DE102008031657A1 - Exhaust converter for exhaust system for catalytic after treatment of combustion engine exhaust gases, has converter housing and carrier body arranged in converter housing - Google Patents

Abstract

The exhaust converter (10) has a converter housing (12) and a carrier body (14) arranged in the converter housing. The converter housing has a curved shape or a shape with a cross sectional area changing in exhaust gas flow direction and an outer outline of the carrier body corresponding in sections to an internal outline of the converter housing.

Description

The The present invention relates to an exhaust gas converter for catalytic Aftertreatment of combustion engine exhaust gases and an exhaust system, comprising at least one such exhaust gas converter.

Exhaust gases of combustion engines contain as environmentally relevant pollutants unburned hydrocarbons HC, carbon monoxide CO and nitrogen oxides NO _x . In order to remove these constituents from the exhaust gas, it is known to integrate one or more exhaust gas converters for the catalytic after-treatment in exhaust systems of internal combustion engines. Depending on the conversion task, the converter can be configured as an oxidation catalyst for the conversion of unburned hydrocarbons and carbon monoxide, as a reduction catalyst for the reduction of nitrogen oxides or as a three-way catalyst which simultaneously supports said oxidizing and reducing reactions. In addition, the converter may be equipped with a storage component for temporarily storing a selected exhaust gas component. In particular, in the case of lean-running internal combustion engines, a converter may be provided which has an NO _x storage component. This stores in lean operating phases, in which the internal combustion engine is supplied with an oxygen-rich air-fuel mixture with λ> 1, NO _x in the form of nitrates, in rich operating intervals, in which the internal combustion engine with air deficit is operated (λ <1), the nitrogen oxides release and reduce with the aid of a suitable catalytic material. As alternatives to such a NO _x storage so-called selective reduction catalysts (SCR catalysts) and hydrolysis catalysts are known for the conversion of nitrogen oxides.

Known Exhaust systems often include multiple converter components, in particular at least one close-coupled preconverter, the characterized by rapid heating after a cold start, and / or at least one further downstream arranged main converter.

Usually If an exhaust gas converter consists of a carrier body, which a variety of exhaust gas flowed through channels formed. The walls of these channels are porous Matrix coated, which is known as "washcoat" is. The washcoat serves to increase the specific surface area and the fixation of a catalytically active substance or a Mixture of several of such. Conventional carrier body consist of a ceramic material (monolith) or a body made of wound metal sheets (Metalith). In both cases have the channels through which the exhaust gas can flow linear, axially extending in the flow direction of the exhaust gas Honeycomb structure on. The carrier body of the exhaust gas converter is usually in a cylindrical or oval cylindrical Section of a converter housing arranged on which each on the inflow and outflow side conically expanding inlet connection or outlet connection followed. The inlet and outlet ports are included connected to the exhaust pipe, for example via a flange connection.

In addition, exhaust converters have recently been developed that consist of a metal foam with an open-cell pore structure. The advantage of the support body consisting of metal foam is that a nonlinear, labyrinth-like structure of the flow channels is formed, which leads to a very good mixing of the exhaust gas. This avoids the formation of so-called Stromfäden and also improves the diagnosability of the converter. For example, describes EP 1 344 907 A1 an exhaust gas converter whose carrier body is constructed of a plurality of successively arranged cylindrical discs made of metal foam.

DE 20 2007 008 447 U1 describes an exhaust manifold having, as usual, a plurality of individual cylinders associated with manifolds, which open into a manifold of the manifold. In the collecting tube, a carrier body of a wound metal foam is arranged, which is laterally on and flows from the effluent from the exhaust manifold exhaust gas.

adversely At the conventional converter systems is that these basically proportionate take up a lot of space and their arrangement due to the cramped Spaces often restrictions subject to the available space be limited and not by the optimal conversion function be determined.

task The present invention is therefore an exhaust gas converter for To provide the lowest possible Construction volume claimed and easy in existing space conditions integrate.

These Task is with an exhaust gas converter for catalytic aftertreatment combustion engine exhaust gases and an exhaust system, the at least one such exhaust gas converter contains the features of the independent claims.

The exhaust gas converter according to the invention holds a converter housing and at least one arranged in this carrier body, which is formed of a metal foam with an open-cell (also known as open-pore) structure which forms flow through the exhaust gas flow channels. According to the invention, the catalyst housing has a curved shape and / or a shape with a cross-sectional area which changes in the exhaust gas flow direction. In this case, the outer contour of the carrier body is at least partially adapted (with respect to the exhaust gas flow direction) an inner contour of the converter housing, that is, it corresponds with this. In other words, both the converter housing and the carrier body each have a complex shape in contrast to the usual in the prior art cylinder or oval-cylindrical configurations. This allows the adaptation of the converter to complex space conditions of a motor vehicle and thus optimal utilization of existing space. In this case, the complex shaping of the carrier body is made possible, in particular, by the use of the metal foam, which can be brought into any configuration very flexibly, for example by foaming the metal or the metal alloy directly in the converter housing.

Of the inventive exhaust gas converter allows in particular, that components of a conventional exhaust system be designed as exhaust gas converter, which in the prior art no Conversion function is added. In this regard, one sees Particularly preferred embodiment of the invention, that the converter housing a curved portion of an exhaust pipe, a Exhaust manifold pipe or a funnel-shaped inlet nozzle and / or outlet port of a catalyst housing, otherwise with a conventional ceramic or metal winding catalyst Is provided. In addition, the converter housing also as an arbitrarily designed insert in a silencer be designed.

When Material of the metal foam of the carrier body comes Any metal or metal alloy in question, that in the exhaust tract an internal combustion engine ruling thermal, mechanical and withstand chemical loads. In this sense can all metals or metal alloys find use, which also for conventional metal winding catalysts are known. Especially Light metals such as aluminum or magnesium come into question here as well as titanium, steels and others.

In a further development of the invention, an inner surface of the flow channels of the carrier body, that is, the walls of the open cells, at least partially coated with a washcoat, which preferably has a porous and thus oberflächenvergrößernde structure and is suitable for receiving at least one catalytically active substance. For the material of the washcoat all common materials in question, in particular porous metal oxides such as alumina (Al ₂ O ₃ ) or silicon oxide (SiO ₂ ) or mixtures, which may optionally contain oxygen storage components, such as cerium oxide. It is further preferably provided that the washcoat is loaded with at least one catalytically active substance which is incorporated in the pores of the washcoat and held there. Also suitable for the catalytically active substance are all materials known in the prior art, in particular noble metals, including those of the platinum group, in question. Particular mention may be made here of palladium (Pd), platinum (Pt), rhodium (Rh), iridium (Ir), ruthenium (Ru) and osmium (Os). The at least one catalytically active substance is chosen according to its conversion task so that it has an oxidizing activity for the catalytic conversion of unburned hydrocarbons (HC) and carbon monoxide (CO) or a reducing activity for the catalytic conversion of nitrogen oxides (NO _x ). Alternatively, it may have a three-way catalytic property and thus have both an oxidizing and reducing activity. Furthermore, the washcoat can be equipped with the memory components explained in the introduction, in particular for nitrogen oxides NO _x .

To Another preferred embodiment of the invention is between the carrier body and the converter housing a means for fixing and damping of the carrier body arranged. This fixation and damping agent can in particular in the form of a mat, for example a fiber mat or a knitted wire. Such mats are The skilled worker well known and require no further Explanation.

Further advantageous embodiments are the subject of the rest Dependent claims.

The Invention will be described below in embodiments the accompanying drawings explained.

It demonstrate:

1 schematically the construction of an exhaust gas converter according to a preferred embodiment of the invention and

2 an exhaust system with possible positioning of exhaust gas converters according to the invention.

1 shows a schematic representation of a total with 10 designated inventive exhaust gas converter, wherein the 1B and 1C ever because enlarged partial sections of the in 1A respectively. 1B represented converter.

The exhaust gas converter 10 includes a converter housing 12 , which is configured in the example shown as an exhaust pipe section and has a curved shape. Such a curved exhaust pipe section is used in an exhaust system, for example, the connection of rectilinear exhaust pipes and the corresponding deflection of an exhaust coming from an internal combustion engine. Inside the converter housing 12 is a carrier body 14 arranged, the outer contour of the inner contour of the converter housing 12 corresponds, that is adapted to this. The carrier body 14 consists of a metal foam (also called metal sponge), which consists of a large number of cells whose wall 16 partially open ( 1B ). The open cells usually have a size in the range of a few micrometers to a few millimeters, for example in the range of 10 microns to 5 mm. Due to the open-cell structure of the metal foam of the carrier body 14 be through the cell walls 16 limited flow channels 18 formed, which are traversed by the exhaust gas.

The cell walls 16 of metal foam are with a washcoat 20 coated, which has a high porosity and / or surface roughness. For example, there is the washcoat 20 made of alumina Al ₂ O ₃ . Into the pores or surface depressions of the washcoat 20 are particles of a catalytically active substance 22 embedded in the finest dispersion and adhere there. At the catalytic substance 22 It is usually a noble metal, in particular the platinum group, preferably platinum, palladium, rhodium, ruthenium, iridium and osmium and their alloys. In addition, cerium, iron, manganese, nickel and / or copper as well as their mixtures and alloys with the abovementioned noble metals may also be present. By selecting the catalytic substance 22 becomes the conversion property of the converter 10 certainly.

The use of a carrier body 14 made of a metal foam has several advantages over conventional support bodies made of a ceramic body or of wound metal foils. In particular, the labyrinth-like channel structure of the metal foam leads to a very good mixing of the exhaust gas and thus to the avoidance of flow filaments of radially inhomogeneous composition. As a result, the diagnosability of the converter is significantly improved over conventional carriers with linear flow channels. In addition, the winding flow channels lead 18 to a longer effective path of the exhaust gas within the converter and thus to extended contact times and improved revenues. Also, metal foams have a good energy absorption behavior, which can be broken down due to thermal stresses occurring in the material well. In addition, metal foams have a higher mechanical strength compared to conventional carrier bodies. Finally, there are virtually no limitations with regard to the shaping of metal foams, since it is possible to apply them directly in the converter housing 12 foams, wherein the metal foam automatically adapts to the contour.

The preparation of the converter according to the invention 10 This can be done by mixing a metal powder, for example aluminum powder, with a suitable metal hydride, such as titanium dihydrate TiH ₂ , and mixing this mixture into the converter housing 12 is introduced and compacted. Subsequently, a heating takes place above the melting point of the metal (aluminum), whereby the metal hydride liberates hydrogen, which leads to a foaming of the material. Alternatively, the production of the metal foam by filling a molten metal into the housing 12 done and then injecting a gas. After solidification of the metal foam, the application of the washcoat 20 For example, by the metal foam body 14 or the converter housing contained therein 12 is placed in a suspension of the washcoat material or such a suspension through the carrier body 14 is directed. After solidification of the washcoat 20 , which is optionally supported by thermal treatment, the impregnation with the catalytic substance takes place 22 , in turn, the converter 10 is placed in a solution of the catalytic metal or such a solution by the carrier body 14 is pressed. If necessary, the metal salt can be converted into the corresponding catalytic metal in a reducing atmosphere.

2 shows a schematic representation of a total with 100 designated exhaust system for the catalytic treatment of a by the arrows 24 indicated exhaust gas of an internal combustion engine, not shown. The exhaust coming from a cylinder head of the internal combustion engine 24 first enters an exhaust manifold 26 , which in the example shown four each associated with a cylinder of the internal combustion engine exhaust manifolds 28 having. From the exhaust manifolds 28 the exhaust gas enters a manifold 30 the exhaust manifold 26 and from there into a turbocharger not shown in detail 32 where it drives a turbine coupled to a compressor for compressing an air mass supplied to the internal combustion engine.

Downstream of the exhaust gas turbocharger 32 the exhaust gas flows into a first straight exhaust pipe section 34 the exhaust system, from where it enters a first curved exhaust pipe section 36 flows and is diverted. Subsequently, the exhaust gas enters an exhaust gas catalyst 38 that with a conventional carrier body 40 made of a ceramic monolith or wound metal foils. The converter housing of the catalyst 38 has a conically widening, funnel-shaped inlet connection on the inflow side 42 on and downstream of a conically tapered funnel-shaped outlet 44 , From the outlet 44 the exhaust gas flows into a second bent exhaust pipe section 46 then into a second straight exhaust pipe section 48 and from there into a particle filter 50 , Downstream of the particulate filter 50 reaches the exhaust gas via a third straight exhaust pipe section 52 a silencer 54 with a deposit 56 , Over a fourth straight exhaust pipe section 58 the post-treated exhaust gas leaves the exhaust system 100 ,

In the 2 illustrated exhaust system 100 can contain the exhaust gas converter according to the invention at various positions, which are indicated in the figure by hatching. A first preferred position are the exhaust manifolds of the exhaust manifold 26 that, in particular, the cylinder head of the internal combustion engine with the manifold 30 the exhaust manifold 26 connect and usually have a curved shape (not shown). Due to the design of the exhaust manifold pipes 28 As the exhaust gas converter according to the present invention, an extremely close arrangement of the catalyst on the engine and thus a particularly rapid heating and an early start of the converter after a cold engine start is achieved.

Another preferred arrangement of the converter according to the invention is through the curved exhaust pipe sections 36 and 46 given, in particular of the motor near first section 36 which is essentially the one in 1 shown converter corresponds.

Further advantageous positioning of the converter according to the invention is through the inlet port 42 and the outlet 44 of the otherwise conventionally formed catalytic converter 38 given. In addition, there is an integrated arrangement in the particulate filter 50 advantageously possible. Finally, the deposit 56 of the muffler 54 be configured in the inventive manner as an exhaust gas converter.

All of the aforementioned preferred positions of the converter according to the invention within the exhaust system 100 , which can be realized individually or in any combination with each other, have the advantage that already existing in the exhaust system components are provided with a catalytic function, without the need for a separate space must be provided. thereby, a volume of a conventional converter can be further reduced.

10

exhaust gas converter

100

exhaust system

12

converter housing

14

support body

16

cell wall

18

flow channel

20

washcoat

22

catalytic substance

24

exhaust

26

exhaust manifold

28

Abgaskrümmerrohr

30

manifold

32

turbocharger (Turbine)

34

first straight exhaust pipe section

36

first curved exhaust pipe section

38

catalytic converter

40

conventional support body

42

inlet port

44

outlet

46

second curved exhaust pipe section

48

second straight exhaust pipe section

50

particulate Filter

52

third straight exhaust pipe section

54

silencer

56

inlay

58

fourth straight exhaust pipe section

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - EP 1344907 A1 [0005]
• - DE 202007008447 U1 [0006]

Claims (9)

Exhaust gas converter ( 10 ) for the catalytic aftertreatment of internal combustion engine exhaust gases, comprising a converter housing ( 12 ) and at least one in the converter housing ( 12 ) arranged carrier body ( 14 ), which consists of a metal foam with an open-cell structure, which flows through the exhaust gas flow channels ( 18 ), is formed, characterized in that the converter housing ( 12 ) has a curved shape and / or a shape with a cross-sectional area that changes in the exhaust gas flow direction, and an outer contour of the carrier body (FIG. 14 ) at least in sections an inner contour of the converter housing ( 12 ) corresponds. Exhaust gas converter ( 10 ) according to claim 1, characterized in that the converter housing ( 12 ) an element is selected from the group consisting of a curved exhaust pipe section ( 36 ), an exhaust manifold ( 28 ), a funnel-shaped inlet nozzle ( 42 ) or outlet nozzle ( 44 ) a catalyst housing and an insert ( 56 ) of a silencer ( 54 ). Exhaust gas converter ( 10 ) according to one of the preceding claims, characterized in that the metal foam of the carrier body ( 14 ) consists of a metal or a metal alloy selected from the group aluminum, magnesium, titanium, steels. Exhaust gas converter ( 10 ) according to one of the preceding claims, characterized in that an inner surface of the flow channels ( 18 ) of the carrier body ( 14 ) at least partially with a washcoat ( 20 ) is coated. Exhaust gas converter ( 10 ) according to claim 4, characterized in that the washcoat ( 20 ) a porous, for receiving at least one catalytically active substance ( 22 ) has suitable structure. Exhaust gas converter ( 10 ) according to claim 4 or 5, characterized in that the washcoat ( 20 ) with at least one catalytically active substance ( 22 ), which in particular contains a noble metal, preferably a platinum group element. Exhaust gas converter ( 10 ) according to claim 6, characterized in that the at least one catalytically active substance ( 22 ) has an oxidizing activity for the catalytic conversion of unburned hydrocarbons and carbon monoxide, a reducing activity for the catalytic conversion of nitrogen oxides or a 3-way catalytic property comprising an oxidizing and a reducing activity. Exhaust gas converter ( 10 ) according to one of the preceding claims, characterized in that between the carrier body ( 14 ) and the converter housing ( 12 ) means for fixing and damping the carrier body ( 14 ) is arranged, in particular in the form of a fiber mat or a wire mesh. Exhaust system ( 100 ) for the catalytic after-treatment of internal combustion engine exhaust gases, comprising at least one exhaust gas converter ( 10 ) according to any one of claims 1 to 8.