Patent Grant
11346267
This application is a U.S. National Stage Application of International Application No. PCT/EP2018/082357 filed Nov. 23, 2018, which designates the United States of America, and claims priority to DE Application No. 10 2018 215 627.1 filed Sep. 13, 2018, and DE Application No. 10 2017 221 358.2 filed Nov. 29, 2017, the contents of which are hereby incorporated by reference in their entirety.
The present disclosure relates to internal combustion engines. Various embodiments of the teachings herein include methods for operating an exhaust-gas aftertreatment system of internal combustion engines, e.g. diesel engines, which exhaust-gas aftertreatment system has a combined SCR particle filter arranged in an exhaust-gas line and has a device for targeted, defined variation of the NH3 and/or NOX concentration in the exhaust-gas mass flow upstream of the SCR particle filter.
In particular vehicles with diesel internal combustion engines (diesel engine), but increasingly also vehicles with Otto-cycle internal combustion engines (gasoline engine), nowadays there may be a particle filter (DPF, PF) for the purposes of avoiding particles (soot, fine dust) in the exhaust-gas emissions and also a so-called SCR catalytic converter (catalytic converter with selective reduction) for the purposes of reducing the NOX fraction in the exhaust-gas emissions. In some examples, a combined filter catalytic converter, hereinafter referred to as SCR particle filter or denoted by the abbreviation SC-PF, is a particle filter with SCR function, that is to say a particle filter which has an additional coating composed of an NOX/NH3 conversion material. In other words, it is therefore a particle filter with an integrated SCR function.
In the case of an SCR catalytic converter, NH3 (ammonia) is formed by adding an aqueous urea solution to the exhaust gas, which ammonia reacts with the NOX in the exhaust gas to form elemental nitrogen (N2) and water. Legislators are continually lowering the emissions limit values for the exhaust gases of vehicles with internal combustion engines (combustion motors) and issuing regulations to monitor their proper functioning. This applies to so-called OBD (on-board diagnosis: ongoing, automatic self-diagnosis during the intended operation of the vehicle) in such vehicles. Nowadays, the SCR particle filter must also be subjected to such a frequent and precise OBD.
Typically, such diagnosis may be performed with regard to the particle emissions by means of a so-called PM sensor (particulate matter sensor, particle sensor). Here, if the PM emissions downstream of the particle filter as measured by means of the particle sensor are higher than a threshold value, the particle filter is diagnosed as faulty. However, a relatively long period of time is required for such diagnosis. Furthermore, the diagnosis is limited to the particle emissions, and the accuracy of the diagnosis is furthermore not good enough to meet the requirements of future, even lower emissions threshold values.
The teachings of the present disclosure include methods and/or corresponding exhaust-gas aftertreatment systems of an internal combustion engine which permit particularly rapid and precise monitoring of an SCR particle filter with regard to its NOX/NH3 conversion and particle filtering during the operation of the internal combustion engine. For example, some embodiments include a method for operating an exhaust-gas aftertreatment system of an internal combustion engine, which exhaust-gas aftertreatment system has an exhaust-gas line (1) for conducting an exhaust-gas mass flow (10) and has an SCR particle filter (3) arranged in the exhaust-gas line (1), wherein a device for targeted, defined variation of the NH3 and/or NOX concentration is arranged in the exhaust-gas mass flow (10) upstream of the SCR particle filter (3), and at least one first concentration sensor (6) is arranged in the exhaust-gas mass flow (10) downstream of the SCR particle filter (3), having the following steps: setting the internal combustion engine to a diagnostic operating mode, wherein certain relevant diagnostic operating parameters (D-BP) of the internal combustion engine are verified for, or set or adjusted to, correspondence with diagnostic default values (D-BP_set); in the presence of the diagnostic operating mode, targeted, defined inducement of an NH3 concentration change and/or of an NOX concentration change in the exhaust-gas mass flow (10) upstream of the SCR particle filter (3) in relation to the values of the NH3 concentration and/or of the NOX concentration that are present in the diagnostic operating mode; measuring the NH3 and/or NOX concentration change in the exhaust-gas mass flow (10) downstream of the SCR particle filter (3) within a specified time window (TW), which directly follows the abovementioned NH3 and/or NOX concentration change measured upstream of the SCR particle filter (3), by means of the at least one first concentration sensor (6), which outputs a corresponding first concentration measurement signal (110); and providing a correlating concentration comparison value (VgW) at least on the basis of the first concentration measurement signal (110); evaluating the NH3 and/or NOX concentration change downstream of the SCR particle filter (3) measured within the specified time window (TW) on the basis of the respective concentration comparison value (VgW) and predefined limit values (GW); and diagnosing the SCR particle filter (3) as defective if the evaluation yields that the concentration comparison value (VgW) has overshot at least one predefined limit value (GW).
In some embodiments, the device for targeted, defined inducement of the NH3 and/or NOX concentration change in the exhaust-gas mass flow (10) upstream of the SCR particle filter (3) has an NH3 feed device (7) for the feed of an NH3 solution (7d) into the exhaust-gas line (1) and/or has a first exhaust-gas recirculation device (2) which branches off from the exhaust-gas line (1) upstream of the SCR particle filter (3) and/or has a further exhaust-gas recirculation device (8) which branches off from the exhaust-gas line (1) downstream of the SCR particle filter (3).
In some embodiments, the diagnostic operating mode is characterized by at least one of the following diagnostic operating parameters: engine speed (RPM) of the internal combustion engine between 1100 and 1900 revolutions/minute; operating temperature (T-SC-PF) of the SCR particle filter (3) between 250° C. and 350° C.; pressure difference of the exhaust-gas mass flow (ΔP_SCR-PF) across the SCR particle filter (3) of between 3 bar and 7 bar; stored NH3 quantity (SM_SC-PF) in the SCR particle filter (3) lies above a predefined threshold value; added NH3 quantity adjusted to a value which is stoichiometric in relation to the NOX concentration in the exhaust gas upstream of the SCR particle filter.
In some embodiments, the defined NOX concentration change upstream of the SCR particle filter (3) consists in an increase or a reduction of the NOX concentration that is set as a result of a defined reduction or increase of an exhaust-gas recirculation rate of the first exhaust-gas recirculation device (2) and/or of the further exhaust-gas recirculation device (8).
In some embodiments, the defined NH3 concentration change upstream of the SCR particle filter (3) consists in a defined increase or reduction of the NH3 concentration that is set as a result of a defined increase or reduction of the added quantity of the NH3 solution (7d) by means of the NH3 feed device (7).
In some embodiments, in the evaluation of the NOX concentration change and/or NH3 concentration change downstream of the particle filter (3) measured within the specified time window (TW), a respective maximum value or minimum value, attained within the defined time window (TW), of the concentration change and/or a gradient, determined within the defined time window (TW), of the concentration change is used as concentration comparison value (VgW).
In some embodiments, in the course of the NH3 and/or NOX concentration change, a concentration increase and an immediately subsequent concentration reduction occur, wherein, after the concentration increase for a particular first period of time, the concentration reduction occurs to such a selected value, and for such a selected second period of time, that a resulting mean value of the NH3 and/or NOX concentration over the duration of the concentration increase and of the concentration reduction corresponds to the value of the NH3 and/or NOX concentration prevailing before the concentration increase.
In some embodiments, for the measurement of the NH3 and/or NOX concentration change in the exhaust-gas mass flow (10), use is made in each case of a combined concentration sensor (6) which combines the NH3 and/or NOX concentration change in a combined concentration measurement signal (110).
In some embodiments, the respective specified time window (TW) has a duration of less than or equal to 5 seconds, in particular less than or equal to 3 seconds.
In some embodiments, after the diagnosis of the SCR particle filter (3), the targeted, defined NH3 and/or NOX concentration change in the exhaust-gas mass flow (10) upstream of the SCR particle filter (3) is withdrawn and, in a manner dependent on the diagnosis result, the internal combustion engine is transferred back into the normal working operating mode (BP_Norm) and continues to be operated, or is restricted to emergency operation (BP_Not).
In some embodiments, an additional concentration sensor (5) is arranged in the exhaust-gas mass flow (10) upstream of the SCR particle filter (3), by means of which additional concentration sensor a second concentration measurement signal (100) which correlates with the NH3 and/or NOX concentration change in the exhaust-gas mass flow (10) upstream of the SCR particle filter (3) is provided, wherein the concentration comparison value (VgW) used for the evaluation of the measured NH3 and/or NOX concentration change downstream of the SCR particle filter (3) is based on the respective NH3 and/or NOX concentration changes downstream and upstream of the SCR particle filter (3) determined within the defined time window (TW).
In some embodiments, the values of the NH3 and/or NOX concentration changes determined within the defined time window at a particular point in time, and/or the gradients of said concentration changes, in each case upstream and downstream of the SCR particle filter (3) are compared with one another or set in relation to one another.
In some embodiments, the NH3 and/or NOX concentration change has a concentration increase and an immediately subsequent concentration reduction, and the values and/or the gradients of the concentration increase and of the concentration reduction in each case upstream and downstream of the SCR particle filter (3) are used in combination with one another for the evaluation of the measured NH3 and/or NOX concentration change downstream of the SCR particle filter (3).
As another example, some embodiments include an exhaust-gas aftertreatment system of an internal combustion engine, which exhaust-gas aftertreatment system has an SCR particle filter (3) arranged in an exhaust-gas line (1) and has at least one device for targeted, defined variation of the NH3 and/or NOX concentration in the exhaust-gas mass flow (10) upstream of the SCR particle filter (3) and has at least one first concentration sensor (6) for measuring the NH3 and/or NOX concentration in the exhaust-gas mass flow (10) downstream of the SCR particle filter (3), characterized in that the exhaust-gas aftertreatment system has an electronic processing and control unit (15) which is configured for targeted, defined variation of the NH3 and/or NOX concentration in the exhaust-gas mass flow (10) upstream of the SCR particle filter (3) by means of at least one of the devices for targeted, defined variation of the NH3 and/or NOX concentration and for detecting a first concentration measurement signal (110) output by the at least one concentration sensor (6), wherein the electronic processing and control unit (15) is furthermore configured to execute the method for operating an exhaust-gas aftertreatment system of an internal combustion engine as described above.
In some embodiments, it has an additional concentration sensor (5) which is arranged in the exhaust-gas mass flow (10) upstream of the SCR particle filter (3) and which serves for measuring the NH3 and/or NOX concentration upstream of the SCR particle filter (3), wherein the electronic processing and control unit (15) is configured to execute the method for operating an exhaust-gas aftertreatment system of an internal combustion engine as claimed in any of claims 11 to 13.
In some embodiments, the device for targeted, defined variation of the NH3 and/or NOX concentration in the exhaust-gas mass flow (10) upstream of the SCR particle filter (3) has an NH3 feed device (7) for the feed of an NH3 solution (7d) into the exhaust-gas line (1) and/or has a first exhaust-gas recirculation device (2) which branches off from the exhaust-gas line (1) upstream of the SCR particle filter (3) and/or has a further exhaust-gas recirculation device (8) which branches off from the exhaust-gas line (1) downstream of the SCR particle filter (3).
In some embodiments, the electronic processing and control unit (15) is an integral constituent part of a central control unit (16) of the internal combustion engine, and the method for being executed is part of an on-board diagnostic system for monitoring the exhaust-gas-relevant functional units of the internal combustion engine during intended operation.
The teachings herein and exemplary embodiments and developments thereof are discussed in detail below with reference to the figures. In the figures:
Objects of identical function and designation are denoted by the same reference signs throughout the figures.
In some embodiments, an exhaust-gas aftertreatment system of an internal combustion engine includes an exhaust-gas line for conducting an exhaust-gas mass flow and has an SCR particle filter arranged in the exhaust-gas line, and wherein a device for targeted, defined variation of the NH3 and/or NOX concentration is arranged in the exhaust-gas mass flow upstream of the SCR particle filter, and at least one first concentration sensor is arranged in the exhaust-gas mass flow downstream of the SCR particle filter.
In such an embodiment:
In some embodiments, an exhaust-gas aftertreatment system of an internal combustion engine has an SCR particle filter arranged in an exhaust-gas line and has at least one device for targeted, defined variation of the NH3 and/or NOX concentration in the exhaust-gas mass flow upstream of the SCR particle filter and has at least one concentration sensor for measuring the NH3 and/or NOX concentration in the exhaust-gas mass flow downstream of the SCR particle filter. Said exhaust-gas aftertreatment system is characterized by the fact that it has an electronic processing and control unit which is configured for targeted, defined variation of the NH3 and/or NOX concentration in the exhaust-gas mass flow upstream of the SCR particle filter by means of the device for targeted, defined variation of the NH3 and/or NOX concentration and for detecting a first concentration measurement signal output by the at least one concentration sensor. Here, the electronic processing and control unit is furthermore configured to execute the method for operating an exhaust-gas aftertreatment system of an internal combustion engine according to any of the embodiments of the methods described above and below.
In some embodiments, a method includes using an NOX and/or NH3 sensor downstream of an SCR particle filter in order, in conjunction with an NH3 concentration change and/or an NOX concentration change in the exhaust-gas mass flow upstream of the SCR particle filter, to subject the SCR particle filter to a functional check, in particular a performance diagnosis. As an SCR particle filter, use is made, for example, of a wall-flow filter with suitable SCR coating. Function-influencing damage to SCR particle filters generally consists in apertures or holes in the substrate of the filter, the number or cross-sectional area of which determines the degree of damage and through which a corresponding fraction of the exhaust gas can pass without being filtered and without being treated. If the overall cross section of the apertures or open holes is above a threshold value, the corresponding particle emissions overshoot a diagnosis threshold value (OBD threshold value).
In order to detect this state in a constant or steady operating state, for example at idle, in the case of a quasi-constant SCR particle filter temperature at which the NOX concentration signal and/or the NH3 concentration signal downstream of the SCR particle filter varies to a small extent, for example less than 1 ppm/sec, the added quantity of the urea solution and/or the NOX untreated emission is increased preferably in one step, for example by 200 ppm NH3/NOX proceeding from the previously present NH3 added quantity or NOX untreated emission, and the NOX and/or NH3 signal course is observed (measurement of the corresponding concentration increase). If the SCR particle filter now lies within the emissions limit, it can be assumed that the total cross section of apertures in the filter substrate is so small that the added urea or the increased NOx concentration is initially for the most part stored in the SCR particle filter. Therefore, the NOx or NH3 signal measured downstream of the filter has only a slight increase over a short period of time of, for example, 3 seconds, in a manner dependent on the air mass flow. The corresponding signal is thereafter stable and has a much lower gradient (less than 1 ppm/sec) than an excessively damaged SCR particle filter.
However, if the threshold value is overshot, the total cross section of apertures in the filter substrate is so large that a major part of the added urea or the increased NOx concentration flows through the SCR particle filter virtually without being decelerated and without being treated, such that, within the specified, immediately subsequent time window, the corresponding sensors downstream of the SCR particle filter register a direct, elevated NH3/NOX concentration increase, following which the corresponding signal returns to a more stable state with a lower gradient.
It has been found that the ratio between the NOx and/or NH3 concentration change downstream of the SCR particle filter and the NOx and/or NH3 concentration change upstream of the SCR particle filter is directly proportional to the total cross section of the apertures in the filter substrate of the SCR particle filter. If this ratio is above a certain threshold value or limit value, the filter is classed as defective with regard to particle conversion.
A corresponding NOx concentration change upstream of the SCR particle filter can be carried out, for example, by reducing the exhaust-gas recirculation rate (EGR rate), in particular in the case of high-pressure exhaust-gas recirculation but also in the case of low-pressure exhaust-gas recirculation. Here, too, it can be seen that the NOx concentration change downstream of the SCR particle filter in relation to the NOx concentration change upstream of the SCR particle filter is directly proportional to the total cross section of the apertures in the filter substrate of the SCR particle filter.
In some embodiments, a concentration comparison value is determined on the basis of the concentration measurement signal provided by means of the at least one concentration sensor. In its simplest form, this concentration comparison value may for example represent the maximum deflection of the concentration measurement signal within the specified time window. The concentration comparison value may however also be a ratio between the NH3 and/or NOx concentration change upstream and downstream of the SCR particle filter. Likewise, the concentration comparison value may be determined on the basis of several successive concentration changes, and the respective gradients of the concentration changes may also be taken into consideration, as will be explained in more detail further below. Here, the concentration change may be understood to mean both a concentration increase and a concentration reduction, or both in succession.
The concentration sensor referred to may be an NH3 sensor or an NOX sensor, depending on whether the NH3 or NOX concentration is changed for the purposes of executing the method. While an NH3 sensor is only suitable for measuring the NH3 concentration, the aforementioned NOx sensor, on the other hand, can measure both the NH3 and the NOx concentration and consequently also a combination of NOx and NH3. In this case it is thus a combined NH3/NOX concentration sensor. Depending on the desired measurement, the appropriate sensors can therefore be provided.
In some embodiments, an exhaust-gas aftertreatment system of an internal combustion engine, in particular of a diesel engine, comprises an SCR particle filter arranged in an exhaust-gas line and has at least one device for targeted, defined variation of the NH3 and/or NOX concentration in the exhaust-gas mass flow upstream of the SCR particle filter and has at least one first concentration sensor for measuring the NH3 and/or NOX concentration in the exhaust-gas mass flow downstream of the SCR particle filter. Here, said exhaust-gas aftertreatment system is characterized by the fact that it has an electronic processing and control unit which is configured for targeted, defined variation of the NH3 and/or NOX concentration in the exhaust-gas mass flow upstream of the SCR particle filter by means of the device for targeted, defined variation of the NH3 and/or NOX concentration and for detecting a first concentration measurement signal output by the at least one first concentration sensor. In some embodiments, the electronic processing and control unit is furthermore configured to execute a method for operating an exhaust-gas aftertreatment system of an internal combustion engine as presented in the embodiments above and in the embodiments described below.
For targeted, defined inducement of an NH3 concentration change in the exhaust-gas mass flow 10 upstream of the SCR particle filter 3, an NH3 feed device 7 is arranged on the exhaust-gas line 1 upstream of the SCR particle filter 3 for the purposes of feeding an NH3 solution 7d into the exhaust-gas line 1. In this exemplary embodiment, the NH3 feed device 7 has a reservoir 7a for storing a suitable aqueous NH3 solution 7d, which is also referred to as urea solution. The reservoir 7a is connected via a feed line to a dosing device 7b, for example an injection valve, which in turn is arranged on the exhaust-gas line 1 and is designed to release defined quantities of the NH3 solution into the exhaust-gas mass flow 10. The NH3 solution that is fed in produces NH3, which converts the NOx fraction contained in the exhaust gas into nitrogen and water. The SCR particle filter therefore performs its function as a diesel particle filter and at the same time causes a reduction of the NOx fraction in the exhaust gas.
Furthermore, for targeted, defined inducement of an NOx concentration change in the exhaust-gas mass flow 10 upstream of the SCR particle filter 3, an exhaust-gas recirculation device 2 which branches off from the exhaust-gas line 1 upstream of the SCR particle filter 3, a so-called high-pressure exhaust-gas recirculation system, is provided, via which a first partial exhaust-gas mass flow 10a of the exhaust-gas mass flow 10 emitted by the internal combustion engine is recirculated into the intake region of the internal combustion engine via a first exhaust-gas recirculation line 2a. The magnitude of the recirculated first partial exhaust-gas mass flow 10a can be set by means of a first exhaust-gas recirculation valve 2b arranged in the first exhaust-gas recirculation line 2a. The branching point of this exhaust-gas recirculation device 2 is expediently arranged on the exhaust-gas line 1 upstream of the NH3 feed device 7, because the NH3 solution 7d that is fed is to be fed in its entirety to the SCR particle filter 3 for the NOx reduction.
In some embodiments, as illustrated in
The functioning of such exhaust-gas recirculation devices for reducing emissions, in particular for influencing the untreated NOx emissions of the internal combustion engine, that is to say the NOx concentration in the exhaust gas, is known to the person skilled in the art from the prior art and will not be explained further here.
Although the embodiment shown in
In some embodiments, at least a first concentration sensor 6 is arranged in the exhaust-gas mass flow 10 for the purposes of measuring the NH3 and/or NOx concentration in the exhaust-gas mass flow 10 downstream of the SCR particle filter 3. This first concentration sensor 6 outputs a corresponding first concentration measurement signal 110, on the basis of which a correlating concentration comparison value (VgW) can be provided.
In some embodiments, there is an additional concentration sensor 5 arranged in the exhaust-gas mass flow 10 upstream of the SCR particle filter 3 for the purposes of measuring the NH3 and/or NOx concentration upstream of the SCR particle filter 3. Said additional concentration sensor is expediently arranged in the exhaust-gas mass flow 10 downstream of the NH3 feed device 7 and the branching point of the first exhaust-gas recirculation device 2 and directly upstream of the SCR particle filter 3, such that, with this additional concentration sensor 5, both the NH3 and the NOX concentration change upstream of the SCR particle filter 3, that is to say the targetedly induced NH3 and/or NOX concentration change, can be detected. This additional concentration sensor 5 also outputs a corresponding second concentration measurement signal 100, which can be used for providing a concentration comparison value (VgW).
In some embodiments, an actually measured value for the NH3 concentration change and/or the NOX concentration change in the exhaust-gas mass flow 10 upstream of the SCR particle filter 3 can be used, for example, for providing a concentration comparison value (VgW), which increases the reliability of the diagnosis of the SCR particle filter. Otherwise, if only the concentration sensor 6 arranged downstream of the SCR particle filter 3 is available, it is for example the case that the default value for the targeted, defined concentration change is adopted as an actual value, wherein it is assumed that the device for the targeted, defined change of the respective concentration value is functioning without errors.
In some embodiments, as illustrated in
The electronic processing and control unit 15 is furthermore configured to execute the methods described herein for operating an exhaust-gas aftertreatment system of an internal combustion engine according to any of the embodiments on the basis of a first concentration measurement signal of the first concentration sensor 6 or on the basis of the two concentration measurement signals of the first and of the additional concentration sensor 6, 5. For this purpose, the sequence of the method, corresponding calculation algorithms, and the required default values for the control of the exhaust-gas aftertreatment system and of the internal combustion engine are stored in the form of executable program code in the electronic control unit 15 or in assigned electronic memory units.
In some embodiments, the electronic processing and control unit 15 is an integral constituent part of a central control unit (CPU) 16 of the internal combustion engine, wherein the method for being executed is part of an on-board diagnostic system for monitoring the exhaust-gas-relevant functional units of the internal combustion engine during intended operation.
An example method for operating an exhaust-gas aftertreatment system of an internal combustion engine in one of the embodiments described above is illustrated, in the main method steps, on the basis of the simplified block sequence program illustrated in
In some embodiments, the diagnostic operating mode is characterized by at least one of the following diagnostic operating parameters:
For this purpose, the corresponding diagnostic default values are stored in an electronic memory of the electronic processing and control unit (ECU), which is denoted by “E_Sp1” in
In some embodiments, the defined NOx concentration change upstream of the SCR particle filter 3 may consist in an increase or a reduction in the NOx concentration, which is achieved, for example, by means of a defined reduction or increase of an exhaust-gas recirculation rate, wherein, here, it is also possible in an assisting manner for yet further operating parameters of the internal combustion engine to be influenced in the sense of an increase of the NOx concentration in the exhaust gas. Here, the exhaust-gas recirculation rate can be set by means of the first exhaust-gas recirculation device 2 or the further exhaust-gas recirculation device 8 or the two exhaust-gas recirculation devices 2, 8 in combination. This is realized, for example, by appropriate control of the first exhaust-gas recirculation valve 2b or of the second exhaust-gas recirculation valve 8b or a combined control of the first and the second exhaust-gas recirculation valves 2b, 8b by means of the electronic processing and control unit (ECU) 15.
In some embodiments, the defined NH3 concentration change upstream of the SCR particle filter 3 may consist in a defined increase or reduction of the NH3 concentration that is set as a result of a defined increase or reduction of the added quantity of the NH3 solution 7d by means of the NH3 feed device 7. This is realized in particular by corresponding control of the metering device 7b by means of the electronic processing and control unit (ECU) 15.
In some embodiments, in the method step denoted “NOX/NH3_Sig”, the NH3 and/or NOX concentration change in the exhaust-gas mass flow 10 downstream of the SCR particle filter 3 is measured within a specified time window (TW) which directly follows the aforementioned NH3 and/or NOx concentration change measured upstream of the SCR particle filter 3. This is performed by means of the at least one first concentration sensor 6, which outputs a corresponding first concentration measurement signal 110, which is fed via the signal line 6c to the electronic processing and control unit for further processing.
In some embodiments, in the course of the abovementioned method step, the NH3 and/or NOx concentration change upstream of the SCR particle filter is additionally measured in the same time window (TW). For this purpose, by means of an additional concentration sensor 5 which is arranged in the exhaust-gas mass flow 10 upstream of the SCR particle filter 3, a second concentration measurement signal 120 that correlates with the NH3 and/or NOx concentration change in the exhaust-gas mass flow 10 upstream of the SCR particle filter 3 is provided, and is fed via a signal line 5c to the electronic processing and control unit ECU. This makes possible not only the relative consideration of the concentration change upstream and downstream of the SCR particle filter 3, and an associated increase in the diagnostic certainty of the method, but also the possibility of assessing the function of the exhaust-gas recirculation devices 2, 8 and of the NH3 feed device 7.
In the following process step, denoted by “(NOX/NH3)VGW”, a correlating concentration comparison value (VgW) is provided at least on the basis of the first concentration measurement signal (110). For example, in different embodiments of the method, a respective maximum value or minimum value of the concentration change attained within the defined time window (TW), and/or a gradient of the concentration change determined within the defined time window (TW), can be used as the concentration comparison value (VgW).
In some embodiments, provided that the NH3 and/or NOx concentration change upstream of the SCR particle filter is additionally measured, the concentration comparison value (VgW) can be based on the respective NH3 and/or NOx concentration changes downstream and upstream of the SCR particle filter 3 determined within the defined time window. For this purpose, it is for example possible, in a further embodiment of the method, for the values of the NH3 and/or NOX concentration changes determined within the defined time window at a particular point in time, and/or the gradients of said concentration changes, in each case upstream and downstream of the SCR particle filter 3 to be compared with one another or set in relation to one another. This makes it possible to provide a particularly reliable concentration comparison value (VgW) and increases the diagnostic certainty of the method, since incorrect diagnoses owing to possibly defective devices for NH3 and/or NOx concentration change can be ruled out.
In the following method step, denoted by “VgW-GW”, the NH3 and/or NOX concentration change downstream of the SCR particle filter (3) measured within the specified time window (TW) is evaluated on the basis of the respective concentration comparison value (VgW) and predefined limit values (GW). Here, depending on the execution of the method, as already mentioned above, a respective maximum value or minimum value of the concentration change and/or a determined gradient of the concentration change, or also comparison or ratio values based on the values or gradients of the concentration change respectively measured in each case upstream and downstream of the SCR particle filter 3, can be used as concentration comparison value. This allows wide variance in the configuration of the methods and the adaptation to the requirements in the respective usage situation. Correspondingly adapted limit values must then be specified in accordance with the concentration comparison value used. These may for example be determined beforehand, empirically or by means of model calculation, and are stored for example in an electronic memory area of the electronic processing and control unit and are retrieved from there for the evaluation of the concentration change. Such an electronic memory area is denoted in
On the basis of the above-described evaluation of the concentration change downstream of the SCR particle filter 3, in the following process step, denoted by “VGW≥GW”, that the SCR particle filter 3 is diagnosed as defective, “SCR-PF=nok”, if the evaluation yields that the concentration comparison value (VgW) has overshot at least one predetermined limit value (GW). Otherwise, the SCR particle filter is diagnosed as functional, “SCR-PF=ok”, if the concentration comparison value has not reached or overshot a limit value. The method is thus completed. In order to ensure permanently error-free operation of the exhaust-gas aftertreatment system, the methods may be repeated in certain cycles during operation, wherein these cycles may be based on a certain operating duration, on a certain operating performance or on demand values determined during operation.
In some embodiments, in the course of the NH3 and/or NOX concentration change, a concentration increase and an immediately subsequent concentration reduction occur. Here, after the concentration increase for a particular first period of time, the concentration reduction occurs to such a selected value, and for such a selected second period of time, that a resulting mean value of the NH3 and/or NOX concentration downstream of the SCR particle filter over the duration of the concentration increase and of the concentration reduction corresponds to the value of the NH3 and/or NOX concentration prevailing before the concentration increase. It is thereby ensured that no increase in pollutant emissions caused by the method occurs over the duration of the method, averaged over time.
In some embodiments, for the measurement of the NH3 and/or NOX concentration change in the exhaust-gas mass flow 10, use is made in each case of a combined concentration sensor 6 which combines the NH3 and/or NOX concentration change in a combined concentration measurement signal 110. This may apply both to the first concentration sensor 6, downstream of the SCR particle filter 3, and to the second concentration sensor 5, upstream of the SCR particle filter 3. In some embodiments, the method specifies both an NH3 concentration change and an NOX concentration change and a combined NH3/NOX concentration change, and thus also opens up a greater scope for the extent of the predetermined concentration change.
In some embodiments, the respective specified time window (TW) for the measurement of the NH3 and/or NOX concentration change in the exhaust-gas mass flow 10 downstream and/or upstream of the SCR particle filter 3 has a duration of less than or equal to 5 seconds, in particular less than or equal to 3 seconds. The length of this time window ensures that only a rapid NH3 and/or NOx concentration change downstream of the SCR particle filter 3, such as occurs only if the SCR particle filter 3 is defective, has an effect in the determination of the concentration comparison value and thus in the diagnosis of the SCR particle filter.
By contrast, the curve 120 shows the NOX/NH3 concentration recorded downstream of the SCR particle filter in the case of an intact SCR particle filter. Here, a minimum value of the NOX/NH3 concentration is present in the phase of the diagnostic operating mode. In this case, too, at the time T1, the NOx/NH3 concentration begins to increase within the time window TW, but with a gradient G2 that is significantly shallower than that of the curve 110. Accordingly, up to the time T2, at the end of the time window TW, it is also the case that only a significantly lower maximum concentration KM2 is attained.
In some embodiments, as concentration comparison value VgW, use may be made of the respective maximum concentration MK1, MK2 attained up to a certain point in time within the time window TW or at the end of the time window TW, or also of the respective gradient G1, G2 of the NOX/NH3 concentration increase within the time window TW. Furthermore, some embodiments consider the concentration values determined downstream of the SCR particle filter and the concentration values specified or determined upstream in combination, and to determine a comparison value therefrom. Here, the NOX/NH3 concentration values upstream of the SCR particle filter may be based on the default values, determined using model considerations or measured by means of a concentration sensor (if present).
For the determination of a concentration comparison value VgW, it is possible for the gradient of the concentration increase downstream of the SCR particle filter determined within the time window TW to be divided by the step-change value of the concentration change upstream of the SCR particle filter. The result is used as concentration comparison value VgW. If, for example, the gradient of the concentration increase downstream of the SCR particle filter is 11.3 ppm/s and the step-change value of the concentration change upstream of the SCR particle filter is 480 ppm (wherein the signs must be observed), the result is a concentration comparison value of:
(11.3 ppm/s)/480 ppm=0.024/s.
If a limit value GW of, for example, 0.016/s is present, this would be overshot (VgW≥GW), and the SCR particle filter would have to be evaluated as defective (SCR-PF=nok).
This approach increases the robustness of the method against disturbance influences.
In some embodiments, the NH3 and/or NOX concentration change has a concentration increase and an immediately subsequent concentration reduction, and the values and/or the gradients of the concentration increase and of the concentration reduction in each case upstream and downstream of the SCR particle filter 3 are used in combination with one another for the evaluation of the measured NH3 and/or NOX concentration change downstream of the SCR particle filter 3. For example, in each case one ratio of the gradient of the concentration increase downstream and the step-change value of the concentration increase upstream of the SCR particle filter and also of the gradient of the subsequent concentration decrease downstream and the associated step-change value of the concentration reduction upstream of the SCR particle filter can be formed, and their sum calculated.
This is illustrated qualitatively in
(+G1a/+KSp1)+(−G1b/−KSp2)=VgW
For example, if a gradient of +7.3 ppm/s downstream arises in the case of a step-change value of the concentration increase of +480 ppm upstream of the SCR particle filter, and subsequently a gradient of −11.3 ppm/s downstream arises in the case of a step-change value of the concentration reduction of −480 ppm/s, then the concentration comparison value is calculated as:
((+7.3 ppm/s)/+480 ppm)+((−11.3 ppm/s)/−480 ppm)=0.015/s+0.024/s=0.039/s.
If a limit value GW of, for example, 0.026/s is present, this would be overshot (VgW≥GW), and the SCR particle filter would have to be evaluated as defective (SCR-PF=nok). This approach further increases the robustness of the method against disturbance influences.
In some embodiments, if the targeted, defined NH3 and/or NOx concentration change in the exhaust-gas mass flow 10 upstream of the SCR particle filter 3 is withdrawn after the diagnosis of the SCR particle filter 3, then the diagnostic operating mode is ended and the NH3 and/or NOx concentration is again set or controlled in a manner dependent on the present operating point of the internal combustion engine. As can be seen from
If the diagnosis yields that the SCR particle filter is intact and functioning correctly (SCR-PF=ok), then, after the execution of the method, that is to say after the diagnosis of the functionality of the SCR particle filter 3, the internal combustion engine can continue to be operated in the normal working operating mode again; this is illustrated in the method step denoted “BP_Norm”.
However, if the diagnosis yields that the SCR particle filter is defective (SCR-PF=nok), then emergency operation of the internal combustion engine can instead be initiated, which for example still makes it possible, with reduced engine performance, to seek out a workshop. At the same time, a fault message can be output to the vehicle driver, prompting them to seek out the nearest workshop immediately and to have the repair carried out. This is illustrated in
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2017 221 358.2 | Nov 2017 | DE | national |
| 10 2018 215 627.1 | Sep 2018 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2018/082357 | 11/23/2018 | WO | 00 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2019/105859 | 6/6/2019 | WO | A |
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| 20160069243 | Hegemann | Mar 2016 | A1 |
| 20170051654 | Gupta | Feb 2017 | A1 |
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| 10 2012 220 151 | Nov 2012 | DE |
| 10 2013 200 623 | Jan 2013 | DE |
| 2009 156159 | Jul 2009 | JP |
| 2007 037730 | Sep 2005 | WO |
| 2011 107686 | Mar 2010 | WO |
| 2013 147653 | Oct 2013 | WO |
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| Search Report for International Application No. PCT/EP2018/082357, 15 pages, dated Jan. 25, 2019. |
| Search Report for DE Patent Application No. 10 2018 215 627.1, 13 pages, dated Apr. 26, 2019. |
| Office Action for DE Patent Application No. 10 2017 221 358.2, 9 pages, dated Jul. 23, 2018. |
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| Number | Date | Country | |
|---|---|---|---|
| 20200378288 A1 | Dec 2020 | US |
