KR20070112245A - Air gap insulated exhaust manifold - Google Patents

Abstract

The invention relates to an air-gap insulated exhaust manifold which comprises several displaceable, interlocked inlet pipes (2 - 6) which lead to a collecting chamber (18). The inlet pipes (2 - 6) are surrounded by an outlet pipe (10), whereby an air gap (20) is produced between the inlet pipes and the outlet pipes (2 - 6 and 10). Two shell-like intermediate sheets of steel (22, 24), which supplement the cavity, are provided in said air gap (20), which prevent the inlet pipe (10) from being directly exposed to leakages. The intermediate sheets of steel (22,24) are produced by deep-drawing an uneven film.

Description

Exhaust manifolds insulated through air gaps {AIR GAP INSULATED EXHAUST MANIFOLD}

The invention comprises at least one cylinder side inlet tube and at least one exhaust pipe side outlet tube, the tubes being disposed on each other in the collection chamber to form an air gap at least partially surrounding the collection chamber. An exhaust manifold is insulated through a gap.

Especially for exhaust manifolds for engines operated by gasoline, the tubes are exposed to significant heat loads. This is why there are so-called air gap adiabatic exhaust manifolds as disclosed, for example, in DE 197 52 773 A1. In the manifold region, a plurality of inlet tubes, usually connected to the engine block by the flanges in the cylinder outlet region, are usually gathered. This inlet tube opens to the collection chamber from which gas flows into the outlet tube which is connected to the exhaust tube by a flange or forms part of the exhaust tube. The inlet tube and the outlet tube are fitted to each other, forming an insulating gap between them in the collection chamber region. In this context, there is a problem and secondary importance for the configuration in which one of the two tubes forms an inner tube and the other forms an outer tube. It is believed that the inlet and outlet tubes are placed in each other in such a way that they can move in the broadest sense in order to be able to compensate for the substantial linear expansion of the tube in operation, so that the load on the tube is reduced. For this purpose, the inlet and outlet tubes are usually welded to the flange on the engine block side. However, the inner tube freely protrudes into the interior of the outer tube so that there is no fear of bending due to the tubes moving relative to each other during thermal expansion. The inlet and outlet tubes are not arranged to be airtight with respect to one another, since a number of inlet tubes are usually fitted to one another and are able to move relative to one another for length compensation. This causes an inevitable leakage flow in the capture chamber area to impinge on the outlet tube. In particular, at the point of leakage of the inner tube, the outer tube will have a so-called hot spot, that is, a point area which receives the maximum heat load.

It is an object of the present invention to reduce the heat load of the outer tube in a very simple manner in the region of the collection chamber.

For that purpose, the exhaust manifold of the type mentioned at the outset is provided with at least one intermediate plate disposed in the air gap. This intermediate plate usually does not have any load carrying function and has an outer tube shielding function.

This is the reason why the intermediate plate can advantageously be configured so thin that its maximum thickness is 0.3 mm, preferably 0.15 mm, in a sense that the intermediate plate is only in the form of a foil sandwiched therebetween. During the experiment, the foil-shaped thin sheet metal alone was found to be quite sufficient to prevent hot spots.

It would be desirable to provide multiple intermediate plates.

Such a number of intermediate plates may surround the collection chamber completely or most of it, and thus may be possible as an intermediate wall between the outer tube and the inner tube.

Preferably, the intermediate plates have a shell-like structure, and in other embodiments may be complementary to one another to form a hollow body. If necessary, the hollow body may be formed of one intermediate plate. In this context, "shelled" structure means an uneven plate with an arcuate cross section, preferably a semicircular cross section.

It is sufficient if the intermediate plates can simply fit into each other at their contact edges.

The intermediate plates or shells need not be secured to one another, for example by brazing or welding, but only by fitting one to the other will already be sufficient to form a closed hollow body to a sufficient degree for the required use. It has been found that such hollow bodies do not need to be confidential or generally confidential.

The intermediate plate is significantly smaller in thickness and significantly more flexible than the inlet or outlet tube, so that in the preferred embodiment the intermediate plate has no load bearing function. The maximum thickness reaches at most 0.3 mm, preferably 0.15 mm. The experiment confirmed that excellent insulation performance from the outer wall to the inner wall was obtained even at the maximum limit of 0.10 mm.

The exposed inner side of the outer wall, which consists of an inlet tube or an outlet tube, defining an air gap (depending on which tube is placed outward) is covered by at least 80% by an intermediate plate, which intermediate plate In particular, it is located in front of the hot spot.

Due to the intermediate plate, the air gap is divided into an inner part and an outer part, thereby improving the thermal insulation effect.

According to one embodiment, the intermediate plate has protrusions that function as spacers, whereby the intermediate plate has two small contact areas, for example point contact areas, with the inlet and / or outlet tubes. It can be clamped between the tubes.

The production of the intermediate plate is carried out in a very simple manner, for example using so-called corrugated foils suitable for use in the present invention, i.e. foils having a non-flat and non-uniform surface whose back side forms a shape opposite to the front side. Deep drawing can be done in a very simple way. Due to such irregular surfaces, sufficient material can still be utilized during deep drawing, thus reducing the risk of crack formation.

The intermediate plate should preferably have a shape corresponding to the outer wall of the collection chamber. In this regard, the term "correspondence" means that the foil must not be in contact with the entire surface area inside the outer wall, as well as having a generally uniform spacing to the outer wall.

The intermediate plate should simply be inserted into the air gap without securing it to the inlet or outlet tubes. However, the clamping effect between the two tubes is sufficient as already explained above.

According to a preferred embodiment, not only one inlet tube is provided, but a plurality of cylinder-side inlet tubes fitted to each other so as to be movable relative to each other are provided to be opened to the collection chamber.

In this case, the intermediate plate preferably surrounds all inlet tubes provided in the collection chamber region.

Other features and advantages of the invention will be apparent from the following detailed description and the accompanying drawings, which are incorporated by reference.

1 is a schematic longitudinal cross section through an exhaust manifold according to the invention,

2 is a cross-sectional view taken along the line II-II of FIG. 1,

3 is a cross-sectional view taken along line III-III of FIG. 1.

1 shows an air gap insulation exhaust manifold in which three cylinder-side inlet tubes 2, 4, 6 are connected to each other. The cylinder outlet is symbolized by the circle 8. Each cylinder 8 has its own inlet tubes 2, 4, 6 associated with it. These inlet tubes 2, 4, 6 enter the exhaust pipe side outlet tube 10 and part 9 (FIG. 3) used to weld the inlet tubes to the cylinder block flange 11 out of the cylinder. It has a free protrusion (see FIGS. 2 and 3) used to further extend the tubes. The exhaust pipe side outlet tube 10 consists of upper and lower shells 12 and 14 and has an outlet side flange 16 on which the exhaust gas tube is to be fixed. The outflow tube 10 is also welded to the cylinder block flange 11 on the inlet side as well. The outlet tube 10 surrounds the inlet tube 2, 4, 6 in the region where the inlet tubes 2, 4, 6 are joined to each other at the side of the flow. In this configuration, the inlet tubes 2, 4, 6 are fitted to each other. To this end, the intermediate inlet tube 4 has a laterally wider receiving opening facing in the opposite direction and movably receiving the left and right inlet tubes 2, 6. In particular, the inlet tubes (2, 4, 6) fitted to each other in the region of the outlet tube (10) has a generally long cylindrical shape and in the left part of the left inlet tube (2) when considered in the drawing of FIG. A collection chamber 18 is formed that extends to the right side of the tube 6.

An air gap 20 is formed between the inlet tubes 2, 4, 6 and the inside of the outlet tube 10 that has a substantially uniform thickness and functions to insulate.

Apart from the adiabatic function, the air gap 20 provides free expansion of the inlet tubes 2, 4, 6 with respect to the outlet tube 10, in which the inlet tube and the outlet tube are connected to each other only at one end. This is because they are fixed and are thus arranged to be able to move through each end and into each other.

The air gap surrounds the collection chamber 18 in its entirety.

Two intermediate plates, deep drawn in a shell shape with a maximum thickness of 0.3 mm (only 0.1 mm in the illustrated embodiment), are disposed in the air gap 20 to completely surround the collection chamber 18. In this configuration, the upper intermediate plate 22 fits into the lower intermediate plate 24 with these intermediate plates 22 and 24 slightly clamped in the area of their contact edges 26 (see FIG. 2).

The intermediate plates 22, 24 cover the inlet tubes 2, 4, 6 immediately after passing through the outlet tube 10 (see FIG. 3) and then extend to the flange 16 as can be seen in FIG. 1. do.

The intermediate plates 22, 24 are very flexible and thin, clamped between the inlet tubes 2, 4, 6 and the outlet tube 10 permanently fixed to them or with no load bearing function. It has a structure complementary to each other to form a hollow body.

Spacers in the form of pointed protrusions 28 generated during the deep drawing of the intermediate plates 22, 24 are brought into contact with the intermediate plates 22, 24 with respect to the inlet tube 2, 4, 6 and the outlet tube 10. By maintaining the contact, the air gap 20 is divided into the inner portion 30 and the outer portion 32 by the intermediate plate.

Intermediate plates 22 and 24 are manufactured by allowing the material to flow during such deep drawing by deep drawing a uniform thickness foil having a uniform thickness but slightly corrugated surface.

In some embodiments, the inlet tubes 2, 4, 6, the outlet tube 10 and / or the intermediate plates 22, 24 each have a thickness of about 0.005 mm to 0.1 mm and a plurality of overlapping foils connected to each other. It may be a multilayer composite component made of a thin metal plate.

In operation, hot exhaust gas flows from the cylinder, through the inlet tubes 2, 4, 6, into a portion of the exhaust manifold consisting of two shells, to reach the collection chamber 18. Due to the inlet tubes 2, 4, 6 being supported to be movable relative to one another, a leakage flow will occur which will cause the exhaust gases to actually collide inside the outlet tube 10 at high speed and result in hot spots at that location. will be. However, since the intermediate plates 22, 24 cover almost the entire interior of the wall (outflow tube 10) that partitions the air gap 20 from the outside, the leakage flow will hit the intermediate plates 22, 24. . In practice, leakage flow may occur in the region of the contact edge 26 but can be neglected with regard to the thermal load of the outlet tube 10.

The intermediate plate is made of a heat resistant material, for example AISI 309.

It is also conceivable to use a rather low temperature stability material for the outlet tube 10 by using the intermediate plates 22 and 24.

Claims (16)

At least one cylinder side inlet tube (2, 4, 6), At least one exhaust pipe side outlet tube (10) Wherein the tubes are insulated through the air gap, which is disposed within each other in the area of the collection chamber 18 to form an air gap 20 that at least partially surrounds the collection chamber 18. To At least one intermediate plate (22, 24) is arranged in the air gap (20). 2. Exhaust manifold according to claim 1, characterized in that a plurality of intermediate plates (22, 24) are provided. 3. Exhaust manifold according to claim 2, characterized in that the intermediate plates (22, 24) are fitted to each other at their contact edges (26). 4. Exhaust manifold according to any one of the preceding claims, characterized in that the intermediate plates (22, 24) are shell shaped. 5. Exhaust manifold according to any of the preceding claims, characterized in that the intermediate plates (22, 24) form a hollow body. Exhaust manifold according to any of the preceding claims, characterized in that the intermediate plates (22, 24) have a maximum thickness of 0.3 mm, preferably 0.15 mm. 7. Exhaust manifold according to any of the preceding claims, characterized in that the intermediate plates (22, 24) cover at least 80% of the exposed inner side of the outer wall that defines the air gap (20). 8. Exhaust manifold according to any of the preceding claims, wherein the intermediate plates (22, 24) divide the air gap (20) into an inner portion (30) and an outer portion (32). . 9. The intermediate plate (22) (24) according to any one of the preceding claims, wherein the intermediate plates (22, 24) comprise protrusions (28), by which the intermediate plates allow the inlet tubes (2, 4, 6) and / or An exhaust manifold, which is supported by the outlet tube (10). 10. The method according to any one of the preceding claims, characterized in that the intermediate plates (22, 24) surround the inner tubes (2, 4, 6) of the two tubes in the region of the collection chamber (18). Exhaust manifold. 11. Exhaust manifold according to any of the preceding claims, characterized in that the intermediate plate (22, 24) is a deep drawn foil, the foil having a corrugated surface prior to deep drawing. 12. Exhaust manifold according to any one of the preceding claims, characterized in that the intermediate plates (22, 24) have a shape corresponding to an outer wall partitioning the air gap (20). 13. The intermediate plate (22) (24) according to any of the preceding claims, wherein the intermediate plates (22, 24) are inserted into the air gap (20) without being fixed to the inlet tubes (2, 4, 6) or the outlet tubes (10). Exhaust manifold, characterized in that. 14. A plurality of cylinder side inlet tubes (2, 4, 6) according to any one of the preceding claims, which are opened to the outlet tube (10) and fitted to each other so as to be movable relative to one another. An exhaust manifold, characterized in that provided. 15. Exhaust manifold according to claim 14, characterized in that the intermediate plate (22, 24) surrounds all the inlet tubes (2, 4, 6) provided in the collection chamber (18) area. The inlet tube (2, 4, 6) and the outlet tube (10) are connected to each other only at one end, so that these two tubes (2, 4, 6; 10). Exhaust manifold, characterized in that freely protrude into the outer tube of the two tubes (2, 4, 6; 10) in the state that the inner tube is not supported.

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