METHOD FOR OPERATING AN EXHAUST GAS AFTERTREATMENT SYSTEM, EXHAUST GAS AFTERTREATMENT SYSTEM, AND INTERNAL COMBUSTION ENGINE WITH AN EXHAUST GAS AFTERTREATMENT SYSTEM

Abstract

A method for operating an exhaust gas aftertreatment system, having the following steps: determining a permissible energy input into at least one exhaust gas aftertreatment element of the exhaust gas aftertreatment system; ascertaining a current energy input into the at least one exhaust gas aftertreatment element by ascertaining at least one energy input variable which characterizes the current energy input; and actuating an adjusting device which varies a distribution of an exhaust gas mass flow to the at least one exhaust gas aftertreatment element and a bypass path that runs about the at least one exhaust gas aftertreatment element depending on the permissible energy input and the current energy input.

Claims

1-9. (canceled)

10. A method for operating an exhaust gas aftertreatment system, comprising the steps of: determining a permissible energy input into at least one exhaust gas aftertreatment element of the exhaust gas aftertreatment system; ascertaining an instantaneous energy input into the at least one exhaust gas aftertreatment element by ascertaining at least one energy input variable which characterizes the instantaneous energy input; and actuating an actuation device which varies, a distribution of an exhaust gas mass flow to the at least one exhaust gas aftertreatment element and varies a bypass path that leads around the at least one exhaust gas aftertreatment element, as a function of the permissible energy input and the instantaneous energy input.

11. The method according to claim 10, including determining the permissible energy input as a function of at least one operating parameter of the at least one exhaust gas aftertreatment element.

12. The method according to claim 11, including determining the permissible energy input as a function of a soot charge of a particle filter, a reducing agent charge of an SCR catalytic converter and/or a hydrocarbon charge of a catalytic converter.

13. The method according to claim 10, wherein an exhaust gas mass flow through the at least one exhaust gas aftertreatment element and/or an exhaust gas temperature are/is ascertained as the energy input variable.

14. The method according to claim 13, including measuring the exhaust gas temperature upstream of the at least one exhaust gas aftertreatment element, downstream of the at least one exhaust gas aftertreatment element, and/or in the at least one exhaust gas aftertreatment element.

15. The method according to claim 10, including ascertaining the exhaust gas mass flow as a function of an instantaneous operating state of an internal combustion engine in combination with which the exhaust gas aftertreatment system is operated, as a function of a pressure loss variable across the at least one exhaust gas aftertreatment element, and/or as a function of a pressure loss variable across at least one actuation element of the actuation device.

16. An exhaust gas aftertreatment system, comprising: at least one exhaust gas aftertreatment element; a bypass path around the at least one exhaust gas aftertreatment element; an actuation device, configured to selectively distribute an exhaust gas mass flow to the at least one exhaust gas aftertreatment element and the bypass path; and a control device having determining means for determining a permissible energy input into the at least one exhaust gas aftertreatment element, ascertaining means for ascertaining an instantaneous energy input into the at least one exhaust gas aftertreatment element, and actuation means for actuating the actuation device, wherein the control device is configured to actuate the actuation device as a function of the permissible energy input and the instantaneous energy input.

17. The exhaust gas aftertreatment system according to claim 16, comprising a plurality of exhaust gas aftertreatment elements, including at least one first exhaust gas aftertreatment element and at least one second exhaust gas aftertreatment element are each assigned a separate bypass path and a separate actuation device.

18. The exhaust gas aftertreatment system according to claim 16, wherein the actuation device has precisely one actuation element for distributing the exhaust gas mass flow.

19. The exhaust gas aftertreatment system according to claim 16, wherein the actuation device has an actuation element in the bypass path and an actuation element upstream of the exhaust gas aftertreatment element, wherein the actuation elements are coupled to one another in opposite directions.

20. An internal combustion engine, comprising an exhaust gas aftertreatment system according to claim 16.

Description

[0037] The invention will be explained in more detail below with reference to the drawing, in which:

[0038] FIG. 1 shows a schematic illustration of a first exemplary embodiment of an internal combustion engine having a first exemplary embodiment of an exhaust gas aftertreatment system;

[0039] FIG. 2 shows a schematic illustration of a second exemplary embodiment of the exhaust gas aftertreatment system, and

[0040] FIG. 3 shows a schematic illustration of a third exemplary embodiment of the exhaust gas aftertreatment system.

[0041] FIG. 1 shows a schematic illustration of a first exemplary embodiment of an internal combustion engine 1 with a first exemplary embodiment of an exhaust gas aftertreatment system 3. In this context, an engine block 5 of the internal combustion engine 1 is connected to the exhaust gas aftertreatment system 3 in such a way that exhaust gas can be fed from the engine block 5 via the exhaust gas aftertreatment system 3 to an outlet, in particular an exhaust, which is illustrated here schematically by an arrow P. The exhaust gas aftertreatment system 3 has at least one exhaust gas aftertreatment element 7 which can be embodied, for example, as a particle filter, as an SCR catalytic converter or as an oxidation catalytic converter. It is possible for the exhaust gas aftertreatment system 3 to have more than one exhaust gas aftertreatment element 7.

[0042] The exhaust gas aftertreatment system 3 also has a bypass path 9 around the at least one exhaust gas aftertreatment element 7, which bypass path 9 is embodied, in particular, as a bypass. In this context it is possible that the bypass path 9 is provided to bypass precisely one exhaust gas aftertreatment element 7, or that it is provided to bypass a group of exhaust gas aftertreatment elements 7 or else also all the exhaust gas aftertreatment elements 7 of the exhaust gas aftertreatment system 3.

[0043] The exhaust gas aftertreatment system 3 also has an actuation device 11 which is configured to distribute an exhaust gas mass flow to the at least one exhaust gas aftertreatment element 7, on the one hand, and the bypass path 9, on the other. In the exemplary embodiment illustrated here, the actuation device 11 has precisely one actuation element 13, which is provided here as an exhaust gas switch in a branch 15, at which a main exhaust gas path 17, comprising the exhaust gas aftertreatment element 7, and the bypass path 9 separate off. Here, the actuation element 13 is preferably embodied as a flap which can pivot along a schematically indicated double arrow, by which flap the exhaust gas mass flow can be divided between the main exhaust gas path 17, on the one hand, and the bypass path 9, on the other.

[0044] The exhaust gas aftertreatment system 3 also has a control device 19. For its part, said control device 19 has a determining means 21 for determining a permissible energy input into the at least one exhaust gas aftertreatment element 7, an ascertaining means 23 for ascertaining an instantaneous energy input into the at least one exhaust gas aftertreatment element 7, and an actuation means 25 for actuating the actuation device 11. In this context, the control device 19 is configured to actuate the actuation device 11 as a function of the permissible energy input and of the instantaneous energy input into the at least one exhaust gas aftertreatment element 7, in particular in order to perform open-loop or closed-loop control of the actuation device 11 and preferably of an actuation position of the actuation element 13.

[0045] In this context it is possible for the permissible energy input to be used as a setpoint value within the scope of an adjustment process, wherein the instantaneous energy input is used as an actual value.

[0046] It is possible for the control device 19 to be embodied as an engine control unit or as a central control unit of the internal combustion engine 1. In particular, the control device 19 is preferably operatively connected to the engine block 5 in order to ascertain an instantaneous operating state of the internal combustion engine 1.

[0047] The ascertaining means 23 is preferably configured to ascertain the instantaneous energy input by ascertaining at least one energy input variable which characterizes the instantaneous energy input. In this context, preferably an exhaust gas mass flow through the at least one exhaust gas aftertreatment element 7 and/or an exhaust gas temperature in the region of the exhaust gas aftertreatment element 7, preferably the exhaust gas mass flow and the exhaust gas temperature, is used as energy input variable. A thermal capacity c.sub.p at a constant pressure of the exhaust gas is preferably stored as a constant in the control device 19, in particular in the ascertaining means 23.

[0048] The determining means is preferably configured to determine the permissible energy input as a function of at least one operating parameter of the at least one exhaust gas aftertreatment element 7.

[0049] In order to ascertain an operating parameter of the at least one exhaust gas aftertreatment element and/or to determine an energy input variable, the exhaust gas aftertreatment system 3 preferably has a multiplicity of sensors, in particular a first pressure sensor 27 upstream of the exhaust gas aftertreatment element 7 and a second pressure sensor 29 downstream of the exhaust gas aftertreatment element 7. In particular, a pressure loss variable can be ascertained across the exhaust gas aftertreatment element 7 by means of the pressure sensors 27, 29. Instead of two separate pressure sensors 27, 29 it is also possible to use one differential pressure sensor.

[0050] A soot load of a particle filter can be ascertained from the pressure loss variable, for example as an operating parameter of the exhaust gas aftertreatment element 7. Additionally or alternatively, an exhaust gas mass flow can be ascertained across the exhaust gas aftertreatment element 7 from the pressure loss variable, preferably using the exhaust gas temperature in the region of the exhaust gas aftertreatment element 7.

[0051] A first temperature sensor 31 is preferably provided upstream of the exhaust gas aftertreatment element 7, wherein a second temperature sensor 32 is provided downstream of the exhaust gas aftertreatment element 7. For example, a mean value for the exhaust gas temperature in the exhaust gas aftertreatment element 7 can be ascertained on the basis of the measured values of the temperature sensors 31, 32. Alternatively or additionally, it is also possible to use a temperature sensor which is integrated into the exhaust gas aftertreatment element 7, or a temperature sensor which is arranged on the exhaust gas aftertreatment element 7 in such a way that it measures an exhaust gas temperature in the exhaust gas aftertreatment element 7. On the basis of a temperature difference between a measuring point upstream of the exhaust gas aftertreatment element 7 and a measuring point downstream of the exhaust gas aftertreatment element 7, in particular therefore on the basis of a temperature difference which is sensed with the temperature sensors 31, 32, it is possible to ascertain energy which is actually taken up by the exhaust gas aftertreatment element 7, by means of the heat loss in the exhaust gas.

[0052] It is also possible to ascertain the instantaneous energy input into the exhaust gas aftertreatment element 7 from the exhaust gas mass flow through the exhaust gas aftertreatment element 7, the known thermal capacity c.sub.p of the exhaust gas at a constant pressure and the exhaust gas temperature. In particular, it is therefore readily possible to ascertain energy which is input per unit of time into the exhaust gas aftertreatment element 7. By integration over a predetermined time period it is therefore also possible to ascertain energy which is in absolute terms input into the exhaust gas aftertreatment element 7 in the predetermined time period.

[0053] The control device 19 is preferably operatively connected to the actuation device 11, in particular to the actuation element 13, in order to actuate it. The control device 19 is also preferably operatively connected to the pressure sensors 27, 29 and the temperature sensors 31, 33.

[0054] If one of the energy input variables which is preferably used to ascertain the instantaneous energy input, that is to say in particular the exhaust gas mass flow and/or the exhaust gas temperature, is not determined by measurement, it is possible to acquire them on the basis of a model calculation or a simulation, in particular for the engine block 5, or to read them out from a characteristic diagram or a characteristic curve of the internal combustion engine 1.

[0055] It is important that within the scope of the method proposed here, not only pure control of the exhaust gas temperature of the actuation device is used but instead the energy input into the exhaust gas aftertreatment element 7 is ascertained, said energy input being actually informative about possible damage or destruction of the exhaust gas aftertreatment element 7.

[0056] FIG. 2 shows a schematic illustration of a second exemplary embodiment of the exhaust gas aftertreatment system 3. Identical and functionally identical elements are provided with the same reference symbols, with the result that in this respect reference is made to the preceding description. Here, the actuation device 11 has precisely one actuation element 13 which is preferably embodied as an actuation flap and is arranged in the bypass path 9. The actuation element 13 is embodied, in particular, as a bypass flap.

[0057] FIG. 3 shows a schematic illustration of a third exemplary embodiment of the exhaust gas aftertreatment system 3. Identical and functionally identical elements are provided with the same reference symbols, with the result that in this respect reference is made to the preceding description. In this exemplary embodiment, the actuation device 11 has in each case one actuation element 13, 13 in the bypass path 9, on the one hand, and in the main exhaust gas path 17, on the other, upstream of the exhaust gas aftertreatment element 7 and downstream of the branch 15. In this context, the two actuation elements 13, 13 are preferably coupled to one another in opposite directions, with the result that on the basis of their actuation positions or actuation angles the exhaust gas mass flow can also be divided clearly into portions which add up overall to 100%. In this context it is also possible to determine the exhaust gas mass flow through the exhaust gas aftertreatment element 7 by determining the exhaust gas mass flow, preferably by means of a pressure loss variable, by means of the actuation element 13 in the bypass path 9. If, in fact, this exhaust gas mass flow is known and at the same time the actuation position of the actuation element 13 is known, it is in turn possible to use this to infer the actuation position of the actuation element 13 in the main exhaust gas path 17, from which it is in turn possible to infer the exhaust gas mass flow through the exhaust gas aftertreatment element 7. For reasons of construction space, it may be appropriate to provide a sensor system for acquiring an exhaust gas mass flow only in the region of the actuation element 13 which is assigned to the bypass path 9.

[0058] Overall it becomes apparent that by means of the method, the exhaust gas aftertreatment system 3 and the internal combustion engine 1 it is possible to acquire in a very precise fashion an energy input into the exhaust gas aftertreatment element 7, with the result that it is possible, under operating conditions which are hazardous for the exhaust gas aftertreatment system 3, to conduct exhaust gas via the bypass path 9 and in doing so actuate the actuation device 11, with the result that the exhaust gas aftertreatment element 7 is enabled in a controlled fashion after a critical situation, or can be disabled in a controlled fashion when a critical situation occurs. In this context it is also to be noted that, in particular in the marine field, bypasses are in any case required around an exhaust gas aftertreatment system, with the result that no additional components are necessary to carry out the method. All that is necessary is to configure a means of actuating the actuation device 11 in such a way that said actuation device 11 is actuated, in particular adjusted, on the basis of the instantaneous energy input and the permissible energy input. Overall, it is therefore possible to prevent excessive ageing, damage or destruction of exhaust gas aftertreatment elements. Furthermore, an undesired emission of stored substances from an exhaust gas aftertreatment element can be prevented.