EP1760285A2 - Catalyst chamber - Google Patents

Abstract

An exhaust gas treatment device comprises a catalyst chamber (20) having two halves (21, 22) forming an exhaust gas channel (23) which is formed as one part in the chamber halves. Preferred Features: The device has an outer housing (10) which is divided into gas-tight regions (18, 19) by the catalyst chamber. An exhaust gas outlet opening (25) of the exhaust gas channel is arranged on the end facing away from the catalyst element (33). Air passages are provided in a front shell (11) for allowing fresh air to pass into the exhaust gas treatment device.

Description

The invention relates to an exhaust system for an internal combustion engine having at least one catalyst element for converting the combustion exhaust gases. This exhaust system can be used for a four-stroke or a two-stroke petrol engine. Since the exhaust system itself has a particularly compact design, it can also be used for hand-operated machines such. As gasoline engine operated cutters, chainsaws, hedge trimmers or the like can be used. Generic exhaust systems have an outer housing, which contains at least one rear shell and a front shell. Furthermore, these exhaust systems are equipped with a catalyst chamber in which at least one catalyst element is arranged and is provided with an exhaust gas duct from which exhaust gas is passed out of the catalyst chamber.

It is known from the prior art to equip exhaust systems for reducing the pollutant emission of internal combustion engines with catalyst elements. By using the catalyst elements, a post-treatment of the exhaust gas with the components contained in the exhaust gas is made possible. In this case, for example, the existing hydrocarbons are converted by means of the residual oxygen content to carbon dioxide or carbon monoxide and water. However, heat is released in this chemical cleaning process or conversion process, which additionally heat the already hot exhaust gases from the internal combustion engine. For example, the conversion of hydrocarbons releases heat to a great extent, which can destroy conventional honeycomb catalysts, especially in the case of hydrocarbon-emitting 2-stroke engines. For this reason, catalysts in the form of coated sheets, expanded metal mesh or wire mesh are used, which have proven to be sufficiently resistant, and which are less heat-stressed by their small depth. To now prevent the entire outer casing of the exhaust system With the hot converted exhaust gases comes into contact, so-called catalyst chambers are used for the catalysts, from which then the purified exhaust gases are passed through an adjacent exhaust duct directly or indirectly from the outer housing to the outside. By this measure it is achieved that the heat load of the housing material is reduced, although a catalyst element is used.

The use of such catalyst chambers in exhaust systems is inter alia from the document DE 38 29 668 A1 known. In the exhaust system disclosed therein, a catalyst chamber is used which has a large opening, whereby the not yet treated exhaust gases are introduced. In this case, the introduced exhaust gases first flow through the catalyst element in order to then reach the exhaust gas channel. Here, the catalyst chamber is structurally separated from the exhaust duct and is held together only via a plug connection or welded connection. Thus, a plurality of parts (sheet metal parts) are used to form the catalyst chamber and the subsequent exhaust passage. This is on the one hand production technology very expensive and is reflected in manufacturing costs and on the other hand arise different temperature expansions through the use of different parts, which are easily generated high thermal stresses in the components.

Against this background, the invention is therefore the object of the invention to provide an exhaust system with a catalyst chamber, which consists of a few parts and is inexpensive to manufacture. Furthermore, harmful thermal stresses in the components of the exhaust system should be largely avoided.

This object is achieved by the measures listed in the characterizing part of claim 1.

According to the invention, the exhaust system for an internal combustion engine has an outer housing, which has at least one rear shell and one front shell contains. So that the combustion exhaust gas from the engine does not enter the environment without being cleaned, a catalyst element is additionally provided in the exhaust system, which is arranged in a catalyst chamber. It goes without saying that a second catalyst chamber can be arranged with a catalyst element within the exhaust system, which can be connected either in parallel or in series with the first catalyst chamber. So that the exhaust gas can escape from the catalyst chamber, an exhaust gas passage is provided, wherein the catalyst chamber simultaneously or additionally forms the exhaust gas passage. In this case, the catalyst chamber contains at least two chamber halves, wherein the exhaust gas channel is provided in at least one chamber half of the same material and in one piece. Consequently, the exhaust duct is formed by at least one chamber half. Thus, the exhaust passage is not an additional component, which is arranged by a somewhat degenerate compound on the catalyst chamber, but the catalyst chamber and the exhaust passage form an indivisible unit. It goes without saying that, of course, the exhaust duct can also be formed by both chamber halves. In this case, the exhaust duct may have any cross-sections.

Further advantageous embodiments of the exhaust system are described in the dependent claims 2-18.

By the solution described above, it is possible that the exhaust duct is formed in one or more chamber halves. This indentation can be done for example by deep drawing, Senkpressen, punching or other transformations. Since the chamber halves of the catalyst chamber can consist of a piece of sheet metal, the exhaust gas channel can be made simultaneously with the formation of the catalyst chamber. Consequently, no additional manufacturing step for the creation of the exhaust duct is necessary. It also becomes clear that the shape, that is to say the cross-section of the exhaust gas duct and the course of the exhaust gas duct, can be achieved simply by the deformation of the chamber half. For example, the exhaust duct may be curved and / or meander-shaped in order to lengthen the length of the exhaust duct in this way. By a sufficient length of the exhaust duct can Flame formation outside the exhaust system can be avoided, even if the exhaust duct is led directly into the open or into the environment.

In order to divide the interior of the exhaust system or the outer housing into at least two separate areas, the catalyst chamber can be used. For this purpose, the catalyst chamber can be configured in terms of area such that it, for example, fills or closes a complete cross section through the exhaust system in terms of area. Required, at least one chamber half is configured circumferentially equal to the cross section of the exhaust system. Of course, both chamber halves may have the same circumferential shape to close a cross section through the exhaust system. By this measure, the exhaust system is divided into at least two separate areas, which may even be configured gas-tight to each other.

In this case, an area can be used as a muffler, in which the unconverted exhaust gas passes first. This area is provided near the cylinder in the exhaust system. After the exhaust gas has passed through the catalyst chamber and the exhaust duct, it can reach a wider area or be led directly into the environment. Thus, the further area serves primarily as heat protection from the converted exhaust gas. This area can also be filled with insulating material such as insulating wool.

As already mentioned, an exhaust gas outlet opening of the exhaust gas channel, which is arranged away from a catalyst element end of the channel, terminate in the interior of the exhaust system or directly to an exhaust gas outlet of the outer housing. In order to achieve additional cooling of the outer housing, ventilation openings may be provided in the outer housing, in particular in the front shell, whereby cool fresh air enters the exhaust system. It is certainly expedient that this fresh air passes only in a closed area of the exhaust system, which is not filled with the unconverted exhaust gases. To increase the cooling effect, a nozzle, in particular a venturi nozzle / injector nozzle, can additionally be provided at the exhaust gas outlet opening of the exhaust gas duct be provided. This causes the fresh air that has entered through the ventilation openings to be entrained with the hot, converted exhaust gas as it exits. The use of the Venturi nozzle creates a cooling airflow, which not only cools the converted hot exhaust gas but also part of the outer housing.

In a particular variant of the exhaust system according to the invention, the front shell of the outer housing simultaneously forms part of the catalyst chamber. Consequently, in this variant, the front shell of the outer housing could be replaced by a chamber half of the catalyst chamber. In this variant, it is obvious that the exhaust gas outlet opening of the exhaust duct leads directly into the open. Overall, this variant of the exhaust system comes with very few components. However, since a partial surface of the exhaust system is very hot, which comes directly into contact with the converted exhaust gases, it is advisable to provide an additional heat shield in front of the hot area of the exhaust system. This heat shield can for example consist of an aluminum shell or sheet in order to dissipate the existing heat well and thus to achieve an acceptable temperature level.

In order to achieve a high conversion rate in the purification of the exhaust gas, it is advisable to design at least one catalyst element over a large area. If grid-like, perforated plate-like or net-like catalyst elements are used, they can be arranged next to one another in order to achieve a higher stability in the arrangement of the catalyst elements next to one another. Of course, honeycomb catalyst elements could also be used. It is also conceivable that at least two catalyst elements are arranged one behind the other in the flow direction of the exhaust gas. In this context, one speaks of a series connection of the catalyst elements. As already mentioned, it is also possible to arrange two catalyst chambers in succession. In this case, an exhaust gas outlet opening of the first exhaust gas channel can end in the inlet openings of the second catalyst chamber.

In addition, it is conceivable to arrange two or more catalyst chambers side by side in parallel.

In order to arrange the existing catalyst element stationary in the catalyst chamber, spacers are provided in at least one chamber half. These spacers can also be realized by simple transformations of the chamber halves. Thus, the catalyst element can be held by the spacers used positively and / or non-positively in the catalyst chamber. If two catalyst elements are provided one behind the other in a catalyst chamber, they can be kept over an additional spacer frame to a predetermined distance. The spacer frame itself consists of a metal sheet or the like, which is punched out inside, so that the frame hardly causes a flow resistance between the catalyst elements. In addition, further spacers may be provided on the spacer frame to increase the sheet thickness of the frame and thus the distance between the catalyst elements.

To avoid heat-related harmful voltages, it is expedient to provide at least one connecting element, whereby the catalyst chamber or the halves of the catalyst chamber are held together. Preferably, this connecting element is to be arranged centrally in the region of the catalyst elements. By this connecting element, the entire catalyst chamber and the catalyst elements arranged inside and a possibly existing spacer frame and spacers is attached. In this case, a reversibly releasable connection element can be used, as well as, for example, a screw / nut connection. Of course, a rivet, a welding point or a Torx connection can be used as a connecting element. In order to simplify the assembly or assembly of the catalyst chamber, the nut may be fixed to a chamber half, for example by a welded connection or a positive connection.

In order that the structure of the exhaust system is further simplified, it is conceivable that the catalyst chamber is clamped by its edge regions between the rear shell and the front shell of the outer housing. Thus, alone by the assembly of the front and rear shell, the catalyst chamber can be held together. Also, the catalyst chamber can be held together even in its edge regions by a bead.

For a better cooling of the catalyst chamber can be achieved, additional cooling surfaces may be provided on the catalyst chamber. These additional cooling surfaces can be made particularly elegant if at the same time the outer casing of the exhaust system is to be divided into two areas by the catalyst chamber. Thus, in addition to the discharge channel, additional surfaces can be provided in both chamber halves on the left and right sides, by means of which the separation of the outer housing into two regions is simultaneously effected.

In order to increase the conversion rate of the catalyst element, it is advisable that a catalyst element is traversed transversely to the flow direction of the exhaust gas passage. By this measure, a large part of the exhaust gas flows several times through the transversely arranged catalyst element, before it can get into the exhaust duct. Of course, the exhaust system according to the invention also works with a catalyst element, which is arranged in the same flow direction to the exhaust duct.

So that the performance of the internal combustion engine is not reduced by the exhaust system, it is advisable to build the lowest possible flow resistance in the exhaust system. For this purpose, a chamber half, which is arranged adjacent to the rear shell with an exhaust gas inlet, have at least one inlet opening, through which the exhaust gas passes into the catalyst chamber. Alternatively or additionally, at least one outlet opening may be present in the other chamber half, which is arranged adjacent to the front shell, whereby the exhaust gases from the catalyst chamber directly or indirectly gets into the open air. The outlet opening is arranged in the front shell. Consequently, the exhaust gas flows more or less once across the exhaust system before it gets cleaned into the environment.

Fig. 1

in dreidimensionaler Explosionsansicht eine erfindungsgemäße Abgasanlage mit einem Katalysatorelement und einem gradlinigen Abgaskanal sowie einem Isolationselement,

Fig. 2

in dreidimensionaler Explosionsansicht eine ähnliche erfindungsgemäße Abgasanlage - wie in Fig. 1 - mit zusätzlichen Lüftungsdurchbrüchen in der Vorderschale und einem Injektor, und

Fig. 3

in dreidimensionaler Explosionsansicht eine weitere erfindungsgemäße Abgasanlage mit zwei Katalysatorelementen und einem mäanderförmigen Abgaskanal.

The invention will be explained in more detail with reference to the accompanying drawings in different embodiments. In a purely schematic representation:

Fig. 1

in a three-dimensional exploded view of an exhaust system according to the invention with a catalyst element and a straight-line exhaust duct and an insulation element,

Fig. 2

in a three-dimensional exploded view of a similar exhaust system according to the invention - as in Fig. 1 - with additional ventilation openings in the front shell and an injector, and

Fig. 3

in a three-dimensional exploded view of another exhaust system according to the invention with two catalyst elements and a meandering exhaust duct.

FIG. 1 shows a first variant of the exhaust system 100 according to the invention. In this case, the outer housing 10 of the exhaust system 100 is substantially cuboid. This consists in the present case of a front shell 11 and a rear shell 12, wherein the invention is not limited to a two-part housing 10. In the rear shell 12, an exhaust gas inlet 16 is provided for the incoming exhaust gas from the internal combustion engine. Since the opening surface of the rear shell 12 and the front shell 11 is closed by the existing catalyst chamber 20, in the front shell 11, a first region 18 and in the rear shell 12, a second region 19, wherein the two regions 18, 19 are separated from each other gas-tight. Thus, the exhaust gas that has entered must enter from the second region 19 through the five circular inlet openings 24 into the catalyst chamber 20. The inlet openings 24 are provided for this purpose in the second chamber half 22. Now that the exhaust gas into the catalyst chamber 20 is reached, it is passed through a catalyst element 33. The actual catalyst chamber 20 is designed cuboid, so that the rectangular catalyst element 33 can be arranged to save space. The cuboid recesses of the catalyst chamber 20 have been formed by a forming process in the two chamber halves 21 and 22. After the exhaust gas has been converted in the catalyst element 33, it can now enter the exhaust gas channel 23. This is a straight line in the first and second chamber half 21, 22, as the actual catalyst chamber, incorporated. In this case, the exhaust gas channel 23 extends over the entire width or length of the catalyst element 33. Thus, a catalyst-side opening 27 of the exhaust gas channel 23 begins approximately flush with the catalyst element 33.

In order to position the catalyst element 33 in a simple manner in the catalyst chamber 20, two spacers 36 are provided, which are provided between the first chamber half 21 and the catalyst element 33 and between the catalyst element 33 and the second chamber half 22. The two chamber halves 21, 22 of the catalyst chamber 20 are held together by the connecting element 32, which is guided by the two spacers 36. The reversibly releasable connecting element 32 is configured in two parts in the present case and consists for example of a screw and a nut.

The converted exhaust gas passes from the exhaust duct 23 through the outlet opening 25. This can end within the outer housing 10 below the front shell 11. It is also conceivable that the outlet opening 25 is also performed by an exhaust gas outlet 13 in the front shell 11, so that the exhaust gas passes directly into the open. Thus, the front shell 11 is not unnecessarily heated, isf an additional insulating member 37 between the catalyst chamber 20 and the first chamber half 21 and the front shell 11 is provided. This insulating element 37 may for example consist of a cushion of glass fibers.

FIG. 2 discloses a similar embodiment of the exhaust system 100 according to the invention from FIG. 1. The rear shell 12 and the catalyst chamber 20 are of identical construction. Only the outlet opening 25 of the exhaust duct 23 and the front shell 11 have structural changes in comparison to the exhaust system 100 of Figure 1. 2, the outlet opening 25 is open, in which an annular gap is provided, are entrained by the gases from the first region 18 with the exiting exhaust gas stream. In addition, for example, an injector 26 or a nozzle 26, in particular venturi, is used at the exhaust gas outlet 13, whereby a cooling flow is generated in the first region 18 under the front shell 11. For this purpose, additional ventilation apertures 14 are provided in the front shell 11, through which fresh air can penetrate into the exhaust system 100. This fresh air is drawn by the generated suction at the exit of the exhaust gas under the front shell 11. By this forced convection cooling of the front shell 11 takes place. At the same time, the hot, converted exhaust gases are mixed with the intake fresh air as it exits the injector 26, which also takes place cooling of the exhaust gas. In the embodiment variant of the exhaust system 100 from FIG. 2, the smaller outlet opening 25 can protrude into the injector 26 or the nozzle 26.

In the figure 3, although the outer housing 10 is constructed identical to the exhaust system 100 of Figure 1, but a differently configured catalyst chamber 20 is used. In addition, two catalyst elements 33 and 34 are used, which are arranged within the catalyst chamber 20. In order to produce a certain minimum distance between the perforated plate-like catalyst elements 33, 34, a spacer frame 35 is used. This spacer frame 35 consists essentially of a rectangular sheet metal, wherein additional spacers are provided in the corner regions in order to increase the distance between the catalyst elements 33, 34. The spacer frame 35 is stamped out in the middle, so that the exhaust gas without flow resistance can pass from the first catalyst element 33 to the second catalyst element 34. In addition, spacers 36 can be inserted between the catalyst elements and the chamber halves 21, 22. In the present embodiment, a total of six large-scale inlet openings 24 are provided in the first chamber half 21, whereby the previously unconverted exhaust gas enters the catalyst chamber 20. So that the catalyst elements 33, 34 do not come into direct contact with the chamber halves 21, 22 over a large area, additional spacers 31 are formed in the chamber halves 21, 22. This indentation can be done for example by punching or pressing or deep drawing. The adjoining the catalyst chamber 20 exhaust duct 23 is configured meandering. This exhaust passage 23 is formed in the first chamber half 21 and the second chamber half 22. It could also be sufficient if the exhaust duct 23 were formed only in a chamber half 21 or 22.

On the one hand to separate the first region 18 from the second region 19 of the interior of the exhaust system 100, the first chamber half 21 is configured over a large area, so that in this way the complete cross section of the outer housing 10 is covered. At the same time, the surfaces on the left and right sides of the exhaust duct 23 serve as cooling surfaces 28, whereby additional heat of the exhaust duct 23 can be derived. In order to save as much material as possible, these cooling surfaces 28 can be dispensed with in the second chamber half 22. Of course, the cooling surfaces 28 may be provided only on the second chamber half 22. In addition, the outer housing remains by the all-round distance to the channel or to the chamber at a low temperature level.

To close the two chamber halves 21, 22 gas-tight, the two chamber halves 21, 22 are held by a connecting element 32. Due to the one-point fixation, the catalyst element does not tend to buckle as it expands due to heating. This connecting element 32 again consists of a screw and a nut. However, a rivet connection or the like can also be used. In addition, the two chamber halves 21, 22 can be held together only in their edge regions 29, 30. This can be done for example by the clamping of the chamber halves between the front shell 11 and the rear shell 12. Also, the two chamber halves 21, 22 welded or soldered.

As already described, the exhaust duct 23 in FIG. 3 is meander-shaped and resembles the number "7". In this case, the catalyst-side opening 27 is not arranged over the entire width of the catalyst elements 33, 34, but overlaps only a small part. The converted exhaust gas must pass through this opening 27 into the exhaust duct 23, in order then to be guided through the various bends or creases 23c in the exhaust gas duct 23. By these kinks and bends 23 c, the length of the exhaust passage 23 can be extended. As a result, a flame outside the exhaust system 100 can be avoided.

Finally, it should be mentioned that the technical features described above can be used individually or in combination in the exhaust system 100 according to the invention, provided that they do not exclude each other. The exhaust system 100 can also be used as an initial, middle or end position for a partially existing exhaust system.

LIST OF REFERENCE NUMBERS

100

exhaust system

10

outer casing

11

front shell

12

backshell

13

Exhaust outlet in 11

14

Ventilation breakthroughs in 11

15

Border area of 11

16

Exhaust inlet in 12

17

Border area of 12

18

first area

19

second area

20

catalyst chamber

21

first chamber half

22

second chamber half

23

exhaust duct

23a

lower part of the exhaust duct

23b

upper part of the exhaust duct

23c

Bow or kink in the exhaust duct

24

Entrance opening of 20

25

Outlet opening of 23

26

Injector or nozzle, in particular Venturi nozzle

27

catalyst side opening of 23

28

cooling surface

29

Border area of 21

30

Border area of 22

31

spacer

32

Connecting element (eg screw and nut)

33

Catalyst element a)

34

Catalyst element b)

35

Spacer frame (with spacers)

36

spacer

37

insulation element

Claims (18)

Exhaust system (100) for an internal combustion engine with an outer housing (10) which contains at least one rear shell (12) and one front shell (11), and
with a catalyst chamber (20), in which at least one catalyst element (33, 34) is arranged, and
with an exhaust gas duct (23) from which exhaust gas is passed from the catalyst chamber (20), characterized in that the catalyst chamber (20) additionally forms the exhaust gas duct (23), the catalyst chamber (20) having at least two chamber halves (21, 22) and the exhaust passage (23) in at least one chamber half (21, 22) of the same material and is provided in one piece. Exhaust system according to claim 1, characterized in that the exhaust gas channel (23) in at least one chamber half (21, 22) is formed. Exhaust system according to claim 1 or 2, characterized in that an interior of the outer housing (10) through the catalyst chamber (20) in at least two separate (gas-tight) areas (18, 19) is divided. Exhaust system according to one of the preceding claims, characterized in that an exhaust gas outlet opening (25) of the exhaust gas duct (23), which is arranged away from a catalyst element (33, 34) end of the exhaust gas duct (23), at an exhaust gas outlet (13) of the outer housing ( 10) is provided. Exhaust system according to one of the preceding claims, characterized in that in the front shell (11) ventilation openings (14) are provided, whereby fresh air enters the exhaust system (100). Exhaust system according to one of the preceding claims, characterized in that the exhaust gas outlet opening (25) of the exhaust gas channel (23) has a venturi nozzle (26) or an injector pump. Exhaust system according to one of the preceding claims, characterized in that the front shell (11) of the outer housing (10) forms part of the catalyst chamber (20). Exhaust system according to one of the preceding claims, characterized in that the exhaust duct (23) is curved and / or meander-shaped. Exhaust system according to one of the preceding claims, characterized in that at least one catalyst element (33, 34) is designed over a large area. Exhaust system according to one of the preceding claims, characterized in that at least two catalyst elements (33, 34) are arranged one behind the other in the flow direction of the exhaust gas. Exhaust system according to one of the preceding claims, characterized in that at least one catalyst element (33, 34) by means of spacers (31) which are formed in at least one chamber half (21, 22), in the catalyst chamber (20) is arranged stationary. Exhaust system according to one of the preceding claims, characterized in that a spacer frame (35) between two catalyst elements (33, 34) is arranged to generate a distance between the two catalyst elements (33, 34). Exhaust system according to one of the preceding claims, characterized in that the catalyst chamber (20) by at least one connecting element (32) is held together. Exhaust system according to claim 13, characterized in that in the catalyst chamber (20) existing elements are fixed by the connecting element (32) and positioned at least substantially free of stress. Exhaust system according to one of the preceding claims, characterized in that the catalyst chamber (20) by a beading in the edge region (29, 30) of the chamber halves (21, 22) is held together. Exhaust system according to one of the preceding claims, characterized in that the catalyst chamber (20) has additional cooling surfaces (28) and thus an all-round distance from the outer housing. Exhaust system according to one of the preceding claims, characterized in that at least one catalyst element (33, 34) is traversed transversely to the flow direction of the exhaust gas channel (23). Exhaust system according to one of the preceding claims, characterized in that in a chamber half (21, 22), which is arranged adjacent to the rear shell (12) with an exhaust gas inlet (16), at least one inlet opening (24) is provided, through which the exhaust gas in the catalyst chamber (20) passes, and
that in another chamber half (21, 22), which is arranged adjacent to the front shell (11), at least one outlet opening (25) in the region of the exhaust outlet (13) of the front shell (11) is present, whereby the exhaust gases from the catalyst chamber (20) get directly or indirectly into the open.

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