EP0757163A1 - Catalyst housing - Google Patents

Abstract

The catalyser includes a housing with two funnels (2) which form a sinusoidal dividing line (5) with each other. The exhaust tubes connect to the funnels (2) in the flow direction (1). The funnels have cylinder-shaped tube sections (3) for the cylinder-shaped exhaust tubes. In the flow direction near to the tube sections the funnels widen. The funnels have a semi-oval outer skin (4) in the areas where they do not contact each other. It is possible to fit a cylindrical catalyser in the area of the engine chamber. Two bend outlets issue in a single, cylindrical exhaust gas tube with a dividing wall in the flow direction. The exhaust gas tube is connected with the cylindrical tube section (3). This tube section, for the exhaust tube, is divided into two parts by a dividing wall and is flanked by a fixation flange.

Description

The invention relates to a catalyst housing for multi-flow, in particular double-flow exhaust systems. For internal combustion engines, it would be advantageous for the optimum yield of the power or the torque to run a separate exhaust line from the outlet of a cylinder to the end of the exhaust system, if possible, in order to oppose the lowest possible resistance to the exhaust gas flow. However, since only a limited installation space is available in the floor assembly of the vehicle for the installation of the exhaust system, the exhaust gases of several cylinders are brought together in a common exhaust line. In this common exhaust line, the exhaust gases flow through the entire exhaust system with their catalysts and silencers. The exhaust gases are brought together in a pant-like tube, the two tube ends corresponding to the pant legs of which are assigned to individual cylinders. The flow cross-section of the exhaust gas line changes in the transition area from the two partial lines corresponding to the trouser legs to the common exhaust line. As a result of this change in cross section, a pressure wave generated by the exhaust gas flow from one sub-branch runs back into the adjacent sub-branch. This is not a problem if the adjacent partial strand itself is not acted upon by an exhaust gas stream at the moment the returning shaft enters. Otherwise, the returning wave would at least impede the outflow of the exhaust gas flow, in extreme cases even completely prevent the decompression of the adjacent cylinder.

The occurrence of the returning wave could in turn be caused by the use of very long pipe sections in the area corresponding to the trouser legs Tube ends of the downpipe are alleviated, but this is practically not possible due to the limited space available. To avoid this problem, the outlets of two cylinders are therefore usually bundled together in a common exhaust line by means of a trouser-like tube, which decompress due to the ignition sequence of the engine neither simultaneously nor briefly in succession. In this way it is effectively prevented that the returning shaft from the pipe end corresponding to the one trouser leg strikes the exhaust gas flow guided in the adjacent pipe end.

In exhaust gas systems with exhaust gas catalysts, it is additionally desirable to mount catalysts, in particular pre- or starting catalysts, as close as possible to the cylinder outlet. This attachment close to the engine ensures that the catalytic converter heats up quickly due to the exhaust gases flowing through it. The warmer the exhaust gases flowing through the catalyst, the faster the catalyst heats up. The catalyst only achieves its full effect when it is heated up.

In the series production of motor vehicles, there is the additional problem that the same body variant is equipped with several engines of different output or different stroke volumes. The main catalytic converter can easily be arranged close to the engine for engines with lower output, which usually also take up little space. With larger engines that completely fill the engine compartment, there is the problem that there is no more space in the engine compartment for arranging the catalytic converter. This problem of space is further exacerbated by the fact that the required catalyst volume is 1 to 1.2 times the engine displacement. The required catalyst volume therefore increases in proportion to the cubic capacity.

It is therefore known - for example from DE-A-27 25 943 - to have several exhaust gas lines open into a catalytic converter housing. In this catalytic converter housing a catalyst monolith with a honeycomb structure is usually arranged. The honeycomb-like structure results from a large number of very thin passage channels running side by side in the flow direction through the monolith. The passage channels are designed so that there is no cross flow between them.

anspringt", also schneller seine Betriebstemperatur, also seine volle Leistungsfähigkeit erlangt.Of course, the use of a single catalytic converter housing has the advantage that the resulting unit is smaller than would be the case if two separate catalytic converter housings were used. Furthermore, the use of only one catalyst housing, that is to say a single sheet metal jacket for a single monolith, has the advantage that the weight of the catalyst is significantly reduced. Because of the reduced effective mass, the temperature radiation from the catalyst housing is also effectively reduced. By reducing the temperature radiation, the thermal behavior of the catalyst is improved in that it is faster

starts ", so it reaches its operating temperature faster, i.e. its full performance.

In addition, the use of only one housing has the advantage that little material is required, which lowers the material costs. In addition, a single part is easier to transport in production. Only one part has to be transported, installed and packed.

Since only one monolith is required for a catalytic converter housing, this further reduces the costs. The necessity of producing only one monolith also brings with it the advantages mentioned in terms of manufacturing technology and logistics. In addition, because of the high proportion of noble metal in the catalyst, it is cost-saving to have to coat only one component with a noble metal.

It is also known to arrange D-shaped exhaust pipes next to one another for introducing two exhaust gas lines into a catalytic converter housing, said exhaust pipes being pivoted through 180 ° to one another. By pivoting through 180 ° they come D flat sides of the D-shaped tubes to lie against each other. A straight dividing line is thus created between the two pipes when the assembly is finished. The disadvantage here is that deformations occur precisely along this straight dividing line due to the heating of the catalyst. In particular if there is a temperature difference between the two exhaust gas flows or, in extreme cases, only one flow is heated, the temperature difference between the two flows also occurs exactly along this straight dividing line. This straight course of the temperature separation line usually leads to a break in the honeycomb-like catalyst monolith. In addition, the fact that the honeycombs of the monolith are usually arranged axially parallel in the catalytic converter housing has an exacerbating effect, so that a straight dividing line here acts as a predetermined breaking line for the ceramic.

Based on these problems, the invention has for its object to design an exhaust gas catalytic converter so that it is as space-saving as possible and at the same time has a high thermal load capacity.

vorprogrammiert" ist.The solution to the problem consists in an extension of the dividing line between the two adjacent exhaust pipes and the inevitably associated enlargement of the separating area on the one hand and the distribution of the temperature gradient over as many exhaust gas channels of the honeycomb-like structured monolith on the other. To achieve the object, it is therefore necessary that the dividing line between the two exhaust gas lines has an essentially odd course. This odd course of the dividing line also has the advantage that less thermal stress occurs along the dividing line. In addition, an odd dividing line has the advantage that, in contrast to a straight dividing line, there is no expansion of the housing in the region of the dividing line, which results in a voltage drop in the swelling mat holding the ceramic monoliths in the housing. A voltage drop in the source mat must be prevented simply because otherwise the catalytic converter will fail completely

is preprogrammed ".

An S-shaped or a sinusoidal course of the dividing line between the two flows of the exhaust line is particularly advantageous.

In this context, it should be noted that the exhaust lines or the exhaust gas flows of the exhaust system in the areas outside the one-piece catalytic converter block are usually cylindrical. The cylindrical tubes then open into D-shaped funnels according to the prior art or into funnels with a curved dividing line according to the invention, preferably into funnels with a sinusoidal dividing line. The funnels are in turn connected to the catalyst housing. The exhaust gas streams flow from the individual floods into the catalytic converter housing and the monoliths arranged therein, flow through the monolith in the individual channels that form the honeycomb structure of the monolith and flow out into conventional exhaust pipes via two further funnels adapted at the catalytic converter outlet.

The use of exhaust pipes with a sinusoidal dividing line also has the advantage that two planes of symmetry are present, so that two identical funnels can be rotated next to each other by 180 °. Only a single funnel tool is then required to manufacture the funnels, which advantageously reduces the tool costs.

However, it should be expressly pointed out that the invention can be implemented with any other odd dividing line, in particular with any zigzag dividing line.

Fig. 1

eine Draufsicht auf ein zweiflutiges Katalysatorgehäuse,

Fig. 2

eine Seitenansicht des Katalysatorgehäuses gemäß Fig. 1, gesehen in Strömungsrichtung,

Fig. 3

eine Seitenansicht analog Fig. 2 einer weiteren Ausführungsform auf den Trichtereingang,

Fig. 4

die Ausführungsform gemäß Fig. 3 mit einer Seitenansicht auf den Trichterausgang.

On the basis of the two exemplary embodiments shown in the figure drawings, the invention is explained with further features and advantages. Show it:

Fig. 1

a plan view of a double-flow catalyst housing,

Fig. 2

2 shows a side view of the catalytic converter housing according to FIG. 1, seen in the flow direction,

Fig. 3

3 shows a side view analogous to FIG. 2 of a further embodiment of the funnel entrance,

Fig. 4

the embodiment of FIG. 3 with a side view of the funnel exit.

The funnels 2 connect to the exhaust pipes (not shown in the drawings) in the direction of flow 1. The funnels 2 have cylindrical pipe sections 3 for the cylindrical exhaust pipes. In the flow direction 1 next to the pipe sections 3, the funnels 2 expand. The funnels 2 have a semi-oval outer skin 4 in those areas in which they do not touch each other. The funnels 2 also form the S-shaped or sinusoidal dividing line 5 with one another.

In a second embodiment according to FIGS. 3 and 4, it is possible to arrange an essentially cylindrical main catalytic converter in the area of the engine compartment. Here, two manifold outlets each open into a single, cylindrical exhaust pipe with a partition in the direction of flow. This exhaust pipe is connected to the cylindrical pipe section 3 in FIG. 3. The pipe section 3 for the exhaust pipe, which is divided in two by means of a partition, is still flanked by a fixing flange 7. Following the pipe section 3, the funnel 2 also widens in the flow direction 1 in this embodiment. In the area of the pipe section 3, the flow channel is initially divided into two parts by a straight partition 6 aligned with the partition in the exhaust pipe. The partition 6 is also S-shaped in the further course. The partition 6 is thus deformed into a sinusoidal dividing line 5. This is clearly visible in the area of the funnel outlet 8 shown in FIG. 4. In the direction of flow 1, the sheet metal jacket 9 of the actual catalyst housing adjoins the funnel outlet 8. The monolith, which cannot be seen in the drawings, is held in the sheet metal jacket 9 by the swelling mat 10.

In the embodiment shown in FIGS. 3 and 4 with an S-shaped partition 6, it must also be taken into account that partition plates in particular tend to flutter at high temperatures around 1000 ° C., which is disadvantageous in terms of noise and in particular affects the strength of the catalyst because can destroy the divider 6 itself by fluttering. This self-destructive effect due to the flutter is effectively avoided by the sinusoidal design of the S-shaped separating plate.

Reference list

1

Flow direction

2nd

funnel

3rd

Pipe section

4th

Outer skin

5

parting line

6

partition wall

7

Fixing flange

8th

Funnel exit

9

Sheet metal jacket

10th

Swelling mat

Claims (2)

Catalytic converter with a housing consisting of a sheet metal jacket (9) and a monolith arranged in the housing, two exhaust lines being connected in line with the monolith by means of two connection funnels (2),
characterized,
that both funnels (2) form an odd dividing line (5) with each other. Catalyst according to claim 1,
characterized,
that the dividing line (5) formed by the two funnels (2) has a sinusoidal shape.

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