EP1311754B1 - Valve device comprising a cover flap and a thermal bridge for an exhaust gas recirculation system and method for the operation thereof - Google Patents

Description

The invention relates to a valve arrangement for an exhaust gas recirculation system an internal combustion engine with a flange for flange mounting on a Heat sink with a defined temperature range according to the Preamble of claim 1.

Driven by increasingly strict emissions regulations, was especially for Passenger cars the development of exhaust gas recirculation systems promoted. Basically, such a system has the task of certain amount of the exhaust gas generated in the internal combustion engine in the provided air-fuel mixture to initiate in this way a Achieve reduction in nitrogen oxides. During the combustion process Hydrocarbons such as gasoline with the oxygen in the air in carbon dioxide and Water converted. However, the airborne substance also reacts Nitrogen with oxygen, producing nitrogen oxides. This in turn leads to lower efficiency and air pollution. It is known that less nitrogen oxides are produced at lower temperatures during combustion. The exhaust gas introduced contains a lower oxygen content. This increases overall the proportion of inert gas in the combustion chamber and the combustion slows down while reducing nitrogen oxide emissions. With an approx. 10% Exhaust gas recirculation is, for example, a nitrogen oxide reduction of about 30% to reach.

Due to different conditions in the combustion chamber, in particular by are dependent on the operating temperature of the internal combustion engine, it is known Exhaust systems with multiple exhaust lines. It is still known to such multi-line exhaust systems with valve assemblies provided, which have coupled exhaust flaps to the exhaust gas flow through the Regulate exhaust pipes.

Such a double flap is described for example in JP 07-198045. There is proposed a valve with two valve flaps made of ceramic equip to improve the heat resistance of the valve. The two Valve flaps are connected via a common shaft and are connected to driven by a motor. The valve flaps are at right angles to each other arranged so that only one of the two exhaust pipes is closed. The different expansion behavior at changing temperatures of the ceramic valve flaps and the metallic exhaust pipes, however lead to a reduced tightness of the valve arrangement.

From DE 44 26 028 is also an exhaust valve system for a multi-flow Exhaust system known. There is an exhaust flap in each of the two exhaust lines provided, both exhaust valves a common pivot axis have and wherein the two exhaust flaps rotated by 90 ° against each other are arranged. The two exhaust lines are thus alternately by the Exhaust flaps closed or released. The ones described there Exhaust flaps are over journals by means of positive plug connections stored. The bearing journals become complete against the force of a spring pressed into the respective bearing sleeves, being between adjacent ones Exhaust lines cylindrical cross-channels are to be provided, in each of which Carrier is rotatably mounted. On one side, the driver shows an as Bearing sleeve formed recess in the bearing journal of the first Exhaust flap to be inserted to create a driving connection can. The other end of the driver is designed as a journal, which also for establishing a driving connection in a recess of the second exhaust flap can be inserted. This exhaust valve system requires a high due to the form-fitting plug connections Manufacturing effort, resulting in the production of such an exhaust valve system is very expensive.

DE 198 41 927 A1 also discloses a valve arrangement with a double flap for an exhaust gas recirculation system. In the two exhaust gas recirculation lines one exhaust flap is provided, both exhaust flaps have a common pivot axis and the two exhaust flaps are rotated by 90 ° to each other. The two return lines are thus alternately closed by the exhaust flaps or Approved. An exhaust gas cooler is arranged in one of the two return paths. The valve arrangement is controlled in such a way that the exhaust gas cooler is cold Internal combustion engine is bypassed, however, when the internal combustion engine is warm the exhaust gases are cooled before being returned.

Proceeding from this, the object of the invention is a valve arrangement for an exhaust gas recirculation system of an internal combustion engine, which is cooled in a different way and also is inexpensive to manufacture and has a long service life.

These tasks are accomplished with a valve assembly according to the characteristics of the Claim 1 , Further advantageous developments are Subject of the respective dependent claims.

The valve arrangement according to the invention for an exhaust gas recirculation system Internal combustion engine, in particular an internal combustion engine for diesel fuel of a passenger car, has a flange for flange mounting a heat sink with a defined temperature range. The heat sink is inventively a water-cooled engine block of the internal combustion engine. Furthermore, the exhaust gas recirculation system with a first and a second Exhaust gas recirculation line executed, in each of which a first and a second Valve flap is arranged. The valve flaps are with a common shaft rotatable to each other in a bearing device with a bearing housing arranged that in each case at least one of the exhaust gas recirculation lines is lockable. The bearing housing is connected to the flange via a structural thermal bridge so that the Bearing housing during the operation of the internal combustion engine Maximum temperature is less than 400 ° C, especially less than 300 ° C. The bearing housing preferably has a maximum temperature of 250 ° C. especially in the event that the bearing housing consists essentially of one Aluminum material exists.

The valve arrangement according to the invention has a common shaft on which both valve flaps are arranged. In this way, making one such valve arrangement very inexpensive. The wave thus extends through Both exhaust gas recirculation lines, which means that they are always one during operation exposed to high temperature because of the flowing past or in front of it stowed exhaust gas shows a temperature of approximately 800 ° C to 1000 ° C. The absorbed thermal energy is transferred to the bearing device via the shaft forwarded. If there is insufficient heat flow from the bearing housing in adjacent components and / or the environment, different thermal expansion behavior of the bearing components Tensions occur affecting the functionality of the storage facility could affect. This is prevented according to the invention in that the Bearing housing connected to the flange via a structural thermal bridge is that the bearing housing at no time during operation of the Internal combustion engine a temperature of 400 ° C, especially 300 ° C, exceeds. Such a thermal bridge preferably has a high one Thermal conductivity to the heat introduced via the shaft over the To drain the housing quickly. If the flange is connected to a heat sink, which has a defined temperature range, the Temperature difference between the heat sink and the bearing device a heat flow to the heat sink. This effect is all the more effective the greater the temperature difference between the heat sink and the Storage device is. Accordingly, the invention teaches the flange to connect a water-cooled engine block of the internal combustion engine, which during operation of the internal combustion engine has a temperature of Usually does not exceed 80 to 100 ° C. So is a simple and Valve arrangement with a shaft and two that can be produced particularly inexpensively Valve flaps created, which due to the structural thermal bridge has a long service life.

According to an advantageous development, the thermal bridge is proposed so that the ratio of the thickness of the thermal bridge to the shortest length is at least 0.1. The ratio is preferred at least 0.3, in particular at least 0.5. The shortest length describes the shortest distance between the flange and the bearing housing. The Thermal bridge has an average thickness perpendicular to this length. The Average thickness is an average of the actual thicknesses of the thermal bridge the shortest length. This ratio of thickness to length ensures one Thermal bridge, which is a cross section suitable for heat transport having. This also ensures that the thermal bridge is a has sufficient heat capacity. According to this ratio, it is particularly advantageous, the valve arrangement according to the invention near the Arrange heat sink, the thermal bridge is made relatively thick-walled is.

According to a further embodiment, the flange has the Internal combustion engine essentially has a temperature like the heat sink on. The heat sink is in particular a water-cooled engine block the internal combustion engine. This ensures that the Temperature difference between the bearing housing and the heat sink in the Essentially the temperature difference between the bearing housing and flange equivalent. The connection between flange and heat sink is accordingly particularly good heat-conducting properties. Are particularly suitable for this metallic fasteners and / or seals with metallic Components.

According to a further advantageous embodiment, the thermal bridge has and / or the bearing housing cooling fins. Such cooling fins enlarge the Surface of the thermal bridge and / or the bearing housing, whereby the Heat radiation from the thermal bridge or the bearing housing is positive being affected. In addition, the cooling fins on the thermal bridge enlarge the Cross-section, which also means the heat transport across the thermal bridge is improved.

According to yet another embodiment, the bearing device is provided with a Running bush made of a material with high thermal conductivity is, preferably with a bronze bushing. Such a socket supports the discharge of the heat introduced via the shaft into the bearing housing. there If possible, the bushing should be made with a large axial length, which means that the contact area with the bearing housing increases and at the same time the Heat flow is improved. In this way, thermal stresses significantly reduced in the storage device. This essentially has one wear-free storage resulting in the life of the valve assembly is increased.

It is particularly advantageous to lubricate the bearing device with graphite perform. Such graphite lubrication ensures smooth operation Storage of the valve flaps without significant loss of friction over a large temperature range.

The first and the second valve flap have a common pivot axis through the shaft and are essentially in a first and a respective arranged second valve flap level. It is according to another Design particularly advantageous if the valve flap planes make an angle include, the included angle is preferably 90 °. The angles included between the first and second valve flap levels ensures that a different one in each of the two exhaust gas recirculation lines Opening cross-section can be set through which the desired Amount of exhaust gas flows. An angle of 90 ° has the advantage that the valve flaps can be adjusted with a common shaft such that exhaust gas recirculation is closed, while the valve flap in the other exhaust gas recirculation does not represents a significant impediment to the exhaust gas flowing through.

According to yet another embodiment, the valve flaps each have one Bulge on, these bulges at least partially the wave enclose and the valve flaps are technically connected to the shaft. The bulges provide in particular a bearing surface for the shaft Available, whereby the valve flaps are aligned on the shaft can. Furthermore, the bulges ensure a suitable fixation of the Valve flaps on the shaft during the formation of the joining technology Connection. It is particularly advantageous to have the valve flaps with the shaft to weld. The welded connection is made even at high temperatures a permanent connection between valve flaps and shaft is guaranteed.

According to yet another embodiment of the valve arrangement for a Exhaust gas recirculation system has the first exhaust gas recirculation line Exhaust gas cooler on. The exhaust gas cooler reduces the temperature of the recirculated Exhaust gas, which also reduces the temperature in the air-fuel mixture is effected. As a result, when the air-fuel mixture is burned a lower combustion temperature is generated, whereby the nitrogen oxide content in the generated exhaust gas is further reduced.

It is particularly advantageous that the thermal bridge is close to the first Exhaust gas recirculation line is arranged. The first exhaust gas recirculation line with the exhaust gas cooler is used in particular when the Internal combustion engine is in an operating state in which it is already very hot Exhaust gases are generated. It is sufficient in this operating phase Cooling of the storage device required, especially in the area of Bearing device via which the shaft is driven. This is through ensures a thermal bridge near the first exhaust gas recirculation line, because so the heat, which is absorbed by the shaft and the exhaust gas, quickly and can be effectively dissipated. This also helps to increase the Lifetime due to reduced thermal stress in the Storage device at.

According to yet another embodiment, the shaft is with a drive connected. It is particularly advantageous if the drive itself a control and / or regulating unit is connected. Because of the very complex Relationships between recirculated exhaust gas and the processes in the Combustion chamber, the exhaust gas recirculation system is dependent on the To operate the operating state of the internal combustion engine. Such a drive with an appropriate control or regulation unit ensures a quantitative and timely admixing of the exhaust gas to the air-fuel mixture.

According to yet another advantageous embodiment, the shaft has a groove and the bearing device on at least one socket, one in the groove Washer is arranged so that the bushing abuts the washer. The disc has an opening through which the shaft extends. she is especially slotted to be easily installed in the groove can. The disc rests against a bearing surface of the bearing housing and is fixed the socket thus axially to the shaft. Such an arrangement has the advantage that the shaft, for example, only on the side with the drive side Bearing device must be fixed exactly axially, this being very inexpensive the groove is designed accordingly. A more expensive design corresponding recordings of the shaft in the walls of the Exhaust gas recirculation lines with narrow tolerances are avoided in this way.

According to another particularly advantageous embodiment, the bearing housing Means for sealing so that, for example, no exhaust gas from the Exhaust gas recirculation line through the bore, which is used to hold the shaft serves, or lubricants or the like can escape to the outside.

The production of a type of labyrinth seal is preferred, in which Bearing housing graphite foil between the bearing device and a sleeve is arranged. This is, for example, deformed into a ring that surrounds the Shaft arranged and further deformed by means of the bearing device and the sleeve becomes. This type of seal is suitable regardless of or in combination with the valve arrangements claimed here with a double flap and one Thermal bridge for sealing through holes in the housing are provided, which contains exhaust gas, this in particular a very has low oxygen content. Typically, graphite seals are only up to Can be used at a temperature of approx. 450 ° C, since they are at higher temperatures react with oxygen and lose their sealing properties. Tests with regard to the suitability of such graphite seals Exhaust gases, such as those from mobile internal combustion engines generated, however, have surprisingly shown that these seals Withstand graphite temperatures up to about 1300 ° C. For use in the mobile exhaust technology is in particular a temperature suitability up to approximately 700 ° C or 900 ° C is required. An essential factor is in this To see connection in the composition of the exhaust gas, which is a kind Inert gas atmosphere generated in the area of the seal. Will now prevents the oxygen in the ambient air from reaching the sealing point, such as for example with a sleeve pressed into the bore, so is one durable, inexpensive and temperature-resistant seal manufactured

According to a further embodiment of the invention is the bearing housing over at least one connector connected to the exhaust gas cooler.

The at least one connecting part, like the thermal bridge, has one for one rapid and intensive heat dissipation from the bearing housing to Suitable heat conductivity and / or heat capacity. The Exhaust gas cooler preferably has a water circuit, the Exhaust gas cooler always a certain temperature well below the Exhaust gas temperature, in particular between 80 ° C and 100 ° C. To this There is a clear temperature difference, which one Guaranteed heat flow from the bearing housing. It is very special advantageous, the bearing housing with a thermal bridge to the flange for flanging to another heat sink, especially one water-cooled engine block of an internal combustion engine to combine. The valve arrangement thus has a common shaft for both valve flaps on, it is very inexpensive to manufacture, and also ensures a high Lifetime due to wear of the bearing due to thermal stress is significantly reduced.

According to a further embodiment of the valve arrangement, this has at least a connector and / or the bearing housing at least one channel which a coolant can be introduced. The cooling medium can be made directly be removed from the exhaust gas cooler, or it is for example an external cooling medium, such as air (especially the Intake air of an internal combustion engine), which if necessary by means of the Exhaust gas cooler cooled before being introduced into the at least one connecting part has been. The channels are particularly inexpensive to manufacture if they are Through holes are executed. The openings not required can for example, be sealed tightly by simply designed closure pieces. The at least one connecting part can be used as an integral part of the Bearing housing executed or attached to a channel as an additional component his. A connecting part designed as a separate component is designed in such a way that that a suitable heat flow takes place over the connection area. This last embodiment has the advantage that the introduction of the cooling medium in the bearing housing is designed variably. So the connector can be arranged that the shortest distance to the heat sink or to the exhaust gas cooler is realized.

Fig. 1

Eine schematische Darstellung einer Verbrennungsmaschine mit einem Abgasrückführungssystem;

Fig. 2

eine schematische Draufsicht auf die Ventilanordnung;

Fig. 3

eine schematische Ansicht einer erfindungsgemäßen Ventilanordnung an einem wassergekühlten Motorblock;

Fig. 4

eine schematische Teilansicht einer weiteren erfindungsgemäßen Ventilanordnung mit einem Anschlussteil;

Fig. 5

eine schematische Schnittansicht des Lagergehäuses in Figur 4 und

Further advantageous and particularly preferred exemplary embodiments will now be explained with reference to the drawings. Show it:

Fig. 1

A schematic representation of an internal combustion engine with an exhaust gas recirculation system;

Fig. 2

a schematic plan view of the valve assembly;

Fig. 3

is a schematic view of a valve assembly according to the invention on a water-cooled engine block;

Fig. 4

a partial schematic view of another valve assembly according to the invention with a connecting part;

Fig. 5

is a schematic sectional view of the bearing housing in Figure 4 and

Figure 1 shows schematically the structure of an internal combustion engine 3 with four Combustion chambers 26. The internal combustion engine 3 is on the Intake air line 5 air supplied to the environment, which then with the Fuel is mixed. The actual one takes place in the combustion chambers 26 Combustion takes place, after which the exhaust gas generated in the exhaust line 27 cleaned and finally released into the environment. The Exhaust gas recirculation system connects the exhaust pipe 27 and the Intake air line 5, wherein the exhaust gas at least partially through the Valve arrangement 1 flows 7. The valve arrangement 1 has a drive 17 connected, which is activated via a control unit 18. Downstream 7 of the Valve arrangement 1 close a first 4a and a second Exhaust gas recirculation line 4b. The first exhaust gas recirculation line 4a has an exhaust gas cooler 6. The exhaust gas cooler 6 ensures that it exhaust gas flowing downstream 7 has a temperature which is so cool that when the air-fuel mixture burns only a small amount Nitric oxide emission takes place.

Figure 2 shows schematically a top view of the shaft 22 with the first Valve flap 8a and the second valve flap 8b. Both valve flaps 8a and 8b have a common pivot axis 15 through the shaft 22. The first Valve flap 8a is arranged in a first valve flap level 19a. The second Valve flap 8b is arranged in the second valve flap level 19b. The Valve flap levels 19a and 19b form an angle 20. In the illustrated embodiment close the valve flap levels 19a and 19b an angle of 90 °. The valve flaps 8a and 8b are connected to the shaft 22 welded 24.

FIG. 3 shows a particularly preferred embodiment according to the invention the valve assembly 1. The valve assembly 1 has a flange 2 with which it is flanged to a water-cooled engine block 11. The valve assembly 1 also has a first 4a and a second exhaust gas recirculation line 4b a first 8a and a second valve flap 8b, the Valve flaps 8a and 8b with a common shaft 22 rotatable in one Bearing device 9 with a bearing housing 12 are arranged relative to one another, that at least one of the exhaust gas recirculation lines 4a and 4b is closed. The first 8a and the second valve flap 8b each have one first 16a and second bulge 16b, which at least partially enclose common shaft 22. The valve flaps 8a and 8b are with the Welded shaft 22. The first valve flap 8a is opposite the second Valve flap 8b arranged offset by 90 °, the valve flaps 8a and 8b have a common pivot axis 15, so that at least one of the Exhaust gas recirculation lines 4a and 4b are closed.

The shaft 22 is guided in particular with a bearing device 9. The Bearing device 9 is arranged in a bearing housing 12 and has one Bushing 13 made of bronze and a graphite lubrication 14 on. The bronze Socket 13 ensures rapid removal of the shaft 22 into the Bearing device 9 heat introduced into the bearing housing 12. Die Graphite lubrication 14 has the task of a relatively large Temperature range, the functionality and smooth running of the bearing guarantee.

The hot exhaust gas flows in the flow direction 7 in accordance with the arrangement of the Valve flaps 8a and 8b through either the first 4a or the second Exhaust gas recirculation line 4b. The exhaust gas also flows around the shaft 22, whereby this absorbs heat and, among other things, into the bearing device 9 forwards. To avoid life-limiting thermal Tension in the bearing device 9 is the bearing housing 12 via a structural thermal bridge 10 connected to the flange so that the Bearing housing 12 during operation of the internal combustion engine 3 a Maximum temperature is less than 400 ° C, especially less than 300 ° C. The structural thermal bridge 10 has a shortest length 21 between flange 2 and Bearing housing 12 and an average thickness 25 aligned perpendicular thereto The ratio of the average thickness 25 to the shortest length 21 is at least 0.1. For improved dissipation of the thermal energy from the storage device 9 the bearing housing 12 and the thermal bridge 10 each have cooling fins 23. In this way, the heat transfer by convection respectively Heat radiation are supported.

The shaft (22) has a groove (28), a disc (29) in the groove (22) is arranged so that the bushing (13) abuts the disc (29). The disc (29) lies against a contact surface of the bearing housing (12) and fixes the bush (13) thus axially (15) to the shaft (22). Such an arrangement has the advantage that the shaft (22) only on the side with the bearing device (9) axially (15) must be fixed exactly, which is very inexpensive by a corresponding The groove (28) is designed.

Figure 4 shows schematically and in a partial view another according to the invention Embodiment of the valve arrangement 1. The valve arrangement 1 has one Flange 2, with which they are attached to a water-cooled engine block 11, for example can be flanged. The valve arrangement 1 has a first 4a and one second exhaust gas recirculation line 4b, each with a first 8a and a second Valve flap 8b (not shown), the valve flaps 8a and 8b with a common shaft 22 rotatable in a bearing device 9 with a Bearing housing 12 are arranged. The first valve flap 8a is opposite to the second valve flap 8b (not shown) arranged offset by 90 ° The shaft 22 is guided on the drive side in a bearing device 9. The Bearing device 9 is arranged in a bearing housing 12 and has one Socket 13 made of bronze. The bronze bush 13 ensures a quick Removal of those introduced by the shaft 22 into the bearing device 9 Heat into the bearing housing 12. The hot exhaust gas either flows through the first 4a or the second exhaust gas recirculation line 4b. The exhaust gas flows around also the shaft 22, whereby this absorbs heat and, inter alia, in the Forwarding device 9. To avoid life-limiting Thermal stresses in the bearing device 9 is the bearing housing 12 a structural thermal bridge 10 connected to the flange 2 to the heat to be able to dissipate. For example, with extremely hot exhaust gases or during High performance operation of an internal combustion engine enables the illustrated Embodiment that over the connector 30, which with a clearly cooler exhaust gas cooler 6 (not shown) is also connected to the heat Exhaust gas cooler 6 is discharged. For this purpose, the connector in particular has the same properties regarding thermal conductivity and / or thermal capacity on like a thermal bridge 10. This ensures that the Bearing housing 12 during operation of the internal combustion engine 3 a Maximum temperature is less than 400 ° C. The illustrated embodiment additionally offers the possibility of cooling medium 32 in a channel 31 is initiated, which also contributes to the cooling of the bearing housing.

FIG. 5 shows a schematic sectional view (V-V) of the bearing housing 12 in FIG. 4. Two connecting pieces 30 are arranged on the bearing housing 12, which are connected to an exhaust gas cooler 6 (not shown). The Coolant 32 (indicated by the arrows) of the exhaust gas cooler 6 flows through the Channels 31 and thus cools the bearing housing 12. The individual channels 31 are Holes, which can also be designed as through holes, the Through bores sealed by means of closure pieces 33 or are sealed so that no leakage occurs. The coolant 32 will then returned to the exhaust gas cooler 6. Such an arrangement of Channels are particularly easy and quick to manufacture. According to a particularly preferred embodiment, this Bearing housing 12 a seal.

The Bearing housing 12 has means for sealing, so that, for example, no exhaust gas from the exhaust gas recirculation line 4a through the bore 37, which for Receiving the shaft 22 is used, or lubricant 14 to the outside got into the environment. The production of a species is preferred Labyrinth seal, 12 graphite foil between in the bearing housing the bearing device 9 and a sleeve is arranged. The graphite foil is as such or in the form of a preformed graphite ring around the shaft 22 wound, laid, or the like and by means of the bearing device 9 and Sleeve 13 deformed, so that preferably no continuous gaps exist between the individual film sections, but the Graphite foil sections always lie at least partially against each other. This kind The seal is suitable for sealing through holes that are provided in the bearing housing 12, which contains exhaust gas, this in particular has a very low oxygen content. The one described Seal is due to its temperature capability up to about 700 ° C or 900 ° C is particularly suitable for use in mobile exhaust technology. at In this embodiment, it is also possible, for example, that the Graphite foil at least partially results in graphite lubrication 14 or supports them. This may lead to minor scratches or the like regarding the graphite foil when moving (In particular rotating about the axis 15) elements of the bearing device 9 or rub the shaft 22 against the graphite foil during operation of the valve arrangement. The resulting graphite particles are then preferably used for lubrication the storage device 9. Also, the at least partial implementation of the Bearing device 9 adjacent areas of the bearing housing 12 made of graphite possible.

The valve arrangement according to the invention for an exhaust gas recirculation system Internal combustion engine is very inexpensive to manufacture and guaranteed at the same time a long service life, since the thermal stresses in the Bearing device clearly during the operation of the internal combustion engine were reduced compared to known valve arrangements.

LIST OF REFERENCE NUMBERS

1

valve assembly

2

flange

3

combustion engine

4a

first exhaust gas recirculation line

4b

second exhaust gas recirculation line

5

intake air line

6

exhaust gas cooler

7

flow direction

8a

first valve flap

8b

second valve flap

9

bearing device

10

thermal bridge

11

block

12

bearing housing

13

Rifle

14

graphite lubrication

15

swivel axis

16a

first bulge

16b

second bulge

17

drive

18

control unit

19a

first valve flap level

19b

second valve flap level

20

angle

21

length

22

wave

23

cooling fin

24

WeldingSpot

25

thickness

26

combustion chamber

27

exhaust pipe

28

groove

29

disc

30

connector

31

channel

32

cooling medium

33

closing piece

Claims (20)

1. Valve arrangement (1) for an exhaust-gas recirculation system of an internal combustion engine (3), having a flange (2) for flanging it onto a heat sink with a defined temperature range, and having a first exhaust-gas recirculation line (4a) and a second exhaust-gas recirculation line (4b) respectively having a first valve flap (8a) and a second valve flap (8b), the valve flaps (8a, 8b) being arranged inside a bearing device (9) with a bearing housing (12) in such a manner that they can rotate with respect to one another with a common shaft (22) in such a way that in each case at least one of the exhaust-gas recirculation lines (4a, 4b) can be closed, the bearing housing (12) being connected to the flange (2) via a structural thermal bridge (10), in such a way that the bearing housing (12), while the internal combustion engine (3) is operating, reaches a maximum temperature of less than 400°C, in particular less than 300°C, and the heat sink is a water-cooled engine block (11) of the internal combustion engine (3).
2. Valve arrangement (1) according to Claim 1, characterized in that the thermal bridge (10) has a shortest length (21) between flange (2) and bearing housing (12) and a medium thickness (25) oriented perpendicular thereto, the ratio of the medium thickness (25) to the shortest length (21) being at least 0.1, preferably at least 0.3.
3. Valve arrangement (1) according to Claim 1 or 2, characterized in that the flange (2), while the internal combustion engine (3) is operating, is at substantially the same temperature as the heat sink, i.e. as the engine block (11).
4. Valve arrangement (1) according to one of Claims 1 to 3, characterized in that the thermal bridge (10) and/or the bearing housing (12) has cooling fins (23).
5. Valve arrangement (1) according to one of Claims 1 to 4, characterized in that the bearing device (9) has a bush (13) which is formed from a material with a high thermal conductivity, preferably from bronze.
6. Valve arrangement (1) according to one of Claims 1 to 5, characterized in that the bearing device (9) has a graphite lubrication (14).
7. Valve arrangement (1) according to one of Claims 1 to 6, in which the first valve flap (8a) and the second valve flap (8b) have a common pivot axis (15) through the shaft (22) and are substantially arranged in a first valve-flap plane (19a) and a second valve-flap plane (19b), respectively, characterized in that the valve-flap planes (19a, 19b) include an angle (20).
8. Valve arrangement (1) according to Claim 7, characterized in that the included angle (20) is 90°.
9. Valve arrangement (1) according to one of Claims 1 to 8, characterized in that the valve flaps (8a, 8b) each have a protruding section (16a, 16b), these protruding sections (16a, 16b) at least partially surrounding the shaft (22), and the valve flaps (8a, 8b) being connected to the shaft (22) by a joining technique.
10. Valve arrangement (1) according to Claim 9, characterized in that the valve flaps (8a, 8b) are welded (24) to the shaft (22).
11. Valve arrangement (1) according to one of Claims 1 to 10, characterized in that the first exhaust-gas recirculation line (4a) includes an exhaust-gas cooler (6).
12. Valve arrangement (1) according to Claim 11, characterized in that the thermal bridge (10) is arranged close to the first exhaust-gas recirculation line (4a).
13. Valve arrangement (1) according to Claim 11 or 12, characterized in that the bearing device (9) is connected to and can be cooled by the exhaust-gas cooler (6).
14. Valve arrangement (1) according to one of Claims 1 to 13, characterized in that the shaft (22) is connected to a drive (17).
15. Valve arrangement (1) according to Claim 14, characterized in that the drive (17) is connected to a control (18) or regulating unit.
16. Valve arrangement (1) according to one of Claims 1 to 15, in which the bearing device (9) is designed with a bush (13), characterized in that the shaft (22) has a groove (28), a disc (29) being arranged in the groove (28), so that the bush (13) bears against the disc (29).
17. Valve arrangement (1) according to one of Claims 1 to 16, characterized in that the bearing housing (12) has sealing means, so that it is impossible for any exhaust gas to escape out into the environment from the exhaust-gas recirculation line (4a, 4b) through a bore for receiving the shaft (22).
18. Valve arrangement (1) according to Claim 17, characterized in that graphite foil is arranged in the bearing housing (12) between the bearing device (9) and a sleeve, the graphite foil preferably being wound around the shaft (22) and being deformed by means of the bearing device (9) and the sleeve, so that a type of labyrinth seal is formed.
19. Valve arrangement (1) according to Claim 11, characterized in that the bearing housing (12) is connected to the exhaust-gas cooler (6) via at least one connection part (30).
20. Valve arrangement (1) according to Claim 19, characterized in that the at least one connection part (30) and/or the bearing housing (12) has at least one passage (31) through which a cooling medium (32), in particular the cooling medium (32) of the exhaust-gas cooler (6), can be introduced.

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