METHOD FOR OPERATING AN EXHAUST GAS AFTERTREATMENT SYSTEM OF AN INTERNAL COMBUSTION ENGINE, AN EXHAUST GAS AFTERTREATMENT SYSTEM FOR AN INTERNAL COMBUSTION ENGINE, AND AN INTERNAL COMBUSTION ENGINE COMPRISING SUCH AN EXHAUST GAS AFTERTREATMENT SYSTEM

Abstract

This version will replace all prior versions in the application: A method for operating an exhaust gas aftertreatment system of an internal combustion engine, wherein at least one operating parameter is detected during the operation of the exhaust gas aftertreatment system, the operating parameter being associated with an oxidation state of an SCR catalyst material of the exhaust gas aftertreatment system, and at least one measure for preventing an ongoing reduction of the SCR catalyst material and/or at least one reoxidizing measure for reoxidizing the SCR catalyst material is introduced in accordance with the at least one operating parameter.

Claims

1-11. (canceled)

12. A method for operating an exhaust gas aftertreatment system of an internal combustion engine, comprising the steps of: detecting at least one operating parameter during operation of the exhaust gas aftertreatment system, which operating parameter is associated with an oxidation state of an SCR catalytic converter material of the exhaust gas aftertreatment system; and initiating at least one measure for preventing a progressing reduction of the SCR catalytic converter material and/or at least one reoxidation measure for reoxidation of the SCR catalytic converter material dependent on the at least one operating parameter.

13. The method according to claim 12, including carrying out the at least one measure for preventing a progressing reduction of the SCR catalytic converter material and/or the at least one reoxidation measure for the reoxidation of the SCR catalytic converter material immediately after the initiation.

14. The method according to claim 12, including carrying out the at least one measure for preventing a progressing reduction of the SCR catalytic converter material and/or the at least one reoxidation measure for the reoxidation of the SCR catalytic converter material in a temporally delayed manner after the initiation.

15. The method according to claim 12, including detecting: an exhaust gas temperature; an operating time; an exhaust gas temperature/operating time integral; a temporally integrally converted nitrogen oxide load; a temporally integrally metered reducing agent quantity, and/or a nitrogen oxide concentration and/or reducing agent concentration downstream of the SCR catalytic converter material in the exhaust gas aftertreatment system as the at least one operating parameter.

16. The method according to claim 12, further including comparing the at least one operating parameter with a predefined threshold value, and initiating the at least one measure for preventing a progressing reduction of the SCR catalytic converter material and/or the at least one reoxidation measure if a) the at least one operating parameter reaches or exceeds the predefined threshold value, or b) the at least one operating parameter reaches or exceeds the predefined threshold value for a predefined time duration.

17. The method according to claim 12, further including determining the oxidation state of the SCR catalytic converter material and/or a nitrogen oxide conversion quantity of the SCR catalytic converter material by a catalytic converter reaction model, the catalytic converter reaction model being fed the at least one operating parameter as an input variable, the at least one measure for preventing a progressing reduction of the SCR catalytic converter material and/or the at least one reoxidation measure being initiated in a manner dependent on the nitrogen oxide conversion quantity and/or the oxidation state determined by the catalytic converter reaction model.

18. The method according to claim 12, further including reducing metering of a reducing agent into an exhaust gas path of the exhaust gas aftertreatment system upstream of the SCR catalytic converter material, raising an oxygen concentration in the exhaust gas upstream of the SCR catalytic converter material, reducing a nitrogen oxide concentration in the exhaust gas upstream of the SCR catalytic converter material, and/or reducing an exhaust gas temperature upstream of the SCR catalytic converter material as the at least one reoxidation measure and/or as the at least one measure for preventing a progressing reduction of the SCR catalytic converter material.

19. The method according to claim 12, including raising oxygen concentration in an exhaust gas upstream of the SCR catalytic converter material and/or reducing exhaust gas temperature upstream of the SCR catalytic converter material, wherein an actuating position of a turbine bypass path actuating device for a bypass path of an exhaust gas turbocharger turbine upstream of the SCR catalytic converter material is changed, and/or an actuating position of a compressor bypass path actuating device for a bypass path of an exhaust gas turbocharger compressor is changed.

20. The method according to claim 18, wherein the nitrogen oxide concentration in the exhaust gas upstream of the SCR catalytic converter material is reduced, by increasing an exhaust gas recirculation rate for recirculation of exhaust gas into a combustion chamber of an Internal combustion engine assigned to the exhaust gas aftertreatment system, and/or charging a location of a center of combustion in the combustion chamber of the internal combustion engine assigned to the exhaust gas aftertreatment system.

21. An exhaust gas aftertreatment system for an internal combustion engine, comprising: an exhaust gas path; an SCR catalytic converter in the exhaust gas path; a reducing agent metering device for metering reducing agent into the exhaust gas path upstream of the SCR catalytic converter; and at least one detection device for detecting at least one operating parameter associated with an oxidation state of an SCR catalytic converter material of the SCR catalytic converter, the detection device including a control device operatively configured to initiate at least one measure for preventing a progressing reduction of the SCR catalytic converter material and/or at least one reoxidation measure for reoxidation of the SCR catalytic converter material dependent on the at least one detected operating parameter.

22. An internal combustion engine, having an exhaust gas aftertreatment system according to claim 21.

Description

[0043] The invention will be described in greater detail in the following text using the drawing, in which:

[0044] FIG. 1 shows a diagrammatic illustration of one exemplary embodiment of an internal combustion engine having an exhaust gas aftertreatment system, and

[0045] FIG. 2 shows a diagrammatic illustration of one embodiment of a method for operating the exhaust gas aftertreatment system and the internal combustion engine according to FIG. 1.

[0046] FIG. 1 shows a diagrammatic illustration of one exemplary embodiment of an internal combustion engine 1 having an exhaust gas aftertreatment system 3 which has an exhaust gas path 5, an SCR catalytic converter 7 being arranged in the exhaust gas path 5, which SCR catalytic converter 7 has an SCR catalytic converter material, the exhaust gas aftertreatment system 3 having, moreover, a reducing agent metering device 9 which is set up to meter a reducing agent, in particular ammonia or an ammonia precursor product, in particular a urea/water solution, into the exhaust gas path 5 upstream of the SCR catalytic converter 7. Moreover, the exhaust gas aftertreatment system 3 has at least one detection device 11 (here, a plurality of detection devices 11) for the detection of at least one operating parameter (here, in particular, for the detection of a plurality of operating parameters), the at least one operating parameter being associated with an oxidation state of the SCR catalytic converter material of the SCR catalytic converter 7. Moreover, the exhaust gas aftertreatment system 3 has a control device 13 which is set up to initiate at least one measure for preventing further reduction of the SCR catalytic converter material and/or at least one reoxidation measure for the reoxidation of the SCR catalytic converter material in a manner which is dependent on the at least one operating parameter. In this way, an (in particular, progressing) reduction of a nitrogen oxide conversion rate of the SCR catalytic converter 7 on account of a reduction of the SCR catalytic converter material can be avoided or reversed, in particular by the SCR catalytic converter material being regenerated by way of reoxidation regularly or as required. This ultimately leads to it being possible for a smaller, inexpensive SCR catalytic converter 7 which saves installation space to be used on the internal combustion engine 1, and/or to it being possible for the internal combustion engine 1 to be optimized to a more pronounced extent with regard to a degree of efficiency at the expense of the nitrogen oxide emissions, which involves fuel savings, it nevertheless being possible for limit values for the nitrogen oxide emissions to be complied with, since the SCR catalytic converter 7 has an increased efficiency.

[0047] Here, in particular, an exhaust gas temperature sensor 15 and a nitrogen oxide sensor 17 are provided (both in the exhaust gas path 5 upstream of the SCR catalytic converter 7) as detection devices 11 for detecting operating parameters, a reducing agent sensor 19, in particular an ammonia sensor, being arranged in the exhaust gas path 5 downstream of the SCR catalytic converter 7 as a further detection device 11. The control device 13 preferably has an operating time detection means, with the result that an operating time of the exhaust gas aftertreatment system 3 and/or an exhaust gas temperature/operating time integral can be detected by way of the control device 13.

[0048] The control device 13 is operatively connected, in particular, to the reducing agent metering device 9 and to the different detection devices 11.

[0049] Moreover, the internal combustion engine 1 has an exhaust gas turbocharger 21 which has an exhaust gas turbocharger turbine 23 and an exhaust gas turbocharger compressor 25, the exhaust gas turbocharger compressor 25 being operatively connected in drive terms to the exhaust gas turbocharger turbine 23. Here, the exhaust gas turbocharger turbine 23 is arranged in the exhaust gas path 5 of the internal combustion engine 1, the exhaust gas turbocharger compressor 25 being arranged in a charge path 27 of the internal combustion engine 1.

[0050] The exhaust gas turbocharger turbine 23 is assigned a turbine bypass path 29 with a turbine bypass path actuating device 31, via which turbine bypass path 29 a certain proportion of exhaust gas can be conducted around the exhaust gas turbocharger turbine 23 in a manner which is dependent on an actuating position of the turbine bypass path actuating device 31 which can be configured, in particular, as a wastegate.

[0051] The exhaust gas turbocharger compressor 25 is assigned a compressor bypass path 33 with a compressor bypass path actuating device 35, it being possible for charge air which flows along the charge path 27 to be conducted past the exhaust gas turbocharger compressor 25 and, in particular, to be returned from a high pressure side of the exhaust gas turbocharger compressor 25 to a low pressure side thereof in a manner which is dependent on an actuating position of the compressor bypass path actuating device 35, which is also called a removal of charge air or bypassing of the exhaust gas turbocharger compressor 25. Here, a proportion of the removed or bypassed charge air can be set by way of a change of the actuating position of the turbine bypass path actuating device 35.

[0052] Moreover, the internal combustion engine 1 has an exhaust gas recirculation device 37 (here, in the form of an exhaust gas recirculation path 39), an exhaust gas recirculation actuating device 41 (in particular, in the form of an exhaust gas recirculation flap) being arranged in the exhaust gas recirculation path 39, by means of which exhaust gas recirculation actuating device 41 an exhaust gas recirculation rate (that is to say, a proportion of exhaust gas which is recirculated into the charge path 27 from the exhaust gas path 5) can be set. Here, FIG. 1 shows a high pressure exhaust gas recirculation means by way of example. It is likewise possible, however, that the internal combustion engine 1 has a low pressure exhaust gas recirculation means.

[0053] The control device 13 is operatively connected to the turbine bypass path actuating device 31, the compressor bypass path actuating device 35 and the exhaust gas recirculation device 37 (here, in particular, to the exhaust gas recirculation actuating device 41), in order to set their actuating positions.

[0054] FIG. 2 shows a diagrammatic illustration of one embodiment of a method for operating an exhaust gas aftertreatment system of an internal combustion engine, in particular for operating the exhaust gas aftertreatment system 3 of the internal combustion engine 1 according to FIG. 1. Here, in a first step S1, at least one operating parameter is detected during operation of the exhaust gas aftertreatment system 3, which operating parameter is associated with an oxidation state of an SCR catalytic converter material of the SCR catalytic converter 7.

[0055] In a second step S2, the at least one detected operating parameter is evaluated, in particular with regard to the oxidation state of the SCR catalytic converter material.

[0056] In a third step S3, at least one measure for preventing further reduction of the SCR catalytic converter material and/or at least one reoxidation measure for the reoxidation of the SCR catalytic converter material are/is initiated in a manner which is dependent on the at least one operating parameter, in particular in a manner which is dependent on the oxidation state of the SCR catalytic converter material which has been determined using the at least one operating parameter in the second step S2.

[0057] Here, an exhaust gas temperature, an operating time, an exhaust gas temperature/operating time integral, a temporally integrally converted nitrogen oxide load, a temporally integrally metered reducing agent quantity, a nitrogen oxide concentration and/or a reducing agent concentration downstream of the SCR catalytic converter 7 in the exhaust gas aftertreatment system 3 are/is preferably detected as the at least one operating parameter.

[0058] The at least one operating parameter is compared with a predefined threshold value which is preferably stored in the control device 13, the measure for preventing further reduction and/or the reoxidation measure being initiated if the at least one operating parameter reaches or exceeds the predefined threshold value, or if the at least one operating parameter reaches or exceeds the predefined threshold value for a predefined time duration.

[0059] A catalytic converter reaction model is preferably stored in the control device 13, the oxidation state of the SCR catalytic converter material and/or a nitrogen oxide conversion value of the SCR catalytic converter material being determined by means of the catalytic converter reaction model, the catalytic converter reaction model being fed the at least one operating parameter as an input variable, the at least one measure for preventing further reduction and/or the at least one reoxidation measure being initiated in a manner which is dependent on the nitrogen oxide conversion value and/or the oxidation state which is determined by way of the catalytic converter reaction model.

[0060] Preferably, metering of a reducing agent into the exhaust gas path 5 of the exhaust gas aftertreatment system 3 upstream of the SCR catalytic converter 7 is reduced, an oxygen concentration in the exhaust gas upstream of the SCR catalytic converter 7 is raised, the exhaust gas temperature upstream of the SCR catalytic converter 7 is lowered, and/or a nitrogen oxide concentration in the exhaust gas upstream of the SCR catalytic converter 7 is reduced as the at least one measure for preventing further reduction and/or the at least one reoxidation measure.

[0061] The oxygen concentration is preferably raised and/or the exhaust gas temperature is lowered, by the actuating position of the turbine bypass path actuating device 31 being changed, and/or by the actuating position of the compressor bypass path actuating device 35 being changed.

[0062] The nitrogen oxide concentration in the exhaust gas is preferably reduced, by the exhaust gas recirculation rate being increased, in particular, by means of the exhaust gas recirculation actuating device 41, and/or by a location of the center of combustion being changed in at least one combustion chamber of the internal combustion engine 1. To this end, the control device 13 is preferably operatively connected to an ignition device or an injector for the direct injection of fuel into the combustion chamber, in order for it to be possible for an ignition time to be set.

[0063] It is shown overall that an increase or regeneration of a nitrogen oxide conversion rate on an SCR catalytic converter 7 is achieved, or its further reduction can at least be prevented, by way of the method which is proposed here, by way of the exhaust gas aftertreatment system 3 which is proposed here and by way of the internal combustion engine 1 which is proposed here, with the result that the SCR catalytic converter 7 can be of smaller, less expensive and installation space-saving configuration, and/or that the internal combustion engine 1 can be optimized to a more pronounced extent with regard to a degree of efficiency and therefore in a fuel-saving manner, whereby associated, higher nitrogen oxide emissions are therefore compensated by way of the higher or at least non-reduced conversion rate of the SCR catalytic converter 7.