DE102021207702A1 - Method and exhaust system for storing exhaust gas during a catalytic converter heating-up phase - Google Patents

Abstract

Disclosed is a method for operating an exhaust system (20) of an internal combustion engine (10), comprising the steps: detecting a temperature (T21) of a catalytic converter (21), diverting exhaust gas (24) via a recirculation line (22) and storing the exhaust gas ( 24) in an exhaust gas reservoir (25) as long as the temperature (T21) is below a limit value (TG), and passing the stored exhaust gas (24) through the catalytic converter (21) when the temperature (T21) exceeds the limit temperature (TG) has reached.

Description

technical field

During a warm-up phase of a catalytic converter, its ability to catalytically convert unburned hydrocarbons, carbon dioxide and nitrogen oxides is not yet available. The reliable conversion of the exhaust gas into nitrogen, water and carbon dioxide is only given above an operating temperature of the catalytic converter.

For this reason, motor vehicles with a 3-way catalytic converter do not comply with future stricter exhaust gas regulations in the first few minutes after a restart. Until now, manufacturers have responded by keeping the heating-up time as short as possible.

The warm-up time of the catalytic converter can be shortened by means of a special engine management system, particularly compact catalytic converters and an arrangement close to the engine.

Even if the heating-up time can be reduced in this way, exhaust gases that have not been catalytically converted still escape into the environment during the heating-up phase.

Heated catalytic converters, which are heated to their operating temperature before the combustion engine is started, are also possible to further reduce emissions during the warm-up phase. However, this results in a delay of a few seconds.

In the EP1205648 A2 describes a heating-up process for a catalytic converter device connected downstream of a multi-cylinder internal combustion engine capable of running lean, with a main catalytic converter and pre-catalytic converters connected in parallel, which are only charged with exhaust gas from a portion of the cylinders via associated exhaust gas paths. The cylinders are controlled individually or in groups so that rich exhaust gas is fed to a pre-catalyst and lean exhaust gas to a pre-catalyst, with the pollutants in the exhaust gas being converted exothermically on the catalyst device depending on the oxygen content present. Due to the different oxygen content in the exhaust gas paths, the conversion of pollutants is partly shifted to the main catalytic converter, so that it is heated accordingly. The temperature of the catalytic converter device, in particular the main catalytic converter, is controlled as required via the lambda values of the exhaust gases fed to the pre-catalytic converters, with the difference or spread between the lambda values being limited to a specific maximum value.

description

According to the present disclosure, a device and a method are to be specified with which these disadvantages can be remedied.

The disadvantages are remedied by the exhaust tract and the method for controlling this exhaust tract according to the independent claims. The dependent claims form advantageous developments of the disclosure. The dependent claims can be combined with one another in a technologically meaningful manner. The description, in particular in connection with the figures, additionally characterizes and specifies the disclosure.

Accordingly, an exhaust system of an internal combustion engine is provided, having a catalytic converter that can be connected in a fluid-conducting manner to an outlet of the internal combustion engine, and a recirculation valve arranged downstream of the catalytic converter, via which a recirculation line can be activated, through which exhaust gas is fed back into the catalytic converter upstream, wherein in an exhaust gas accumulator for storing exhaust gas during a warm-up phase of the catalytic converter is arranged in the recirculation line.

By storing exhaust gas, it is possible to only finally conduct exhaust gas through the catalytic converter into the environment when the catalytic converter has been heated to operating temperature and catalytic conversion can be guaranteed. During the warm-up phase of the catalytic converter, it is then no longer possible for unreduced exhaust gas to escape into the environment. The exhaust tract connects an outlet for exhaust gas of an internal combustion engine to the environment in a fluid-conducting manner. Turbines and valves, wastegates and a catalytic converter as well as an accumulator in the exhaust tract can be provided in the manner disclosed herein. A line or an element is fluid-conducting if it can largely conduct fluids through it in relation to the environment. In connection with exhaust gas, this also means that there is less heat loss to the environment, in particular so that hot exhaust gas is applied to the catalytic converter. The non-return valve must be designed in such a way that it can work at the temperatures prevailing in the exhaust gas.

In one embodiment, it is provided that the return line upstream of the catalytic converter can be shut off by a switchable 3-way valve.

The 3-way valve can establish a fluid-conducting line between the outlet of the internal combustion engine and the inlet of the catalytic converter. Furthermore, there can be a fluid-conducting connection between between the exhaust gas reservoir and the catalytic converter. During the warm-up phase, the accumulator is therefore a dead volume in which exhaust gas collects. As soon as the catalytic converter has reached its operating temperature, the 3-way valve can be opened.

In one embodiment, it is provided that exhaust gas can be expanded in a turbine, which is arranged in a fluid-conducting manner between the outlet and the 3-way valve.

The turbine can be a turbine of a turbocharger. The turbine can be rigidly connected to a compressor. The compressor can compress ambient air for the internal combustion engine and supply it.

In one embodiment, it is provided that the catalytic converter can be heated by a heating device.

The heating device can work electrically or chemically via recrystallization. The heating device shortens the warm-up phase of the catalytic converter.

The faster the catalytic converter can be heated up, the smaller the exhaust gas accumulator can be built. The exhaust gas accumulator can be thermally insulated. Nevertheless, exhaust gas cools down in the exhaust gas storage tank. So that the exhaust gas does not cool down again when passing through the catalytic converter, it can be successively mixed with the hot, fresh exhaust gas from the combustion engine via the 3-way valve.

1. i. Erfassen einer Temperatur eines Katalysators,
2. ii. Umleiten von Abgas über eine Rückführleitung und Speicherung des Abgases in einem Abgasspeicher, solange die Temperatur unterhalb von einem Grenzwert liegt, und
3. iii. Durchleiten des gespeicherten Abgases durch den Katalysator, wenn die Temperatur die Grenztemperatur erreicht hat.

A method with the following steps is also proposed for operating the exhaust system:

1. i. detecting a temperature of a catalyst,
2. ii. diverting exhaust gas via a recirculation line and storing the exhaust gas in an exhaust gas accumulator while the temperature is below a threshold, and
3. iii. Passing the stored exhaust gas through the catalytic converter when the temperature has reached the limit temperature.

In one embodiment of the method, the catalytic converter is heated by an electrical heating device at least until the temperature has reached the limit temperature. In addition, the heating device of the catalytic converter can remain in operation so that the catalytic converter is not cooled down as a result of the recirculated, cooled exhaust gas.

One embodiment relates to a computer program product with program code means that are stored on a computer-readable data carrier in order to carry out the method described above when the computer program product is executed on a computer, in particular in control electronics of a control system. The control system can be designed and developed as described above.

One embodiment relates to a computer program with encoded instructions for carrying out the method described above when the computer program is executed on a computer, in particular control electronics of a control system. The control system can be designed and developed as described above. The computer program can be stored in particular on the computer program product described above, for example a floppy disk, CD-ROM, DVD, memory, a processor unit connected to the Internet. The computer program can in particular be in the form of a compiled or not yet compiled data sequence, which is preferably based on a higher, in particular object-based, computer language.

One embodiment relates to a signal sequence with computer-readable instructions for carrying out the method described above when the signal sequence is processed by a computer, in particular by control electronics of a control system. The control system can be designed and developed as described above. The signal sequence can be generated in particular with the aid of the computer program described above and/or with the aid of the computer program product described above. The signal sequence can be provided wirelessly or wired as electrical pulses and/or electromagnetic waves and/or optical pulses.

A means for implementing the method steps within the meaning of the present disclosure can be designed in terms of hardware and/or software, in particular a processing unit, in particular a digital processing unit, in particular a control unit with microprocessors, preferably connected to a memory and/or bus system for data or signals ( CPU) and/or one or more programs or program modules. The CPU can be designed to process commands that are implemented as a program, to detect input signals from a data bus and/or to emit output signals to a data bus. The program can be stored on a storage system. The storage system can have one or more, in particular different, storage media, in particular optical, magnetic, solid and/or other non-volatile media. The program may be arranged to embody or perform the methods described herein ren so that the CPU can execute the steps of such methods. In one embodiment, one or more, in particular all, steps of the method can be carried out fully or partially automatically, in particular by the controller or its means.

character list

• 1: zum Teil schematisch einen Verbrennungsmotor mit einem Abgastrakt, wobei in dem Abgastrakt eine Turbine und stromabwärts davon ein Katalysator angeordnet ist, der sich in der Darstellung in einer Aufwärmphase befindet, mit einem Rückführventil, durch welches der Abgastrakt vollständig von der Umgebung abgetrennt ist, und durch welches Abgas in einen Abgasspeicher gelangt;
• 2: den Abgastrakt aus 1, bei dem der Katalysator eine Betriebstemperatur und mindestens eine Grenztemperatur erreicht hat, wobei in diesem Zustand das Rückführventil den Katalysatorauslass fluidleitend mit der Umgebung verbindet und auch gespeichertes Abgas durch den Katalysator strömt; und
• 3: ein Flussdiagramm eines Verfahrens zur Steuerung eines Katalysators und eines Abgasspeichers.

The drawings described herein are for illustrative purposes only and are not intended to limit the scope of the present disclosure in any way. Show it:

• 1 : a partially schematic view of an internal combustion engine with an exhaust gas tract, with a turbine and downstream of it a turbine being arranged in the exhaust gas tract, which is in a warming-up phase in the illustration, with a recirculation valve by which the exhaust gas tract is completely separated from the environment, and through which exhaust gas enters an exhaust gas reservoir;
• 2 : the exhaust tract 1 in which the catalytic converter has reached an operating temperature and at least one limit temperature, in which state the recirculation valve fluidly connects the catalytic converter outlet to the environment and stored exhaust gas also flows through the catalytic converter; and
• 3 : a flow chart of a method for controlling a catalytic converter and an exhaust gas reservoir.

The following description is merely illustrative in nature. For the sake of clarity, the same reference numbers will be used in the drawings to designate similar elements. It should be appreciated that some steps within a method may be performed in a different order without changing the principles of the present disclosure. Steps of the method can be multiplications, summations and selections as well as assignments, for example assignment of output values to input values in characteristic diagrams.

1 shows an exhaust tract 20 of an internal combustion engine 10. The exhaust tract 20 has a catalytic converter 21 which can be connected in a fluid-conducting manner to an outlet 12 of the internal combustion engine 10, and a recirculation valve 23 arranged downstream of the catalytic converter 21. A recirculation line 22 can be switched on via the recirculation valve 23, through which exhaust gas 24 can be fed back into the catalytic converter 21 upstream of it.

An exhaust gas reservoir 25 for storing exhaust gas 24 during a warm-up phase of the catalytic converter 21 is arranged in the recirculation line 22 . By storing exhaust gas 24 in the exhaust gas reservoir 25, it is possible to conduct exhaust gas 24 through the catalytic converter 21 into the environment only when the catalytic converter 21 has reached an operating temperature and a catalytic conversion can be guaranteed. The operating temperature corresponds to a temperature above a limit temperature TG (see 3 ).

The return line 22 opens out again upstream of the catalytic converter 21 into a main line which leads into the catalytic converter 21 . At this point, the return line 22 can be shut off by a switchable 3-way valve 26 . During the warm-up phase of the catalytic converter 21, the 3-way valve 26 for exhaust gas 24 from the exhaust gas reservoir 25 remains closed.

In 2 a temperature T21 of the catalytic converter 21 has reached an operating temperature. The recirculation valve 26 and the 3-way valve are opened so that exhaust gas from the exhaust gas reservoir 25 and the internal combustion engine 10 can pass through the catalytic converter 21 into the environment.

It is further provided that exhaust gas can be expanded in a turbine 13 which is arranged in a fluid-conducting manner between the outlet 12 and the 3-way valve 26 . The turbine 13 is a turbine 13 of an exhaust gas turbocharger in which the turbine 13 drives a compressor 14 which compresses air for an inlet 11 of the internal combustion engine 10 . A charge air cooler 15 for cooling compressed air is also provided downstream of the compressor 14 .

In order to shorten the warm-up phase, it is provided that the catalytic converter 21 can be heated via a heating device 27 .

3 shows a method for operating an exhaust system 20 of an internal combustion engine 10. Regarding the reference numbers of the technical components mentioned in the method, reference is made to FIG 1 and 2 referred.

After a start 31, a temperature T21 of a catalytic converter 21 is detected in step 32. In step 33, a query is made as to whether the temperature T21 is greater than a limit temperature TG.

In step 35, the exhaust gas is recirculated and stored as long as it has not yet reached the limit temperature. This is done by diverting exhaust gas 24 via a recirculation line 22 and storing the exhaust gas 24 in an exhaust gas reservoir 25.

As long as the temperature T21 is below a limit value TG, the repeats itself Query in step 33 and also storage in step 35.

In step 36, the stored exhaust gas 24 is passed through the catalytic converter 21 when the temperature T21 has reached the limit temperature TG.

It is provided that the catalytic converter 21 is heated in step 34 via an electric heating device 27 at least until the temperature T21 has reached the limit temperature TG.

In the 1 and 2 a control unit 30 for controlling an exhaust system 20 is also shown schematically. The control unit 30 is connected in a signal-conducting or signal-transmitting manner to the internal combustion engine 10, the heating device 27 and the recirculation valve 23 and the 3-way valve 26 in order to control them accordingly.

Although at least one exemplary embodiment has been presented in the foregoing description as well as the description of the figures, it should be recognized that a large number of variations exist. Furthermore, it should be appreciated that the embodiment(s) are only examples and are not intended to limit the scope, applicability, or precise configuration in any way. Rather, the description and description of the figures provide useful guidance for those skilled in the art for implementing at least one embodiment, it being understood that various changes in form and function of the described features may be made without departing from the scope of the claims and their equivalents .

Reference List

10

combustion engine

11

Combustion engine intake

12

Combustion engine exhaust

13

turbine

14

compressor

15

intercooler

20

exhaust tract

21

catalyst

22

return line

23

recirculation valve

24

exhaust

25

exhaust gas accumulator

26

3-way valve

27

heating device

30

control unit

31

Step

32

Step

33

Step

34

Step

35

Step

36

Step

37

Step

S

flow direction

T21

temperature

QUOTES INCLUDED IN DESCRIPTION

This list of the 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

• EP 1205648 A2 [0006]

Claims (10)

Exhaust system (20) of an internal combustion engine (10), having a catalytic converter (21) which can be connected in a fluid-conducting manner to an outlet (12) of the internal combustion engine (10), and a recirculation valve (23) which is arranged downstream of the catalytic converter (21) and via which a recirculation line ( 22) can be switched on, through which the exhaust gas (24) is fed back into the catalytic converter (21) upstream, with an exhaust gas reservoir (25) for storing exhaust gas (24) during a warm-up phase of the catalytic converter (21 ) is arranged. Exhaust tract (20) after claim 1 , wherein the return line (22) upstream of the catalytic converter (21) can be shut off by a switchable 3-way valve (26). Exhaust tract (20) after claim 1 and/or 2, wherein exhaust gas can be expanded in a turbine (13) which is arranged in a fluid-conducting manner between the outlet (12) and the 3-way valve (26). Exhaust tract according to one or more of Claims 1 until 3 , wherein the catalyst (21) via a heating device (27) can be heated. Method for operating an exhaust system (20) of an internal combustion engine (10), comprising the steps: i. detecting a temperature (T21) of a catalytic converter (21), ii. Diverting exhaust gas (24) via a recirculation line (22) and storing the exhaust gas (24) in an exhaust gas reservoir (25) as long as the temperature (T21) is below a limit value (TG), and iii. Passing the stored exhaust gas (24) through the catalytic converter (21) when the temperature (T21) has reached the limit temperature (TG). procedure after claim 5 , wherein the catalytic converter (21) is heated by an electric heating device (27) at least until the temperature (T21) has reached the limit temperature (TG). Control unit (30) for controlling an exhaust system (20) according to one of Claims 1 until 4 according to a method according to any one of Claims 5 and/or 6. Computer program product with program code means, which are stored on a computer-readable data medium, in order to implement the method according to one of Claims 5 until 6 carried out if the computer program product on a computer, in particular a control unit (30). claim 7 is performed. Computer program with encoded instructions for carrying out the method according to any one of Claims 5 until 6 , if the computer program on a computer, in particular a computer in a control unit (30). claim 7 is performed. Signal sequence with computer-readable instructions for carrying out the method according to any one of Claims 5 until 6 , if the signal sequence from a computer, in particular a control unit (30). claim 7 is processed.

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