EP3405666B1 - Apparatus and method for exhaust gas recirculation - Google Patents

Description

The invention relates to the recirculation of exhaust gas from a combustion chamber of an internal combustion engine, preferably a motor vehicle, back into the combustion chamber.

Exhaust gas recirculation systems are used in particular to reduce emissions of nitrogen oxides. When fuel is burned in a combustion chamber of an internal combustion engine, among other things, environmentally harmful nitrogen oxides are produced, especially when there is a high oxygen content in the combustion chamber. To reduce the emission of nitrogen oxides, exhaust gas from a combustion chamber of an internal combustion engine can be diverted through pipelines and mixed with clean air that is fed to the combustion chamber. Passing through the combustion chamber again reduces the nitrogen oxide content in the exhaust gas. At the same time, the formation of nitric oxide itself is minimized.

Devices for cooling clean air and recirculated exhaust gas, which are fed to the combustion chamber, are also known. By cooling the clean air and the recirculated exhaust gas that are fed to the combustion chamber, the combustion chamber can take in more clean air. This increases the output and the efficiency of the internal combustion engine, because more oxygen is available for the combustion of fuel.

The known systems often have the disadvantage that the cooling power with which the recirculated exhaust gas is cooled in the cooling device cannot be adjusted sufficiently. This is particularly disadvantageous in low-load phases. Low load is to be understood as meaning that the internal combustion engine only provides part of its maximum output. In Such low load phases of the internal combustion engine can have too great a cooling capacity. Too low a temperature of the recirculated exhaust gas can lead to sooting of the components. Sooting means that components of the exhaust gas condense out in exhaust gas that is too cold. This can in particular be water vapor, unburned hydrocarbons or acids.

From the DE 10 2008 033 823 A1 an exhaust gas recirculation device with several cooling stages is known, in which the cooling stages can be controlled by means of flaps which are held next to one another in a housing head.

From the pamphlets EP 1 275 838 A1 , DE 197 33 964 A1 , US 2011/108013 A1 and WO 2012/152601 A1 Various embodiments of exhaust gas recirculation devices with EGR valves are known.

Proceeding from this, the object of the present invention is to continue to solve or at least alleviate the technical problems described in connection with the prior art. In particular, an internal combustion engine with an exhaust gas recirculation device is to be presented which enables the cooling capacity with which the recirculated exhaust gas is cooled to be easily adjusted.

These objects are achieved with an internal combustion engine according to the features of patent claim 1 and with a method according to the features of patent claim 6. Further advantageous configurations of the internal combustion engine are specified in the dependent claims. The features listed individually in the patent claims can be combined with one another in any desired, technologically sensible manner and can be supplemented by explanatory facts from the description, with further variants of the invention being shown.

• mindestens einen Abgaskühler, durch welchen ein erster Strömungsweg zur Rückführung von Abgas verläuft, aufweisend mindestens eine erste Kühlstufe und mindestens eine zusätzliche Kühlstufe,
• mindestens eine Klappenanordnung, mit welcher die mindestens eine zusätzliche Kühlstufe zuschaltbar ist,
• eine Bypassleitung, durch welche ein zweiter Strömungsweg zur Rückführung von Abgas verläuft, mit welcher der Abgaskühler bei der Rückführung von Abgas gebypasst werden kann,
• ein AGR-Ventil mit mindestens drei möglichen Stellungen:
  • ∘ eine Ruhestellung, in welcher die Abgasrückführungseinrichtung geschlossen ist,
  • ∘ eine erste Stellung, in welcher der erster Strömungsweg durch den Abgaskühler geöffnet ist, und
  • ∘ eine zweite Stellung, in welcher der zweiter Strömungsweg durch die Bypassleitung geöffnet ist;

wobei die mindestens eine erste Kühlstufe, die mindestens eine zusätzliche Kühlstufe, die Bypassleitung, das AGR-Ventil und die Klappenanordnung in einem Gehäuse der Abgasrückführungseinrichtung integriert sind und wobei das AGR-Ventil und die Klappenanordnung derart angeordnet sind, dass eine Verankerung der Klappe an einer Außenwand des AGR-Ventils vorgesehen ist, wobei die Außenwand des AGR-Ventils zugleich eine Innenwand der mindestens einen ersten Kühlstufe und der mindestens einen zweiten Kühlstufe darstellt, wobei das AGR-Ventil zylinderförmig ausgeführt ist und wobei die Klappenanordnung an einer Mantelfläche des AGR-Ventils befestigt ist.The device according to the invention is an internal combustion engine with an exhaust gas recirculation device for recirculating exhaust gases from the internal combustion engine into an intake area of the internal combustion engine. The exhaust gas recirculation device has the following components:

• having at least one exhaust gas cooler through which a first flow path for recirculating exhaust gas runs a first cooling stage and at least one additional cooling stage,
• at least one flap arrangement with which the at least one additional cooling stage can be switched on,
• a bypass line, through which a second flow path for recirculating exhaust gas runs, with which the exhaust gas cooler can be bypassed when recirculating exhaust gas,
• an EGR valve with at least three possible positions:
  • ∘ a rest position in which the exhaust gas recirculation device is closed,
  • ∘ a first position in which the first flow path through the exhaust gas cooler is open, and
  • ∘ a second position in which the second flow path through the bypass line is open;

wherein the at least one first cooling stage, the at least one additional cooling stage, the bypass line, the EGR valve and the flap arrangement are integrated in a housing of the exhaust gas recirculation device, and wherein the EGR valve and the flap arrangement are arranged such that an anchoring of the flap on a Outer wall of the EGR valve is provided, the outer wall of the EGR valve at the same time representing an inner wall of the at least one first cooling stage and the at least one second cooling stage, the EGR valve being cylindrical and the flap arrangement on a lateral surface of the EGR valve is attached.

In a preferred embodiment variant, the internal combustion engine is an internal combustion engine with an exhaust gas turbocharger. In such internal combustion engines, a distinction can be made between high pressure exhaust gas recirculation and low pressure exhaust gas recirculation. In the case of high-pressure exhaust gas recirculation, the exhaust gas is usually branched off upstream of an exhaust side of the turbocharger and supplied to the compressed clean air downstream of a clean air side of the turbocharger. Upstream means in the flow direction of the clean air before the compressor. Downstream means in the flow direction of the clean air after the compressor. With the low-pressure exhaust gas recirculation, exhaust gas is branched off downstream of the exhaust gas side of the turbocharger and fed to the not yet compressed clean air upstream of the clean air side of the turbocharger. Mixed forms and combinations of high pressure exhaust gas recirculation and low pressure exhaust gas recirculation are also known and technically possible.

The internal combustion engine can in particular be intended for a motor vehicle, a work machine, an aircraft or similar machines. The internal combustion engine usually has combustion chambers that are designed in the manner of cylinders. Clean air can be supplied to these combustion chambers via a clean air duct. After fuel has burned in the combustion chambers, exhaust gas can be discharged via an exhaust system. The exhaust system usually has an exhaust aftertreatment device, e.g. B. having a catalyst and / or a particle filter for exhaust gas purification. An exhaust gas recirculation device is connected to the exhaust system. This exhaust gas recirculation device comprises an exhaust gas recirculation line between lines carrying exhaust gas and the clean air duct. The exhaust gas recirculation line can be formed at least partially by a hose or a tube made of rubber or plastic. Exhaust gas can be fed to the clean air duct via the exhaust gas recirculation device. As described above, this recirculation of exhaust gas is advantageous in terms of minimizing nitrogen oxide emissions from an internal combustion engine. The exhaust gases can be returned to an intake area of the internal combustion engine.

In the embodiment described here, the exhaust gas recirculation device has at least one exhaust gas cooler, through which a first flow path runs, and a bypass line, through which a second flow path runs.

The exhaust gas cooler is configured such that exhaust gas flowing along the first flow path is cooled. This cooling can take place in that exhaust gas passes the at least one first cooling stage on the first flow path.

The exhaust gas cooler has an additional cooling stage beyond the first cooling stage. Passing several cooling levels means increased cooling performance. A flow path for exhaust gas through the additional cooling stage is also referred to here as a first flow path or as part of the first flow path.

The bypass line is constructed in such a way that exhaust gas flowing along the second flow path is not cooled. This means that exhaust gas is routed past the exhaust gas cooler, that is to say the exhaust gas cooler is bypassed.

In the exhaust gas cooler, an increased cooling capacity can be switched on via the at least one flap arrangement. There can also be several additional cooling stages. A flap arrangement is then preferably provided for each additional cooling stage. The flap arrangement can, for example, be a simple flap which in a first position closes an opening to the additional cooling stage in a gas-tight manner, and which in a second position releases the opening for the passage of exhaust gas to the additional cooling stage. The flap arrangement is integrated into the exhaust gas cooler in such a way that when the flap is in the first position, only the at least one first cooling stage is accessible for exhaust gas, and that in the second position of the flap the at least one additional cooling stage is also accessible.

In addition, an EGR valve is provided which is used to selectively open the first cooling stage or the bypass line or to completely close the exhaust gas recirculation device. The abbreviation "EGR" stands for exhaust gas recirculation. The EGR valve is a valve with at least the three possible positions discussed above: a rest position, a first position and a second position. The EGR valve can be a multi-way valve. The EGR valve enables adjustment of which of the described flow paths the exhaust gas takes. The EGR valve is normally in the rest position. This is especially true when there are no forces acting on the EGR valve. The EGR valve is pressed into the rest position, for example by a spring. If the EGR valve is in the rest position, the exhaust gas recirculation device is closed. This means that exhaust gas can flow neither via the first flow path nor via the second flow path. So there is no exhaust gas from the exhaust gas lines in the clean air duct of the internal combustion engine. If the EGR valve is brought into the first position, exhaust gas can flow via the first flow path. The exhaust gas passes through the exhaust gas cooler. Depending on the position of the flap arrangement, the at least one first cooling stage and possibly also an additional cooling stage (of the at least one additional cooling stage) occurs. If the EGR valve is brought into the second position, the second flow path is released. This means that exhaust gas flows past the cooling stages through the bypass line. The exhaust gas is not actively cooled.

The arrangement described makes it possible to adjust the cooling capacity of the exhaust gas cooler in at least three stages. The second flow path enables exhaust gas recirculation without any active cooling, the first flow path enables exhaust gas recirculation with cooling, with a different cooling output depending on the number of accessible cooling stages.

According to the invention, the at least one first cooling stage, the at least one additional cooling stage, the bypass line, the EGR valve and the flap arrangement are integrated in a housing of the exhaust gas recirculation device.

Integrating the elements mentioned in a housing means that a compact design is possible.

In addition, the EGR valve and the flap arrangement are arranged such that an anchoring of the flap is provided on an outer wall of the EGR valve, the outer wall of the EGR valve simultaneously representing an inner wall of the at least one first cooling stage and the at least one second cooling stage .

The outer wall here means in particular a section of a housing of the EGR valve and the cooling stages. The EGR valve is cylindrical. The outer wall of the EGR valve is thus a jacket surface of a housing. The EGR valve is integrated into the exhaust gas cooler in such a way that the jacket surface is suitable for fastening the flap arrangement to it. This embodiment enables a particularly compact design of the exhaust gas recirculation device.

In a further embodiment of the internal combustion engine described, the bypass line is thermally insulated.

In particular, there is thermal insulation from the at least one first cooling stage and the at least one additional cooling stage. For thermal insulation, a thermally insulating foam or a comparable material can be used, for example, which is usually used for thermal insulation in an internal combustion engine. This material is applied in particular between the at least one additional cooling stage and the bypass line in such a way that thermal contact between the cooling stages and the bypass line is at least minimized. The at least one additional cooling stage is preferably arranged between the first cooling stage and the bypass line. The additional cooling stage is often not traversed by exhaust gas. The additional cooling stage therefore helps to improve the insulation of the bypass line from the environment.

Thermal insulation of the bypass line enables the temperature of the exhaust gas recirculated through the bypass line to be maintained. Such temperature maintenance is useful in low-load phases in order not to reduce the temperature of the recirculated exhaust gases too far and, in particular, to prevent the exhaust gas from condensing out and the formation of deposits in the bypass line (thermally). Thermal insulation preferably takes place not only with respect to the exhaust gas cooler and the cooling stages, but also with respect to the environment.

In a further embodiment of the internal combustion engine described, the EGR valve is a poppet valve which has an inlet, a first outlet and a second outlet. The two outlets are arranged opposite one another. A first closure element is provided at the first outlet and a second closure element is provided at the second outlet. The two closure elements are braced against one another with the aid of a spring in order to close the outlets in a rest position. There is also a slide that can be operated by an actuator in order to selectively open the closure element at the first outlet or the closure element at the second outlet.

This embodiment variant defines a particularly advantageous structure of an EGR valve which enables the three possible positions mentioned (rest position, first position, second position). The poppet valve is a valve in which the closure elements are shaped like a plate. The poppet valve described here is a three-way valve with one inlet and two outlets. A medium, such as e.g. B. a gas into the valve and possibly through one of the both outlets out of the valve. In the rest position, the closure elements are pressed against openings in the outlets by the spring. The one spring is preferably used jointly for both closure elements. The two outlets are therefore arranged opposite one another. This makes it possible to use a (common) spring for both outlets. In the rest position the valve is completely closed, ie both outlets are closed and the medium cannot pass through the valve. The fact that one of the outlets of the valve is open means that the closure element of the corresponding outlet is removed from the opening in such a way that an annular gap between the closure element and the opening enables the medium to pass through. With this variant it is normally only possible for one outlet to be open on its own and not both outlets at the same time. The slide establishes a connection between the valve and the actuator. The actuator can use the slide to set the position of both locking elements. This can take place electronically controlled, for example. For this purpose, the actuator can be designed, for example, as an electric motor. The slide or the actuator also have a rest position and a deflected position. In the rest position, the slide does not move either of the two closure elements. A movement out of the rest position of the actuator and slide in a first direction displaces the first closure element at the first outlet. A movement out of the rest position of the actuator and slide in a second direction moves the second closure element at the second outlet.

It is also advantageous if the actuator is designed in such a way that the opening widths of the first outlet and of the second outlet can be continuously adjusted with the aid of the slide.

This means in particular that the opening width of the first outlet and the opening width of the second outlet can each be continuously adjusted are. It is usually not meant that the first outlet and the second outlet can be controlled separately from one another in such a way that both outlets (first outlet and second outlet) can be open at the same time. Preferably, only either the first outlet or the second outlet can ever be open.

In a further embodiment of the internal combustion engine described, the at least one first cooling stage and the at least one additional cooling stage are arranged parallel to one another.

If the two cooling stages are in the form of tubes, for example, a parallel course allows a compact arrangement. In addition, the flow density of the exhaust gas through the cooling stages remains almost constant, regardless of how many cooling stages have been activated. This is advantageous because it can be cooled in an energy-efficient manner without the cooling capacity being lost at the interfaces between the cooling stages.

1. a) Abschaltung der Abgasrückführung durch Absperrung der Abgasrückführungseinrichtung unter Einstellung des AGR-Ventils (12) in der Ruhestellung,
2. b) Abgasrückführung während einer Niedriglastphase, wobei die Abgasrückführung durch die Bypassleitung (11) unter Einstellung des AGR-Ventils (12) in der zweiten Stellung erfolgt, wobei keine Kühlung des rückgeführten Abgases stattfindet,
3. c) Abgasrückführung während eines Lastbetriebs, wobei die Abgasrückführung durch den Abgaskühler (5) durch Einstellung des AGR-Ventils (12) in der zweiten Stellung erfolgt, und
4. d) Freischalten mindestens einer zusätzlicher Kühlstufe (9) mit Hilfe der mindestens einen Klappenanordnung (10), wenn ein Hochlastbetrieb vorliegt.

Furthermore, a method for operating an internal combustion engine according to one of the described embodiments is presented, having the following method steps:

1. a) Shutdown of exhaust gas recirculation by shutting off the exhaust gas recirculation device while setting the EGR valve (12) in the rest position,
2. b) exhaust gas recirculation during a low load phase, the exhaust gas recirculation taking place through the bypass line (11) with the EGR valve (12) in the second position, with no cooling of the recirculated exhaust gas taking place,
3. c) exhaust gas recirculation during load operation, the exhaust gas recirculation taking place through the exhaust gas cooler (5) by setting the EGR valve (12) in the second position, and
4. d) activation of at least one additional cooling stage (9) with the aid of the at least one flap arrangement (10) when high-load operation is present.

The process steps a) to d) do not have to be processed one after the other, but can be carried out in any technically meaningful sequence during the operation of an internal combustion engine.

Process step a) enables the internal combustion engine to be operated without exhaust gas recirculation. The EGR valve closes both the first outlet and the second outlet. This corresponds to the rest position of the EGR valve already described above.

Process step b) can be used to enable exhaust gas recirculation without cooling in a low load phase. As described above, by setting the EGR valve to the second position, the second flow path through the bypass line becomes accessible for exhaust gas.

Method step c) is suitable for operating the internal combustion engine with a higher load than the low load described under method step b). The EGR valve is in the second position so that the first flow path is released. The at least one first cooling stage of the exhaust gas cooler is accessible. This first cooling stage cools the recirculated exhaust gas.

If the at least one additional cooling stage is also switched on in accordance with method step d), the cooling output can be increased. For this purpose, the flap arrangement is brought into the second position.

The particular advantages and design features shown for the internal combustion engine described can be applied and transferred to the method described in any desired, technologically sensible manner. The same applies to the particular advantages and design features described for the method described, which can be used and transferred to the device described.

The invention is preferably used in a motor vehicle having an internal combustion engine with an exhaust gas recirculation device which is designed in accordance with one of the embodiments described above and which is operated with the method described.

Fig. 1:

eine schematische Darstellung eines Kraftfahrzeugs mit einer Verbrennungskraftmaschine mit einer Abgasrückführungseinrichtung entsprechend der Erfindung,

Fig. 2:

eine schematische Darstellung einer Abgasrückführungseinrichtung für eine Verbrennungskraftmaschine,

Fig. 3:

eine schematische Darstellung der Abgasrückführungseinrichtung aus Fig. 2, bei welcher der zweite Strömungsweg freigegeben ist,

Fig. 4:

eine schematische Darstellung der Abgasrückführungseinrichtung aus Fig. 2, bei welcher der erste Strömungsweg freigegeben ist,

Fig. 5:

eine schematische Darstellung der Abgasrückführungseinrichtung aus Fig. 2, bei welcher der erste Strömungsweg freigegeben ist, und bei welcher eine zusätzliche Kühlstufe zugeschaltet ist.

The invention and the technical environment are explained in more detail below with reference to the figures. The figures show particularly preferred exemplary embodiments to which, however, the invention is not limited. In particular, it should be pointed out that the figures and in particular the size relationships shown are only schematic. Show it:

Fig. 1:

a schematic representation of a motor vehicle with an internal combustion engine with an exhaust gas recirculation device according to the invention,

Fig. 2:

a schematic representation of an exhaust gas recirculation device for an internal combustion engine,

Fig. 3:

a schematic representation of the exhaust gas recirculation device Fig. 2 , in which the second flow path is released,

Fig. 4:

a schematic representation of the exhaust gas recirculation device Fig. 2 , in which the first flow path is released,

Fig. 5:

a schematic representation of the exhaust gas recirculation device Fig. 2 , in which the first flow path is released and in which an additional cooling stage is switched on.

Fig. 1 shows a motor vehicle 1 in which an internal combustion engine 2 is integrated. Through a clean air duct 22, clean air can be drawn in from the environment into an intake area 4.2 of the internal combustion engine 2. In one or more combustion chambers of the internal combustion engine, fuel can be burned with the clean air, as a result of which motor vehicle 1 can be driven. Exhaust gas produced in the process can be discharged from the internal combustion engine 2 through an exhaust gas line 23 through an exhaust gas outlet 4.1. It passes through an exhaust gas aftertreatment device 25 which comprises a catalytic converter 26. Through an exhaust gas recirculation line 24, exhaust gas can be recirculated from the exhaust gas line 23 into the clean air duct 22. It can be cooled in an exhaust gas cooler 5. The direction of flow of the clean air and the exhaust gas is indicated by arrows.

Fig. 2 shows a schematic illustration of an exhaust gas recirculation device 3 with an exhaust gas cooler 5. In the illustration shown, a first cooling stage 8 is arranged parallel to an additional cooling stage 9. A bypass line 11 is arranged, separated from the cooling stages 8 and 9 by thermal insulation 20. The bypass line 11 is preferably also isolated from the environment. An EGR valve 12 is also shown. This comprises an inlet 15 through which exhaust gas can enter the exhaust gas cooler 5, a first outlet 16.1 on the bypass line 11 and a second outlet 16.2 on the first cooling stage 8. The EGR valve 12 is cylindrical. It has an outer wall 14. In the interior of the EGR valve 12, a first closure element 17.1 and a second closure element 17.2 are arranged such that the first outlet 16.1 and the second outlet 16.2 can be closed with them. Due to the opposite arrangement of the first outlet 16.1 and the second outlet 16.2, both the first outlet 16.1 and the second outlet 16.2 can be closed with a spring 21 via the closure elements 17.1 and 17.2. A slide 18 enables the two closure elements 17.1 and 17.2 to be adjusted continuously. The slide 18 is operated via an actuator 19. This is preferably electronically controllable. The first cooling stage 8 and the additional cooling stage 9 can be connected via a flap arrangement 10. The flap arrangement 10 is arranged on the outer wall 14 of the ARG valve 12, whereby exhaust gas that reaches the first cooling stage 8 via the second outlet 16.2 of the EGR valve 12 can reach the second cooling stage 9 via the flap arrangement 10, so that the additional cooling stage 9 can be run through in full length. A first flow path 6 runs through the first outlet 16.1 and the exhaust gas cooler 5. A second flow path 7 runs through the second outlet 16.2 and the bypass line 11.

Fig. 3 shows all elements and the same section of the exhaust gas cooler 5 Fig. 2 . For the sake of clarity, in Fig. 3 not all reference characters repeated. It will be on Fig. 2 referenced. It is shown that the second flow path 7 is released through the bypass line 11. For this purpose, the first closure element 17.1 of the EGR valve 12 is in a position which releases the first outlet 16.1 of the EGR valve 12. With this, exhaust gas can flow through the bypass line 11, as indicated by the arrows. The first cooling stage 8 and the additional cooling stage 9 are not accessible to exhaust gas.

Fig. 4 also shows the same section of the exhaust gas cooler 5 from Fig. 2 . Hence, here too Fig. 2 referenced. A situation is shown in which the first flow path 6 is released. As indicated by arrows, exhaust gas can flow through the EGR valve 12 and through the first cooling stage 8. It is cooled in the first cooling stage 8. The second closure element 17.2 is in a position that the second outlet 16.2 of the EGR valve releases. The flap arrangement 10 is closed, as a result of which the additional cooling stage 9 is not accessible to exhaust gas. The bypass line 11 is also not accessible.

Fig. 5 differs from Fig. 4 only to the extent that the flap arrangement 10 is open here. This enables the additional cooling stage 9. As shown by arrows, exhaust gas can flow not only through the first cooling stage 8, but also through the additional cooling stage 9. It is also cooled in the additional cooling stage 9, and for this purpose the first flow path 6 is widened in such a way that it also runs through the additional cooling stage 9. Overall, the cooling capacity of the in Fig. 5 situation shown stronger than the cooling capacity of the in Fig. 4 presented situation.

List of reference symbols

1

Motor vehicle

2

Internal combustion engine

3

Exhaust gas recirculation device

4th

Exhaust outlet

4.2

Suction area

5

Exhaust gas cooler

6th

first flow path

7th

second flow path

8th

first cooling stage

9

additional cooling stage

10

Flap arrangement

11

Bypass line

12

AGR valve

13

casing

14th

Outer wall

15th

inlet

16.1

first outlet

16.2

second outlet

17.1

first closure element

17.2

second closure element

18th

Slider

19th

Actuator

20th

thermal insulation

21st

feather

22nd

Clean air duct

23

Exhaust pipe

24

Exhaust gas recirculation line

25th

Exhaust aftertreatment device

26th

catalyst

Claims (7)

1. Internal combustion engine (2) having an exhaust-gas recirculation device (3) for the recirculation of exhaust gases of the internal combustion engine into an intake region (4.2) of the internal combustion engine (2), wherein the exhaust-gas recirculation device (3) has the following components:

   - at least one exhaust-gas cooler (5) through which a first flow path (6) for the recirculation of exhaust gas runs and which has at least one first cooling stage (8) and at least one additional cooling stage (9),

   - at least one flap arrangement (10) with a flap by means of which the at least one additional cooling stage (9) is activatable,

   - a bypass line (11) through which a second flow path (7) for the recirculation of exhaust gas runs and by means of which the exhaust-gas cooler (5) can be bypassed during the recirculation of exhaust gas,

   - an EGR valve (12) having at least three possible positions:

   ∘ a rest position, in which the exhaust-gas recirculation device is closed,

   ∘ a first position, in which the first flow path (6) through the exhaust-gas cooler is open, and

   ∘ a second position, in which the second flow path (7) through the bypass line (11) is open;

   wherein the at least one first cooling stage (8), the at least one additional cooling stage (9), the bypass line (11), the EGR valve (12) and the flap arrangement (10) are integrated in a housing (13) of the exhaust-gas recirculation device (3), and wherein the EGR valve (12) and the flap arrangement (10) are arranged such that an anchoring of the flap is provided on an outer wall (14) of the EGR valve (12), wherein the outer wall (14) of the EGR valve (12) simultaneously constitutes an inner wall of the at least one first cooling stage (8) and of the at least one second cooling stage (9), wherein the EGR valve (12) is of cylindrical design and wherein the flap arrangement (10) is fastened to a shell surface of the EGR valve (12).
2. Internal combustion engine (2) according to one of the preceding claims, wherein the bypass line (11) is thermally insulated.
3. Internal combustion engine (2) according to one of the preceding claims, wherein the EGR valve (12) is a disc valve which has an inlet (15), a first outlet (16.1) and a second outlet (16.2), wherein the two outlets (16.1, 16.2) are arranged opposite one another and a first closure element (17.1) is provided at the first outlet (16.1) and a second closure element (17.2) is provided at the second outlet (16.2), wherein the two closure elements (17.1, 17.2) are braced relative to one another by means of a spring (21) in order to close the outlets (16.1, 16.2) in a rest position, and wherein furthermore, a slide (18) is provided which can be actuated by an actuator (19) in order to selectively open the first closure element (17.1) at the first outlet (16.1) or the second closure element (17.2) at the second outlet (16.2).
4. Internal combustion engine (2) according to Claim 3, wherein the actuator (19) is designed such that the opening widths of the first outlet (16.1) and of the second outlet (16.2) can be adjusted in continuously variable fashion by means of the slide (18) .
5. Internal combustion engine (2) according to one of the preceding claims, wherein the at least one first cooling stage (8) and the at least one additional cooling stage (9) are arranged in parallel with respect to one another.
6. Method for operating an internal combustion engine (2) according to one of the preceding claims, having the following method steps:

   a) operating the internal combustion engine (2) without exhaust-gas recirculation by shutting off the exhaust-gas recirculation device (3), with the EGR valve (12) set in the rest position,

   b) exhaust-gas recirculation during a low-load phase, wherein the exhaust-gas recirculation takes place through the bypass line (11), with the EGR valve (12) set in the second position, wherein no cooling of the recirculated exhaust gas takes place,

   c) exhaust-gas recirculation during load operation, wherein the exhaust-gas recirculation takes place through the exhaust-gas cooler (5), with the EGR valve (12) set in the second position, and

   d) enabling at least one additional cooling stage (9) by means of the at least one flap arrangement (10) if high-load operation is present.
7. Motor vehicle (1) having an internal combustion engine (2) with an exhaust-gas recirculation device (3) which is designed according to one of Claims 1 to 5 and which is operated using a method according to Claim 6.

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