DE102019122921B4 - Catalyst arrangement and exhaust aftertreatment system with such a catalyst arrangement - Google Patents

Abstract

Catalyst arrangement (52), comprising an exhaust gas channel segment (54), in which an electrically heatable catalyst (28) and in the flow direction of an exhaust gas stream of an internal combustion engine (10) through the exhaust gas channel segment (54) downstream of the electrically heatable catalyst (28) a catalyst (32) are arranged, and with a sensor (40) arranged upstream of the electrically heatable catalytic converter (28), with a shielding element (42) being arranged downstream of the sensor (40) and upstream of the electrically heatable catalytic converter (28), which enables heat transfer by means of thermal radiation from the electrically heatable catalytic converter (28) on the sensor (40) is reduced or avoided, characterized in that the shielding element (42) comprises or is a catalytic converter disc (44) with a thickness of 5 mm to 35 mm.

Description

The invention relates to a catalytic converter arrangement in an exhaust system of an internal combustion engine and an exhaust gas aftertreatment system for an internal combustion engine with such a catalytic converter arrangement according to the preamble of the independent patent claims.

The continuous tightening of the exhaust gas legislation places high demands on the vehicle manufacturers, which are solved by appropriate measures to reduce engine raw emissions and appropriate exhaust gas aftertreatment. Catalysts coated with precious metal are installed in the exhaust system of the internal combustion engine in order to be able to effectively convert the raw emissions that cannot be completely avoided into the engine. So that these catalytic converters can convert the pollutants, a minimum temperature level of the exhaust gas and the catalytic converter is necessary. In order to bring the catalytic converter up to operating temperature as quickly as possible after a cold start of the combustion engine, engine heating measures such as adjusting the ignition angle or fuel injection in the "retarded" direction or substoichiometric operation of the combustion engine with the simultaneous introduction of secondary air are used. In order to bring even more thermal energy into the exhaust system, it is possible to heat the catalytic converter electrically or to install a switchable exhaust gas burner on the exhaust system in order to feed hot exhaust gas into the exhaust system and to heat the exhaust gas aftertreatment components arranged in the exhaust system independently of the combustion engine. As a result, emissions can already be significantly reduced in the heating phase of the catalytic converter.

In diesel engines, late post-injection and/or a late shift in the center of combustion are known to increase the exhaust gas temperature, with the thermal efficiency of the internal combustion engine decreasing and more energy being introduced into the exhaust system. At the same time, raw emissions of nitrogen oxides can be reduced by shifting the main injection towards "late".

A disadvantage of the solutions known from the prior art, however, is that internal engine heating measures only become effective after the internal combustion engine has been started. In addition, these internal engine heating measures can lead to fuel entering the engine oil, which increases wear or the oil change intervals have to be shortened.

Furthermore, external heating means in the exhaust system, such as an exhaust gas burner or an electric heating element, are known from the prior art. The exhaust gas aftertreatment components can be heated essentially independently of the exhaust gas flow of the internal combustion engine by means of external heating means and thus reach their operating temperature more quickly, as a result of which the tailpipe emissions can be reduced in particular in a cold start phase of the internal combustion engine.

the DE 10 2011 018 293 A1 discloses a catalyst heating system for a catalyst in an exhaust system of an internal combustion engine. The catalyst heating system includes a monitor module, a mode selection module, and an electrically heated catalyst control module. The control module controls a current to the electrically heatable catalyst.

From the DE 10 2017 113 366 A1 an exhaust aftertreatment system for a spark-ignited internal combustion engine is known. In the exhaust system, in the flow direction of an exhaust gas through the exhaust system, there is an electrically heatable three-way catalytic converter, downstream of the electrically heatable three-way catalytic converter a four-way catalytic converter and downstream of the four-way catalytic converter another three-way Catalyst arranged. Before the internal combustion engine is started, the electrically heatable three-way catalytic converter and preferably also the four-way catalytic converter are heated in order to enable efficient exhaust aftertreatment of the raw emissions from the internal combustion engine as soon as the internal combustion engine is started. The exhaust aftertreatment system is set up to enable efficient conversion of the pollutants even during regeneration of the four-way catalytic converter and thus to ensure particularly low emissions in all operating states of the motor vehicle.

the U.S. 2015/0 165 376 A1 discloses a catalytic converter device with an electrically heatable catalytic converter, a catalytically active structure of the electrically heatable catalytic converter being formed downstream of an electric heating element. The catalytic converter includes an outer cylinder surrounding the electric heating element and an insulator formed on the inner surface of the outer cylinder. The catalytically active structure is divided into two parts, with a partial exhaust gas flow through the outer region of the catalyst body being larger than the partial exhaust gas flow through the inner region of the catalyst body.

the DE 10 2017 218 374 A1 discloses a device for determining a heating temperature of a heating element for an electrically heatable catalytic converter. The device includes the heating element and the catalyst arranged within a catalyst housing, and a first temperature sensor and a second temperature sensor arranged within the catalyst housing, wherein the first temperature sensor is arranged closer to the heating element than with respect to an exhaust gas flow direction within the catalyst housing the second temperature sensor.

From the DE 10 2012 214 378 A1 a system for thermal regulation in an exhaust aftertreatment system is known. The system includes an enabling module, a status module, and a temperature control module. The enable module enables production of ammonia for use in SCR catalysts of the exhaust aftertreatment system. The status module determines whether the exhaust aftertreatment system is operating in a passive SCR mode and generates an active passive SCR signal. The passive SCR mode includes operating an internal combustion engine with an air-fuel ratio lean of stoichiometry. The temperature control module activates an electric oxidation catalyst heater based on the passive SCR active signal and a temperature of the oxidation catalyst.

The object of the invention is now to increase the measuring accuracy of a temperature sensor in an exhaust system and, in particular, to reduce measuring errors caused by an electrical heating element and to improve the catalytic effect of the catalytic converter arrangement.

According to the invention, this object is achieved by a catalytic converter arrangement with an exhaust gas duct segment, in which an electrically heatable catalytic converter and in the direction of flow of an exhaust gas stream of an internal combustion engine through the exhaust gas duct segment, a further catalytic converter are arranged downstream of the electrically heatable catalytic converter, and with a sensor arranged upstream of the electrically heatable catalytic converter . Provision is made for a shielding element to be arranged downstream of the sensor and upstream of the electrically heatable catalytic converter, which shielding element reduces or prevents heat transmission by means of thermal radiation from the electrically heatable catalytic converter to the sensor. When using an electrically heatable catalytic converter, the heat of the electrically heatable catalytic converter is given off to the environment via convection and radiation. The thermal radiation also acts on components arranged in the exhaust system upstream of the electrically heatable catalytic converter. Thus, for example, a temperature sensor arranged directly in front of the electrically heatable catalytic converter or an exhaust gas sensor is heated by the thermal radiation of the electrically heatable catalytic converter, as a result of which the measurement signal can be falsified. In order to reduce or eliminate the falsification of the measurement signal, a shielding element is arranged downstream of the sensor and upstream of the electrically heatable catalytic converter, which reduces or prevents heating of the sensor by thermal radiation and thus increases the measurement accuracy of the sensor.

Advantageous improvements and further developments of the catalytic converter arrangement specified in the independent claim are possible as a result of the features listed in the dependent claims.

According to the invention it is provided that the shielding element comprises or is a catalytic converter disc. A catalytic converter disc upstream of the electrically heatable catalytic converter allows the further catalytic converter downstream of the electrically heatable catalytic converter to be made smaller. Both the catalytic converter disk and the further catalytic converter are heated by the thermal radiation of the electrically heatable catalytic converter in addition to the convective heat transfer to the further catalytic converter, as a result of which all components of the catalytic converter arrangement reach their light-off temperature more quickly. In this way, the conversion performance can be improved, especially when the exhaust system is cold, and tailpipe emissions can be reduced.

According to the invention, it is provided that the catalyst disc has a thickness of 5 mm to 35 mm, preferably 10 mm to 25 mm, in particular about 15 mm. In the case of a thin catalytic converter disk, the heat transferred from the electrically heatable catalytic converter to the catalytic converter disk by means of thermal radiation means that this catalytic converter disk also heats up quickly and thus reaches its light-off temperature immediately after activation of the electrically heatable catalytic converter. As a result, the pollutants contained in the exhaust gas flow of the internal combustion engine can be converted or stored immediately after a cold start of the internal combustion engine, as a result of which the tailpipe emissions, particularly in the cold start phase, can be reduced.

In an advantageous embodiment of the catalytic converter arrangement, it is provided that the catalytic converter disc is spaced upstream from 2 mm to 50 mm, preferably from 2 mm to 15 mm an electric heating element of the electrically heatable catalyst is arranged. Since the thermal radiation spreads and is distributed to all adjacent components, it is expedient to arrange the catalytic converter disk as close as possible to the electrically heatable catalytic converter in order to enable the catalytic converter disk and not the adjacent wall to be heated as exclusively as possible by the thermal radiation of the electrically heatable catalytic converter. The distance from an outlet-side end face of the catalytic converter disc to an inlet-side end face of the electrically heatable catalytic converter is measured. A maximum distance of 50 mm ensures that strong heating of the electrically heated catalytic converter leads to functionally reliable heating of the catalytic converter disc to its light-off temperature and thus pollutants in the exhaust gas flow of the combustion engine are converted by the catalytic converter disc immediately after a cold start of the combustion engine or can be saved.

In a preferred embodiment of the catalytic converter arrangement, it is provided that the sensor is a temperature sensor or an exhaust gas sensor. In order to enable efficient control of the catalytic converter arrangement, it is advantageous if the sensor is designed as a temperature sensor in order to know the temperature of the exhaust gas flow before it enters the subsequent catalytic converters and thus to be able to estimate the extent to which the pollutants contained in the exhaust gas flow of the internal combustion engine are converted is possible. Alternatively, the sensor can also be an exhaust gas sensor, with which a pollutant concentration of a limited exhaust gas component is detected before it enters the catalytic converter.

In a further preferred embodiment of the invention it is provided that the shielding element comprises or is a shielding plate. A shielding plate can prevent the thermal radiation from the electrically heatable catalytic converter leading to heat input into the sensor upstream of the electrically heatable catalytic converter and leading to a falsification of the measurement results at this sensor, particularly when measuring a temperature.

In a further preferred embodiment of the invention, it is provided that the catalytic converter is designed as an oxidation catalytic converter or as a NOx storage catalytic converter. Since electrically heatable catalytic converters are often used in exhaust gas systems of diesel engines, the use of such an electrically heatable catalytic converter upstream of an oxidation catalytic converter or a NOx storage catalytic converter as the first catalytic converter in the direction of flow of an exhaust gas from the internal combustion engine makes sense. In particular, partial oxidation of nitrogen oxides can take place in order to set an ideal ratio of nitrogen monoxide (NO) to nitrogen dioxide (NO2) for a downstream exhaust gas aftertreatment component for the selective, catalytic reduction of nitrogen oxides.

Alternatively, it is advantageously provided that the catalytic converter is designed as a three-way catalytic converter or as a four-way catalytic converter. In the case of Otto engines, the arrangement of an electrically heatable catalytic converter as the first catalytic converter directly in front of a catalytic converter close to the engine, in particular a three-way catalytic converter or four-way catalytic converter, is helpful in order to reduce cold-start emissions. In this context, a catalytic converter close to the engine is to be understood as meaning a catalytic converter whose inlet-side end face is arranged with an exhaust gas path length of less than 80 cm, preferably less than 50 cm, from an outlet of the internal combustion engine.

In a further preferred embodiment of the invention, it is provided that the catalytic converter is designed as an SCR catalytic converter or as a particle filter with a catalytically active coating, in particular a coating for the selective, catalytic reduction of nitrogen oxides. In diesel engines in particular, it can be helpful to arrange an electrically heatable catalytic converter immediately upstream of an SCR catalytic converter or a particle filter with an SCR coating in order to heat the SCR catalytic converter or the particle filter to a temperature required for selective catalytic reduction.

In a preferred embodiment of the catalytic converter arrangement, it is provided that the electrically heatable catalytic converter comprises an electric heating element, in particular an electric heating disc. An electrical heating element, which is connected upstream of a catalytic converter, can ensure rapid heating of the catalytic converter by convective means of the exhaust gas flow. The electric heating element emits heat, which can be used to heat the catalytic converter disk upstream of the electrically heatable catalytic converter and thus enables the catalytic converter disk to be heated more quickly. As a result, limited exhaust gas components in the exhaust gas flow of the internal combustion engine can be converted into unlimited exhaust gas components promptly after a cold start of the internal combustion engine. Alternatively, it is advantageously provided that the catalytically active structure of the electrically heatable catalyst is designed to be electrically conductive and thus directly heatable.

According to the invention, an exhaust gas aftertreatment system is provided, comprising an exhaust system in which such a catalytic converter arrangement is provided downstream of a turbine of an exhaust gas turbocharger in the flow direction of an exhaust gas of the internal combustion engine. An exhaust gas aftertreatment system according to the invention makes it possible to reduce tailpipe emissions, especially immediately after a cold start of the internal combustion engine, since the exhaust gas aftertreatment components reach their light-off temperature more quickly, from which point efficient conversion of pollutants is possible. In addition, the control accuracy of the exhaust gas aftertreatment system can be improved, since improved measurement accuracy can be achieved by shielding the sensor and the control of the exhaust gas aftertreatment components can be carried out more precisely.

In a preferred embodiment of the exhaust gas aftertreatment system, a dosing element for metering in a reducing agent is arranged downstream of the catalytic converter and an SCR catalytic converter or a particle filter with a coating for the selective, catalytic reduction of nitrogen oxides is arranged further downstream. This enables a particularly efficient conversion of the pollutants in the exhaust system of a diesel engine. The oxidation catalytic converter or the NOx storage catalytic converter can help ensure that the ratio of nitrogen monoxide (NO) to nitrogen dioxide (NO2) is ideal for the selective, catalytic reduction of nitrogen oxides, in order to improve the efficiency of the selective, catalytic reduction.

Unless stated otherwise in the individual case, the various embodiments of the invention mentioned in this application can advantageously be combined with one another.

• 1 ein Ausführungsbeispiel für eine erfindungsgemäße Katalysatoranordnung mit einem elektrisch beheizbaren Katalysator, einem Abschirmelement und einem Sensor;
• 2 ein weiteres Ausführungsbeispiel für eine erfindungsgemäße Katalysatoranordnung mit einem elektrisch beheizbaren Katalysator;
• 3 einen Verbrennungsmotor mit einem Abgasnachbehandlungssystem, welches eine erfindungsgemäße Katalysatoranordnung aufweist; und
• 4 ein weiteres Ausführungsbeispiel für einen Verbrennungsmotor mit einem Abgasnachbehandlungssystem, welches eine solche Katalysatoranordnung aufweist.

The invention is explained below in exemplary embodiments with reference to the associated drawings. Identical components or components with the same function are identified in the different figures with the same reference symbols. Show it:

• 1 an embodiment of a catalyst arrangement according to the invention with an electrically heatable catalyst, a shielding element and a sensor;
• 2 a further exemplary embodiment of a catalytic converter arrangement according to the invention with an electrically heatable catalytic converter;
• 3 an internal combustion engine with an exhaust gas aftertreatment system which has a catalyst arrangement according to the invention; and
• 4 a further exemplary embodiment of an internal combustion engine with an exhaust gas aftertreatment system which has such a catalytic converter arrangement.

In 1 a catalytic converter arrangement 52 according to the invention for arrangement in an exhaust system 20 of an internal combustion engine 10 is shown. Catalyst arrangement 52 comprises an exhaust gas duct segment 54, in which, in the flow direction of an exhaust gas stream of internal combustion engine 10, is a sensor 40, in particular a temperature sensor 58 or an exhaust gas sensor 64, downstream of sensor 40 a shielding element 42, further downstream an electrically heatable catalytic converter 28 and downstream of the electrically heatable Catalyst 28, a further catalyst 32, in particular an oxidation catalyst 34 or a NOx storage catalyst 36, are arranged. The shielding element 42 is preferably designed as a catalytic converter disk 44 , in particular as a catalytic converter disk 44 with the function of an oxidation catalytic converter 34 or a NOx storage catalytic converter 36 . The catalyst disc 44 has a thickness of 5 mm to 35 mm, preferably 10 mm to 25 mm, in the direction of flow. The electrically heatable catalytic converter 28 includes an electrical heating element 30 which is connected to a control unit 50 via a first signal line 46 . Sensor 40 is also connected to control unit 50 via a second signal line 48 . When the electrical heating element 30 is activated, the electrically heatable catalytic converter 28 heats up independently of the heat input through the exhaust gas flow of the internal combustion engine. In this case, heat is convectively transferred to the further catalytic converter 32 arranged downstream of the electrically heatable catalytic converter 28 in order to heat it up to its operating temperature as quickly as possible, in particular after a cold start of the internal combustion engine. Heat is also introduced into the further catalytic converter 32 and into the catalytic converter disk 44 as a result of the heat radiation from the electrically heatable catalytic converter 28 , in particular from the electric heating element 30 . As a result, the thin catalytic converter disk 44 reaches the in 3 illustrated internal combustion engine 10 their light-off temperature. After the light-off temperature has been reached, the catalytic converter disk 44 can contribute to further heating of the components arranged downstream of the catalytic converter disk 44 through an exothermic conversion of unburned exhaust gas components, in particular unburned hydrocarbons, hydrogen or carbon monoxide. In addition, the sensor 40 is shielded from the thermal radiation of the electrically heatable catalytic converter 30 by the catalytic converter disc 44 . This can prevent the sensor 40 from being heated up by the thermal radiation of the electrically heatable catalytic converter 28 and thus the measurement results of the sensor 40 are falsified.

In 2 An alternative exemplary embodiment of a catalytic converter arrangement 52 according to the invention is shown. With essentially the same structure as 1 executed, the shielding element 42 is designed as a shielding plate 52 in this exemplary embodiment. The shielding plate also prevents the sensor 40 from being disturbed by the heat radiation from the electrically heatable catalytic converter 28, in particular by the heat radiation from the electric heating element 30, and the function of the sensor 40 being impaired or disturbed.

3 shows a schematic representation of an internal combustion engine 10 whose outlet 18 is connected to an exhaust system 20 of an exhaust gas aftertreatment system 60 according to the invention for exhaust gas aftertreatment of an exhaust gas stream of the internal combustion engine 10 . The internal combustion engine 10 is preferably designed as a diesel engine. Internal combustion engine 10 has a plurality of combustion chambers 12 in which a fuel-air mixture is burned.

For this purpose, a fuel injector 14 is provided on each of the combustion chambers 12 in order to inject fuel into the combustion chambers 12 . The internal combustion engine 10 is preferably embodied as an internal combustion engine 10 charged by means of an exhaust gas turbocharger 24, a turbine 26 of the exhaust gas turbocharger 24 being arranged downstream of the outlet 18 and upstream of the exhaust gas aftertreatment components 28, 30, 32, 34, 36, 44, 66, 68. Exhaust system 20 comprises an exhaust gas duct 22, in which, in the flow direction of an exhaust gas through exhaust gas duct 22, is an electrically heatable catalytic converter 28 downstream of turbine 26 of exhaust gas turbocharger 24 and, downstream of electrically heatable catalytic converter 28, a preferably close-coupled catalytic converter 32, in particular an oxidation catalytic converter 34 or a NOx - Storage catalytic converter 36 is arranged. A particulate filter 68 with a coating for the selective, catalytic reduction of nitrogen oxides and an SCR catalytic converter 66 are arranged downstream of the oxidation catalytic converter 34 or the NOx storage catalytic converter 36 . For this purpose, at least one dosing element 70 is arranged downstream of the oxidation catalytic converter 34 or the NOx storage catalytic converter 36 on the exhaust gas duct 22, with which a reducing agent, in particular an aqueous urea solution, can be metered into the exhaust gas duct 22 upstream of the particle filter 68 and/or the SCR catalytic converter 66. The electrically heatable catalytic converter 28 comprises an electric heating element 30, in particular an electric heating disc, via which the exhaust gas aftertreatment components 32, 34, 36, 66, 68 arranged downstream of the electrically heatable catalytic converter 28 can be heated essentially independently of the exhaust gas flow of the internal combustion engine 10. The electrically heatable catalytic converter 28 is connected to a control unit 50 of the internal combustion engine 10, via which the heat output and/or the duration of activation of the electrically heatable catalytic converter 28 can be controlled.

A sensor 40, in particular a temperature sensor 58, is arranged downstream of the turbine 26 of the exhaust gas turbocharger 24 and upstream of the electrically heatable catalytic converter 28, with which a temperature in the exhaust gas duct 22 upstream of the electrically heatable catalytic converter 28 can be determined. Temperature sensor 40, 58 is also connected to control unit 50 and transmits a temperature measured in exhaust gas duct 22 to control unit 50. A shielding element 42 is arranged downstream of temperature sensor 58 and upstream of electrically heatable catalytic converter 28, which is preferably configured as a catalytic converter disc 44, in particular as a Oxidation catalytic converter 34 or as a NOx storage catalytic converter 36 is in the form of a disc and preferably has a thickness of 5 mm to 35 mm, particularly preferably 10 mm to 25 mm, in the direction of flow. This catalytic converter disk is heated by the heat of the electrical heating element 30 via thermal radiation, so that the catalytic converter disk 44 is also heated up by the thermal radiation of the electrical heating element 30 in addition to the convective heat transfer by the exhaust gas flow of the internal combustion engine 10 . As a result of this heat input and the small thickness of the catalytic converter disk 44, the catalytic converter disk 44 reaches its light-off temperature immediately after a cold start of the internal combustion engine 10, so that pollutants, in particular unburned hydrocarbons, can be efficiently converted from this point in time. The exothermic conversion of the unburned hydrocarbons results in additional heat input into the exhaust system 20, as a result of which the catalytic converter 32 immediately following the electrically heatable catalytic converter 28 also heats up more quickly to its operating temperature.

As an alternative or in addition to a temperature sensor 58, the sensor 40 can also be designed as an exhaust gas sensor 64. Alternatively or additionally, an electrically heatable catalytic converter 28 can also be arranged upstream of the SCR catalytic converter 66 or the particle filter 68 .

As an alternative to a catalytic converter disk 44, the shielding element 42 can also be designed as a shielding plate 56 in order to prevent a measurement signal from the sensor 40 being distorted by the heat Radiation of the electrically heatable catalyst 28 and / or the electric heating element 30 to prevent.

In 4 an alternative exemplary embodiment of an exhaust system 20 for an internal combustion engine 10 is illustrated. In this exemplary embodiment, internal combustion engine 10 is designed as a spark-ignition Otto engine. The internal combustion engine 10 has at least one combustion chamber 12 on which a spark plug 16 for igniting a fuel-air mixture in the combustion chamber 12 is arranged. The internal combustion engine 10 is preferably designed as a direct-injection internal combustion engine 10 . For this purpose, a fuel injector 14 is arranged on the combustion chamber 12, with which a combustible fuel can be injected into the respective combustion chamber 12. Alternatively or additionally, a fuel injection valve for introducing the combustible fuel can also be provided in the intake tract of the internal combustion engine 10 .

The internal combustion engine 10 is connected at its outlet 18 to an exhaust system 20 in which a turbine 26 of an exhaust gas turbocharger 24 and downstream of the turbine 26 an electrically heatable catalytic converter 28 are arranged in the flow direction of an exhaust gas of the internal combustion engine 10 . In this exemplary embodiment, a three-way catalytic converter 38 close to the engine and an electrically heatable four-way catalytic converter 64 are provided in the underbody position of a motor vehicle. The electrically heatable catalytic converter 28 comprises an electric heating element 30, in particular an electric heated disc, with which the components for exhaust gas aftertreatment 32, 38, 62, in particular a four-way catalytic converter 62, which are arranged downstream of the electrically heatable catalytic converter 28, can be heated essentially independently of the exhaust gas flow of the Internal combustion engine 10 can be heated. The electrically heatable catalytic converter 28 and/or the electric heating element 30 are connected via a signal line 46 to a control unit 50 of the internal combustion engine 10, via which the heating output and heating duration of the electrically heatable catalytic converter 28 and/or the electric heating element 30 can be controlled.

A sensor 40, in particular a temperature sensor 58, is arranged downstream of the close-coupled three-way catalytic converter 38 and upstream of the electrically heatable catalytic converter 28, with which a temperature in the exhaust gas duct 22 upstream of the electrically heatable catalytic converter 28 can be determined. Temperature sensor 58 is also connected to control unit 50 via a further signal line 48 and transmits a temperature measured in exhaust gas duct 22 to control unit 50. Alternatively or additionally, an electrically heatable catalytic converter 28 can also be arranged upstream of close-coupled three-way catalytic converter 38, 64 be.

The electrically heatable catalytic converter 28 can reduce the emissions in the cold start phase of the internal combustion engine 10 and/or after the internal combustion engine 10 has been stopped. This applies both to internal combustion engines in motor vehicles and to stationary internal combustion engines. In particular, an electrically heatable catalytic converter 28 can also be used in a motor vehicle with a hybrid drive, since in such a motor vehicle the exhaust gas aftertreatment components can cool below their operating temperature in purely electric driving mode. The thermal radiation from the electrically heatable catalytic converter 28 and/or the electric heating element 30 is kept away from the sensor 40 by the shielding element 42, so that a measurement signal from the sensor 40, in particular a temperature, is not affected by the thermal radiation from the electrically heatable catalytic converter 28 and/or the electric Heating element 30 is falsified.

Reference List

10

combustion engine

12

combustion chamber

14

fuel injector

16

spark plug

18

outlet

20

exhaust system

22

exhaust duct

24

exhaust gas turbocharger

26

turbine

28

electrically heated catalytic converter

30

electric heating element

32

catalyst

34

oxidation catalyst

36

NOx storage catalyst

38

Three-way catalytic converter

40

sensor

42

shielding element

44

catalyst disc

46

signal line

48

signal line

50

control unit

52

Catalyst arrangement

54

exhaust duct segment

56

shield plate

58

temperature sensor

60

exhaust aftertreatment system

62

Four-way catalytic converter

64

exhaust gas sensor

66

SCR catalytic converter

68

particle filter

70

dosing element

Claims (8)

Catalyst arrangement (52), comprising an exhaust gas channel segment (54), in which an electrically heatable catalyst (28) and in the flow direction of an exhaust gas stream of an internal combustion engine (10) through the exhaust gas channel segment (54) downstream of the electrically heatable catalyst (28) a catalyst (32) are arranged, and with a sensor (40) arranged upstream of the electrically heatable catalytic converter (28), with a shielding element (42) being arranged downstream of the sensor (40) and upstream of the electrically heatable catalytic converter (28), which enables heat transfer by means of thermal radiation from the electrically heatable catalytic converter (28) on the sensor (40) is reduced or avoided, characterized in that the shielding element (42) comprises or is a catalytic converter disk (44) with a thickness of 5 mm to 35 mm. Catalyst assembly (52) after claim 1 , characterized in that the catalyst disc (52) is arranged at a distance of 2 mm to 50 mm upstream of an electrical heating element (30) of the electrically heatable catalyst (28). Catalyst arrangement (52) according to one of Claims 1 or 2 , characterized in that the sensor (40) is a temperature sensor (58) or an exhaust gas sensor (64). Catalyst arrangement (52) according to one of Claims 1 until 3 , characterized in that the shielding element (42) comprises a shielding plate (56). Catalyst arrangement (52) according to one of Claims 1 until 4 , characterized in that the catalytic converter (32) is designed as an oxidation catalytic converter (34) or as a NOx storage catalytic converter (36). Catalyst arrangement (52) according to one of Claims 1 until 4 , characterized in that the catalytic converter (32) is designed as a three-way catalytic converter (38) or as a four-way catalytic converter (62). Exhaust gas aftertreatment system (60), comprising an exhaust system (20), in which in the direction of flow of an exhaust gas of the internal combustion engine (10) downstream of a turbine (26) of an exhaust gas turbocharger (24) has a catalyst arrangement (52) according to one of Claims 1 until 6 is arranged. Exhaust aftertreatment system (60) after claim 7 , characterized in that downstream of the catalytic converter (32) a metering element for metering in a reducing agent and further downstream an SCR catalytic converter (66) or a particle filter (68) with a coating for the selective, catalytic reduction of nitrogen oxides are arranged.

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