DE102020106240A1 - Exhaust gas recirculation device for an internal combustion engine and internal combustion engine for a motor vehicle - Google Patents

Abstract

The invention relates to an exhaust gas recirculation device for an internal combustion engine, with an exhaust gas flap, which is pivotably received on a bearing element of the exhaust gas recirculation device for adjusting exhaust gas to be recirculated via a pipe interior of an exhaust gas recirculation pipe, and with a shaft element which is coupled to the exhaust gas flap and via which the exhaust gas flap is rotated of the shaft element is pivotable at least between an open position and at least one further position. The exhaust gas recirculation device comprises a bearing bush arrangement formed from at least one metallic material, which has at least one bearing bush clamped in a receiving space between the shaft element and the bearing element and sealing the receiving space against a passage of exhaust gas. Another aspect of the invention relates to an internal combustion engine for a motor vehicle, with at least one exhaust gas recirculation device.

Description

The invention relates to an exhaust gas recirculation device for an internal combustion engine, with an exhaust gas flap, which is pivotably received on a bearing element of the exhaust gas recirculation device for adjusting exhaust gas to be recirculated via a pipe interior of an exhaust gas recirculation pipe, and with a shaft element which is coupled to the exhaust gas flap and via which the exhaust gas flap is rotated of the shaft element is pivotable at least between an open position and at least one further position. Another aspect of the invention relates to an internal combustion engine with an exhaust gas recirculation device.

With exhaust gas recirculation, also called EGR for short, exhaust gas is fed to the respective combustion chambers of an internal combustion engine, which acts as a so-called drag gas and enables an effective reduction of a peak temperature in the combustion chambers that is decisive for nitrogen oxide emissions. The EGR is mainly used in partial load operation, i.e. when the internal combustion engine is operated under partial load, but in order to comply with currently applicable exhaust gas standards, such as the exhaust gas standard EU6d-Temp as well as exhaust gas standards that will become increasingly strict in the future, an expansion of the use of the EGR over the entire engine map appears, including the use of EGR in full-load operation of internal combustion engines makes sense. To set so-called exhaust gas recirculation rates, also known as EGR rates, exhaust gas recirculation devices are used which include, for example, pivotable exhaust gas flaps or so-called exhaust gas recirculation valves with height-adjustable valve bodies.

The object of the present invention is to create an exhaust gas recirculation device of the type mentioned at the beginning which is particularly fail-safe. Another object of the invention is to create an internal combustion engine with an exhaust gas recirculation device that can be operated in a particularly fail-safe manner.

These objects are achieved by an exhaust gas recirculation device with the features of claim 1 and by an internal combustion engine with the features of claim 10. Advantageous configurations with expedient developments of the invention are specified in the subclaims.

A first aspect of the invention relates to an exhaust gas recirculation device for an internal combustion engine, with an exhaust gas flap, which is pivotably received on a bearing element of the exhaust gas recirculation device for adjusting exhaust gas to be recirculated via a pipe interior of an exhaust gas recirculation pipe and with a shaft element which is coupled to the exhaust gas flap and via which the Exhaust flap is pivotable by rotating the shaft element at least between an open position and at least one further position. The exhaust gas recirculation device may include the exhaust gas recirculation pipe. The exhaust flap can be accommodated in the pipe interior. The bearing element can be supported at least indirectly on the exhaust gas recirculation pipe. For example, the exhaust gas recirculation device can comprise a holding element which can be designed as a cover, for example, and via which the bearing element can be held on the exhaust gas recirculation pipe. As a result, the bearing element can be supported on the exhaust gas recirculation pipe by means of the holding element (and thus indirectly). The shaft element can, for example, be designed as a so-called shift shaft. The exhaust gas recirculation pipe can be designed, for example, as an exhaust gas diffuser.

According to the invention it is provided that the exhaust gas recirculation device comprises a bearing bush arrangement formed from at least one metallic material, which has at least one bearing bush which is clamped in a receiving space between the shaft element and the bearing element and which seals the receiving space against the passage of exhaust gas, in particular from the pipe interior . This is advantageous because the bearing bush arrangement formed from the metallic material is particularly durable and resilient even at high exhaust gas temperatures, so that the entire exhaust gas recirculation device can be operated in a particularly fail-safe manner even at these high exhaust gas temperatures, which can occur, for example, during exhaust gas recirculation in full-load operation of the internal combustion engine .

Surprisingly, it has been shown that the bearing bush arrangement formed from the metallic material has a sufficiently high level of tightness at different EGR rates over an entire engine map of the internal combustion engine. Accordingly, the bearing bush clamped in the receiving space can be formed from the metallic material and reliably seal the receiving space at different EGR rates without an inadmissibly large leakage of the exhaust gas occurring. The invention is based on the knowledge that conventional seals, for example made of an elastomer, have a permanently high level of tightness at low exhaust gas temperatures, but can fail at high temperatures, as can occur, for example, with EGR in full load operation, which leads to leakage of Exhaust gas and / or to Clamping of individual components can occur. The metallic material can preferably have a lower hardness than a shaft element material from which the shaft element can be formed. The shaft element material can preferably be steel, as a result of which the shaft element is particularly temperature-resistant and resilient. The bearing bush can be supported on the one hand, in particular directly, on the bearing element and, on the other hand, in particular directly, on the shaft element.

In an advantageous further development of the invention, it is provided that the at least one bearing bushing is supported on the shaft element and / or on the bearing element while forming at least one line load and is thereby braced. This is advantageous because the line load enables a particularly high, locally limited contact pressure and thus a particularly high level of tightness against the escape of exhaust gas to be achieved. The line load can be exerted on the shaft element in particular as a radial force, that is to say as a force acting in the radial extension direction of the shaft element.

In a further advantageous development of the invention it is provided that the at least one bearing bushing comprises a bearing bushing section designed to exert the at least one linear load, which has a cross-section that is at least partially conical and / or at least partially cylindrical and / or corrugated. This is advantageous because the at least partially conical and additionally or alternatively at least partially cylindrical and additionally or alternatively at least partially corrugated cross section enables a particularly uniform application of the line load in the circumferential direction of the shaft element.

In a further advantageous development of the invention it is provided that the bearing bushing is designed as a collar bushing and has a collar for supporting at least one axial force on the bearing element. This is advantageous because it enables any undesirable axial offset between the bearing bush and the bearing element to be avoided in a particularly simple manner.

In a further advantageous development of the invention it is provided that the bearing bush arrangement comprises a second bearing bush which is clamped in the receiving space and seals the receiving space against the passage of exhaust gas, an intermediate space filled with a lubricant extending between the bearing bush and the second bearing bush . This is advantageous since the second bearing bushing and the lubricant in the intermediate space bring about a particularly effective increase in the tightness. In other words, through the combination of the bearing bushes and the lubricant, the passage of exhaust gas from the pipe interior through the receiving space is particularly reliably and largely prevented.

In a further advantageous development of the invention it is provided that the lubricant is designed as a grease. This is advantageous because grease, as the lubricant contained in the space, enables maintenance-free and permanently fail-safe lubrication, so that the shaft element can be rotated relative to the bearing element with particularly low friction. The substance Krytox, for example, which has a particularly high temperature resistance, can be used as the fat.

In a further advantageous development of the invention it is provided that the bearing bushing and / or the second bearing bushing is braced relative to the bearing element in the axial extension direction of the shaft element. This is advantageous because this creates an axial preload of the bearing bush and, additionally or alternatively, the second bearing bush with respect to the bearing element, whereby an undesired, axial offset can be avoided.

In a further advantageous development of the invention it is provided that the second bearing bushing is arranged in the axial direction between the bearing bushing and at least one graphite bushing of the exhaust gas recirculation device received between the shaft element and the bearing element. This is advantageous because the graphite bushing is particularly temperature-resistant, the graphite bushing being able to prevent the second bearing bushing from being directly exposed to exhaust gas exiting from the pipe interior in the direction of the receiving space. As a result, extremely different heating of the bearing bush and the second bearing bush can be avoided. Accordingly, excessive differences in the respective temperature-related thermal expansion between the bearing bush and the second bearing bush can be prevented.

In a further advantageous development of the invention it is provided that the metallic material comprises bronze, copper and / or tin. This is advantageous because bronze, copper or tin are particularly soft metallic materials, through the use of which signs of wear and tear on the shaft element can be avoided despite the bracing of the bearing bush relative to the shaft element. Alternatively, it is also conceivable that the material is a spring steel.

A second aspect of the invention relates to an internal combustion engine for a motor vehicle, with at least one exhaust gas recirculation device according to the first aspect of the invention.

The preferred embodiments presented in relation to the exhaust gas recirculation device according to the invention and their advantages apply accordingly to the internal combustion engine according to the invention and vice versa.

The features and combinations of features mentioned above in the description as well as the features and combinations of features mentioned below in the description of the figures and / or shown alone in the figures can be used not only in the respectively specified combination, but also in other combinations or alone, without the scope of the Invention to leave.

Further advantages, features and details of the invention emerge from the claims, the following description of preferred embodiments and on the basis of the drawings.

• 1 eine schematische Perspektivansicht einer Abgasrückführungsvorrichtung;
• 2 eine weitere schematische Schnittdarstellung, welche eine Abgasklappe der Abgasrückführungsvorrichtung zeigt;
• 3 eine Detailansicht eines in 2 umrandeten Bereichs Z, welcher einen Lagerbereich der Abgasrückführungsvorrichtung zeigt;
• 4 eine schematische Perspektivansicht zweier Lagerbuchsen einer Lagerbuchsenanordnung der Abgasrückführungsvorrichtung;
• 5 eine schematische Schnittansicht einer Variante der Lagerbuchsen; und
• 6 eine schematische Darstellung eines Querschnitts einer weiteren Variante der Lagerbuchsen.

The invention is explained again below using a specific exemplary embodiment. This shows:

• 1 a schematic perspective view of an exhaust gas recirculation device;
• 2 a further schematic sectional view showing an exhaust flap of the exhaust gas recirculation device;
• 3 a detailed view of an in 2 bordered area Z, which shows a storage area of the exhaust gas recirculation device;
• 4th a schematic perspective view of two bearing bushes of a bearing bush arrangement of the exhaust gas recirculation device;
• 5 a schematic sectional view of a variant of the bearing bushes; and
• 6th a schematic representation of a cross section of a further variant of the bearing bushes.

1 shows an internal combustion engine in a highly abstracted representation 100 for a motor vehicle not further illustrated here. The internal combustion engine 100 comprises an exhaust gas recirculation device 10 , which is an exhaust gas recirculation pipe 12th includes. The exhaust gas recirculation pipe 12th can on the one hand with an exhaust tract of the internal combustion engine, which is not further shown here 100 and on the other hand with an intake tract of the internal combustion engine, which is likewise not further shown here 100 be connected to conduct the exhaust gas.

The exhaust gas recirculation device 10 serves to set a respective combustion chamber of the internal combustion engine, not shown further 100 exhaust gas mass flow to be returned, and thus for setting a so-called EGR rate. In other words: the exhaust gas recirculation device 10 is used to switch from an EGR gas flow to provide the combustion chambers with either uncooled or cooled exhaust gas. Alternatively, the exhaust gas recirculation device 10 can also be used to switch between at least two cooling channels (cascade or power split).

The exhaust gas recirculation device 10 includes an in 2 exhaust flap shown enlarged 20th , which is used to adjust via a pipe interior of the exhaust gas recirculation pipe 12th recirculated exhaust gas pivotable on a bearing element 30th the exhaust gas recirculation device 10 is recorded. The exhaust flap 20th can also be referred to as a switching flap. The bearing element 30th is present on a holding element 18th the exhaust gas recirculation device 10 added, the holding element 18th on the exhaust gas recirculation pipe 12th is fixed and thus kept. The holding element 18th can, as with 1 can be seen, for example, be designed as a cover over which an insertion opening of the exhaust gas recirculation pipe 12th can be sealed gas-tight. The introduction opening can be used during the assembly of the exhaust gas recirculation device 10 for inserting the exhaust flap 20th into the pipe interior of the exhaust gas recirculation pipe 12th to serve.

Furthermore, the exhaust gas recirculation device comprises 10 a shaft element 40 , which with the exhaust flap 20th is coupled and via which the exhaust flap 20th by turning the shaft element 40 continuously between an open position and a plurality of other positions, including a closed position of the exhaust flap 20th heard, is pivotable. By swiveling the exhaust flap 20th Between the open position and the other positions, the interior of the pipe can be narrowed locally as required in order to increase the EGR rate as a function of the respective operating state of the internal combustion engine 100 to adjust.

Based on 1 it can be seen that the exhaust gas recirculation device 10 an adjusting mechanism 14th may include which is rotatable with a lever 16 the exhaust gas recirculation device 10 can be coupled. The adjusting mechanism 14th can for example comprise a linear motor. The lever 16 is in turn non-rotatable. for example form-fitting and additionally or alternatively force-fitting with the shaft element 40 coupled as using 2 and 3 is recognizable. Thus, the exhaust flap can overall 20th over the shaft element 40 and the lever 16 by means of the adjusting mechanism 14th be swiveled.

The exhaust gas recirculation device 10 includes a bushing assembly 50 , which in the present case have two bearing bushes, namely a first bearing bush 60 and a second bearing bush 70 , includes. The bearing bushes 60 , 70 are each made of a soft metallic material, which can include, for example, bronze, copper and additionally or alternatively tin. Alternatively, it is also conceivable that the material is a spring steel. In the present case, it is the metallic material from which the bearing bush arrangement is made 50 and with it the bearing bushes 60 , 70 are formed to bronze or a mixture of bronzes.

The bearing bushes 60 , 70 are presently mirror-symmetrical with respect to a perpendicular to a central axis M. of the shaft element 40 oriented plane of symmetry, not shown further here, aligned with one another. In other words, a normal vector of the plane of symmetry runs along the central axis M. . Due to the mirror-symmetrical arrangement of the bearing bushes 60 , 70 can the exhaust gas recirculation device 10 be operated or adjusted with a particularly favorable flow of force.

The bearing bushes 60 , 70 are each in a recording room 80 between the shaft element 40 and the bearing element 30th tense and seal the recording space 80 against a passage of exhaust gas. The bearing bushes 60 , 70 thus prevent exhaust gas from the pipe interior through the receiving space 80 towards the lever 16 flows or even to the environment of the exhaust gas recirculation device 10 got. In order to achieve a particularly effective seal, there is an intermediate space 82 between the first bearing bush 60 and the second bearing bush 70 a lubricant in the form of grease, which can be, for example, Krytox.

The respective bearing bushes 60 , 70 are each under the formation of at least one line load F_R on the shaft element 40 and additionally or alternatively on the bearing element 30th supported and thus braced. Form the respective bearing bushes 60 , 70 line loads in each case F_R on the shaft element 40 and on the bearing element 30th off, a particularly effective seal can thereby be achieved. The line load (s) F_R runs parallel to a radial extension direction R. of the shaft element 40 , like using 3 is recognizable.

The respective bearing bushes 60 , 70 each include one to exert the line loads F_R trained bearing bush section 62 respectively. 72 , which has an at least partially conical and additionally or alternatively at least partially corrugated cross-section 64 respectively. 74 exhibit. Assign the bearing bushes 60 , 70 the wavy shaped cross-sections 64 respectively. 74 on, so can the bushings 60 , 70 preferably be designed as metal lip seals and thereby seal particularly effectively.

While 4th the bushing arrangement 50 occasionally with the bearing bushes 60 , 70 shows is in 5 a variant with conical cross-sections 64 , 74 shown, where 6th using the example of the bearing bush 60 shows a variant in which the cross-section 64 is at least partially shaped corrugated. The wavy cross-section in some areas 64 allows multiple line loads F_R for example on the shaft element 40 exercise as in 6th is indicated. It is clear that in terms of the bearing bush 60 presented features and their advantages accordingly also for the bearing bush 70 are valid.

The two bearing bushes 60 , 70 are each designed as collar bushings and have a collar 66 respectively. 76 to support a respective axial force FA on the bearing element 30th on. This makes the bearing bushes 60 , 70 each opposite the bearing element 30th tense. The axial force FA is parallel to a direction of axial extension A. of the shaft element 40 oriented. The direction of axial extension A. runs along the central axis M. .

The exhaust gas recirculation device 10 also includes at least one graphite bushing 90 , in this case two graphite sockets 90 are provided. The second bearing bush 70 is in the axial extension direction A. between the bearing bush 60 and the present between the shaft element 40 and the bearing element 30th recorded graphite bushings 90 arranged. Alternatively, however, it is also conceivable that in addition or as an alternative to the graphite bushings 90 at least one wire mesh, for example pressed with ceramic powder, is provided for sealing. Bushings sintered by powder metallurgy are another alternative.

The bearing bushes formed from the metallic material 60 , 70 the bearing bush arrangement 50 In contrast to conventional O-rings, for example formed from an elastomer, have particularly good temperature resistance, so that damage to the bearing bush arrangement 50 even at high exhaust gas temperatures, such as those when the internal combustion engine is operating 100 can occur under full load can be avoided. By tightening the bearing bushes 60 , 70 compared to the shaft element 40 a so-called shaft seal is provided, which also withstands temperatures of, for example, more than 300 ° C, and even for example up to 950 ° C. Due to the defined contour of the bearing bushes 60 , 70 in the form of the cylindrical, conical and additionally or alternatively corrugated cross-section 64 respectively. 74 on the one hand the line loads F_R exercised and thus provided respective line seals, on the other hand, an additional bearing of the shaft element is provided 40 created.

List of reference symbols

10

Exhaust gas recirculation device

12th

Exhaust gas recirculation pipe

14th

Adjusting mechanism

16

lever

18th

Retaining element

20th

Exhaust flap

30th

Bearing element

40

Shaft element

50

Bushing arrangement

60

Bearing bush

62

Bushing section

64

cross-section

66

collar

70

second bearing bush

72

Bushing section

74

cross-section

76

collar

80

Recording room

82

Space

90

Graphite bushing

100

Internal combustion engine

A.

Direction of axial extension

FA

Axial force

F_R

Line load

M.

Central axis

R.

Radial direction of extent

Claims (10)

Exhaust gas recirculation device (10) for an internal combustion engine (100), with an exhaust gas flap (20) which is pivotably received on a bearing element (30) of the exhaust gas recirculation device (10) for adjusting exhaust gas to be recirculated via a pipe interior of an exhaust gas recirculation pipe (12) and with a shaft element (40), which is coupled to the exhaust flap (20) and via which the exhaust flap (20) can be pivoted by rotating the shaft element (40) at least between an open position and at least one further position, characterized in that the exhaust gas recirculation device (10) has a comprising at least one bearing bush arrangement (50) formed from at least one metallic material, which has at least one bearing bush (60) clamped in a receiving space (80) between the shaft element (40) and the bearing element (30) and sealing the receiving space (80) against the passage of exhaust gas ) having. Exhaust gas recirculation device (10) according to Claim 1 , characterized in that the at least one bearing bushing (60) is supported on the shaft element (40) and / or on the bearing element (30) while forming at least one line load (F_R) and is thereby braced. Exhaust gas recirculation device (10) according to Claim 2 , characterized in that the at least one bearing bush (60) comprises a bearing bush section (62) which is designed to exert the at least one line load (F_R) and which has a cross-section which is at least partially conical and / or at least partially cylindrical and / or at least partially corrugated ( 64). Exhaust gas recirculation device (10) according to one of the preceding claims, characterized in that the bearing bushing (60) is designed as a collar bushing and has a collar (66) for supporting at least one axial force (F_A) on the bearing element (30). Exhaust gas recirculation device (10) according to one of the preceding claims, characterized in that the bearing bush arrangement (50) comprises a second bearing bush (70) which is clamped in the receiving space (80) and seals the receiving space (80) against the passage of exhaust gas, wherein an intermediate space (82) filled with a lubricant extends between the bearing bush (60) and the second bearing bush (70). Exhaust gas recirculation device (10) according to Claim 5 , characterized in that the lubricant is designed as a grease. Exhaust gas recirculation device (10) according to Claim 5 or 6th , characterized in that the bearing bush (60) and / or the second bearing bush (70) is braced in the axial extension direction (A) of the shaft element (40) with respect to the bearing element (30). Exhaust gas recirculation device (10) according to one of the Claims 5 until 7th , characterized in that the second bearing bush (70) is arranged in the axial extension direction (A) between the bearing bush (60) and at least one graphite bushing (90) of the exhaust gas recirculation device (10) received between the shaft element (40) and the bearing element (30) . Exhaust gas recirculation device (10) according to one of the preceding claims, characterized in that the metallic material comprises bronze, copper and / or tin. Internal combustion engine (100) for a motor vehicle, with at least one exhaust gas recirculation device (10) according to one of the Claims 1 until 9 .

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