EP3708798A1 - Air gap-insulated exhaust manifold - Google Patents

Abstract

Air-gap-insulated exhaust manifold for an internal combustion engine in a motor vehicle and its manufacturing method comprising an inner element, the inner element having at least two tubular hollow bodies made of sheet metal, the hollow bodies being slidably connected to one another and an outer element, the outer element being spaced from the inner element by an air gap, the The outer element is designed as a one-piece cast part, with no direct contact between the inner element and the outer element.

Description

The invention relates to an air-gap-insulated exhaust manifold for an internal combustion engine in a motor vehicle and its manufacturing method including an inner element, the inner element having at least two tubular hollow bodies made of sheet metal, the hollow bodies being slidably connected to one another and an outer element, the outer element being spaced from the inner element by an air gap is, wherein the outer element is designed as a one-piece cast part.

The pipes in an exhaust manifold are subject to enormous thermal loads, especially in gasoline engines, since the exhaust gases that flow through the exhaust manifold can have a temperature of over 1050 ° C. Air-gap-insulated exhaust manifolds are therefore known from the prior art, which are usually welded together from several high-alloy sheet metal parts, which means that such exhaust manifolds are expensive to produce.

The WO 2006/097187 discloses such an air-gap-insulated exhaust manifold made from sheet metal.

Exhaust manifolds are also known from the prior art which have an inner tube made of sheet metal, which withstands the high temperatures of the exhaust gas and is surrounded by a cast part. The production time for such an exhaust manifold compared to a complete sheet metal version is shorter and is therefore more suitable for series production, but very high demands are made on the cast material, since the high temperatures that the exhaust gas has on the inner pipe via the contact points between The inner tube and the cast outer jacket are passed on directly via the heat conduction or conduction, and the cast outer jacket is therefore also subjected to high temperatures.

The US 2008/0083216 A1 discloses such a solution, whereby it can be clearly seen in the figures that the cast outer jacket in the area of the nozzle has contact with the inner tube as well as contact with the hot, inflowing exhaust gas. That sets The prerequisite is that the cast material used can withstand high requirements and that a high-quality cast material must be used, which is correspondingly expensive.

The solutions known from the prior art are, if they want to meet the temperature requirements for gasoline engines, correspondingly expensive, be it due to the high-alloy cast steel that has to be used or a welded sheet metal construction that requires a lot of time.

The object of the invention is to propose a device and an associated method which provides an air-gap-insulated exhaust manifold which, thanks to its structure, enables cost-effective implementation, both in terms of the materials to be used and in the manufacturing process, and yet can be used for gasoline engines with high exhaust gas temperatures .

According to the invention, this object is achieved in that there is no direct contact between the inner element and the outer element. The air-gap-insulated exhaust manifold has an inner element, the inner element being formed from at least two tubular hollow bodies made of sheet metal. The tubular hollow bodies preferably have several nozzles, which are inlet nozzles and / or outlet nozzles. The hollow bodies, which are connected to one another to form an inner element, preferably have a different configuration of the course of the connecting pieces in order to enable an optimal configuration or course with regard to the available installation space in an engine of the exhaust manifold. The tubular hollow bodies connected to one another to form an inner element are arranged displaceably to one another, preferably in the axial direction corresponding to the connection point of the interconnected hollow bodies, this enables the inner element to react to the temperature change in the exhaust manifold and to expand or contract accordingly or that the socket connection has a allows axial displacement of the hollow body to each other. Furthermore, the exhaust manifold has an outer element which is spaced from the inner element by an air gap, the outer element being designed as a one-piece cast part. To achieve the most effective insulation possible through the air gap between the inner element and To achieve the outer element, there is no direct contact between the inner element and the outer element. The outer element does not touch the inner element at any point, so that heat conduction or conduction is avoided and the air gap between them ensures optimal insulation.

In the case of the air-gap-insulated exhaust manifold according to the invention, there is preferably no direct contact between the outer surface of the cast-in inner element and the inner surface of the outer element made of cast, rather there is an air gap everywhere between them. As a result, a significantly lower temperature acts on the outer element made of cast, whereby a cast material can be used that is suitable for lower temperatures and a high-alloy steel casting can be dispensed with, which can save significant costs.

It has been shown to be advantageous if the exhaust gas flowing through the air-gap-insulated exhaust manifold is in contact exclusively with the inner surface of the inner element. Here, too, it is avoided that the exhaust gas comes into direct contact with the cast outer element and is thus directly subjected to extremely high temperatures. There is therefore a continuous air gap between the outer surface of the inner element and the inner surface of the outer element.

Another embodiment of the invention consists in that the tubular hollow bodies are made from sheet steel.

It is advantageous if the air-gap-insulated exhaust manifold according to the invention has an outer element made of cast iron, preferably nodular cast iron. This material is well suited for automotive engineering.

The invention is preferably characterized in that the tubular hollow bodies of the inner element are slidably connected to one another by means of a sleeve connection. A socket connection is characterized in that a pipe end, which has not undergone any deformation and thus corresponds to the pipe diameter of the hollow body, is pushed into a widened pipe end. The pipe ends are arranged concentrically to one another and can move axially to each other because the expanded pipe end leads the inserted pipe end over the length of the socket connection, whereby an expansion or displacement of the hollow bodies to each other, which act on the exhaust manifold due to the high temperatures, is easily possible through the socket connection, as well as that Contraction when the temperature is reduced.
According to a preferred embodiment, the air-gap-insulated exhaust manifold according to the invention has spacer elements on the outer surface of the inner element. The spacer elements should ensure that the inner element does not touch the outer element at any point.

• Herstellen eines Innenelements, wobei dazu mindestens zwei rohrförmige Hohlkörper aus Blech verschiebbar miteinander verbunden werden,
• Herstellen des Kerns durch Aufbringen des Kernsands an der äusseren Oberfläche des Innenelements, vorzugsweise durch Einlegen des Innenelements in eine Kernbüchse und Einschiessen des Kernsands,
• Einlegen des Kerns in eine Gussform, vorzugsweise Sandgussform,
• Umgiessen des Kerns mit der Schmelze,
• Ausformen und Entfernen des Kernsands, wobei sich der Kernsand zwischen der äusseren Oberfläche des Innenelements und der inneren Oberfläche des Aussenelements aus Guss befindet.

In addition, the present object is achieved with the method according to the invention for producing an air-gap-insulated exhaust manifold, which has the following steps:

• Manufacture of an inner element, at least two tubular hollow bodies made of sheet metal being connected to one another in a displaceable manner,
• Production of the core by applying the core sand to the outer surface of the inner element, preferably by placing the inner element in a core box and shooting in the core sand,
• Insertion of the core into a casting mold, preferably a sand casting mold,
• Pouring the melt around the core,
• Forming and removing the core sand, the core sand being located between the outer surface of the inner element and the inner surface of the outer element made of casting.

The tubular hollow bodies connected to one another to form the inner element preferably have a socket connection and are preferably plugged together. This allows them to move axially to one another according to the temperature change.

Core sand is preferably applied to the outer surface of the inner element; the core sand enables the air gap between the inner element and the outer element to be made from cast.

The core, which is formed from the inner element and the surrounding core sand, is placed in a casting mold, preferably a sand casting mold. The casting mold is then filled with the melt and the core is poured over, whereby the melt does not touch the inner element at any point.

After cooling, the cast part or the exhaust manifold according to the invention is shaped and the core sand is removed.

The core sand is preferably shaken out via the annular gap on the nozzle, which is formed by the air gap between the inner element and the outer element. This means that no additional openings are required in the cast outer element.

The inner element preferably has ends of the connecting pieces of the inner element protruding beyond the outer element after the shaping, the protruding connecting pieces being separated after the shaping and cooling.

It has been shown as an advantageous embodiment of the method according to the invention and of the device if an adapter flange is attached to each socket. It is advantageous if the adapter flange is welded to the socket of the inner element. To increase the stability, the outer element preferably has cast-on flanges on which the adapter flanges rest and in turn serve to ensure the air gap between the inner element and the outer element.

All configuration options can be freely combined with one another, and the features mentioned in relation to the device can be freely combined with the features mentioned in relation to the method or vice versa.

Fig. 1

eine dreidimensionale Ansicht eines erfindungsgemässen luftspaltisolierten Abgaskrümmers,

Fig. 2

eine Draufsicht eines erfindungsgemässen luftspaltisolierten Abgaskrümmers,

Fig. 3

einen Längsschnitt eines erfindungsgemässen luftspaltisolierten Abgaskrümmers,

Fig. 4

eine dreidimensionale Ansicht eines Innenelements eines erfindungsgemässen Abgaskrümmers,

Fig. 5

eine Draufsicht eines Innenelements eines erfindungsgemässen Abgaskrümmers in einer geschnittenen Kernbüchse,

Fig. 6

eine Draufsicht eines Kerns,

Fig. 7

einen Längsschnitt durch einen Kern,

Fig. 8

einen Längsschnitt durch eine Gussform mit eingelegtem Kern,

Fig. 9

einen Längsschnitt durch einen Abgaskrümmer nach dem Ausformen und dem Entfernen des Kernsands und

Fig. 10

eine dreidimensionale Ansicht eines Abgaskrümmers nach dem Ausformen und dem Entfernen des Kernsands.

An exemplary embodiment of the invention is described with reference to the figures, the invention not being restricted to the exemplary embodiment. Show it:

Fig. 1

a three-dimensional view of an air-gap-insulated exhaust manifold according to the invention,

Fig. 2

a top view of an air-gap-insulated exhaust manifold according to the invention,

Fig. 3

a longitudinal section of an air-gap-insulated exhaust manifold according to the invention,

Fig. 4

a three-dimensional view of an inner element of an exhaust manifold according to the invention,

Fig. 5

a top view of an inner element of an exhaust manifold according to the invention in a cut core liner,

Fig. 6

a top view of a core,

Fig. 7

a longitudinal section through a core,

Fig. 8

a longitudinal section through a mold with an inserted core,

Fig. 9

a longitudinal section through an exhaust manifold after the molding and removal of the core sand and

Fig. 10

Fig. 3 is a three-dimensional view of an exhaust manifold after molding and removal of the core sand.

In the Figures 1 to 3 the air-gap-insulated exhaust manifold 1 according to the invention is shown. The exhaust manifold 1 shown has several inlet connections 9 such as an outlet connection 10, the embodiment shown being only to be regarded as a possible design and the exhaust manifold according to the invention can also have other designs. The air-gap-insulated exhaust manifold 1 has an inner element 2, the inner element 2 being formed from at least two tubular hollow bodies 4. The hollow bodies 4 are tubes which preferably have several branches. The hollow bodies 4 connected to one another to form an inner element 2 are preferably not configured identically, but rather have different branches. The tubular hollow bodies 4 are formed from sheet metal, preferably a sheet steel. The hollow bodies 4 preferably have a sleeve connection 8 for mutual displaceability; this is shown in FIG Fig. 3 evident. The socket connection 8 is preferably formed by an expanded pipe end at one end of the one hollow body 4 and a non-deformed pipe end which is pushed into the expanded pipe end. Furthermore, the exhaust manifold 1 has an outer element 3, the outer element 3 being spaced apart from the inner element 2 by an air gap 5. The outer element 3 is designed as a one-piece cast part and surrounds it Inner element 2. In Fig. 3 it can be clearly seen that the cast outer element 3 does not contact the inner element 2 anywhere. Preferably, only the adapter flanges 12, which are mounted after the casting process has been completed, serve to distance the inner element 2 and outer element 3 and keep the air gap 5 constant. By avoiding direct contact between the inner element 2 and the outer element 3, there is no direct heat transfer from the hot inner element 2 through which the hot exhaust gas flows to the outer element 3. There is therefore no direct contact between the outer surface 6 of the encapsulated or cast-in inner element and the inner surface 7 of the outer element made of casting. The hot exhaust gas flowing through the inner element 2 contacts only the inner surface 22 of the inner element 2, whereby direct contact between the hot exhaust gases and the outer element 3 is avoided, whereby the outer element 3 heats up less. Spacer elements 13 can preferably be arranged between the outer surface 6 of the inner element 2 and the inner surface 7 of the outer element 3 in order to ensure the air gap 5 between the elements 2, 3.

Fig. 4 shows the inner element 2 before further processing into the exhaust manifold 1 according to the invention. The inner element 2 has at least two tubular hollow bodies 4 which are made of sheet metal. The tubular hollow bodies 4 are displaceably connected to one another, whereby they are preferably axially displaceably connected to one another in order to take into account the heating and cooling of the exhaust manifold and to expand and contract accordingly or to be able to move towards one another. The connection of the hollow bodies 4 is preferably implemented via a socket connection 8, other types of connections also being conceivable which allow the inner element 2 or the hollow bodies 4 to be lengthened or shortened. The inner element 2 is then placed in a mold or a core sleeve 15, which is shown in Fig. 5 can be seen. The core sleeve 15 has the negative shape of the core into which the core sand 18 is poured and which together with the inner element 2 forms the core 17. Fig. 6 shows the molded core 17 with the surrounding core sand 18, which serves as a placeholder for the air gap 5. Of the Core sand 18 surrounds the outer surface 6 of the inner element 2, which is shown in FIG Fig. 7 is easily recognizable.
As a further step, the core 17 is placed in a casting mold 20. Out Fig. 8 it can be seen that the negative shape 19 of the outer element 3 is depicted in the casting mold 20 and that a gap is consequently formed between the outer surface of the core 17 and the molding sand in the casting mold 20, which is filled with casting material and thus forms the outer element 3. The casting melt, which is placed around the core 17 and thus forms the outer element 3, is then poured into the casting mold 20. After the melt has solidified, the exhaust manifold is molded from the casting mold 20. The core sand 18 is still located between the outer element 3 and the inner element 2; this is preferably shaken out of the exhaust manifold 1 by shaking or shaking. The core sand 18 can flow out through the annular gap 14, can be seen in FIG Fig. 9 . As a result of the removal of the core sand 18, the air gap 5 is then present between the inner element 2 and the outer element 3, which ensures the insulation of the exhaust manifold 1. The protruding ends 21 of the connecting pieces 9, 10 of the inner element 2 are then cut off. Also visible in Fig. 10 are the possible spacer elements 13 that are already attached to the core 17 if this is required. The adapter flanges 12 are attached to the connecting pieces 9, 10. The adapter flanges 12 are preferably welded to the connecting pieces 9, 10 of the inner element 2. It is advantageous if the outer element 3 is designed in such a way that it has flanges formed on the nozzle 9, 10, which are part of the one-piece outer element 3 made of cast iron, so that the adapter flanges 12 can rest thereon and ensure a high level of stability of the exhaust manifold according to the invention what good of the Figures 1 to 3 is recognizable.

List of reference symbols

1

Air gap insulated exhaust manifold

2

Interior element

3

Exterior element

4th

Tubular hollow body

5

Air gap

6th

External surface of internal element

7th

Inner surface outer element

8th

Socket connection

9

Inlet port

10

Outlet port

11

flange

12

Adapter flange

13

Spacer element

14th

Annular gap

15th

Core box / form for core sand

16

Negative shape for core sand

17th

core

18th

Core sand

19th

Negative mold for casting material

20th

mold

21st

Protruding ends of the nozzle

22nd

Inner surface inner element

Claims (11)

Air-gap-insulated exhaust manifold (1) for an internal combustion engine in a motor vehicle, containing an inner element (2), the inner element (2) having at least two tubular hollow bodies (4) made of sheet metal, the hollow bodies (4) being connected to one another and an outer element (3) ), the outer element (3) being spaced apart from the inner element (2) by an air gap (5), the outer element (3) being designed as a one-piece cast part, characterized in that no direct contact between the inner element (2) and the outer element ( 3) exists. Air-gap-insulated exhaust manifold (1) according to claim 1, characterized in that there is no direct contact between the outer surface (6) of the cast-in / cast-in inner element (2) and the inner surface (7) of the outer element (3) made of cast. Air-gap-insulated exhaust manifold (1) according to one of Claims 1 or 2, characterized in that exhaust gas flowing through the exhaust manifold (1) is in contact exclusively with the inner surface (22) of the inner element (2). Air-gap-insulated exhaust manifold (1) according to one of Claims 1 to 3, characterized in that the tubular hollow bodies (4) are made from sheet steel. Air-gap-insulated exhaust manifold (1) according to one of Claims 1 to 4, characterized in that the outer element (3) is made of cast iron, preferably nodular cast iron. Air-gap-insulated exhaust manifold (1) according to one of Claims 1 to 5, characterized in that the tubular hollow bodies (4) of the inner element (2) are slidably connected to one another by means of a sleeve connection (8). Air-gap-insulated exhaust manifold (1) according to one of Claims 1 to 6, characterized in that spacer elements (13) are arranged on the outer surface (6) of the inner element (2). Method for producing an air-gap-insulated exhaust manifold (1), preferably according to one of Claims 1 to 7, the method comprising the following steps: • Production of an inner element (2), with at least two tubular hollow bodies (4) made of sheet metal being connected to one another in a displaceable manner, • Production of the core (17) by applying the core sand (18) to the outer surface (6) of the inner element (2), preferably by inserting the inner element (2) into a core sleeve (15) and shooting in the core sand (18), • Insertion of the core (17) into a casting mold (20), preferably a sand casting mold, • pouring the melt around the core (17), • Forming and removing the core sand (18), the core sand (18) being located between the outer surface (6) of the inner element (2) and the inner surface (7) of the outer element (3) made of casting. Method for producing an air-gap-insulated exhaust manifold (1) according to claim 8, characterized in that the core sand (18) via the annular gap (14) to the connecting piece (9, 10) which passes through the air gap (5) between the inner element (2) and Outer element (3) is formed, is shaken out. Method for producing an air-gap-insulated exhaust manifold (1) according to one of Claims 8 or 9, characterized in that the ends (21) of the connecting pieces (9, 10) of the inner element (2) protruding beyond the outer element (3) are cut off. Method for producing an air-gap-insulated exhaust manifold (1) according to one of Claims 8 to 10, characterized in that an adapter flange (12) is attached to each connection piece (9, 10).

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