WO2004113694A1

WO2004113694A1 - Catalytic converter component and exhaust system

Info

Publication number: WO2004113694A1
Application number: PCT/EP2004/006411
Authority: WO
Inventors: Rainer Horlacher; Frank Jacobi; Martin Matt; Volker Siedle
Original assignee: Daimlerchrysler Ag
Priority date: 2003-06-24
Filing date: 2004-06-15
Publication date: 2004-12-29
Also published as: DE10328168A1

Abstract

The invention relates to a catalytic converter component for an exhaust system of an internal combustion engine, comprising a housing (10) and a catalytic converter support that is disposed inside the housing. According to the invention, the housing (10) defines a first flow path for exhaust gas that flows into the catalytic converter component by penetrating the catalytic converter support (18), and a second flow path which bypasses the catalytic converter support (18) and extends essentially parallel to an inlet area and/or an outlet area of the catalytic converter support (18). The inventive catalytic converter component is used for primary catalytic converters of internal combustion engines comprising an exhaust gas turbocharger, said primary catalytic converters being positioned close to the engine.

Description

Catalyst component and 7 gas system

The invention relates to a catalyst component for an exhaust system of an internal combustion engine with a housing and a catalyst carrier arranged in the housing. The invention also relates to an exhaust system for an internal combustion engine, in particular with an exhaust gas turbocharger, with a catalyst component according to the invention.

From the German patent DE 43 11 904 C2, an exhaust system for an internal combustion engine with an exhaust gas turbocharger and a catalyst is known, in which exhaust gases coming from the exhaust gas turbine and exhaust gases flowing into the exhaust system bypassing the exhaust gas turbine are directed to different areas of a catalyst. For this purpose, the exhaust gases coming from the exhaust gas turbine are conducted to a central area of the catalytic converter by means of a pipeline and the bypass line opens into an annular area which surrounds the pipeline. An annular outer region of the catalyst is acted upon by the bypass line via the ring line. The catalyst carrier is flowed through axially and both its central region and the annular, outer region are coated catalytically.

An exhaust system for an internal combustion engine with an exhaust gas turbocharger is known from German published patent application DE 196 54 026 AI, in which exhaust gases also coming from the exhaust gas turbine are introduced into a central region of a catalyst carrier. Exhaust gas flowing into the exhaust system via a bypass valve is passed into an outer, annular area of the catalytic converter surrounding the central area. initiated. The catalyst carrier is flowed through in the axial direction and both the outer and the central area are coated catalytically. A heat transfer between the central area acted upon by the exhaust gas turbine and the outer area acted upon via the bypass line is limited in that a separating layer which hinders the heat transfer within the catalyst matrix is provided between these two areas.

An exhaust gas system for an internal combustion engine with an exhaust gas turbocharger is known from US Pat. No. 4,444,012, in which exhaust gases coming from an exhaust gas turbine are passed over a catalytic converter. A bypass line only opens into the exhaust system downstream of the catalytic converter. When the bypass valve is open, part of the exhaust gas flow is directed past the catalytic converter.

An exhaust system for an internal combustion engine with an exhaust gas turbocharger is known from US Pat. No. 4,202,176, in which a catalytic converter can be arranged upstream or downstream of an exhaust gas turbine. Regardless of the arrangement of the catalytic converter, a bypass line opens into the exhaust system downstream of the catalytic converter. With the bypass valve open, part of the exhaust gas is thus directed past the exhaust gas turbine and the catalytic converter.

The invention is intended to achieve effective exhaust gas purification with a low exhaust back pressure.

According to the invention, a catalyst component for an exhaust system of an internal combustion engine is provided with a housing and a catalyst carrier arranged in the housing, in which the housing has a first flow path for exhaust gas flowing into the catalyst component through the catalyst carrier and a second flow path past the catalyst carrier and essentially in parallel to a Entry surface and / or exit surface of the catalyst carrier defined.

By defining two flow paths in the housing of the catalytic converter component, an exhaust gas flow can thereby be divided or directed differently, for example depending on the engine load. In this way, all exhaust gas, for example, could be passed through the catalyst carrier via the first flow path immediately after a cold start, and in the event of high or full load, the exhaust gas stream is passed essentially completely along the second flow path past the catalyst carrier. The catalytic converter component according to the invention is advantageously used as a so-called starting catalytic converter and is combined in an exhaust system with a conventional underfloor catalytic converter arranged downstream. The definition of two flow paths in the housing enables a compact design of the catalytic converter component and, at the same time, creates the prerequisites for a quick start of the catalytic converter after a cold start and low exhaust gas counterpressure under high load and full load and at the same time a significantly reduced aging of the catalytic converter.

The invention also proposes a catalyst component for an exhaust system of an internal combustion engine with a housing and a catalyst carrier arranged in the housing, in which the catalyst carrier defines an interior and is arranged in the housing for a flow of exhaust gas going beyond the interior.

These measures make it possible to achieve a low exhaust gas counterpressure, since the exhaust gas passes through the wall of the catalyst carrier which delimits the interior. The shape of the catalyst carrier is largely optional, which results in great flexibility with regard to the accommodation in an exhaust system of a motor vehicle. In particular, axial flow is becoming more conventional Avoided catalysts that are always particularly heavily loaded in the entry area by hot exhaust gas. In the invention, the hot exhaust gas is first distributed around the catalyst carrier in the interior or in an exterior space and can then enter the catalyst carrier essentially over the entire wall surface of the catalyst carrier. The temperature load on the inflow surface of the catalyst carrier can thereby be considerably reduced compared to conventional catalyst carriers, which is of considerable advantage particularly in the case of starting catalysts arranged close to the engine.

The invention also proposes a catalyst component for an exhaust system of an internal combustion engine with a housing and a catalyst carrier arranged in the housing, in which the catalyst carrier is designed in a flexible manner in such a way that the free cross-sectional area available for an exhaust gas flow through the catalyst carrier is dependent on the Catalyst carrier applied exhaust pressure is changeable.

These measures can also achieve a low exhaust gas back pressure with effective exhaust gas purification. For example, pores of the flexibly designed catalyst carrier are widened at an increased inlet-side exhaust gas pressure, so that a lower back pressure is built up. The catalyst carrier advantageously defines an interior space into which exhaust gas from the internal combustion engine can flow and, depending on the exhaust gas pressure in the interior space, the catalyst carrier or only passage openings in the catalyst carrier are widened or reduced.

In a further development of the invention, the catalyst carrier is formed at least in sections like a knit or a fabric.

By means of such a design, a flexible design of the catalyst carrier can be achieved with which one Change in pore size depending on the existing exhaust gas pressure can be achieved. A fiber composite in which there is a bond between the fibers and which allows the fibers to move relative to one another at least in sections and thus a variable pore size is also referred to as knitted or fabric-like.

In a further development of the invention, the catalyst carrier is formed at least in sections as a glass fiber fabric or glass fiber knit.

Because of their good temperature resistance, glass fibers are suitable for use as catalyst supports. A textile-like material made of glass fibers is also referred to as glass fiber fabric or glass fiber knitted fabric, in which a kind of bond is created between the individual fibers, which enables the fibers to move relative to one another in order to be able to change the pore size of the catalyst carrier.

In a development of the invention, the catalyst carrier is covered by means of a wire mesh.

In this way, the flexible catalyst carrier, which is designed, for example, as a glass fiber fabric, can be kept in shape even with high exhaust gas throughputs and only provides little resistance to the exhaust gas flowing through. The use of knitted wire also allows the shape of the catalyst carrier to be changed.

In a development of the invention, the catalyst carrier consists at least in sections of wire mesh or wire mesh.

In a further development of the invention, the catalyst carrier has a hollow cylindrical shape and is for an essentially Chen radial flow of exhaust gas arranged in the housing.

In this way, a compact arrangement with a large inflow area and outflow area of the catalyst carrier can be achieved. Since a large inflow and outflow area is available compared to conventional catalysts and the thickness of the catalyst carrier to be traversed by the exhaust gas is comparatively small, a very low exhaust gas back pressure can be realized.

In a further development of the invention, the catalyst carrier is arranged for an essentially radial flow from the inside to the outside.

Such a design is particularly advantageous in the case of starting catalytic converters close to the engine, since as a result, after a cold start, only slight heat losses occur through the exhaust gas routing.

In a development of the invention, the catalyst carrier surrounds an inner tube of the housing provided with through openings.

In this way, the flexible catalyst carrier can be securely fixed and a stable construction of the housing is possible.

In a further development of the invention it is provided that the inner tube consists of porous material. The inner tube advantageously consists of wire mesh or wire mesh at least in sections.

The use of wire mesh or wire mesh allows the inner tube and the entire catalyst component to be shaped flexibly, so that the shape of the catalyst component can be adapted to the available installation space. In addition, by using wire mesh the wire mesh a low exhaust back pressure can be realized.

In a further development of the invention, the catalyst carrier defines an interior space and the housing defines an exterior space surrounding the catalyst carrier, the interior space or the exterior space merely having an inflow opening for exhaust gas.

In this way, an exhaust gas flow can be achieved through the wall of the catalyst carrier with a compact design of the catalyst component.

In a further development of the invention, the catalyst carrier has a hollow cylindrical shape and the interior of the catalyst carrier has an upstream inflow opening and is closed at its downstream end.

These measures, on the one hand, achieve a low exhaust gas counterpressure, since the exhaust gas can enter the catalyst carrier essentially via the entire inner wall surface and can exit it again via the outer wall surface. In addition, a good light-off behavior of the catalytic converter is achieved, since the exhaust gas enters the interior and, as a result, heat cannot be released to a surrounding outer wall of the casing before it passes through the catalytic converter support.

In a further development of the invention, means are provided for selectively setting a first flow path through the catalyst carrier and / or a second flow path past the catalyst carrier and essentially parallel to an inlet surface and / or an outlet surface of the catalyst carrier.

These measures can, for example depending on the engine load, one of the two flow paths or a grain combination of the flow paths can be set. In this way, a good starting behavior of the catalytic converter after a cold start and also a low exhaust gas back pressure with little aging of the catalytic converter under high load or full load can be achieved. For example, exhaust gas flaps can be provided in the catalytic converter component, which either open and close automatically as a function of the applied exhaust gas pressure or can be actuated by means of a control unit.

The problem underlying the invention is also solved by an exhaust gas system for an internal combustion engine, in particular with an exhaust gas turbocharger, with a catalyst component, with a housing and a catalyst carrier, in which the housing has a first flow path for exhaust gas flowing into the catalyst component through the catalyst carrier and a second flow path defined past the catalyst carrier and essentially parallel to an inlet surface and / or outlet surface of the catalyst carrier and in which means for directing an exhaust gas stream after a cold start are provided exclusively via the first flow path and, in full load operation, largely via the second flow path.

The setting of the first and / or second flow path can be carried out, for example, by means of a bypass valve of a turbocharger if the exhaust gases from the exhaust gas turbine of the turbocharger are directed via the first flow path and the exhaust gases passing through the bypass valve via the second flow path. As a result, the catalytic converter is only acted upon by the exhaust gas stream that passes the turbine through the first flow path. The turbine extracts energy from the exhaust gas to drive the turbocharger, which leads to a comparatively strong reduction in the exhaust gas temperature, in particular at full load, and reduces the thermal load on the catalytic converter or the aging of the catalytic converter. At full load, which the exhaust gases are preferably largely routed via the second flow path.

The setting of the first and / or second flow path can also be carried out, for example, via exhaust gas flaps, which are carried out by means of a control unit as a function of the engine load, the exhaust gas temperature and / or further operating parameters of the internal combustion engine. Specifically, ^" the choice of the second flow path substantially reduces its aging substantially parallel to an inlet surface and / or outlet surface of the catalyst carrier, since when the second flow path is selected, the flow through the catalyst carrier is negligible or only to an insignificant extent. Especially in the case of full load at high exhaust gas temperatures and As a result, high exhaust gas pressure causes less flow through the catalyst carrier, so that the temperature load and mechanical load are also reduced.

Further features and advantages of the invention result from the claims and the following description of preferred embodiments of the invention in connection with the drawings. The drawings show:

Fig. 1 is a schematic sectional view of a catalyst component according to the invention according to a first embodiment and

Fig. 2 is a schematic sectional view of a catalyst component according to the invention according to a second embodiment.

The schematic sectional view of FIG. 1 shows a catalyst component according to the invention with a housing 10. The housing 10 has a cylindrical outer wall 12 and a likewise cylindrical inner tube 14. The inner tube 14 is perforated and some through openings 16 are indicated in the inner tube 14. The inner tube 14 is surrounded by a catalyst carrier 18, which rests on the outer surface of the inner tube 14 and also has a hollow cylindrical shape. In addition to the preferred circular cylindrical cross-sectional shape, other cross-sectional shapes are also conceivable, such as an oval cross-section, an asymmetrical cross-section, and a cross-section that changes in the axial direction. The catalyst carrier 18 consists of a glass fiber mat, the glass fibers of which are coated in a catalytically effective manner. The glass fiber mat 18 can be designed as a glass fiber knit or glass fiber fabric, but any form of fiber composite made of temperature-resistant fibers such as ceramic fibers or glass fibers is also conceivable. The glass fiber mat is surrounded by a wire mesh 20, which is also hollow cylindrical and is intended to hold the glass fiber mat on the outer surface of the inner tube 14.

Both the glass fiber mat 18 and the wire mesh 20 are flexible and designed in such a way that their pore size can increase and contract again depending on the exhaust gas pressure present in the inner tube 14. When the flow rate of exhaust gas or the exhaust gas pressure is increased, the glass fiber mat 18 and optionally the wire mesh 20 can expand outwards, so that the respective pore size increases. If the pollutants in the exhaust gas passing through are still well converted, the increase in flow resistance compared to conventional catalysts can be reduced.

The housing 10 of the catalyst component is connected to a feed line component 22, via which exhaust gas is introduced into the catalyst component. An exhaust system continues downstream of the catalytic converter component and, for example, a conventional underfloor catalytic converter is provided downstream of the catalytic converter component. The feed line component 22 has a central pipeline 24 which is connected to a schematically illustrated exhaust gas turbine 25 of an internal combustion engine, also not shown. Exhaust gas thus flows from the exhaust gas turbine in the feed line 24, which is indicated by an arrow 26. The feed line 24 is surrounded by a ring line 28 which is connected to a bypass line of the exhaust gas turbocharger, shown schematically. Such a bypass line connects an exhaust manifold of the internal combustion engine directly bypassing the exhaust gas turbine to the exhaust system. The bypass line is usually by means of a bypass valve

29 or so-called wastegate valve opened and closed. The bypass valve 29 is opened and closed, inter alia, depending on the boost pressure present on the intake side of the engine. Exhaust gas flowing into the ring line 28 via the bypass line is by means of two arrows

30 indicated. The bypass valve 29 opens when, for example, the boost pressure exceeds a predetermined threshold. The bypass valve 29 is therefore usually closed at idle and at partial load and the bypass valve 29 opens only in the high-load and full-load range, so that exhaust gas only flows into the ring line 28.

When idling and in the case of partial load, the essentially complete exhaust gas flow thus flows via the feed line 24 into the inner tube 14 of the catalytic converter component. The exhaust gas stream then passes essentially radially outward through the catalyst carrier 18 and through the wire mesh 20 which surrounds the glass fiber mat of the catalyst carrier 18. After the exhaust gas has passed through the wire mesh 20, it is collected in an outer annular space between the outer surface of the wire mesh 20 and the inner surface of the cylindrical outer wall 12 and, starting from this annular space, is emitted from the housing 10 of the catalyst component. The inner tube 14 is in the manner of a blind hole on its downstream, the supply line 24 opposite Overlying end closed, so that all exhaust gas that enters the inner tube 14 must enter the catalyst carrier 18 through the through openings 16. This path of the exhaust gas from the supply line 24 through the catalyst carrier 18 corresponds to a first flow path defined by the housing 12. Effective exhaust gas cleaning is achieved in idle and partial load situations. Especially after a cold start, the coated catalyst carrier 18 is rapidly heated, since the inflowing exhaust gas 26 is conducted directly into the inner tube 14 and therefore cannot pass any heat to the outer wall 12 of the housing 10 before it passes through the catalyst carrier 18. With a higher gas throughput through the exhaust gas turbine, a uniform loading of the catalyst carrier 18 is achieved, since the exhaust gas stream 26 is initially distributed in the inner tube 14 and then passes approximately uniformly through the openings 16 in the inner tube 14 and the catalyst carrier 18. In contrast to conventional, axially flowing catalyst carriers, the high inlet-side loading of axially flowing catalyst carriers is avoided.

In the high-load and full-load range, the bypass valve opens, so that a substantial proportion of the exhaust gas then flows into the catalytic converter component via the ring line 28. As can be seen from FIG. 1, the exhaust gas stream 30 coming via the bypass line directly enters the annular space between the wire mesh 20 and the outer wall 12 of the housing 10. The exhaust gas stream 30 is thereby passed along a second flow path defined by the housing 12 essentially parallel to the outlet surface of the catalyst carrier 18 and leaves the catalyst component without having flowed through the catalyst carrier 18. In the high-load and full-load range, a low exhaust gas back pressure can be realized, whereby an effective exhaust gas cleaning can be achieved by a downstream, conventional underbody catalytic converter. In addition, in the high-load and full-load range, the aging of the lysator carrier 18 significantly reduced, since this is only penetrated by the exhaust gas stream 26, which comes from the exhaust gas turbine. It is conceivable in the high-load and full-load range to conduct all of the exhaust gas via the ring line 28 in order to then completely bypass the catalyst carrier 18. This could be achieved, for example, by arranging and appropriately controlling exhaust gas flaps upstream of the catalytic converter component.

A second embodiment of the catalytic converter component according to the invention is shown in the schematic sectional view in FIG. 2. The structure of the catalytic converter component 32 shown in FIG. 2 is similar to the catalytic converter component shown in FIG. 1. A cylindrical housing 34 with a perforated, cylindrical inner tube 36 is thus provided. The inner tube 36 is surrounded by a catalyst carrier in the form of a glass fiber mat 38 which is catalytically coated and is held on the inner tube 36 by a wire mesh 40.

In contrast to the catalytic converter component of FIG. 1, the inner tube 36 is closed at its upstream end, so that exhaust gas coming from the internal combustion engine cannot enter the inner tube 36 directly. Rather, the exhaust gas coming from the internal combustion engine first enters the outer space between the wire mesh 40 and the outer wall 34 of the housing and from there through the glass fiber mat 38 and the through openings into the inner tube 36. From the inner tube 36, the exhaust gas is then passed on to an exhaust system, which has, for example, a conventional underbody catalytic converter.

Claims

claims

Catalyst component for an exhaust system of an internal combustion engine with a housing and a catalyst carrier arranged in the housing, characterized in that the housing (10) has a first flow path for exhaust gas flowing into the catalyst component through the catalyst carrier (18) and a second flow path past the catalyst carrier (18 ) and defined essentially parallel to an entry surface and / or exit surface of the catalyst carrier (18).

Catalyst component for an exhaust gas system of an internal combustion engine with a housing and a catalyst carrier arranged in the housing, in particular according to claim 1, characterized in that the catalyst carrier (18; 38) defines an interior space and for a through-flow of exhaust gas in the housing (10 ; 34) is arranged.

Catalyst component for an exhaust system of an internal combustion engine with a housing and a catalyst carrier arranged in the housing, in particular according to claim 1 or 2, characterized in that the catalyst carrier (18; 38) is designed to be flexible in such a way that the exhaust gas flow through the catalyst carrier ( 18; 38) available cross-sectional area can be changed depending on the exhaust gas pressure applied to the catalyst carrier (18; 38).

4. Catalyst component according to one of the preceding claims, that the catalyst carrier (18; 38) is formed at least in sections in a knitted or fabric-like manner.

5. The catalytic converter component according to claim 4, wherein the catalyst carrier (18; 38) is formed at least in sections as a glass fiber fabric or glass fiber knitted fabric.

6. Catalyst component according to claim 4 or 5, d a d u r c h g e k e n e z e i c h n e t, that the catalyst carrier is at least partially formed as a wire mesh or wire mesh.

7. Catalyst component according to one of the preceding claims, d a d u r c h g e k e n n z e i c h n e t d a s s the catalyst carrier (18; 38) is covered by a wire mesh.

8. Catalytic converter component according to one of the preceding claims, that the catalyst carrier (18; 38) has a hollow cylindrical shape and is arranged in the housing (10; 34) for an essentially radial flow of exhaust gas.

9. The catalytic converter component according to claim 8, wherein the catalytic converter support (18) is arranged for an essentially radial flow from the inside to the outside.

10. A catalyst component according to claim 8 or 9, characterized in that the catalyst carrier (18; 38) surrounds an inner tube (14; 36) of the housing (10; 34) provided with through-openings (16).

11. The catalyst component according to claim 10, which comprises the inner tube made of porous material.

12. Catalyst component according to claim 10 or 11, d a d u r c h g e k e n e z e i c h n e t, that the inner tube consists at least in sections of wire mesh or wire mesh.

13. Catalyst component according to one of the preceding claims, characterized in that the catalyst carrier (18; 38) defines an interior and the housing (10; 34) defines an exterior space surrounding the catalyst carrier (18; 38), the interior space or the exterior space merely having an inflow opening for exhaust gas.

14. The catalyst component according to claim 13, wherein the catalyst carrier (18) has a hollow cylindrical shape and the interior of the catalyst carrier (18) has an upstream inlet opening and is closed at its downstream end.

15. The catalyst component according to claim 13, wherein the catalyst carrier (38) has a hollow cylindrical shape and the outer space has an upstream inlet opening and is closed at its downstream end.

16. Catalyst component according to one of the preceding claims, characterized in that means for selectively setting a first flow path through the catalyst carrier and / or a second flow path past the catalyst and in the- substantially parallel to an inlet surface and / or outlet surface of the catalyst carrier are provided.

17. Exhaust system for an internal combustion engine, in particular with an exhaust gas turbocharger, with a catalyst component with a housing and a catalyst carrier, characterized in that the housing (10) has a first flow path for exhaust gas flowing into the catalyst component through the catalyst carrier and a second flow path past the catalyst carrier and defined essentially parallel to an inlet surface and / or outlet surface of the catalyst carrier, and means (29) for guiding an exhaust gas flow after a cold start are provided exclusively via the first flow path and largely under full load operation via the second flow path.