DE102021121029A1 - Metering system for metering a reducing agent into the exhaust system of a combustion engine - Google Patents

Abstract

The invention relates to a metering system (40) for metering a reducing agent (86) into an exhaust system (20) of an internal combustion engine (10). The metering system (40) comprises a reducing agent tank (42) for storing the reducing agent (86), a reducing agent feed pump (44) for feeding the reducing agent (86) from the reducing agent tank (42) to a metering element (48) and a reducing agent line (46). The reducing agent line (46) connects an outlet (50) of the reducing agent tank (42) to the metering element (48) in order to ensure that the metering element (48) is supplied with reducing agent. It is provided that a reducing agent intermediate store (52) is arranged in the conveying direction of the reducing agent (86) downstream of the outlet (50) and upstream of the metering element (48). The invention also relates to a method for metering a reducing agent (86) with such a metering system (40 ) and an internal combustion engine (10) with an exhaust system (20) on which such a metering system (40) is arranged.

Description

The invention relates to a metering system for metering a reducing agent into the exhaust system of an internal combustion engine and an internal combustion engine with an exhaust system on which such a metering system is arranged.

The current exhaust gas legislation and one that will become increasingly strict in the future places high demands on engine raw emissions and the exhaust gas aftertreatment of combustion engines. The demands for a further reduction in consumption and the further tightening of the exhaust gas standards with regard to the permitted nitrogen oxide emissions pose a challenge for the engine developers. In petrol engines, the exhaust gas cleaning takes place in the known way via a three-way catalytic converter and before the three-way catalytic converter - and further downstream catalysts. Exhaust gas aftertreatment systems are currently used in diesel engines, which have an oxidation catalytic converter, a catalytic converter for the selective catalytic reduction of nitrogen oxides (SCR catalytic converter) and a particle filter for separating soot particles and optionally further catalytic converters. Ammonia is preferably used as the reducing agent. Because handling pure ammonia is expensive, vehicles usually use a synthetic, aqueous urea solution, which is mixed with the hot exhaust gas stream from the internal combustion engine. This mixing heats up the aqueous urea solution, with the aqueous urea solution releasing ammonia in the exhaust gas duct. A commercially available, aqueous urea solution is generally made up of 32.5% urea and 67.5% water.

At low outside temperatures, in particular at a temperature below -7° C., in particular below -10° C., the urea-water solution can freeze depending on the urea content of the urea-water solution. In order to enable the reducing agent to be metered in, electric heating elements are known which heat at least part of the reservoir in which the urea-water solution is stored, in order to liquefy at least a portion of the urea-water solution and pass it into the exhaust system to be able to dose.

From the U.S. 2013/0 061 949 A1 an internal combustion engine with an exhaust aftertreatment system is known, which comprises a urea metering system for metering aqueous urea solution into an exhaust duct of the exhaust system of the internal combustion engine. A reservoir for the urea solution is surrounded by the coolant circuit of the combustion engine and can be heated using the waste heat.

From the DE 10 2014 001 879 A1 An internal combustion engine with at least one exhaust system is known, with at least one exhaust gas aftertreatment device and at least one urea-water solution tank being arranged in the exhaust system. It is provided that the urea-water solution tank is arranged close to the engine and can be heated directly or indirectly via a coolant circuit, in particular by the waste heat from the internal combustion engine.

The DE 10 2018 105 129 A1 discloses an electric motor in which, in addition to the drive power of an electric motor, the heating power of the electric motor can also be used. For example, when conveying a urea-water solution (eg Adblue) that is used for exhaust gas treatment, heating of the urea-water solution may be desirable. The electric motor used to drive a pump also generates heat, e.g. B. can be used to thaw the urea-water solution.

A disadvantage of the known solutions, however, is that the known heating solutions for heating the reservoir for storing the urea-water solution require a lot of energy and a comparatively long time and therefore cannot contribute directly to reducing emissions in the cold start phase.

The object of the invention is now to be able to provide a liquid urea-water solution as soon as possible after a cold start, even at low outside temperatures, and to meter this into the exhaust system to reduce emissions.

The object is achieved by a metering system for metering a reducing agent, in particular an aqueous urea solution, into an exhaust system of an internal combustion engine, comprising a reducing agent tank for storing the reducing agent, a reducing agent feed pump for conveying the reducing agent from the reducing agent tank to a metering element, and a reducing agent line which has an outlet of the reducing agent tank connects to the dosing element, solved.

According to the invention, a reducing agent buffer store is arranged downstream of the outlet and upstream of the dosing element in the conveying direction of the reducing agent.

The proposed dosing system makes it possible to thaw a small amount of reducing agent, in particular aqueous urea solution, which is stored in the intermediate reducing agent tank, by means of thermal conduction, thermal radiation or convection. In this way, a reducing agent can be injected promptly after a cold start of the internal combustion engine, even at low outside temperatures, in order to be able to efficiently reduce nitrogen oxide emissions in the cold start phase.

The features listed in the dependent claims allow advantageous improvements and non-trivial further developments of the dosing system listed in the independent claim.

In a preferred embodiment of the invention, it is provided that the reducing agent intermediate store has a storage volume of at least 20 cm ³ , preferably at least 50 cm ³ . The storage volume of the reducing agent intermediate tank should be large enough to bridge the period until the reducing agent in the reducing agent tank of the metering system has thawed and the metering element can be supplied with the reducing agent from the reducing agent tank. Depending on the heat output of a tank heater of the reducing agent tank, a reducing agent volume of at least 20 cm ³ has proven to be advantageous.

In a preferred embodiment of the intermediate reducing agent store, it is provided that the intermediate reducing agent store has a maximum storage volume of 500 cm ³ , preferably a maximum of 300 cm ³ , particularly preferably a maximum of 200 cm ³ . In order to enable rapid thawing of the reducing agent in the reducing agent buffer store, this reducing agent buffer store should not exceed a maximum size in order to have advantages over the reducing agent tank with regard to the heating behavior. It has been found that from a storage volume of 500 cm ³ the thawing of the reducing agent takes place so slowly that there are only minor advantages over the reducing agent tank.

According to an advantageous embodiment of the dosing system, it is provided that the reducing agent intermediate store is designed as a pressure store, the pressure store having a pressure source which is set up to deliver the reducing agent stored in the pressure store to the dosing element. A pressure accumulator makes it possible to dispense with an additional delivery element in order to deliver the reducing agent to the dosing element after a cold start of the internal combustion engine. In addition, the freezing point of the reducing agent is lowered when it is stored under pressure, so that the reducing agent only freezes at lower temperatures.

It is particularly preferred if the pressure reservoir is designed as a gas pressure reservoir, the gas pressure reservoir comprising a gas pressure chamber and a liquid reservoir for receiving the reducing agent, which are separated from one another by a membrane. By means of a gas pressure accumulator with a gas pressure space, a membrane and a liquid accumulator, a pressure accumulator can be formed in a constructive, simple and cost-effective manner, which allows the reducing agent to be temporarily stored. By separating the gas pressure chamber from the liquid accumulator by a membrane, the liquid can also expand when it freezes without damaging the pressure accumulator.

Alternatively, an additional conveying element, in particular a pump, can also be arranged on the reducing agent buffer store in order to convey the reducing agent stored in the reducing agent buffer store to the dosing element.

In an advantageous embodiment of the dosing system, it is provided that the reducing agent container is designed as a flexible container with a structure that can be changed as a function of the reducing agent volume stored in the reducing agent buffer store. It can thereby be ensured that the container of the reducing agent intermediate store is not damaged during filling and subsequent freezing of the reducing agent. Furthermore, it can be ensured that the reducing agent can be sucked out of the container without a conveying element sucking in air for conveying the reducing agent.

It is particularly preferred if the flexible container is made from a shape-memory material and/or has a shape-memory structure. A shape-memory material or a shape-memory structure ensures that the container returns to its original shape after deformation when the dosing system is correspondingly relieved.

In a further preferred embodiment of the invention, it is provided that the reducing agent buffer store is connected to the reducing agent line via a connecting line, the connecting line opening into the reducing agent line at a branch downstream of the reducing agent feed pump and upstream of the dosing element. Due to the branching, the reducing agent buffer store has only one connection opening, as a result of which the sealing of the reducing agent buffer is facilitated. In addition, an additional degree of freedom is gained in the design of the exhaust gas aftertreatment system, since the connecting line simplifies the arrangement of the reducing agent buffer store near a hot component.

• - Start des Verbrennungsmotors,
• - Aufheizen der Abgasanlage und zumindest indirektes Auftauen des Reduktionsmittels im Reduktionsmittelzwischenspeichers und in der Reduktionsmittelleitung zwischen dem Reduktionsmittelzwischenspeicher und dem Dosierelement
• - Betreiben des Dosiersystems in einem ersten Betriebszustand, wobei eine Eindosierung des im Reduktionsmittelzwischenspeicher bevorrateten Reduktionsmittels in die Abgasanlage des Verbrennungsmotors erfolgt und parallel das Reduktionsmittel im Reduktionsmitteltank aufgeheizt wird, und
• - Betreiben des Dosiersystems in einem zweiten Betriebszustand, wobei eine Eindosierung des im Reduktionsmitteltank bevorrateten Reduktionsmittels in die Abgasanlage erfolgt.

Another aspect of the invention relates to a method for metering a reducing agent into the exhaust system of an internal combustion engine with such a metering system, which comprises the following steps:

• - starting the internal combustion engine,
• - Heating of the exhaust system and at least indirect thawing of the reducing agent in the reducing agent buffer store and in the reducing agent line between the reducing agent buffer store and the dosing element
• - Operating the dosing system in a first operating state, wherein the reducing agent stored in the reducing agent intermediate store is metered into the exhaust system of the internal combustion engine and the reducing agent in the reducing agent tank is heated in parallel, and
• - Operating the dosing system in a second operating state, wherein the reducing agent stored in the reducing agent tank is metered into the exhaust system.

The method according to the invention makes it possible to provide a small amount of reducing agent immediately after a cold start of the internal combustion engine and thus to bridge the period until the reducing agent in the reducing agent tank has thawed to such an extent that a continuous supply of the dosing element from the reducing agent tank is ensured. This means that the time from a cold start to when the dosing system is ready for operation can be shortened and nitrogen oxide emissions reduced.

In an advantageous embodiment of the method, it is provided that the reducing agent buffer store is filled with reducing agent after the reducing agent in the reducing agent tank and in the reducing agent feed pump has thawed.

It can thereby be ensured that the reducing agent buffer store is sufficiently filled with reducing agent when the internal combustion engine is restarted and that the dosing element can be supplied with liquid reducing agent from the reducing agent buffer store in a cold start phase.

In a further advantageous refinement of the method, it is provided that the reducing agent buffer store is filled with reducing agent when the internal combustion engine is requested to be switched off. When a switch-off request is made, the reducing agent is generally pumped out of the dosing element back into the reducing agent tank in order to prevent the dosing element from being damaged by freezing reducing agent. Alternatively, the reducing agent intermediate store can also be refilled with reducing agent at any time after the reducing agent in the reducing agent tank has thawed, in order to be sufficiently filled with reducing agent during a subsequent cold start.

A further partial aspect of the invention relates to an internal combustion engine with at least one combustion chamber, with an outlet of the internal combustion engine being connected to an exhaust system. At least one oxidation catalytic converter and one exhaust gas aftertreatment component downstream of the oxidation catalytic converter in the flow direction of an exhaust gas stream of the internal combustion engine are arranged in the exhaust system for the selective, catalytic reduction of nitrogen oxides. The internal combustion engine also includes a metering system for metering a reducing agent into an exhaust system of an internal combustion engine, comprising a reducing agent tank for storing the reducing agent, a reducing agent feed pump for conveying the reducing agent from the reducing agent tank to a metering element, and a reducing agent line, which connects an outlet of the reducing agent tank to the metering element. In this case, it is provided that a reducing agent buffer store is arranged downstream of the outlet and upstream of the dosing element in the conveying direction of the reducing agent. The reducing agent buffer store is at least indirectly heated by a component of the internal combustion engine or the exhaust system that heats up quickly after a cold start of the internal combustion engine.

Such an internal combustion engine enables a significant reduction in nitrogen oxide emissions during a cold start at cold ambient temperatures, in particular at temperatures below -5 °C, since the dosing system is ready for use immediately after a cold start and when the light-off temperature of the exhaust gas aftertreatment component is reached for selective, catalytic reduction can provide a sufficient quantity of reducing agent until the dosing element can be supplied by the reducing agent stored and thawed in the reducing agent tank.

It is preferred if the component that heats up quickly after a cold start of the internal combustion engine is an engine block or cylinder head of the Internal combustion engine, an exhaust manifold, a turbine of an exhaust gas turbocharger, an exhaust gas aftertreatment component or a starter generator, in particular a belt starter generator. The listed components heat up comparatively quickly after a cold start of the internal combustion engine, so that the heat from these components can be transferred to the reducing agent buffer store by thermal conduction, thermal radiation and/or convection. The reducing agent stored in the reducing agent buffer store can thus be thawed comparatively quickly and fed to the dosing element.

In an advantageous embodiment of the internal combustion engine, it is provided that an electric heating element or an exhaust gas burner for heating up at least one exhaust gas aftertreatment component is arranged on the exhaust system, with the heat introduced into the exhaust system by the electric heating element or the exhaust gas burner being transferred at least indirectly to the reducing agent buffer store in order to to liquefy the reducing agent stored in the reducing agent buffer store or to reduce the viscosity of the reducing agent. A large amount of energy is introduced into the exhaust system by an electric heating element for an exhaust gas aftertreatment component or by an exhaust gas burner in order to heat the exhaust gas aftertreatment component to its respective operating temperature as soon as possible after a cold start. If this heat is transferred at least indirectly to the reducing agent buffer store, then this can be heated by the electrical heating element or the exhaust gas burner and rapid thawing of the reducing agent can be ensured.

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 erstes Ausführungsbeispiel für ein erfindungsgemäßes Dosiersystem zur Eindosierung eines Reduktionsmittels in eine Abgasanlage eines Verbrennungsmotors;
• 2 ein zweites Ausführungsbeispiel für ein erfindungsgemäßes Dosiersystem zur Eindosierung von Reduktionsmittel;
• 3 ein weiteres Ausführungsbeispiel für ein erfindungsgemäßes Dosiersystem zur Eindosierung von Reduktionsmittel in die Abgasanlage eines Verbrennungsmotors;
• 4 ein weiteres Ausführungsbeispiel für ein erfindungsgemäßes Dosiersystem zur Einbringung von wässriger Harnstofflösung für eine selektive, katalytische Reduktion in eine Abgasanlage eines Verbrennungsmotors;
• 5 ein Phasendiagramm einer wässrigen Harnstofflösung mit 32,5% Harnstoffanteil; und
• 6 einen Verbrennungsmotor mit einer Abgasanlage, wobei ein erfindungsgemäßes Dosiersystem vorgesehen ist, um Reduktionsmittel in die Abgasanlage einzubringen.

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 numbers. Show it:

• 1 a first exemplary embodiment of a metering system according to the invention for metering a reducing agent into an exhaust system of an internal combustion engine;
• 2 a second exemplary embodiment of a metering system according to the invention for metering in reducing agent;
• 3 a further exemplary embodiment of a dosing system according to the invention for dosing reducing agent into the exhaust system of an internal combustion engine;
• 4 a further exemplary embodiment of a dosing system according to the invention for introducing aqueous urea solution for a selective, catalytic reduction into an exhaust system of an internal combustion engine;
• 5 a phase diagram of an aqueous urea solution with 32.5% urea content; and
• 6 an internal combustion engine with an exhaust system, a dosing system according to the invention being provided in order to introduce reducing agents into the exhaust system.

1 shows a preferred embodiment of a metering system 40 for metering a reducing agent 86 into an exhaust system 20 of an internal combustion engine. Metering system 40 includes a reducing agent tank 42 for storing reducing agent 86, a reducing agent feed pump 44 for feeding reducing agent 86 from reducing agent tank 42 to a metering element 48, and a reducing agent line 46, which connects an outlet 50 of reducing agent tank 42 to metering element 48. A reducing agent buffer store 52 is arranged downstream of the outlet 50 of the reducing agent tank 42 and upstream of the dosing element 48 in the conveying direction of the reducing agent 86 . In this case, the reducing agent buffer store 52 is arranged in the immediate vicinity of the dosing element 48 . The reducing agent feed pump 44 is preferably designed as an electrically driven pump and is arranged in the reducing agent tank 42 so that the waste heat from the reducing agent feed pump 44 can be used to heat the reducing agent 86 in the reducing agent tank 42 . The reducing agent feed pump 44 feeds the reducing agent 86 from the reducing agent tank 42 or the reducing agent buffer store 52 to the metering element 48 in order to be able to be metered into the exhaust system 20 by means of the metering element 48 .

The exhaust system 20 comprises an exhaust gas duct 22, in which a turbine 26 of an exhaust gas turbocharger 24, downstream of the turbine 26 of the exhaust gas turbocharger 24 an oxidation catalytic converter 28 and upstream of the oxidation catalytic converter 28 at least one exhaust gas aftertreatment component 30 for the selective, catalytic reduction of nitrogen oxides are arranged. The exhaust gas aftertreatment component 30 for the selective, catalytic reduction of nitrogen oxides is preferably designed as a particle filter 34 with an SCR coating. Alternatively, the exhaust gas aftertreatment component 30 can also be designed as an SCR catalytic converter 32 . The dosing element 48 is arranged downstream of the oxidation catalytic converter 28 and upstream of the exhaust gas aftertreatment component 30 for the selective, catalytic reduction of nitrogen oxides. An exhaust gas mixer 38 is arranged downstream of the dosing element 48 and upstream of the exhaust gas aftertreatment component 30 for the selective, catalytic reduction of nitrogen oxides in order to mix the reducing agent 86 with the exhaust gas flow of the internal combustion engine before it enters the exhaust gas aftertreatment component 30 . A branch 36 is formed on the exhaust gas duct 22 downstream of the exhaust gas aftertreatment component 30, at which branch an exhaust gas recirculation line 72 of a low-pressure exhaust gas recirculation system 70 branches off from the exhaust gas duct 22 of the exhaust system.

2 shows another preferred embodiment of a metering system 40 for metering a reducing agent 86 into an exhaust system 20 of an internal combustion engine. Metering system 40 includes a reducing agent tank 42 for storing reducing agent 86, a reducing agent feed pump 44 for feeding reducing agent 86 from reducing agent tank 42 to a metering element 48, and a reducing agent line 46, which connects an outlet 50 of reducing agent tank 42 to metering element 48. A reducing agent buffer store 52 is arranged downstream of the outlet 50 of the reducing agent tank 42 and upstream of the dosing element 48 in the conveying direction of the reducing agent 86 . In this case, the reducing agent buffer store 52 is arranged downstream of the outlet 50 and upstream of the reducing agent feed pump 44 in the reducing agent line 46 . In this exemplary embodiment, the reducing agent buffer store 52 has a flexible container 66 with a shape memory structure 68 . The reducing agent buffer store is designed in such a way that when the reducing agent 86 is removed by the reducing agent feed pump 44 and at the same time the reducing agent line 46 is frozen upstream of the reducing agent buffer store 52, it deforms in such a way that the container yields and the volume enclosed by the container is reduced. As soon as the reducing agent line 46 has completely thawed, the reducing agent buffer store 52 expands back to its original shape and fills with reducing agent 86 from the reducing agent tank 42. The reducing agent feed pump 44 is arranged downstream of the reducing agent buffer store 52 and upstream of the dosing element 48. The reducing agent feed pump 44 feeds the reducing agent 86 from the reducing agent tank 42 or the reducing agent buffer store 52 to the metering element 48 in order to be able to be metered into the exhaust system 20 by means of the metering element 48 .

3 shows another preferred embodiment of a metering system 40 for metering a reducing agent 86 into an exhaust system 20 of an internal combustion engine. Metering system 40 includes a reducing agent tank 42 for storing reducing agent 86, a reducing agent feed pump 44 for feeding reducing agent 86 from reducing agent tank 42 to a metering element 48, and a reducing agent line 46, which connects an outlet 50 of reducing agent tank 42 to metering element 48. A reducing agent buffer store 52 is arranged downstream of the outlet 50 of the reducing agent tank 42 and upstream of the dosing element 48 in the conveying direction of the reducing agent 86 . The reducing agent line 46 has a branch 54 at which a connecting line 56 which connects the reducing agent buffer store 52 to the reducing agent line 46 opens into the reducing agent line 46 . In this embodiment, the reducing agent buffer store 52 is preferably embodied as a pressure store 58 which, by means of a pressure source 88 , is subjected to a pressure which is higher than the pressure in the reducing agent line 46 . As an alternative to a pressure accumulator, a further conveying element, in particular a further pump, can also be provided, which conveys the reducing agent stored in the intermediate reducing agent store 52 to the dosing element 48 . The reducing agent feed pump 44 is preferably designed as an electrically driven pump and is arranged in the reducing agent tank 42 so that the waste heat from the reducing agent feed pump 44 can be used to heat the reducing agent 86 in the reducing agent tank 42 . The reducing agent 86 is conveyed from the reducing agent tank 42 to the metering element 48 by the reducing agent feed pump 44 in order to be able to be metered into the exhaust system 20 by means of the metering element 48 .

4 shows another preferred embodiment of a metering system 40 for metering a reducing agent 86 into an exhaust system 20 of an internal combustion engine. Metering system 40 includes a reducing agent tank 42 for storing reducing agent 86, a reducing agent feed pump 44 for feeding reducing agent 86 from reducing agent tank 42 to a metering element 48, and a reducing agent line 46, which connects an outlet 50 of reducing agent tank 42 to metering element 48. In the conveying direction of the reducing agent 86 downstream of the outlet 50 of the reducing agent tank 42 and upstream of the dosing element 48 there is a reducing agent in between memory 52 arranged. The reducing agent line 46 has a branch 54 at which a connecting line 56 which connects the reducing agent buffer store 52 to the reducing agent line 46 opens into the reducing agent line 46 . In this embodiment, the reducing agent buffer store 52 is designed as a gas pressure store 60 which comprises a gas pressure chamber 98 and a liquid store 64 for receiving the reducing agent 86, which are separated from one another by a membrane 62.

The reducing agent feed pump 44 is preferably designed as an electrically driven pump and is arranged in the reducing agent tank 42 so that the waste heat from the reducing agent feed pump 44 can be used to heat the reducing agent 86 in the reducing agent tank 42 . The reducing agent 86 is conveyed from the reducing agent tank 42 to the metering element 48 by the reducing agent feed pump 44 in order to be able to be metered into the exhaust system 20 by means of the metering element 48 .

In normal operation, ie when the reducing agent 86 stored in the reducing agent tank 42 has thawed, the gas pressure tank 60 is filled with reducing agent 86 until the gas pressure in the gas pressure chamber 98 corresponds to the delivery pressure of the reducing agent delivery pump 44 . In this case, the liquid reservoir 64 of the gas pressure reservoir 60 must be dimensioned sufficiently large in order to store a defined minimum quantity of reducing agent 86 at a pressure sufficient for dosing.

In 5 a phase diagram of an aqueous urea solution with 32.5% urea content is shown. Phase I corresponds to an area in which the urea solution is present in the form of ice and crystals. Phase II is the area where the urea solution is in the form of ice and liquid solution. Phase III is the area in which the urea solution is completely in the form of a liquid solution. Phase IV is the area where the urea solution is in the form of liquid solution and crystals. Furthermore, the solidus line S, the liquidus line L and the eutectic E are drawn in the phase diagram. Points 1 and 2 also show how the position of the eutectic and the four phases I - IV change when the urea content increases from 32.5% (point 1) to 38% (point 2).

In 6 an internal combustion engine 10 with a plurality of combustion chambers 12 is shown, a fuel injector 14 for injecting fuel into the respective combustion chamber 12 being arranged on each combustion chamber 12 . The internal combustion engine 10 has an inlet 16 with which the internal combustion engine 10 can be connected to an air supply system (not shown). The internal combustion engine 10 also has an outlet 18 with which the internal combustion engine 10 can be connected to an exhaust system 20 . The internal combustion engine 10 has an engine block and a cylinder head 82 . The internal combustion engine 10 is connected to a belt alternator starter 74 via a belt 76 . Furthermore, the internal combustion engine 10 is connected to a transmission 78 . A high-pressure fuel pump and a high-pressure fuel reservoir 84 are provided for supplying fuel to the fuel injectors 14 , which is supplied with fuel by the high-pressure fuel pump 116 .

The exhaust system 20 includes an exhaust manifold 80 which supplies the exhaust gases from a plurality of combustion chambers 12 to a common exhaust gas duct 22 . A turbine 24 of an exhaust gas turbocharger 26, downstream of the turbine 26 of the exhaust gas turbocharger 24 an oxidation catalytic converter 28 and upstream of the oxidation catalytic converter 28 at least one exhaust gas aftertreatment component 30 for the selective, catalytic reduction of nitrogen oxides are arranged in the exhaust gas duct 22. The exhaust gas aftertreatment component 30 for the selective, catalytic reduction of nitrogen oxides is preferably designed as a particle filter 34 with an SCR coating. Alternatively, the exhaust gas aftertreatment component 30 can also be designed as an SCR catalytic converter 32 . The dosing element 48 is arranged downstream of the oxidation catalytic converter 28 and upstream of the exhaust gas aftertreatment component 30 for the selective, catalytic reduction of nitrogen oxides. An exhaust gas mixer 38 is arranged downstream of the dosing element 48 and upstream of the exhaust gas aftertreatment component 30 for the selective, catalytic reduction of nitrogen oxides in order to mix the reducing agent 86 with the exhaust gas flow of the internal combustion engine before it enters the exhaust gas aftertreatment component 30 . A branch 36 is formed on the exhaust gas duct 22 downstream of the exhaust gas aftertreatment component 30, at which branch an exhaust gas recirculation line 72 of a low-pressure exhaust gas recirculation system 70 branches off from the exhaust gas duct 22 of the exhaust system.

Furthermore, an electric heating element 100 and/or an exhaust gas burner 102 can be arranged on the exhaust system, with which at least one exhaust gas aftertreatment component 28, 30 can be heated independently of the operating state of the internal combustion engine 10. The exhaust gas burner 102 has a combustion chamber 108 in which a fuel is burned. The combustion chamber 108 can be filled with a combustible fuel-air mixture by means of a fuel supply 104 and an air supply 106 . Furthermore, at the combustion chamber 108 is a Ignition element 112 arranged to ignite the fuel-air mixture. Combustion chamber 108 is connected via an exhaust gas line 114 to an inlet point 104 upstream of exhaust gas aftertreatment component 28, 30 to be heated.

The reducing agent buffer store 52 is arranged on a component of the internal combustion engine 10 that heats up quickly after a cold start of the internal combustion engine 10 or on a component of the exhaust system 20 that heats up quickly. In particular, the reducing agent buffer store 52 can be arranged in the immediate vicinity of the belt starter generator 74, the high-pressure fuel store 84, the high-pressure fuel pump 116 or an exhaust gas aftertreatment component 28, 30. Alternatively, the reducing agent buffer store 52 can also be arranged in the immediate vicinity of the exhaust manifold 80, the engine block, the cylinder head 82 or the turbine 26 of the exhaust gas turbocharger 24 and can be heated in a suitable manner by means of thermal radiation, thermal conduction and/or convection. Furthermore, the reducing agent buffer store can be heated in that an exhaust gas aftertreatment component 28, 30 is heated by the electric heating element 100 or the exhaust gas burner 102 and this heat is also used to thaw the reducing agent 86 in the reducing agent buffer store 52.

Internal combustion engine 10 is operatively connected to a control unit 90 which includes a storage unit 94 and a computing unit 92 . A program code 96 is stored in memory unit 94, which executes a method for metering a reducing agent 86 into exhaust system 20 of internal combustion engine 10 with such a metering system 40 when program code 96 is executed by processing unit 92 of control unit 90.

Reference List

10

combustion engine

12

combustion chamber

14

fuel injector

16

inlet

18

outlet

20

exhaust system

22

exhaust duct

24

exhaust gas turbocharger

26

turbine

28

oxidation catalyst

30

Exhaust aftertreatment component for selective catalytic reduction

32

SCR catalytic converter

34

Particulate filter with SCR coating

36

branch

38

exhaust mixer

40

dosing system

42

reducing agent tank

44

reducing agent feed pump

46

reducing agent line

48

dosing element

50

outlet

52

Reducing agent buffer

54

branch

56

connection line

58

accumulator

60

gas accumulator

62

membrane

64

liquid storage

66

flexible container

68

shape memory structure

70

low-pressure exhaust gas recirculation

72

exhaust gas recirculation line

74

Belt starter generator

76

belt

78

transmission

80

exhaust manifold

82

cylinder head

84

high-pressure fuel accumulator

86

reducing agent

88

pressure source

90

control unit

92

unit of account

94

storage unit

96

machine-readable program code

98

gas pressure room

100

electric heating element

102

exhaust burner

104

fuel delivery

106

air supply

108

combustion chamber

110

discharge point

112

ignition element

114

exhaust pipe

116

high-pressure fuel pump

I

Zone I, Ice and Crystals

II

Zone II, ice and solution

III

Zone III, solution

IV

Zone IV, solution and crystals

E

eutectic

H

Urea content [%]

L

liquidus line

S

solidus line

T

Temperature [°C]

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• US20130061949A1 [0004]
• DE 102014001879 A1 [0005]
• DE 102018105129 A1 [0006]

Claims (10)

Metering system (40) for metering a reducing agent (86) into an exhaust system (20) of an internal combustion engine (10), comprising a reducing agent tank (42) for storing the reducing agent (86), a reducing agent feed pump (44) for feeding the reducing agent (86). the reducing agent tank (42) to a dosing element (48) and a reducing agent line (46) which connects an outlet (50) of the reducing agent tank (42) to the dosing element (48), characterized by a reducing agent buffer store (52) which runs in the conveying direction of the reducing agent (86) is arranged downstream of the outlet (50) and upstream of the dosing element (48). Dosing system (40) after claim 1 , wherein the reducing agent buffer (52) has a storage volume of at least 20 cm ³ . Dosing system (40) after claim 1 or 2 , wherein the reducing agent intermediate store (52) is designed as a pressure store (58), wherein the pressure store (58) has a pressure source (88) which is set up to deliver the reducing agent (86) stored in the pressure store to the dosing element (48). Dosing system (40) after claim 3 , wherein the pressure accumulator (58) is designed as a gas pressure accumulator (60), the gas pressure accumulator (60) comprising a gas pressure chamber (98) and a liquid accumulator (64) for receiving the reducing agent (86), which are separated from one another by a membrane (62). are. Metering system (40) according to one of Claims 1 until 4 , wherein the intermediate storage (52) for reducing agent is designed as a flexible container (66) with a structure that can be changed depending on the volume of reducing agent stored in the intermediate storage for reducing agent (52). Metering system (40) according to one of Claims 1 until 5 , wherein the reducing agent buffer store (52) is connected to the reducing agent line (46) via a connecting line (56), the connecting line (56) entering the reducing agent line at a branch (54) downstream of the reducing agent feed pump (44) and upstream of the dosing element (48). (46) flows. Method for metering a reducing agent (86) into the exhaust system (20) of an internal combustion engine (10) with a metering system according to one of Claims 1 until 6 , comprising the following steps: - starting the internal combustion engine (10), - heating the exhaust system (20) and at least indirect thawing of the reducing agent (86) in the reducing agent intermediate store (52) and the reducing agent line (46) between the reducing agent intermediate store (52) and the dosing element (48), - operating the metering system (40) in a first operating state, with the reducing agent (86) stored in the intermediate reducing agent store (52) being metered into the exhaust system (20) of the internal combustion engine (10) and the reducing agent (86) being reducing agent tank (42) is heated, and - operating the dosing system (40) in a second operating state, wherein the reducing agent (86) stored in the reducing agent tank (42) is metered into the exhaust system (20). Method for dosing a reducing agent (86). claim 7 , wherein the intermediate reducing agent store (52) is filled with reducing agent (86) after the reducing agent (86) in the reducing agent tank (42) and in the reducing agent feed pump (44) has thawed, or the intermediate reducing agent store (52) is filled with reducing agent when the internal combustion engine (10) is requested to be switched off (86) is filled. Internal combustion engine (10) with at least one combustion chamber (12), wherein an outlet (18) of the internal combustion engine (10) is connected to an exhaust system (20), wherein in the exhaust system (20) at least one oxidation catalytic converter (28) and one associated with the oxidation catalytic converter ( 28) downstream exhaust gas aftertreatment components (30) for the selective, catalytic reduction of nitrogen oxides are arranged in the flow direction of an exhaust gas stream of the internal combustion engine (10), and with a dosing system (40) according to one of Claims 1 until 6 , wherein the intermediate reducing agent store (52) is heated at least indirectly by a component of the internal combustion engine (10) or the exhaust system (20) that quickly heats up after a cold start of the internal combustion engine (10). Internal combustion engine (10) after claim 9 , wherein an electric heating element (100) or an exhaust gas burner (102) for heating up at least one exhaust gas after-treatment component (28, 30) is arranged on the exhaust system (20), the gas being fed through the electric heating element (100) or the exhaust gas burner (102) into the The heat introduced into the exhaust system (20) is transferred at least indirectly to the reducing agent buffer store (52) in order to increase the reducing agent (86) stored in the reducing agent buffer store (52). liquid or to reduce the viscosity of the reducing agent (86).

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