Exhaust gas aftertreatment method for an internal combustion engine and motor vehicle having an exhaust gas aftertreatment system

Abstract

The invention relates to a method for post-treatment of exhaust gas of an externally ignited internal combustion engine in a motor vehicle. The internal combustion engine is connected on the exhaust side to an exhaust gas post-treatment system, in which a first exhaust gas post-treatment component is arranged along the flow direction of the exhaust gas flow, an external heating device is arranged downstream of the first exhaust gas post-treatment component, and a second exhaust gas post-treatment component is further arranged downstream. The component temperature of the exhaust gas post-treatment component and the current conversion power of the exhaust gas post-treatment component are determined. Depending on the determined component temperature and current conversion power and the load demand on the internal combustion engine, if the determined component temperature of the second exhaust gas post-treatment component is below a first threshold temperature and the conversion power of the first exhaust gas post-treatment component is expected to be insufficient to ensure complete conversion of the specified harmful substances in the exhaust gas flow of the internal combustion engine for the determined load demand on the internal combustion engine, the external heating device is activated.

Description

Field of the Invention

[0001] The present invention relates to a method for post-treatment of exhaust gas of an internal combustion engine in a motor vehicle and a motor vehicle having an internal combustion engine, which has an exhaust gas post-treatment system for carrying out such a method. Background Art

[0002] Current and future increasingly stringent emission regulations place high demands on the raw emissions of the engine and the post-treatment of the exhaust gas of the internal combustion engine. In gasoline engines, exhaust gas purification is achieved in a known manner by a three-way catalytic converter and other catalytic converters and particulate filters arranged upstream or downstream of the three-way catalytic converter. Each device for catalytically cleaning the exhaust gas requires a temperature above a minimum temperature, i.e., the so-called light-off temperature, to be effective. When the motor vehicle is cold-started, the temperature levels of the internal combustion engine and the components for exhaust gas post-treatment are approximately equal to the ambient temperature. Even by inputting high energy into the exhaust system, it is necessary to first overcome the thermally tubular mass of the exhaust system and compensate for radiation losses or convective losses in order to at least achieve a partial effect of the exhaust gas post-treatment components. During this period, the raw emissions of the internal combustion engine are largely emitted without being cleaned. Depending on the energy input in the exhaust system, this time period can be shortened, but it cannot be reduced to zero. The faster the light-off temperature of the catalytic converter is reached, the lower the emissions of the internal combustion engine can operate in combination with the exhaust gas post-treatment system. In addition, the volume of the actively heated catalytic converter has a significant impact on the conversion power. Therefore, in order to meet future emission regulations, it may be necessary to assist by additional external heating measures to reach the component temperature of the exhaust gas post-treatment components.

[0003] A method for controlling or regulating a burner operating with air and fuel is known from document DE 10 2012 021 573 A1. The burner exhaust gas of the burner is mixed with the internal combustion engine exhaust gas of an externally ignited internal combustion engine, and the mixed exhaust gas thus obtained is fed into an exhaust gas catalytic converter having a three-way catalytic function. Document DE 10 2012 021 573 A1 also discloses an exhaust system provided for carrying out this method. It is provided to measure the actual oxygen content of the mixed exhaust gas or a variable related thereto, and to influence the fuel quantity fed into the burner in such a way that the actual oxygen content at least approaches the predetermined oxygen content of the mixed exhaust gas.

[0004] Document DE 10 2008 032 601 A1 discloses a method for regulating the state of the exhaust gas flow of a motor vehicle internal combustion engine. Here, an exhaust gas burner is arranged in the exhaust system of the internal combustion engine. In order to achieve an improvement in the regulation of the exhaust gas flow state, the injection quantity of fuel injected into the burner and the secondary air fed into the burner are regulated in such a way that a fuel-rich combustion gas is adjusted by the injection quantity and the secondary air mass flow. The burner is used in particular to reduce a diesel particulate filter in the exhaust system.

[0005] Document DE 10 2017 113 366 A1 describes a method for heating an exhaust gas aftertreatment component in an exhaust gas system of an internal combustion engine before starting the internal combustion engine. Here, an electrically heatable three-way catalytic converter is heated and preferably also a four-way catalytic converter arranged downstream of the three-way catalytic converter is heated in order to enable an efficient exhaust gas aftertreatment of the raw emissions of the internal combustion engine from the start of starting the internal combustion engine. The exhaust gas aftertreatment system is also configured to enable an efficient conversion of harmful substances even during regeneration of the four-way catalytic converter and thus to ensure particularly low emissions in all operating states of the internal combustion engine. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to ensure the highest possible conversion power of the exhaust gas aftertreatment components in all operating states of a motor vehicle in an externally ignited internal combustion engine of the motor vehicle.

[0007] The above technical problem is solved according to the present invention by a method for exhaust gas aftertreatment of an externally ignited internal combustion engine of a motor vehicle. The internal combustion engine is connected to an exhaust gas aftertreatment system via its exhaust port. The exhaust gas aftertreatment system has an exhaust gas system, in which a first exhaust gas aftertreatment component is arranged along the flow direction of the exhaust gas flow in the exhaust gas passage of the exhaust gas system through which the exhaust gas of the internal combustion engine flows. An external heating device is arranged downstream of the first exhaust gas aftertreatment component, and a second exhaust gas aftertreatment component is arranged further downstream. The method has the following steps:

[0008] - Determining the component temperature and the conversion power of the first exhaust gas aftertreatment component,

[0009] - Determining the component temperature and / or the conversion power of the second exhaust gas aftertreatment component,

[0010] - Comparing the component temperature of the second exhaust gas aftertreatment component with a first threshold temperature,

[0011] - Determining the load demand on the internal combustion engine, and

[0012] - If the determined component temperature of the second exhaust gas aftertreatment component is lower than the first threshold temperature and the conversion power of the first exhaust gas aftertreatment component is expected to be insufficient to ensure complete conversion of the specified harmful substances in the exhaust gas flow of the internal combustion engine for the determined load demand on the internal combustion engine, activating the external heating device.

[0013] The determination of the component temperature of an exhaust gas aftertreatment component can be achieved by a temperature measuring device in the exhaust system, in particular by a temperature sensor on one of the exhaust gas aftertreatment components or by a calculation model which calculates the temperature of the exhaust gas aftertreatment component based on the load of the internal combustion engine and, if necessary, based on other parameters, in particular the ambient temperature. This method enables the exhaust gas aftertreatment component to reach its corresponding operating temperature as required and thereby enables a particularly efficient conversion of harmful substances in the exhaust gas stream of the internal combustion engine. In addition, it is possible to avoid a reduction in the efficiency of the internal combustion engine and unnecessary heating measures which may lead to additional consumption. An external heating device is understood to be a heating measure in the exhaust device outside the engine, i.e. a heat input into the exhaust device from the outside. The external heating device particularly includes an exhaust gas burner or an electrical heating element.

[0014] In a preferred embodiment of the invention, it is provided that the external heating device is activated immediately after the motor of the internal combustion engine is started. Since not all exhaust gas aftertreatment components reach their operating temperature immediately after the motor is started, a larger catalytically effective volume can be provided immediately by heating the first exhaust gas aftertreatment component by means of an internal engine heating measure and heating the second exhaust gas aftertreatment component by means of an external heating device.

[0015] In other preferred embodiments of the invention, it is provided that the external heating device is activated if a current or impending higher load demand on the internal combustion engine is detected. Thereby, it is possible to avoid an emission breakthrough of the first exhaust gas aftertreatment component during a sudden load change and the emission of this emission into the environment without conversion.

[0016] Alternatively, in an advantageous embodiment of the method, it is provided that the external heating device is activated if a situation in which the load demand on the internal combustion engine is below a threshold has lasted for a defined period of time. During a long-term low-load operation, the second exhaust gas aftertreatment component located at the bottom may cool below its ignition temperature. To avoid this, the external heating device is activated during a long-term low-load phase in order to keep the second exhaust gas aftertreatment component at a temperature at which harmful substances can be efficiently converted.

[0017] In an advantageous embodiment of the method for exhaust gas aftertreatment, it is provided that the external heating device is activated if the temperature of the second exhaust gas aftertreatment component is below a second threshold. Alternatively, if the temperature of the second exhaust gas aftertreatment component is close to the ignition temperature and there is a risk of ineffectiveness of the second exhaust gas aftertreatment component, the external heating device can also be directly controlled by the temperature of the second exhaust gas aftertreatment component.

[0018] On the other hand, the present invention relates to a motor vehicle having an internal combustion engine with external ignition, wherein the internal combustion engine is connected to an exhaust device of an exhaust gas aftertreatment system via its exhaust port. A first exhaust gas aftertreatment component is arranged in the exhaust device in the flow direction of the exhaust gas flow through the exhaust gas passage of the exhaust device of the internal combustion engine. An external heating device is arranged downstream of the first exhaust gas aftertreatment component, and a second exhaust gas aftertreatment component is arranged further downstream. The motor vehicle also has a control device, in particular a motor control device, which is configured to implement the aforementioned method when executing machine-readable program code by the control device. In such a motor vehicle, particularly effective and energy-efficient exhaust gas aftertreatment of the internal combustion engine can be achieved.

[0019] In a preferred design of the motor vehicle, it is provided that the external heating device is an exhaust gas burner. With an exhaust gas burner, a relatively large amount of heat can be introduced into the exhaust device in a short time, thereby heating the second exhaust gas aftertreatment component particularly quickly. Thereby, the time until the second exhaust gas aftertreatment component reaches its ignition temperature can be shortened.

[0020] Alternatively or additionally, it is advantageously provided that the external heating device includes an electrical heating element. With an electrical heating element, the temperature in the exhaust device can be controlled particularly accurately. In addition, the electrical heating element is smaller and less costly than an exhaust gas burner.

[0021] Here, it is particularly preferred that the external heating device has a heating power of at least 5 kW. With a heating power of at least 5 kW, preferably at least 8 kW, and particularly preferably at least 10 kW, the second exhaust gas aftertreatment component can be heated to its ignition temperature in a particularly short period of time. This is particularly advantageous during (impending) load changes, especially during full-load acceleration, in order to heat the second exhaust gas aftertreatment component to its ignition temperature before an emissions breakthrough through the first exhaust gas aftertreatment component occurs.

[0022] In an advantageous design of the motor vehicle, it is provided that the first exhaust gas aftertreatment component and the second exhaust gas aftertreatment component each have a three-way catalytic function. With two exhaust gas aftertreatment components having a three-way catalytic function, a particularly large catalytically effective volume can be provided in a simple manner in order to effectively convert the exhaust gas of the internal combustion engine at each operating point.

[0023] In a preferred design of a motor vehicle, it is provided that the motor vehicle has at least one detection device by which an impending increase in the load demand on the internal combustion engine can be recognized, wherein if the detection device detects an impending increase in the load demand on the internal combustion engine, the control device activates the external heating device. The detection device can determine the environment around the motor vehicle and / or the position of the motor vehicle. The detection device particularly includes a camera and / or a GPS sensor herein. Herein, the impending load demand on the internal combustion engine can be determined based on the driving distance and / or based on the traffic situation. For example, when driving onto a highway or to the bottom of a slope, a high load demand can be recognized as impending, and the second exhaust gas aftertreatment component can be heated by means of an external heating device before the corresponding load demand on the internal combustion engine is realized. In this way, the emissions of the internal combustion engine can be reduced particularly effectively.

[0024] The various embodiments of the present invention mentioned in this application can be advantageously combined with each other if not otherwise stated separately. Description of the Drawings

[0025] The present invention will be described hereinafter in embodiments with reference to the drawings. Herein, the same components or components with the same functions are provided with the same reference numerals in different drawings. In the drawings:

[0026] Figure 1 A schematic diagram of a motor vehicle is shown;

[0027] Figure 2 A schematic diagram of an internal combustion engine with an exhaust gas aftertreatment system is shown;

[0028] Figure 3 An alternative design of an internal combustion engine with an exhaust gas aftertreatment system is shown in the schematic diagram;

[0029] Figure 4 Another alternative design of an internal combustion engine with an exhaust gas aftertreatment system is shown in the schematic diagram; and

[0030] Figure 5 A flowchart showing a method for exhaust gas aftertreatment of an internal combustion engine in a motor vehicle according to the present invention is shown. Detailed Description of the Invention

[0031] Figure 1A motor vehicle 1 with an internal combustion engine 10 is shown. The internal combustion engine 10 is designed as an externally ignited internal combustion engine 10 according to the Otto principle and has a plurality of combustion chambers 12, on which a fuel injector 14 and a spark plug 16 are respectively arranged. The internal combustion engine 10 is connected via its exhaust port 18 to the exhaust device 22 of an exhaust gas aftertreatment system 20. The motor vehicle 1 has at least one detection device 76, preferably a plurality of detection devices 76, by means of which the surroundings of the motor vehicle, the position of the motor vehicle, the driving direction, the speed, the environment and possibly other parameters can be detected. The detection device 76 can in particular include a GPS sensor 66 for detecting the position and position changes of the motor vehicle 1. The detection device 76 can also include one or more optical detection devices 76, in particular one or more cameras 68. The detection device 76 is connected to a data transmission unit 70, which processes the information of the detection device and exchanges the information with other data sources inside or outside the vehicle, in particular the driving assistance system, the navigation system of the motor vehicle 1 or an external computing center. For this purpose, the motor vehicle 1 has a sending unit 62 and a receiving unit 64. The sending unit 62 and the receiving unit 64 can also be integrated into a component.

[0032] Figure 2 A schematic view of the internal combustion engine 10 is shown, which is connected via its exhaust port 18 to the exhaust device 22. The internal combustion engine 10 is preferably designed as a gasoline engine with a direct gasoline injection device and has a plurality of combustion chambers 12, on which fuel injectors 14 for injecting fuel into the respective combustion chambers 12 are arranged. In addition, each combustion chamber 12 is equipped with a spark plug 16 in order to ignite the ignitable fuel-air mixture in the respective combustion chamber 12 of the internal combustion engine 10.

[0033] The internal combustion engine 10 has an exhaust gas aftertreatment system 20, which has an exhaust device 22. The exhaust device 22 includes an exhaust gas passage 24, in which a turbine 28 of an exhaust gas turbocharger 26 is arranged along the flow direction of the exhaust gas flowing through the exhaust gas passage 24 of the internal combustion engine. Downstream of the turbine, a first exhaust gas aftertreatment component 30, in particular a three-way catalytic converter 44, is arranged. Downstream of the first exhaust gas aftertreatment component 30, an external heating device 36, in particular an exhaust gas burner 38, is arranged, and further downstream, a second exhaust gas aftertreatment component 32, in particular a second three-way catalytic converter 46, is arranged. The first exhaust gas aftertreatment component 30 is arranged as an exhaust gas aftertreatment component 72 close to the engine, and the second exhaust gas aftertreatment component 32 is arranged as an exhaust gas aftertreatment component in the bottom position 74 of the motor vehicle 1. A first temperature sensor 52 is arranged on the first exhaust gas aftertreatment component 30. The second exhaust gas aftertreatment component 32 has a second temperature sensor 54. Downstream of the second exhaust gas aftertreatment component 32, an exhaust gas sensor 58, in particular a sensor for detecting the concentration of harmful substances in the exhaust gas passage 24, is arranged. The internal combustion engine 10 can alternatively also be designed as a naturally aspirated engine, in which case the exhaust gas turbocharger having the turbine 28 is omitted. In addition, one of the two exhaust gas aftertreatment components 30, 32 can alternatively be designed as a four-way catalytic converter 50 in order to filter particulate matter from the exhaust gas flow of the internal combustion engine 10 in addition to the catalytic function. An introduction position 40 is designed on the exhaust gas passage 24, through which the exhaust gas of the exhaust gas burner 38 can be introduced into the exhaust gas passage 24 of the internal combustion engine 10. As an alternative to the exhaust gas burner 38, the external heating device 36 can also be designed as an electrical heating element 42 as Figure 4 shown.

[0034] In Figure 3 a further alternative embodiment of the internal combustion engine 10 having the exhaust gas aftertreatment system 20 is shown. In a structure substantially identical to the Figure 2 structure shown, a further exhaust gas aftertreatment component 34, 72 close to the engine is arranged downstream of the first exhaust gas aftertreatment component 30. The further exhaust gas aftertreatment component can in particular be a gasoline particulate filter 48. In this case, the introduction position 40 of the external heating device 36 or the exhaust gas burner 38 is located downstream of the further exhaust gas aftertreatment component 34 and upstream of the second exhaust gas aftertreatment component 32, which is arranged in the bottom position of the motor vehicle 1. As an alternative to the gasoline particulate filter 48, the further exhaust gas aftertreatment component 34 can also be designed as another catalytic converter.

[0035] In Figure 4 a further alternative embodiment of the internal combustion engine 10 having the exhaust gas aftertreatment system 20 is shown. In a structure substantially identical to the Figure 2and Figure 3 in the substantially same structure as Figure 4 the exhaust gas aftertreatment system 20 shown therein has an exhaust gas aftertreatment component 72 close to the engine and two exhaust gas aftertreatment components 32, 34, 74 in the bottom position. Here, the first exhaust gas aftertreatment component 30, 72 close to the engine is preferably designed as a three-way catalytic converter 44. The two exhaust gas aftertreatment components 32, 34, 74 in the bottom position are preferably designed as a second three-way catalytic converter 46 and a gasoline particulate filter 48, wherein the order of flow through the second three-way catalytic converter 46 and the gasoline particulate filter 48 is arbitrary. The external heating device 36 is Figure 4 designed as an electrical heating element 42 in Figure 2 or Figure 3 alternatively, an exhaust gas burner 38 can be provided at the same position as shown

[0036] The object of the method for exhaust gas aftertreatment according to the invention is to provide as high a conversion power as possible as required in all driving states of the motor vehicle 1 during the entire driving cycle. Compared with heating the exhaust gas aftertreatment components only by heating measures inside the engine, heating the exhaust gas aftertreatment components 32, 74 far from the engine in the bottom position provides a larger catalytically effective volume for converting emissions.

[0037] The method determines whether it makes sense to heat the second exhaust gas aftertreatment component 32, preferably the exhaust gas aftertreatment component in the bottom position 74, based on the states of the two exhaust gas aftertreatment components 30, 32 and other conditions. In this way, the method can simultaneously prevent unnecessary overheating of the second exhaust gas aftertreatment component 32 in terms of energy and ensure a consistently high conversion power of the exhaust gas aftertreatment system 20.

[0038] Starting from the engine start of the internal combustion engine 10, the exhaust gas aftertreatment system 20 can heat the second exhaust gas aftertreatment component 32 to its operating temperature by means of an external heating device 36 in parallel with heating measures inside the engine that mainly rapidly heat the first exhaust gas aftertreatment component. This reduces emissions. If the second exhaust gas aftertreatment component 32, in particular the second three-way catalytic converter 46, reaches the operating temperature, the external heating device 36 can be switched off. If the second exhaust gas aftertreatment component 32 cools down again during the continued operation of the motor vehicle 1 and a higher conversion power is foreseeable based on different operating parameters of the internal combustion engine 10 or signals from the detection device 76, the external heating device 36 can be reactivated in order to heat the second exhaust gas aftertreatment component 32 at least again to its light-off temperature. Influencing factors in this regard can in particular be the temperature of the exhaust gas aftertreatment components 30, 32, the exhaust gas mass flow of the internal combustion engine 10, the aging state of the exhaust gas aftertreatment components 30, 32, the exhaust gas temperature, the ambient temperature and the power demand or torque demand at the internal combustion engine 10.

[0039] The heating measure by means of the external heating device 36 is particularly suitable for the engine start of the internal combustion engine 10 when not all exhaust gas aftertreatment components 30, 32, 34 have reached the operating temperature. In this context, a temperature of at least 350 °C is regarded as the operating temperature for the catalytic converter. The heating measure by means of the external heating device 36 is also suitable for bringing the exhaust gas aftertreatment component, in particular the three-way catalytic converter 46, in the bottom position 74 back to its operating temperature after a long period of low-load operation. The relevant component temperatures can be determined by the temperature sensors 52, 54, 56 or calculated in the control device 60 based on a temperature model.

[0040] In Figure 5 FIG. shows a flow chart of a method for exhaust gas aftertreatment according to the invention. In method step <100> it is checked whether the internal combustion engine 10 is activated. If the internal combustion engine 10 is not activated, the method is interrupted in method step <105> and the external heating device 36 is not activated. If the internal combustion engine 10 is activated, the temperature T of the second exhaust gas aftertreatment component 32, 74 in the bottom position is checked in method step <110> ANK2 whether it is less than a first threshold temperature T S1 . If the temperature T of the second exhaust gas aftertreatment component ANK2 is higher than the first threshold temperature T S1 , the method is terminated in method step <115> and the external heating device 36 is not activated or switched off. If the temperature T of the second exhaust gas aftertreatment component ANK2 is lower than the first threshold temperature T S1 , the temperature T of the first exhaust gas aftertreatment component 30, 72 close to the engine is checked in method step <120> ANK1whether it is below its light-off temperature. If the temperature T ANK1 is above its light-off temperature, it is checked in method step <125> whether the load demand on the internal combustion engine 10 is higher than a threshold load at which sufficient conversion of harmful substances can be achieved solely by the first exhaust gas aftertreatment component 30. If the load demand on the internal combustion engine is not higher than the threshold load, the method is interrupted again in method step <115>. If the load demand is higher than this threshold load or the temperature T ANK1 of the first exhaust gas aftertreatment component is below its light-off temperature, an external heating device 36 is activated in method step <130> in order to heat at least the second exhaust gas aftertreatment component 32 to its light-off temperature, preferably to its operating temperature.

[0041] If the detection device detects an impending high power demand on the internal combustion engine 10, in particular a full-load acceleration, the external heating device 36 is still activated if the conversion power of the current first exhaust gas aftertreatment component 30 is still sufficient to completely convert the emissions of the internal combustion engine 10. This can prevent the first exhaust gas aftertreatment component 30 from being "overloaded" during full-load acceleration and not being able to provide a sufficient catalytic volume for the conversion of additional harmful substances. For example, it can generally be assumed that a full-load acceleration is impending when driving onto a road. This can be recognized by the detection device 76 mentioned, in particular by the GPS sensor 66 and / or the camera 68.

[0042] List of reference numerals

[0043] 1 Motor vehicle

[0044] 10 Internal combustion engine

[0045] 12 Combustion chamber

[0046] 14 Fuel injector

[0047] 16 Spark plug

[0048] 18 Exhaust port

[0049] 20 Exhaust gas aftertreatment system

[0050] 22 Exhaust device

[0051] 24 Exhaust gas passage

[0052] 26 Exhaust gas turbocharger

[0053] 28 Turbine

[0054] 30 First exhaust gas aftertreatment component

[0055] 32 Second exhaust gas aftertreatment component

[0056] 34 Third exhaust gas aftertreatment component

[0057] 36 External heating device

[0058] 38 Exhaust gas burner

[0059] 40 Introduction position

[0060] 42 Electrical heating element

[0061] 44 First three-way catalytic converter

[0062] 46 Second three-way catalytic converter

[0063] 48 Gasoline particulate filter

[0064] 50 Four-way catalytic converter

[0065] 52 First temperature sensor

[0066] 54 Second temperature sensor

[0067] 56 Third temperature sensor

[0068] 58 Exhaust gas sensor

[0069] 60 Engine control equipment

[0070] 62 Sending unit

[0071] 64 Receiving unit

[0072] 66 GPS sensor

[0073] 68 Camera

[0074] 70 Data transmission unit

[0075] 72 Third exhaust gas after-treatment component near the engine

[0076] 74 Exhaust gas after-treatment component in the bottom position

[0077] 76 Detection device

Claims

1. A method for post-treatment of exhaust gases of an externally ignited internal combustion engine (10) of a motor vehicle (1), the motor vehicle having an exhaust gas post-treatment system (20), the exhaust gas post-treatment system having an exhaust device (22), in which a first exhaust gas post-treatment component (30) is arranged in the flow direction of the exhaust gas flow through an exhaust gas passage (24) of the exhaust device (22) of the internal combustion engine (10), an external heating device (36) is arranged downstream of the first exhaust gas post-treatment component (30), and a second exhaust gas post-treatment component (32) is arranged further downstream, the method having the following steps: - Determine the component temperature T of the first exhaust gas aftertreatment component (30) ANK1 and the conversion power of the first exhaust gas aftertreatment component (30), -Determine the component temperature T of the second exhaust gas aftertreatment component (32) ANK2 and / or the conversion power of the second exhaust gas aftertreatment component (32), - Compare the component temperature T of the second exhaust gas post-treatment component (32) ANK2 with the first threshold temperature T S1 and - determining the load demand for the internal combustion engine (10), and - activating the external heating device (36) if: -- If the component temperature T of the determined second exhaust gas aftertreatment component (32) ANK2 is lower than the first threshold temperature T S1 , and -- the conversion power of the first exhaust gas post-treatment component (30) is expected to be insufficient to ensure complete conversion of specified harmful substances in the exhaust gas flow of the internal combustion engine (10) for the determined load demand for the internal combustion engine (10), and -- if a current or upcoming higher load demand for the internal combustion engine (10) is detected, or if a situation where the load demand for the internal combustion engine (36) is below a threshold has elapsed for a defined period of time.

2. The method according to claim 1, wherein The external heating device (36) is activated immediately after starting the motor of the internal combustion engine (10).

3. The method according to claim 1, wherein If the temperature T of the second exhaust gas after-treatment component ANK2 is lower than the second threshold temperature T S2 , then the external heating device (36) is activated.

4. A motor vehicle (1) having an internal combustion engine (10) with external ignition, wherein, The internal combustion engine (10) is connected to the exhaust device (22) of the exhaust gas post-treatment system (20) via its exhaust port (18), in which a first exhaust gas post-treatment component (30) is arranged in the flow direction of the exhaust gas flow through the exhaust gas passage (24) of the exhaust device (22) of the internal combustion engine (10), an external heating device (36) is arranged downstream of the first exhaust gas post-treatment component (30), and a second exhaust gas post-treatment component (32) is arranged further downstream, the motor vehicle further having a control device (60) which is arranged to carry out the method according to one of claims 1 to 3 when executing machine-readable program code by means of the control device (60).

5. The motor vehicle (1) according to claim 4, characterized in that, The external heating device (36) is an exhaust gas burner (38) or an electrical heating element (42).

6. The motor vehicle (1) according to claim 5, characterized in that, The external heating device (36) has a heating power of at least 5 kW.

7. The motor vehicle (1) according to claim 4, characterized in that, The first exhaust gas post-treatment component (30) and the second exhaust gas post-treatment component (32) each have a three-way catalytic function.

8. The motor vehicle (1) according to claim 4, characterized in that, The motor vehicle (1) has at least one detection device (76) by means of which an upcoming increase in the load demand for the internal combustion engine (10) can be recognized, wherein if the detection device (76) detects an upcoming increase in the load demand for the internal combustion engine (10), the control device (60) activates the external heating device.

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