EP4112892B1 - Sound absorber - Google Patents

Description

The present invention relates to a silencer for an exhaust system of an internal combustion engine, for example in a motor vehicle, and a method for its production.

One from the EP 1 888 891 B2 known silencer comprises a silencer housing with a peripheral wall and a plurality of base walls which are surrounded by the peripheral wall and supported on it. In the two axial end regions of the peripheral wall, such base walls form respective end walls which close off the interior of the silencer housing to the outside in the direction of a housing longitudinal axis. In the region of the silencer housing lying between the two end walls, such base walls form respective intermediate walls which separate chambers formed in the interior of the silencer housing from one another. Such chambers can be connected to one another by openings provided in a respective intermediate wall, but can also form a resonator chamber for a Helmholtz resonator.

In order to be able to guide an exhaust pipe, which can also provide a resonator neck for such a Helmholtz resonance, through such a base wall, it is known to form an opening edge region that surrounds a base wall opening and extends from a substantially flat region of a respective base wall in the direction of an opening center axis of a respective base wall opening by forming a passage. This has a substantially cylindrical structure and accommodates an exhaust pipe. Such base wall openings surrounded by a respective opening edge region have an oversize with respect to an external dimension, i.e. for example the external diameter of an exhaust pipe constructed with a substantially circular cross-section, so that an exhaust pipe can be accommodated in such a base wall opening with little play in terms of movement and can thus be brought into a designated installation position. In this position, each exhaust pipe is then connected to the floor wall through which it passes through by means of a material bond, generally by welding, to form a solid bond.

A silencer according to the preamble of claim 1 is known from US 6 659 222 B1 known. A bottom wall separating two chambers from one another and providing an intermediate wall has, in association with an inlet pipe and an outlet pipe, a bottom wall opening surrounded by an opening edge region running in the circumferential direction and protruding from a substantially flat bottom wall region. The inlet pipe and the outlet pipe are held in the respectively associated bottom wall opening by a press fit.

From the US 2006/0096805 A1 A silencer with a base wall providing an intermediate wall is known. An exhaust pipe engages in a base wall opening of this base wall. An opening edge region surrounding the base wall opening is interrupted in the circumferential direction and has several opening edge region segments, between which circumferential recesses are formed in the essentially flat base wall region supporting the opening edge region. The opening edge region segments are fixed to the exhaust pipe engaging in the base wall opening by welding or soldering.

It is the object of the present invention to provide a silencer for an exhaust system of an internal combustion engine and a method for producing such a silencer, with which a connection between a base wall and an exhaust pipe passing through it that prevents the generation of noise is obtained with a simplified structure.

According to a first aspect of the present invention, this object is achieved by a silencer for an exhaust system of an internal combustion engine, according to claim 1. The silencer comprises a silencer housing with a peripheral wall elongated in the direction of a housing longitudinal axis and at least a bottom wall which is surrounded by the peripheral wall and/or held on the peripheral wall and delimits a chamber in the silencer housing, wherein in at least one bottom wall at least one bottom wall opening is provided which is surrounded by an opening edge region which is bent essentially in the direction of the longitudinal axis of the housing on a substantially flat bottom wall region of the bottom wall and which receives an exhaust pipe with a press fit.

In the silencer according to the invention, at least one exhaust pipe is held in an associated base wall opening by means of a press fit, whereby on the one hand a stable connection is achieved, and on the other hand the occurrence of relative movements between the base wall and the exhaust pipe passing through it, which can lead to impact noises or rattling noises, is avoided due to the constant contact under pressure or pre-tension. Further measures to provide a solid connection are basically not necessary.

In the silencer constructed according to the invention, the opening edge region is designed to be interrupted in the circumferential direction around an opening center axis of the base wall opening. For example, this is achieved in that the opening edge region comprises a plurality of opening edge region segments arranged at a distance from one another in the circumferential direction around an opening center axis of the base wall opening.

In a design that can be implemented cost-effectively and is also resistant to high temperatures and aggressive components of exhaust gases from an internal combustion engine, the at least one base wall can be designed as a sheet metal formed part. In particular, if the opening edge area is to be closed in the circumferential direction, for example in order to achieve a substantially gas-tight closure, it is advantageous if at least one base wall has a wall thickness of a maximum of 1 mm, preferably a maximum of 0.6 mm. In this case, the base wall is also in the area of the closed opening edge area in order to create the press fit when inserting or pressing the exhaust pipe into the base wall opening. The material is sufficiently deformable within its elastic deformability range to accommodate an exhaust pipe and to generate a sufficiently strong contact pressure against its outer peripheral surface.

The opening edge region has a first edge section adjoining the essentially flat base wall region in a first bending region and a second edge section adjoining the first edge section in a second bending region, wherein a radial distance of the first edge section to an opening center axis of the base wall opening preferably decreases essentially constantly in the direction from the first bending region to the second bending region. The region of the minimum distance of the opening edge region to the opening center axis can then be provided in the region of the second bending region.

For a design that supports the easy pressing of the exhaust pipe into a base wall opening receiving it and avoids the occurrence of jamming when inserting an exhaust pipe into a base wall opening, a radial distance of the second edge section with respect to the opening center axis preferably increases substantially constantly in the direction away from the second bending region.

Furthermore, it can be provided that the opening edge region extends in a curved manner from a first axial end region of the opening edge region adjoining the substantially flat region of the bottom wall to an axial region of the opening edge region with a minimum distance from an opening center axis of the bottom wall opening.

If the opening edge region extends in a curved manner from the region of the opening edge region with a minimum distance to the opening center axis of the bottom wall opening to a second axial end region of the opening edge region remote from the substantially flat region of the bottom wall, the entire opening edge region can be designed as, for example, with A deformation region of the bottom wall with an approximately constant radius of curvature in the axial direction can be provided.

The at least one base wall is an intermediate wall separating two chambers in the silencer housing. It should be noted that, of course, one or more intermediate walls in a silencer can be designed as a base wall with the structure described above. It should also be noted that several base wall openings can also be formed in one or more such base walls, of which one or possibly several or all can have the structure described above for receiving a respective exhaust pipe with a press fit.

1. a) Bereitstellen wenigstens einer Bodenwand für ein Schalldämpfergehäuse derart, dass wenigstens eine in der Bodenwand ausgebildete Bodenwandöffnung von einem von einem im Wesentlichen ebenen Bodenwandbereich im Wesentlichen in Richtung einer Öffnungsmittenachse abgebogenen Öffnungsrandbereich derart umgeben ist, dass die Bodenwandöffnung eine vorbestimmte Innenabmessung, vorzugsweise Innendurchmesser, aufweist,
2. b) Bereitstellen eines in der von dem Öffnungsrandbereich umgebenen Bodenwandöffnung aufzunehmenden Abgasrohrs mit einer vorbestimmten Außenabmessung, vorzugsweise Außendurchmesser, wobei die vorbestimmte Außenabmessung des Abgasrohrs größer ist als die vorbestimmte Innenabmessung der Bodenwandöffnung,
3. c) Einführen des Abgasrohrs in die von dem Öffnungsrandbereich umgebene Bodenwandöffnung derart, dass das Abgasrohr in der von dem Öffnungsrandbereich umgebenen Bodenwandöffnung durch Presspassung gehalten ist.

According to a further aspect, the object specified at the outset is achieved by a method for producing a silencer constructed according to the invention for an exhaust system of an internal combustion engine, comprising the measures:

1. a) providing at least one bottom wall for a silencer housing such that at least one bottom wall opening formed in the bottom wall is surrounded by an opening edge region bent from a substantially flat bottom wall region substantially in the direction of an opening center axis such that the bottom wall opening has a predetermined inner dimension, preferably inner diameter,
2. b) providing an exhaust pipe to be accommodated in the bottom wall opening surrounded by the opening edge region and having a predetermined external dimension, preferably an external diameter, wherein the predetermined external dimension of the exhaust pipe is larger than the predetermined internal dimension of the bottom wall opening,
3. c) Inserting the exhaust pipe into the bottom wall opening surrounded by the opening edge region such that the exhaust pipe is held in the bottom wall opening surrounded by the opening edge region by a press fit.

It should be noted that the dimensions that must be coordinated with one another must be taken into account in those areas that interact with one another when the silencer is installed. This means that the exhaust pipe in the area where it passes through a floor wall when the silencer is installed has an oversize compared to the floor wall opening formed in the floor wall to accommodate this exhaust pipe, but in other length areas it can have a smaller cross-sectional dimension or possibly an even larger cross-sectional dimension than this floor wall opening.

It should also be pointed out that, preferably in a silencer constructed according to the invention or the method to be carried out according to the invention, such a bottom wall opening and an exhaust pipe to be accommodated therein are preferably each designed with a circular cross-section, so that the inner dimension can be represented, for example, by the inner diameter and the outer dimension can be represented, for example, by the outer diameter.

In measure a), the opening edge region is provided interrupted in at least one peripheral region. For this purpose, the opening edge region is formed with a plurality of opening edge region segments arranged at a distance from one another in the circumferential direction around the opening center axis.

In measure a), the opening edge region is provided, starting from the substantially flat region of the base wall, with a decreasing distance from the opening centre axis up to an axial region of the opening edge region with a minimum distance from the opening centre axis.

Furthermore, in measure a), the opening edge region is provided with an increasing distance from the opening center axis from the region of the opening edge region with a minimum distance from the opening center axis to the free axial end region of the opening edge region.

In order to enable the insertion of an exhaust pipe into a floor wall opening on the one hand and to achieve a sufficiently firm press fit on the other hand, it is proposed that a difference between the predetermined external dimension of the exhaust pipe and the predetermined internal dimension of the floor wall opening provided for receiving the exhaust pipe is in the range of 0.2 mm to 0.6 mm, preferably around 0.4 mm. For this purpose, it can further be provided that in measure a) the at least one floor wall is provided as a formed sheet metal part and/or with a wall thickness of a maximum of 1 mm, preferably a maximum of 0.6 mm.

Fig. 1

eine Teil-Axialansicht einer erfindungsgemäß aufgebauten Bodenwand für einen Schalldämpfer im Bereich einer Bodenwandöffnung;

Fig. 2

eine Teil-Axialschnittansicht der Bodenwand der Fig. 1;

Fig. 3

eine Teilansicht der Bodenwand der Fig. 1 und 2 im Bereich der von einem Abgasrohr durchsetzten Bodenwandöffnung;

Fig. 4

eine der Fig. 3 entsprechende Prinzipdarstellung einer alternativen erfindungsgemäß aufgebauten Ausgestaltungsart;

Fig. 5

eine weitere der Fig. 3 entsprechende Prinzipdarstellung zum Erläutern von Größenverhältnissen;

Fig. 6

eine weitere der Fig. 3 entsprechende Darstellung einer nicht erfindungsgemäßen Ausgestaltung;

Fig. 7

eine prinzipartige Längsschnittdarstellung eines eine Mehrzahl von Bodenwände umfassenden Schalldämpfers.

The present invention is described in detail below with reference to the accompanying figures.

Fig.1

a partial axial view of a base wall constructed according to the invention for a silencer in the region of a base wall opening;

Fig.2

a partial axial section view of the bottom wall of the Fig.1 ;

Fig.3

a partial view of the floor wall of the Fig. 1 and 2 in the area of the floor wall opening penetrated by an exhaust pipe;

Fig.4

one of the Fig.3 corresponding schematic representation of an alternative embodiment constructed according to the invention;

Fig.5

another of the Fig.3 corresponding schematic diagram to explain size relationships;

Fig.6

another of the Fig.3 corresponding representation of an embodiment not according to the invention;

Fig.7

a schematic longitudinal sectional view of a silencer comprising a plurality of base walls.

Before referring to the Fig. 1 to 6 In the following, various types of design or design details of a bottom wall of a silencer for an exhaust system of an internal combustion engine, for example in a vehicle, are explained, first with reference to the Fig.7 an example of a basic structure of a silencer 10 is explained, which in the example shown comprises a total of four base walls 12, 14, 16, 18. A silencer housing 20 of the silencer 10 further comprises an elongated, for example essentially cylindrical, peripheral wall 22 in the direction of a housing longitudinal axis L, which is connected to the radially outer region of the base walls 12, 14, 16, 18 or surrounds them.

The base walls 12, 18 arranged at the axial end regions 24, 26 of the peripheral wall 22 form respective end walls of the silencer housing 20, which close off the silencer interior at the two axial ends. The base walls 12, 18 can be firmly and gas-tightly connected to the peripheral wall 22 in their radially outer region by material bonding, for example welding. Alternatively or additionally, the base walls 12, 18 providing the respective end walls can be firmly and gas-tightly connected to the peripheral wall 22 in the axial end regions 24, 26 by form-fitting, for example by flanging.

The base walls 14, 16 arranged between the two end walls providing base walls 12, 18 form respective intermediate walls which, together or in connection with the base walls 12, 18 providing the end walls, divide the silencer interior into a total of three chambers 28, 30, 32. The base walls 14, 16 providing intermediate walls can be held in a defined position, for example, on the inner circumference of the peripheral wall 22 by a clamping effect and/or material bonding, for example welding.

In the example shown, the floor walls 12, 14, 16, 18 each have a floor wall opening 34, 36, 38, 40 in a central area, the structure of which is explained in more detail below. The floor wall openings 34, 36 of the The bottom walls 12, 14 are penetrated by an exhaust pipe 42, which can form an inlet pipe, for example, through which exhaust gas is introduced into the silencer interior. The bottom wall openings 38, 40 of the bottom walls 16, 18 are penetrated by an exhaust pipe 44, which can provide an outlet pipe, for example, through which exhaust gas is discharged from the silencer 10.

The exhaust pipe 42 can, for example, be open to the chamber 28 formed between the two bottom walls 12, 14 and can be open in an axial end region thereof to the chamber formed between the two bottom walls 14, 16. The chamber 28 can be connected to the chamber 30 via one or more flow openings formed in the bottom wall 14. The chamber 32 can form a resonator chamber of a Helmholtz resonator and can be connected to the chamber 30 via an exhaust pipe 46 provided in the bottom wall 16 and providing a resonator neck.

It should be noted that the above with reference to the Fig.7 The structure of a silencer described is only an example and this structure can be varied in many different aspects. This can affect the number and positioning of the base walls provided on the silencer, as well as the number of exhaust pipes introducing exhaust gas into the silencer or exhaust pipes discharging exhaust gas from the silencer. The exhaust gas routing inside the silencer can also be implemented differently than in the example shown.

The following is based on the Fig. 1 to 5 the design of a base wall provided on the silencer 10 and constructed according to the invention in the area in which an exhaust pipe passes through a base wall opening is described in detail. It is of course possible that differently designed base wall openings are provided in a base wall in order to guide an exhaust pipe through them, or that not all base wall openings provided in one or in different base walls have to have the structure described below.

In the following, the structure of such a bottom wall is described, for example, with reference to the bottom wall 14, which forms an intermediate wall and separates the silencer interior from two chambers 28, 30 that are in exhaust gas exchange communication with one another.

The Fig. 1 to 3 show the area of the base wall 14 in which the base wall opening 36 provided therein is penetrated by the exhaust pipe 42. In this area, an opening edge area 50, designed for example as a passage, is bent on the base wall 14 from a substantially flat base wall area 48 of the base wall 14 that is oriented substantially orthogonally to the longitudinal axis L of the housing in the direction of the longitudinal axis L of the housing, which in the embodiment example shown corresponds to an opening center axis M. For this purpose, the base wall 14 constructed of sheet metal material is formed using appropriate tools in the area of the base wall opening 36. It should be noted that an edge area bent in the direction of the longitudinal axis L of the housing can also be formed in the radially outer area, i.e. where the base wall 14 is held on the peripheral wall 22.

In the embodiment of the base wall 14, which separates two chambers 28, 30 that are in exhaust gas exchange communication with one another, the opening edge region 50 can be interrupted in the circumferential direction and can be constructed, for example, with four opening edge region segments 52 that follow one another in the circumferential direction and are arranged at a circumferential distance from one another, between which respective circumferential recesses 54 are formed in the base wall 14 or the essentially flat base wall region 48, via which the two chambers 28, 30 separated from one another by the base wall 14 are in exhaust gas exchange communication with one another.

If a gas-tight closure is to be provided by such a bottom wall, as is the case, for example, in connection with the bottom walls 12, 18 providing the end walls or the bottom wall 16 providing an intermediate wall, the opening edge region 50 can be designed as a circumferentially An opening edge region which completely surrounds a respective opening center axis M of the respective bottom wall opening 34, 40 or 38 and is not interrupted in the circumferential direction can be formed.

In the example of the Fig. 1 to 3 the opening edge region 50 has a first edge section 58 which adjoins the essentially flat bottom wall region 48 in a first bend region 56. The first edge section 58 has a structure which tapers essentially conically or truncated conically with respect to the opening center axis M starting from the first bend region 56, so that, starting from the first bend region 56, the distance of the first edge section 58 to the opening center axis M decreases essentially constantly. This means that the first edge section 58, viewed in the axial direction, is essentially not curved, and of course has a structure which is, for example, circularly curved around the opening center axis M. In a second bend region 60, a second edge section 62 adjoins the first edge section 58. The second edge section 62 likewise has a conical or truncated cone-like structure, so that its radial distance from the opening center axis M increases essentially constantly, starting from the second bending region 60. The opening edge region 50 thus has a structure that is essentially V-shaped in longitudinal section between a first axial end region 64 adjoining the essentially flat bottom wall region 48 in the region of the first bending region 56 and a second axial end region 66 of the same that is remote from the bottom wall region 48.

Where the two edge sections 58, 62 adjoin one another, i.e. essentially in the area of the second bending area 60, the opening edge area 50 has a minimum distance from the opening center axis M of the bottom wall opening 36. In the Fig.5 illustrated state, in which the exhaust pipe 42 does not yet penetrate the bottom wall 14 or the bottom wall opening 36 formed therein, this minimum distance corresponds to a predetermined inner dimension a, which, in particular in the case of a substantially circular design of the bottom wall opening 36, the radius of the bottom wall opening 36 with respect to the opening center axis M or the inner diameter, i.e. twice the radius.

The exhaust pipe 42 is dimensioned such that its predetermined outer dimension A, for example also represented by the radius or twice the radius, i.e. the diameter, of the exhaust pipe 42, which is designed with a circular cross-section, for example, is larger than the corresponding predetermined inner dimension a of the base wall opening 36. For example, the outer dimension A, i.e. for example the diameter of the exhaust pipe 42 corresponding to twice the radius R, can be designed with an excess in the range of 0.2 mm to 0.6 mm, preferably about 0.4 mm, with respect to the corresponding inner dimension a, i.e. for example the inner diameter of the base wall opening 36.

When assembling the silencer 10, after the base wall 14 has been provided with the shape intended for this purpose and has been surrounded by the peripheral wall 22 if necessary, the exhaust pipe 42 is inserted into the base wall opening 36 in the direction of the opening center axis M or the housing longitudinal axis L of the silencer 10. Due to the excess size of the exhaust pipe 42 with respect to the base wall opening 36 that accommodates it, the opening edge region 50 is slightly spread radially when the exhaust pipe 42 is inserted, so that the exhaust pipe 42 is held in the base wall opening 36 by a press fit and thus by a frictional connection. The opening edge region 50 or its opening edge region segments 52, which are radially spread out in the region of their elastic deformability, press with a force F radially inward against the outer circumference of the exhaust pipe 42, so that on the one hand the exhaust pipe 42 is held in a defined position with respect to the base wall 14, and on the other hand a defined contact is produced on the exhaust pipe 42 by the opening edge region segments 52 pressing with the force F against the outer circumference of the exhaust pipe 42, so that the occurrence of rattling noises can be avoided.

By designing the opening edge region 50 with its two essentially V-shaped contours providing the opening edge region 50, An insertion bevel is formed on the edge sections 58, 62 for the exhaust pipe 42 to be accommodated in the bottom wall opening 36, which allows easy insertion of the exhaust pipe 42 into the bottom wall opening 36 and avoids getting caught due to sharp-edged contact.

An alternative design of the bottom wall 14 is shown in Fig.4 illustrated. In this embodiment, the opening edge region 50 is also formed with two edge sections 58, 62. The edge section 58 adjoins the essentially flat bottom wall region 48 in the axial end region 64 of the opening edge region 50, while the edge section 62 provides the second axial end region 66 remote from the bottom wall region 48. Both edge sections 58, 62 are curved in the axial direction and have a significantly larger radius of curvature than, for example, the two bending regions 56, 60 of the Fig.3 illustrated embodiment. For example, a substantially constant radius of curvature could be provided in each of the edge sections 58, 62 up to the region 68 with the minimum diameter of the opening edge region 50, and the radii of curvature in the two edge sections 58, 62 could, for example, be the same as one another, but could of course also be designed differently. For example, the radius of curvature in the edge section 62 could be smaller than the radius of curvature in the edge section 58.

Even in the Fig.4 In the embodiment shown, the opening edge region 50 is provided with the previously described circumferentially segmented configuration in order, on the one hand, to provide increased flexibility in the region of the bottom wall opening and, on the other hand, to enable gas to pass through the bottom wall opening in this region.

An embodiment not according to the invention is shown in Fig.6 shown. In this embodiment, the opening edge region 50 has neither the two edge sections 58, 62, which adjoin the substantially flat bottom wall region 48 or each other in respective bending regions 56, 60. The edge section 58 has, for example, the Fig.3 recognizable cone-like or

frustoconical structure with a substantially constant decrease in the distance to the opening center axis M between the two bending regions 56, 60. The second edge section 62 has a substantially cylindrical structure, i.e. has a substantially constant distance to the opening center axis M between the second bending region 60 and the second axial end region 66, so that the minimum distance to the opening center axis M is provided between the second bending region 60 and the second axial end region 66. In this embodiment, a substantially flat, i.e. axially further extended, contact region is provided between the opening edge region 50 and the exhaust pipe 42. This is suitable for providing, in addition to the press fit generated by the force F exerted radially inward, a firm connection between the bottom wall 14 and the exhaust pipe 42 by material bonding, for example by a circumferential weld seam 70, which can be formed as a fillet weld between a substantially axially oriented end face of the second edge portion 62 and the outer circumferential surface of the exhaust pipe 42.

At the Fig.6 In the embodiment shown and not according to the invention, the opening edge region 50 can be designed to run all the way around in the circumferential direction, i.e. without interruption, or can be provided as an opening edge region interrupted in the circumferential direction at least at one point, for example as an opening edge region with a plurality of opening edge region segments following one another in the circumferential direction.

In each of the previously described designs of a base wall, it is possible to simply push an exhaust pipe through a respective base wall by hand or by machine or to insert it into a base wall opening provided for receiving an exhaust pipe, whereby the respective opening edge area is spread open and the frictional connection required to create the press fit is created. When a silencer constructed in this way is in operation, the various components of the silencer heat up and expand so that the press fit or the pressure applied through a respective opening edge area on a The force exerted on the associated exhaust pipe increases, thus generating an even stronger holding effect.

Claims (8)

1. A muffler for an exhaust system of an internal combustion engine, comprising a muffler housing (20) with a circumferential wall (22) which extends longitudinally in the direction of a housing longitudinal axis (L) and at least one base wall (14, 16) which is surrounded by the circumferential wall (22) or/and retained on the circumferential wall (22) separating two chambers (28, 30, 32) in the muffler housing (20) and providing an intermediate wall, wherein at least one base wall opening (36, 38), which is surrounded by an opening edge region (50) which is bent at an essentially plane base wall region (48) of the base wall (14, 16) essentially in the direction of the housing longitudinal axis (L), and receives an exhaust pipe (42) with a press fit, is provided in at least one base wall (14, 16),
   characterized in that

   - the opening edge region (50) is designed so that is interrupted circumferentially about an opening centre axis (M) of the base wall opening (36, 38), wherein the opening edge region (50) comprises a plurality of opening edge region segments (52) arranged spaced apart from another circumferentially about an opening centre axis (M) of the base wall opening (36, 384) and wherein circumferential recesses (54) are formed in the essentially plane base wall region (48) between opening edge region segments (52) succeeding each other in the circumferential direction, wherein the chambers (28, 30, 32) separated by the at least one base wall (14, 16) are in exhaust gas exchange communication via the circumferential recesses,

   - the opening edge region (50) has a first edge section (58) adjoining the essentially plane base wall region (48) in a first bending region (56) and a second edge section (62) adjoining the first edge section (58) in a second bending region (60), wherein a radial spacing of the first edge section (58) from an opening centre axis (M) of the base wall opening (34, 36, 38, 40) decreases in the direction from the first bending region (56) to the second bending region (60), and

   - a radial spacing of the second edge section (62) from the opening centre axis (M) increases in the direction away from the second bending region (60).
2. The muffler as claimed in claim 1, characterized in that the at least one base wall (14, 16) is designed as a deformed sheet-metal part or/and in that the at least one base wall (14, 16) has a wall thickness (W) of no more than 1 mm, preferably no more than 0.6 mm.
3. The muffler as claimed in one of the preceding claims, characterized in that the radial spacing of the first edge section (58) from an opening centre axis (M) of the base wall opening (36, 38) decreases essentially constantly in the direction from the first bending region (56) to the second bending region (60).
4. The muffler as claimed in one of the preceding claims, characterized in that the radial spacing of the second edge section (62) from the opening centre axis (M) increases essentially constantly in the direction away from the second bending region (60).
5. The muffler as claimed in one of the preceding claims, characterized in that the opening edge region (50) runs in bent form from a first axial end region (64), adjoining the essentially plane base wall region (48), of the opening edge region (50) to an axial region (68) of the opening edge region (50) with a minimum spacing from an opening centre axis (M) of the base wall opening (36, 38).
6. The muffler as claimed in claim 5, characterized in that the opening edge region (50) runs in bent form from the region (68) of the opening edge region (50) with a minimum spacing from the opening centre axis (M) of the base wall opening (36, 38) to a second axial end region (66), remote from the essentially plane base wall region (48), of the opening edge region (50).
7. A method for producing a muffler (10) for an exhaust system of an internal combustion engine as claimed in one of the preceding claims, comprising the steps:

   a) Providing at least one base wall (14, 16) for a muffler housing (20) in such a way that at least one base wall opening (36, 38) formed in the base wall (14, 16) is surrounded by an opening edge region (50) bent away from an essentially plane base wall region (48) essentially in the direction of an opening centre axis (M) in such a way that the base wall opening (36, 38) has a predetermined internal dimension a), preferably an internal diameter,

   b) Providing an exhaust pipe (42, 44), to be received in the base wall opening (50) surrounded by the opening edge region (50), with a predetermined external dimension (A), preferably an external diameter, wherein the predetermined external dimension (A) of the exhaust pipe (42, 44) is greater than the predetermined internal dimension a) of the base wall opening (36, 38),

   c) Introducing the exhaust pipe (42, 44) into the base wall opening (36, 38) surrounded by the opening edge region (50) in such a way that the exhaust pipe (42, 44) is retained in the base wall opening (36, 38) surrounded by the opening edge region (50) by a press fit,

   characterized in that

   - in step a) the opening edge region (50) is provided so that it is interrupted in at least one circumferential region, with a plurality of opening edge region segments (52) arranged spaced apart from one another circumferentially about the opening centre axis (M),

   - in step a) the opening edge region (50) is provided, starting from the essentially plane base wall region (48), with a spacing from the opening centre axis (M) which decreases as far as an axial region (68) of the opening edge region (50) with a minimum spacing from the opening centre axis (M), and

   - in step a) the opening edge region (50) is provided with a spacing from the opening centre axis (M) which increases from the region (68) of the opening edge region (50) with a minimum spacing from the opening centre axis (M) as far as the free axial end region (50) of the opening edge region.
8. The method as claimed in claim 7, characterized in that a difference between the predetermined external dimension (A) of the exhaust pipe (42, 44) and the predetermined internal dimension (a) of the base wall opening (36, 38) provided to receive the exhaust pipe (42, 44) is in the range from 0.2 mm to 0.6 mm, preferably is approximately 0.4 mm, or/and wherein, in step a), the at least one base wall (14, 16) is provided as a deformed sheet-metal part or/and with a wall thickness (W) of no more than 1 mm, preferably no more than 0.6 mm.

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