exhaust passage of the internal combustion engine is given because unfavorable operating conditions that can lead to an uncontrolled increase in exhaust gas temperature can be detected. In this case, an additional temperature sensor omitted in the exhaust duct, which reduces the cost.

According to a preferred embodiment of the method, it is provided that, at a temperature above a threshold value in the exhaust gas duct, a coasting operation of the internal combustion engine is prevented. This prevents fresh air from being pumped through the cylinders of the internal combustion engine into the exhaust gas duct and thus sufficient oxygen being available to lead to an uncontrolled burnup of the soot on the particulate filter. In this way, an undesirable excess of oxygen in the exhaust duct can be avoided, which favors an uncontrolled Rußabbrand.

In a preferred embodiment of the method according to the invention, it is provided that, when the temperature in the exhaust gas duct is too high, the ignition angle of the internal combustion engine is adjusted in the "early" direction. By adjusting the firing angle in the "early" direction, combustion of the fuel may begin earlier and is substantially complete when the exhaust valves open. As a result, the temperature in the exhaust passage of the internal combustion engine decreases, whereby the temperature can drop back into the favorable for a regeneration of the particulate filter area and thermal damage to the particulate filter is avoided.

According to an alternative embodiment of the method according to the invention, it is provided that an increase in the exhaust gas temperature takes place by an adjustment of the ignition angle of the internal combustion engine in the direction of late. By adjusting the ignition angle in the direction of "late" the combustion starts later and is not completed when the exhaust valves are opened, so that the temperature increases in the exhaust duct.

According to a preferred further development of the method, it is provided that the heating element of the lambda probe is deactivated during the regeneration of the particulate filter. Thereby, a simplified measurement of the internal resistance of the lambda probe and based on a calculation of the exhaust gas temperature during the regeneration of the particulate filter is possible.

For efficient regeneration of the particulate filter without the risk of thermal component damage, it is advantageous if the regeneration of the particulate filter takes place in a temperature range between 600 ° C. and 700 ° C. and at a combustion air ratio λ _{E of} the internal combustion engine between 1.1 and 1.3. In order to enable efficient oxidation of the soot retained in the particle filter and thus regeneration of the particle filter, the temperature at the inlet to the particle filter should be at least 600 ° C. in order to achieve a significant rate of carbon black turnover. Furthermore, this oxidation should be carried out with a slight excess of oxygen in the exhaust gas channel in order to provide sufficient oxygen for the oxidation of the soot particles, but to avoid a high excess of oxygen and thus the risk of uncontrolled Rußabbrandes.

According to the invention, a device for exhaust aftertreatment of an internal combustion engine is proposed, which comprises an exhaust duct, a catalyst arranged in the exhaust duct, a particulate filter arranged in the exhaust duct and a control device, wherein in the flow direction of the exhaust gas downstream of the catalyst and upstream of the particulate filter, a first lambda sensor is arranged, by means the first lambda probe, an oxygen content in the exhaust gas is measured, wherein the first lambda probe is heated via a heating element, wherein by means of an internal resistance of the first lambda probe, a temperature in the exhaust duct, preferably immediately before entering the particulate filter, can be determined, and based on this information a Regeneration of the particulate filter can be prevented to prevent uncontrolled Rußabbrand on the particulate filter.

In a preferred embodiment, a first catalyst, preferably a close-coupled primary catalyst and a second catalyst are arranged in the exhaust passage, the second catalyst as a so-called four-way catalyst, ie as a three-way catalyst with additional particulate filter function, especially as a particulate filter with three Path-effective catalytic coating is formed. In a preferred embodiment, upstream of the first catalytic converter, a second lambda probe, in particular a broadband lambda probe, and upstream of the four-way catalytic converter, a first lambda probe are arranged, the first lambda probe being designed as a jump probe. At least the first lambda probe is heatable. A particle filter with three-way effective catalytic coating is compared with an uncoated particulate filter in a regeneration thermally more stressed, since here the Exothermic reaction of Rußabbrands and superimpose the exothermic catalytic reaction of the three-way catalyst. Therefore, the inventive device for exhaust aftertreatment is particularly preferably provided in exhaust systems with four-way catalyst.

According to a preferred embodiment, it is provided that the catalyst comprises a precatalyst and a main catalyst, wherein the lambda probe is arranged downstream of the precatalyst or upstream of the postcatalyst. By arranging the lambda probe between the precatalyst and the postcatalyst, the lambda probe serves to adjust an overall lambda control in the exhaust gas duct. The post-catalyst is a so-called four-way catalyst and is used in addition to the conversion of gaseous pollutants for the filtration of solid pollutants.

Preferably, the particulate filter is arranged in a bottom layer of a motor vehicle. In a subfloor position, a remote engine arrangement of the particulate filter is possible, so that the particulate filter is thermally less heavily loaded. In addition, an underfloor layer makes it possible to achieve radiative and convective heat removal at the particle filter in comparison to installation in the engine compartment. An arrangement remote from the engine in this context means an arrangement at least 80 cm, preferably at least 100 cm, downstream of an outlet of the internal combustion engine. Improved heat dissipation at the particle filter can reduce the risk of thermal damage, in particular during regeneration of the particle filter.

Further preferred embodiments of the invention will become apparent from the remaining, mentioned in the dependent claims characteristics.

The various embodiments of the invention mentioned in this application are, unless otherwise stated in the individual case, advantageously combinable with each other.

The invention will be explained below in embodiments with reference to the accompanying drawings. Show it:

1 an internal combustion engine with an exhaust gas aftertreatment device according to the invention,

2 a flowchart for carrying out a method according to the invention for the exhaust aftertreatment of an internal combustion engine,

3 an alternative embodiment of an inventive device for the exhaust aftertreatment of an internal combustion engine.

1 shows a device according to the invention for the exhaust aftertreatment of an internal combustion engine 10 , The device includes one with the internal combustion engine 10 connected exhaust duct 12 in which in the flow direction of an exhaust gas of the internal combustion engine 10 through the exhaust duct 12 a second lambda probe 30 , a precatalyst 24 , a first lambda probe 20 and an aftercatalyst 28 in the form of a particle filter with three-way catalytic coating 26 are arranged. The precatalyst 24 is designed as a three-way catalyst, the post-catalyst 28 is as a four-way catalyst, so as a particle filter with a three-way effective catalytic coating 26 , educated. Alternatively, as in 3 represented an uncoated particulate filter 18 be used. The internal combustion engine 10 and the lambda probes 20 . 30 are each via signal lines to a controller 22 for controlling the internal combustion engine 10 connected. At the first lambda probe 20 is a heating element 16 provided with which the first lambda probe 20 can be brought to an operating temperature. This is an unillustrated heating controller, which, for example, in the control unit 22 can be integrated, provided, via which the temperature of the lambda probe 20 can be adjusted to a predefined operating temperature.

Temperature measurements in the exhaust duct 12 provide important information about the condition of the exhaust system. Thus, for example, protective measures against overheating of components of the exhaust aftertreatment, in particular of a catalyst 14 or a particle filter 18 . 26 , by a corresponding control of the internal combustion engine 10 as a function of the temperature T _A in the exhaust duct 12 to be hit.

In exhaust systems with two catalysts 14 , Especially with a close-coupled pre-catalyst 24 and a arranged in the bottom layer of a motor vehicle Nachkatalysator 26 serves the first lambda probe 20 , which is designed as a jump lambda probe, for adjusting the overall lambda control in the exhaust duct 12 , This first lambda probe 20 is downstream of the precatalyst 24 and upstream of the postcatalyst 28 , The probe temperature of the first lambda probe 20 can through the control unit 22 either controlled or regulated. In this case, the internal resistance of the first lambda probe 20 together with an applied heating voltage and possibly other parameters, such as measured ambient conditions, are used to correlate with the exhaust gas temperature manufacture. About this measure, the downstream of the first lambda probe 20 lying second catalyst 28 and / or the particulate filter 18 . 26 be protected against overheating.

In operation of the internal combustion engine 10 becomes the particle filter 18 . 26 loaded with soot particles, so that the flow resistance in the exhaust passage 12 increases with the load. This particle filter 18 . 26 must be regenerated periodically. For an application of a particle filter 18 . 26 in the exhaust duct 12 a spark-ignited internal combustion engine 10 in underfloor position of a motor vehicle high demands are placed on the component protection of the particulate filter 18 . 26 , in particular during a regeneration of the particulate filter 18 . 26 , posed. The exhaust gas temperature T _A must not exceed a certain threshold during regeneration, so that the particulate filter 18 . 26 no thermal damage is experienced and the particulate filter 18 . 26 by an exothermic combustion reaction of the soot on the particulate filter 18 . 26 not destroyed.

By using a first lambda probe 20 upstream of, preferably installed in the bottom layer of a motor vehicle, particulate filter 18 . 26 can monitor the heating power and the internal resistance of the first lambda probe 20 used to determine the temperature of the exhaust gas when entering the particulate filter 18 . 26 to determine and if necessary by means of the control unit 22 such influence on the operation of the internal combustion engine 10 to take that of the particle filter 18 . 26 is protected from overheating.

Here is the internal resistance of the first lambda probe 20 proportional to the temperature of the first lambda probe 20 , The higher the temperature of the first lambda probe 20 is, the lower is their internal resistance. The heating of the first lambda probe 20 happens during operation of the internal combustion engine 10 both by the hot exhaust gas of the internal combustion engine 10 as well as through the heating element 16 , which preferably as a heating resistor, in particular as in the first lambda probe 20 integrated heating wire, is formed. The operating temperature of the first lambda probe 20 is precisely defined and is applied via a control or regulation for all occurring exhaust gas temperatures. The more heat over the exhaust gas to the first lambda probe 20 is discharged, the lower is the over the heating element 16 introduced heating power.

In the case of a regeneration request of the particulate filter 18 . 26 high exhaust gas temperatures in the range of> 600 ° C are required to those in the particulate filter 18 . 26 to burn off retained carbon black. This oxidation reaction is in the particulate filter 18 . 26 An exothermic reaction is started, which in turn passes through the particulate filter 18 . 26 causes a temperature increase. This is particularly critical for a particulate filter with three-way effective catalytic coating 26 because this is where the exothermic reactions of Rußabbrands and the three-way effective catalytic coating overlap. This temperature rise can be harmful to the particulate filter 18 . 26 act when it exceeds defined limits. Therefore, the input enthalpy, ie the temperature at the inlet to the particle filter, may be 18 . 26 , do not exceed a certain threshold.

For regeneration of the particle filter 18 . 26 and to burn off the soot can now the heating element 16 be disabled to the first lambda probe 20 exclusively via the exhaust gas of the internal combustion engine 10 to heat. In this case, the internal resistance of the first lambda probe 20 measured, and from the internal resistance of the first lambda probe 20 on the exhaust gas temperature in the exhaust duct 12 closed. Based on this measurement can then by the control unit 22 Measures for component protection of the particle filter 18 . 26 be initiated. As measures are, for example, an adjustment of the ignition angle of the engine 10 in the direction of "early" and / or an adjustment of the injection quantity or the injection time of the fuel injection.

The lambda sensors deliver 20 . 30 not just information about the temperature T _A in the exhaust duct 12 , but also about the exhaust gas composition and the oxygen content in the exhaust gas. For the regeneration of the particle filter 18 . 26 In addition to the temperature, the amount of residual oxygen in the exhaust gas is also relevant. The supply of a large amount of fresh air in a hot particulate filter 18 . 26 as well as too high a temperature can damage the component of the particle filter 18 . 26 lead, as in this case, an uncontrolled burning of the soot on the particulate filter 18 . 26 can come. As a further protective measure, via the lambda probes 20 . 30 is controlled, for example, a suppression of a fuel cut of the internal combustion engine 10 to be hit.

In 2 is a flowchart of a method according to the invention for the exhaust aftertreatment of an internal combustion engine 10 shown.

In a first step < 100 > becomes a loading condition of the particulate filter 18 . 26 determines what, for example, a differential pressure measurement over the particulate filter 18 . 26 or via a modeling of the soot entry and Rußaustrags from the particulate filter 18 . 26 can be done. In a further process step < 110 > is the temperature T _A in the exhaust duct 12 of the internal combustion engine 10 by a measurement of the internal resistance of the first lambda probe 20 determined. In another Process step < 120 > the oxygen content in the exhaust duct becomes 12 through at least one of the lambda probes 20 . 30 determined. The process steps < 100 >, < 110 > and < 120 > in parallel or in any order.

Dependent on the measured values of the method steps < 100 >, < 110 > and < 120 > becomes in a following process step < 140 > a regeneration of the particulate filter 18 . 26 initiated when a corresponding load condition of the particulate filter 18 . 26 is reached and the temperature T _A in the exhaust duct 12 as well as the oxygen concentration in the exhaust gas channel 12 in one for a regeneration of the particulate filter 18 . 26 predefined range lie.

If the temperature T _A in the exhaust duct 12 Below this predefined range, in particular below a defined threshold value T _SU , in an upstream method step < 130 > the particle filter 18 . 26 preconditioned by the introduction of appropriate engine measures and the exhaust gas temperature in the for a regeneration of the particulate filter 18 . 26 necessary area raised.

Is the temperature in the exhaust channel 12 above certain defined limits, in particular above a threshold value T _SO , in a method step < 150 > a regeneration of the particulate filter 18 . 26 avoided by the introduction of appropriate engine measures to thermal damage to the particulate filter 18 . 26 to avoid.

3 shows an alternative embodiment of a device according to the invention for the exhaust aftertreatment of an internal combustion engine 10 , With substantially the same structure as in the embodiment according to 1 is used instead of a particulate filter with three-way catalytically active coating 26 an uncoated particle filter 18 used. The first catalyst 14 is designed here as a close-coupled three-way catalyst.

LIST OF REFERENCE NUMBERS

10

internal combustion engine

12

exhaust duct

14

catalyst

16

heating element

18

particulate Filter

20

first lambda probe (before particle filter)

22

control unit

24

precatalyzer

26

Particulate filter with integrated aftercatalyst

28

post-catalytic converter

30

second lambda probe (pre-catalyst)

λ _E

Combustion air ratio

T _A

exhaust gas temperature

_SO

upper threshold

T _SU

lower threshold

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 102013220899 A1 [0002]
• DE 102008011833 A1 [0004]

Claims (10)

Method for exhaust aftertreatment of an internal combustion engine ( 10 ) with an exhaust duct ( 12 ), one in the exhaust passage ( 12 ) arranged catalyst ( 14 ), one in the exhaust duct ( 12 ), by means of a heating element ( 16 ) heated first lambda probe ( 20 ) as well as with a particle filter ( 18 . 26 ), comprising the following steps: - determination of a loading state of the particulate filter ( 18 . 26 ), - determination of an exhaust gas temperature in the exhaust duct ( 12 ) of the internal combustion engine ( 10 ) by measuring the internal resistance R _{i of} the first lambda probe ( 20 ), - determination of an oxygen content in the exhaust gas by the first lambda probe ( 20 ), - initiation of a regeneration of the particulate filter ( 18 . 26 ), when a corresponding loading state is reached, the temperature (T _A ) in the exhaust duct ( 12 ) and the combustion air ratio (λ _E ) of the internal combustion engine ( 10 ) in one for a regeneration of the particulate filter ( 18 . 26 ) predefined area, - avoiding the initiation of a regeneration by appropriate motor measures when the temperature (T _A ) in the exhaust gas channel ( 12 ) and / or the oxygen content in the exhaust gas are above certain, defined limits, - conditioning of the particulate filter ( 18 . 26 ) for regeneration by introducing appropriate engine measures when the temperature in the exhaust gas channel ( 12 ) is below a defined threshold. A method according to claim 1, characterized in that at a temperature (T _A ) in the exhaust duct ( 12 ) above a threshold value, a coasting operation of the internal combustion engine ( 10 ) is prevented. A method according to claim 1 or 2, characterized in that at too high temperatures (T _A ) in the exhaust duct ( 12 ) the ignition angle of the internal combustion engine ( 10 ) is adjusted in the direction of "early". Method according to one of claims 1 to 3, characterized in that during the regeneration of the particulate filter ( 18 . 26 ) the heating element ( 16 ) of the first lambda probe ( 20 ) is deactivated. Method according to one of claims 1 to 4, characterized in that an increase in the exhaust gas temperature (T _A ) by adjusting the ignition angle in the direction of "late". Method according to one of claims 1 to 5, characterized in that a regeneration of the particulate filter ( 18 . 26 ) in a temperature range of 600 ° to 700 ° and at a combustion air ratio (λ _E ) of the internal combustion engine ( 10 ) in the range 1.1 <λ _E <1.3. Device for exhaust aftertreatment of an internal combustion engine ( 10 ), with an exhaust duct ( 12 ), one in the exhaust duct ( 12 ) arranged catalyst ( 14 ), one in the exhaust duct ( 12 ) arranged particulate filter ( 18 . 26 ), by means of a heating element ( 16 ) heated first lambda probe ( 20 ) for controlling a combustion air ratio (λ _E ) of the internal combustion engine ( 10 ), as well as with a control unit ( 22 ), characterized in that the control unit ( 22 ) is arranged to perform a method according to one of claims 1 to 6. Aftertreatment device according to claim 7, characterized in that the particulate filter ( 18 ) as a particle filter with catalytically active coating ( 26 ) is trained. Aftertreatment device according to one of claims 7 or 8, characterized in that the catalyst ( 14 ) a precatalyst ( 24 ) and an aftercatalyst ( 28 ), wherein the first lambda probe ( 20 ) downstream of the precatalyst ( 24 ) and upstream of the particulate filter ( 26 ) is arranged. Device for exhaust gas aftertreatment according to one of claims 7 to 9, characterized in that a second lambda probe upstream of the precatalyst ( 24 ) is provided.

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