DE102014201085B4 - Exhaust gas recirculation valve - Google Patents

Abstract

Exhaust gas recirculation valve (26) with a in a valve housing (42) guided valve rod (30) comprising a exhaust gas side valve disk (32) and with the valve rod (30) drivingly coupled actuator (36, 38, 40), wherein the valve rod (30) at least partially in a valve bearing (40) of the valve housing (42) is displaceably guided, characterized in that the valve bearing (40) to the valve rod (30) towards a recess (44), so that in the region of the recess (44) has a bearing gap ( 46) between the valve bearing (40) and the valve rod (30) is enlarged and the recess (44) is limited at both ends of areas with a reduced, normal bearing gap (46).

Description

The invention relates to an exhaust gas recirculation valve with a guided in a valve housing valve rod comprising a exhaust gas-side valve disk and a drive-coupled with the valve rod actuating device, wherein the valve rod is at least partially displaceably guided in a valve bearing of the valve housing.

Such an exhaust gas recirculation valve is for example from the DE 198 31 140 B4 refer to. The valve stem of this exhaust gas recirculation valve is guided in the manner of a plain bearing in a guide bush.

The exhaust gas recirculation valve is typically part of an exhaust gas recirculation system of an internal combustion engine. Such exhaust gas recirculation systems are often used to reduce the emission of nitrogen oxides, which arise during the combustion of fuel in the internal combustion engine. With regard to environmental protection, it makes sense to keep the formation of nitrogen oxides as low as possible during the combustion process.

Particularly in the case of diesel engines, exhaust gas recirculation is one of the most important measures for reducing nitrogen oxide emission and compliance with prescribed exhaust gas regulations, since only the use of exhaust aftertreatments (for example by means of an exhaust gas catalytic converter) is not sufficient for this purpose.

The exhaust gas recirculation valve is conventionally mounted near an exhaust manifold, and accordingly operates with a hot exhaust flow of about 850 ° C. In this installation situation, the storage of the exhaust gas recirculation valve is usually carried out by means of a slide bearing with dry friction, wherein the hard valve rod is guided in a valve bearing made of copper or brass alloys. Alternatively, a chrome-plated stainless steel valve stem is guided in a stainless steel bearing. The valve actuation is preferably carried out either by means of electric motors or gear stages on a backdrop or directly via a rotary magnet and backdrop. Through the backdrop, a rotational movement is converted into a translatory. In principle, transverse forces act on the valve rod, which are typically supported by means of the valve bearing.

The recirculated exhaust gas stream comprises, in addition to the nitrogen oxides, inter alia soot components, engine oil residues or diesel components which can disadvantageously reach the valve store as condensate entries. Due to the constantly controlled valve actuation, there is the risk of sooting, whereby condensate residues clump together as firmly adhering deposits on the valve bearing inner walls and thereby can use up a bearing gap between the valve rod and the valve bearing. As a result, the bearing friction is disadvantageously increased, whereby the exhaust gas recirculation valve over a period of time becomes increasingly stiff. This can sometimes lead to blockage of the valve stem. Such blocking the exhaust gas recirculation valve can only be repaired by a workshop stay with a complete replacement of the exhaust gas recirculation valve.

Measures to protect the valve stem from impinging dirt are for example in the EP 1 450 030 A1 described. There, a disc is mounted around the valve stem, which redirects incoming exhaust gases and prevents it from contact with the valve stem.

One solution to minimize the penetration of exhaust gases into the valve bearing is in the US 2004/0041115 A1 described. There, a labyrinthine path is created by means of annular extensions, which must first pass the exhaust gases to reach the valve stem. Due to the correspondingly enlarged surface along the path, the amount of exhaust gases that actually reach the valve store during operation is minimized.

The invention has for its object to provide an exhaust gas recirculation valve, which is improved in terms of sooting due to exhaust gas flow deposits during operation and blocking is avoided.

This object is achieved by the features of claim 1. With respect to an exhaust gas recirculation system equipped with an exhaust gas recirculation valve according to the invention, the object is achieved by the features of claim 10. Advantageous embodiments and further developments are the subject of the dependent claims.

For this purpose, an exhaust gas recirculation valve comprises a valve stem guided in a valve rod with a exhaust gas-side valve disk, and a drive-coupled with the valve rod actuator. The valve rod is at least partially guided displaceably in the manner of a sliding bearing in a valve bearing of the valve housing. The valve bearing has a recess towards the valve rod, so that a bearing gap between the valve bearing and the valve rod is increased in the region of the recess.

Viewed in the longitudinal direction of the valve rod, the recess is therefore limited on both sides by areas with a reduced, normal bearing gap. Under normal bearing gap is this understood that distance between the valve bearing and valve rod, which is required for a sliding bearing but also sufficient. Through the introduction of the recess, a friction increase as a result of deposits is kept as low as possible compared to conventional plain bearings in a structurally simple manner. The valve bearing is therefore characterized over the normal life by an improved friction behavior.

Due to the two spaced-apart areas with the narrow bearing gaps, which ultimately form spaced bearing points for the valve rod, a blocking of the valve rod is also avoided. Investigations have shown that a blocking of the valve rod is due to a self-locking of the valve stem due to deposits that are very close to each other in the longitudinal direction of the valve stem. The deposits can be positioned so unfavorable that the valve stem is clamped by the deposits in the manner of a screw clamp self-locking. With only a small distance in the longitudinal direction of these deposits a corresponding lever arm, so the length in the longitudinal direction of the valve stem is so small that the valve stem can not be solved. As a result of the design of the recess, such a short lever arm length, which promotes self-locking, is reliably reliably avoided, since the free movement of the valve rod is ensured in the region of the recess. Closely located and caused by deposits clamping points or points are avoided.

The exhaust gas recirculation valve is designed in particular as a poppet valve. For the purpose of a long life, the embodiment and the material of the exhaust gas recirculation valve is selected such that it has a high durability corresponding to the frequent opening operations, a high temperature and exhaust gas resistance, the lowest possible flow resistance during opening and a high density.

In a preferred embodiment, the recess is formed in a central region of the valve bearing, and encloses the valve rod cylindrical. For this purpose, the valve bearing is preferably free in a central region.

In an advantageous embodiment, the recess extends over a large part of the length of the valve bearing, in particular preferably over 50% to 80% of the length. This ensures that any deposits are pulled apart as far as possible to reliably prevent self-locking.

For the purpose of a particularly simple and cost-effective production, the recess is made in a suitable embodiment by means of an undercut of a valve bearing inner side of the valve bearing. The undercut is preferably designed in the radial and axial direction of the valve bearing, so that the recess encloses the valve rod approximately cylindrical.

In a preferred embodiment, a guide bushing is used as the valve bearing. As a result, a simple production is possible. The guide or plain bearing bush is usually pressed in the valve housing. The length of the valve bearing or the guide bush is preferably a multiple of the diameter of the valve rod, preferably two or four times. The recess is formed by an undercut on the inside of the guide bush.

In an alternative embodiment, the valve bearing comprises two separate, through the recess in the axial direction spaced bearing bushes. These are pressed into a hole in the valve body. In the region of the recess, the valve housing in particular has an undercut.

The valve bearing is generally inserted into a bore in the valve housing. Conveniently, the valve bearing is spaced from a lower, oriented to the valve disk bore end, so that a chamber is formed. This serves as a kind of defined collecting space for the absorption of soot particles and therefore additionally serves to avoid deposits in the storage area.

In an advantageous embodiment, the valve rod is spring-loaded by means of a spring element in a closing direction of the valve disk. In particular, in a suitable development, the spring element is a spiral spring. The coil spring is preferably mounted on the adjusting device end of the valve rod and is supported at least partially on an end face of the valve bearing, in particular on a shaft seal or washer mounted there. When opening the valve disk by means of the adjusting device, the coil spring is compressed. When the valve disk is closed, the spiral spring thus helps to reset the valve rod. In particular, this allows a lateral force-free provision, since the spring force acts substantially along the valve rod. As a result, a possible self-locking of the valve rod and the valve bearing due to deposits is advantageously and easily avoided.

In an expedient embodiment, a sealing element is arranged in the region of the spring element. Preferably, the sealing element arranged frontally to the valve bearing and seals the area between the valve bearing and the valve stem. This prevents that the exhaust gas flow and thus possible deposits penetrate into the region of the adjusting device. This prevents the adjusting mechanism of the adjusting device is blocked by deposits or even damaged. The sealing element is in a possible embodiment, for example structurally particularly simple designed as a shaft seal.

In a suitable embodiment, the adjusting device comprises a drive unit and a link guide coupled to the valve rod. The drive unit is designed for example as an electric motor, in particular as a DC motor, and coupled by means of a cam as a slide guide driving technology with the valve stem. By the cam a rotational movement of a motor shaft is converted into a linear movement of the valve rod in the direction of the open or closed position. Possible transverse forces on the valve rod are supported here on the valve housing, wherein the coil spring allows a substantially lateral force-free provision in a process in the closed position.

In the intended application situation, the exhaust gas recirculation valve according to the invention is installed as part of an exhaust gas recirculation system in an internal combustion engine of a motor vehicle. The internal combustion engine is preferably a diesel engine comprising an exhaust gas turbocharger with a turbine and a compressor. Furthermore, the internal combustion engine has a throttle with an adjustable opening degree, which is preferably arranged in a fresh air tract upstream of the compressor. With the exhaust gas recirculation valve open, the exhaust gas recirculation system branches off exhaust gas upstream of the turbine and supplies it to the fresh air tract downstream of the throttle. In a typical installation situation, the exhaust gas recirculation valve is arranged between an exhaust gas recirculation passage and an exhaust gas carrying exhaust passage. The valve disk is used for a fluidic closing of the exhaust gas recirculation passage with respect to the exhaust gas passage. For the purpose of opening the exhaust gas recirculation channel by means of the adjusting device, the valve disk is at least partially moved into an open position from a closed position into the exhaust gas channel. In the open state, an exhaust gas flow from the exhaust passage via the exhaust gas recirculation passage flows in a fresh air cycle of an internal combustion engine. The exhaust passage is preferably formed by an exhaust manifold.

• 1 in schematischer Darstellung einen Verbrennungsmotor mit einem Abgasturbolader, einem Abgaskrümmer und einem Abgasrückführungssystem,
• 2 in Seitenansicht den Abgaskrümmer und einen Abgasrückführkanal des Abgasrückführsystems mit einem geschlossenen Abgasrückführventil,
• 3 in schematischer ausschnittsweiser Darstellung eine erste Ausführungsvariante des Abgasrückführventils mit einer Führungsbuchse mit einem mittig angeordneten Freistich sowie
• 4 in schematischer ausschnittsweiser Darstellung eine zweite Ausführungsvariante des Abgasrückführventils, bei dem das Ventillager zwei getrennte Lagerbuchsen aufweist.

An embodiment of the invention will be explained in more detail with reference to a drawing. Show it:

• 1 a schematic representation of an internal combustion engine with an exhaust gas turbocharger, an exhaust manifold and an exhaust gas recirculation system,
• 2 side view of the exhaust manifold and an exhaust gas recirculation channel of the exhaust gas recirculation system with a closed exhaust gas recirculation valve,
• 3 in a schematic partial view of a first embodiment of the exhaust gas recirculation valve with a guide bush with a centrally arranged undercut and
• 4 in a schematic partial view of a second embodiment of the exhaust gas recirculation valve, wherein the valve bearing has two separate bearing bushes.

Corresponding parts and sizes are always provided with the same reference numerals in all figures.

The in 1 illustrated internal combustion engine 2 is an exhaust gas turbocharger 4 and an exhaust manifold 6 assigned to which an exhaust gas recirculation channel 8th as part of an exhaust gas recirculation system 10 connected. The internal combustion engine 2 In this embodiment, there are four cylinders schematically represented by circles 12 of which only one is provided by way of example with a reference numeral. The internal combustion engine 2 essentially comprises a fresh air side fresh air tract 14 to supply the cylinders 12 with oxygen-containing fresh air F , as well as an exhaust tract 16 for the removal of exhaust gases A ,

exhaust A that occurs when burning fuel in the cylinders 12 are created by the exhaust manifold 6 derived, and through the exhaust tract 16 a turbine 18 the exhaust gas turbocharger 4 fed. The turbine 18 drives in a manner not shown a fresh air side compressor 20 the exhaust gas turbocharger 4 at. Downstream of the compressor 20 is a fresh air cooler 22 arranged the fresh air F cooled down to a certain temperature.

exhaust A be via the exhaust gas recirculation channel 8th upstream of the turbine 18 at a branch point 24 branched off and upstream of the fresh air cooling 22 for mixing with the fresh air F fed. The recirculated exhaust gas mass flow is dependent on the degree of opening of an exhaust gas recirculation valve 26 , To regulate the exhaust gas temperature includes the exhaust gas recirculation system 10 furthermore an exhaust gas cooler 28 ,

As it turned out 2 results, is the exhaust gas recirculation valve 26 is as a poppet valve with a valve rod 30 and an exhaust manifold-side valve disk formed thereon 32 executed. For the purpose of the longest possible life is the embodiment and the material of the exhaust gas recirculation valve 26 chosen such that it has a high durability corresponding to the frequent opening operations, a high temperature and exhaust gas resistance, the lowest possible flow resistance when opening and a high density.

In the 2 is the exhaust manifold 6 , the exhaust gas recirculation channel 8th and the branch point 24 shown in more detail. The valve plate 32 the exhaust gas recirculation valve 26 is as a shut-off between the exhaust manifold 6 and the exhaust gas recirculation passage 8th arranged. For the purpose of opening and closing the exhaust gas recirculation valve is the valve rod 30 in the exemplary embodiment drive technology via a cam 34 to an electric motor 36 coupled. Alternatively, the coupling can also take place via a gearbox or another suitable coupling mechanism. With the electric motor 36 is the exhaust gas recirculation valve 26 from a closed position to an open position within the exhaust manifold 6 movable into it. The electric motor 36 is designed in particular as a DC motor or rotary magnet, and the cam 34 serves as a gate guide for the translation of the rotational movement of a motor shaft 38 of the electric motor 36 in a linear movement of the valve stem 30 , In principle, other valve drives are possible.

The valve rod 30 is inside a valve store 40 slidably mounted. the valve store 40 basically comprises two axially spaced bearings 45 and a recess disposed therebetween 44 , The valve bearing is in a hole 41 a valve housing 42 used, in particular pressed. For the valve rod 30 and the valve store 40 is preferably a possible frictionless material pairing provided. The valve store 40 For example, is made of a copper or brass alloy, and the valve rod 30 made of a hard metal material such as steel. Alternatively, stainless steel is provided as material pairing, in particular for the valve bearing, and chromed stainless steel.

According to a first in the 3 illustrated embodiment is the valve bearing 40 through a guide bush 40A formed in which the valve stem 30 is displaceably stored. The guide bush 40A is here in particular designed in the manner of a sliding bearing with dry friction. The length of the guide bush 40A is about four times the diameter of the valve stem so that it is guided safely.

In an open state of the exhaust gas recirculation valve 26 in which the valve plate 30 through the electric motor 36 into the chamber of the exhaust manifold 6 is moved in, exhaust gases flow A at least partially by the exhaust gas recirculation system 10 to the fresh air tract 14 ,

The exhaust A has in addition to the combustion of nitrogen oxides, inter alia, soot components, engine oil residues or diesel components, which disadvantageously as condensate entries in the valve bearing 40 reach. During operation, the risk of sooting due to the constantly controlled valve actuation, wherein the condensate residues of the exhaust gas A as adherent deposits on guide bush inner walls clump and thereby the sliding bearing between the valve stem 30 and the valve store 40 make it increasingly difficult.

To avoid such Versottung has in the first preferred embodiment, the guide bush 40A to the valve rod 30 towards a recess 44 on, at the two ends of the guide bush 40A from the bearings 45 are limited. The bearings 45 are compared to the cylindrical recess 44 designed as annular thickenings. Between the bearings 45 and the valve stem 30 is a suitable bearing clearance for the slide bearing 46 formed in the range of a few microns. This is virtually through the recess 44 in the middle area of the guide bush 44 increased. The bearing gap 46 serves the well-known sliding bearing. The recess 44 is manufacturing technology by means of an undercut in the inner wall of the guide bush 40 brought in.

As in 3 the recess is visible 44 in a central area of the guide bush 40 trained, and encloses the valve stem 30 approximately cylindrical. For this purpose, the guide bush 40 freed in the middle region by means of the radially and axially extending undercut. The recess 44 extends substantially over 80% of the length of the guide bushing 40 ,

In the alternative, in 4 illustrated embodiment, instead of the one-piece guide bushing 40A two separate, the bearing points 45 forming sliding bushings 40B into the hole 41 pressed. Conveniently, the bore here in the region of the recess between the bushings 40B one compared to the bearings 45 enlarged diameter on to the lower bushing 40B Reliable to the intended place within the hole 41 to be able to press in.

In both variants is through the recess 44 formed a radial clearance in which soot particles can be deposited without the slide bearing properties are affected. Investigations have shown that this extends the life of the valve bearing 30 decisively increased.

In addition, suitably a Rußkammer 49 towards the valve plate 32 trained. The valve store 40 therefore ends within the hole 41 and has a distance to the bore end, which through a bottleneck of the valve housing 42 is formed. In the area of the bottleneck points the valve stem 30 a much bigger game than in the area of the camp column 46 on. Through the soot chamber 49 is another collection space for soot deposits formed without the slide bearing properties are affected.

The valve rod 30 is by means of a spiral spring 50 along the closing direction of the valve disk 32 spring-loaded. The spiral spring 50 is at the electric motor end of the valve stem 30 attached, and is supported at least partially on a shaft seal 52 from. The shaft seal 52 is essentially frontal to the guide bushing 40A or to the upper bearing bush 40B arranged, and lies between the guide bushing 40A or the upper bearing bush 40B and the valve stem 30 at. This will prevent the exhaust A and thus possible deposits in the area of the electric motor 36 and the cam 34 penetration. Thus, it is further prevented that the adjusting mechanism on the part of the electric motor 36 and the cam 34 by deposits of the exhaust gas A blocked or even damaged.

When opening the valve disk 32 by means of the electric motor 36 , the cam disc 34 and the valve stem 30 becomes the spiral spring 50 compressed. When closing the valve disk 32 supports the spiral spring 50 thus a reset of the valve stem 30 along the valve store 40 , In particular, a largely lateral force-free provision is made possible as a result, since the spring force substantially along the valve rod 30 acts.

The invention is not limited to the embodiments described above. On the contrary, other variants of the invention can be derived therefrom by the person skilled in the art without departing from the subject matter of the invention. In particular, furthermore, all individual features described in connection with the various exemplary embodiments can also be combined with one another in other ways, without departing from the subject matter of the invention.

LIST OF REFERENCE NUMBERS

2

internal combustion engine

4

turbocharger

6

exhaust manifold

8th

Exhaust gas recirculation passage

10

Exhaust gas recirculation system

12

cylinder

14

Fresh air tract

16

exhaust tract

18

turbine

20

compressor

22

Fresh air coolers

24

branching point

26

Exhaust gas recirculation valve

28

exhaust gas cooler

30

valve rod

32

valve disc

34

cam

36

electric motor

38

motor shaft

40

valve bearings

40A

guide bush

40B

bearing bush

41

drilling

42

valve housing

44

recess

45

depository

46

bearing gap

48

Freeway

49

Rußkammer

50

spiral spring

52

Shaft seal

F

fresh air

A

exhaust

Claims (11)

Exhaust gas recirculation valve (26) with a in a valve housing (42) guided valve rod (30) comprising a exhaust gas side valve disk (32) and with the valve rod (30) drivingly coupled actuator (36, 38, 40), wherein the valve rod (30) at least partly in one Valve bearing (40) of the valve housing (42) is displaceably guided guided, characterized in that the valve bearing (40) to the valve rod (30) towards a recess (44), so that in the region of the recess (44) has a bearing gap (46) between the valve bearing (40) and the valve rod (30) is increased and the recess (44) is limited at both ends of areas with a reduced, normal bearing gap (46). Exhaust gas recirculation valve (26) after Claim 1 , characterized in that the recess (44) in a central region of the valve bearing (40) is formed and the valve rod (30) surrounds cylindrical. Exhaust gas recirculation valve (26) after Claim 1 or 2 , characterized in that the recess (44) extends over a majority of the length of the valve bearing (40), in particular over 50% to 80% of the length. Exhaust gas recirculation valve (26) according to one of Claims 1 to 3 , characterized in that the recess (44) by means of an undercut (48) of a valve bearing inner side of the valve bearing (40) is made. Exhaust gas recirculation valve (26) one of Claims 1 to 4 , characterized in that as a valve bearing (40) is a guide bush (40A) with two by the recess (44) separate bearing points (45) is used. Exhaust gas recirculation valve (26) one of Claims 1 to 4 , characterized in that the valve bearing (40) comprises two separate in a bore (41) inserted in the valve housing bearing bushes (40 B) and between the bearing bushes (40 B) the recess (44). Exhaust gas recirculation valve (26) according to one of Claims 1 to 6 , characterized in that the valve rod (30) by means of a spring element (50) in a closing direction of the valve disc (32) is spring-loaded. Exhaust gas recirculation valve (26) after Claim 7 , characterized in that the spring element (50) is a spiral spring. Exhaust gas recirculation valve (26) according to one of Claims 7 or 8th , characterized in that in the region of the spring element (50) a sealing element (52) is arranged. Exhaust gas recirculation valve (26) according to one of Claims 1 to 9 , characterized in that the adjusting device (36, 38, 40) comprises a drive unit (36) and a link guide (34) coupled to the valve rod (30). Exhaust gas recirculation system (10) for an internal combustion engine (2) of a motor vehicle, comprising an exhaust gas duct (16) to which an exhaust gas recirculation channel (8) is connected, in which an exhaust gas recirculation valve (26) according to any one of Claims 1 to 10 is arranged.

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