Component of an exhaust system and method of manufacturing such a component

Abstract

A component of an exhaust system, in particular of an exhaust system of an internal combustion engine, has a double-walled pipe which encloses at least one air gap. The double-walled pipe includes at least two layers positioned radially over each other and attached to each other at a plurality of fixing points distributed over a periphery. At least one of the layers is a structured layer and has a wave structure with a plurality of wave crests and wave troughs distributed along the periphery. For manufacturing the component, at least one sheet metal strip is provided, which is structured in sections to give it a wave form. A brazing material is applied at the intended fixing points. The sheet metal strip is then wound up to form the double-walled pipe. The latter is calibrated, and the layers are connected at the fixing points by induction brazing.

Claims

1. A component of an exhaust system comprising: a double-walled pipe which encloses at least one air gap, the double-walled pipe enclosing a cavity in an interior of the double-walled pipe, and the double-walled pipe being an exhaust pipe, a muffler or a housing for a part received within the cavity of the double-walled pipe, and wherein the double-walled pipe includes at least two layers positioned radially over each other and attached to each other at a plurality of fixing points distributed over a periphery, at least one of the layers being a structured layer and having a wave structure with a plurality of wave crests and wave troughs distributed along the periphery; wherein the wave structure has essentially a sinusoidal shape and at least one of the fixing points is positioned outside the wave crests or wave troughs of the sinusoidal shape wherein two structured layers are provided, both of which are bent in a sinusoidal shape with the same frequency and amplitude; and wherein the two structured layers are shifted relative to one another by a phase of about π/4 and the fixing points are positioned between a zero crossing and the wave trough of one structured layer and/or in a region of a zero crossing of the other structured layer.

2. The component of claim 1 wherein at least one of the structured layers does not extend in a straight line between two neighboring fixing points, at least in sections.

3. The component of claim 1 wherein the structured layer does not extend in a straight line between each wave crest and each wave trough.

4. The component of claim 3 wherein, formed between the wave crest and the wave trough, is a bend in which two straight-line sections adjoin each other.

5. The component of claim 1 wherein at least a majority of the fixing points are positioned outside the wave crests or wave troughs of the sinusoidal shape.

6. The component of claim 1 wherein a radially innermost and/or a radially outermost layer is/are formed to be flat.

7. The component of claim 6 wherein the flat radially innermost layer and the flat radially outermost layer are provided, between which the structured layer having the wave structure is arranged, the structured layer being attached at the wave crests and the wave troughs to the flat radially outermost layer and the flat radially innermost layer and, more particularly, the structured layer having a respective bend between neighboring wave crests and wave troughs.

8. The component of claim 1 wherein at least two of the layers are formed by winding.

9. The component of claim 8 wherein at least two of the layers are formed by winding a one-piece sheet metal strip that is structured in sections.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will be described in more detail below by several exemplary embodiments with reference to the accompanying drawings, in which:

(2) FIG. 1 shows a schematic sectional view of a component of an exhaust system according to a first embodiment of the invention;

(3) FIG. 2 shows a sheet metal strip which is structured in sections and from which the layers of the component shown in FIG. 1 are wound;

(4) FIG. 3 shows a schematic sectional view of a stack of layers for a component of an exhaust system according to a second embodiment, prior to the rolling-up process; and

(5) FIG. 4 shows a schematic illustration of a device for producing a component according to the invention.

DETAILED DESCRIPTION

(6) FIGS. 1 and 2 show a component 10 of an exhaust system according to a first embodiment. For reasons of clarity, where features occur several times, only some of them are provided with reference numerals in the figures.

(7) The component 10 comprises a double-walled pipe 12, which may extend over any desired length and encloses a cavity in its interior. The component 10 may be made use of as an exhaust pipe, for example, but also in a muffler or as a housing for other suitable parts of an exhaust system which may be received in the interior of the double-walled pipe 12, if appropriate.

(8) In this example, the double-walled pipe 12 includes three layers 14, 16, 18, of which the layer 14 constitutes the radially innermost layer and the layer 18 constitutes the radially outermost layer. The layer 16 is positioned between the layers 14 and 18 as viewed in the radial direction.

(9) The layer 16 is a structured layer which has a wave structure with quite a number of wave crests 20 and wave troughs 22 distributed over the periphery of the double-walled pipe 12. The wave crests 20 are arbitrarily chosen as being directed radially outward here, while the wave troughs 22 accordingly constitute the radially most inward points of the wave structure.

(10) The period of the wave structure is selected such that more than ten wave crests are provided and distributed over the periphery. Depending on the selected wave structure and the selected diameter of the double-walled pipe 12, this number may also be smaller, but may also be considerably higher.

(11) At least some of the wave crests 20 and/or the wave troughs 22 have fixing points 24 provided thereon, at which the layers 14, 16 and also the layers 16, 18 are attached to each other. It is possible to provide a fixing point 24 at each of the wave crests 20 and each of the wave troughs 22, or only at some of the wave crests 20 and wave troughs 22.

(12) The attachment to the fixing points 24 is effected using brazing material at these locations as indicated in the figures.

(13) In this example, all of the layers 14, 16, 18 are made of a metal sheet. The wall thickness of the sheet is between 0.1 and 0.3 mm, and in particular about 0.2 mm.

(14) To produce the double-walled pipe 12, the sheet metal strips, which later form the layers 14, 16, 18, are rolled up.

(15) In this embodiment, all three layers 14, 16, 18 are integrally connected with each other and form part of a single elongated sheet metal strip 28, with the layers 14, 16, 18 following each other linearly. It is only by rolling in the winding direction W (see FIG. 2) that the layer structure of the double-walled pipe 12 is obtained. The lengths 11, 12, 13 of the later layers 14, 16, 18 are exactly selected such that they correspond to the respective periphery of the layers 14, 16, 18 in the finished double-walled pipe 12, and if necessary including an overlap of a few millimeters in order to attach the layers 14, 16, 18 to the respective neighboring layer.

(16) For manufacturing the double-walled pipe 12, a device is provided which is not illustrated in more detail, but which is designed similar to the production device 25 shown in FIG. 4, to which reference is therefore made here.

(17) One of the sheet metal strips 28 having the desired wall thickness is fed from a supply roll 26.

(18) The sheet metal strip 28 is provided with a brazing material at predetermined points, these points forming the fixing points 24 later.

(19) The brazing material may also be fed in strips from corresponding supply rolls 30. The fixing points 24 may each extend over the entire length of the double-walled pipe 12 (i.e. into the drawing plane) or be formed with interruptions.

(20) Openings may also be applied into the sheet metal strips 28 at predefined points, for example by punching or laser cutting, such as (micro)-perforations for noise reduction (indicated by device 32).

(21) The structured layer 16 is brought into the desired wave form in the production device 25, e.g. by a suitable embossing tool 34.

(22) In addition, spacers and/or seals (not shown) may already be arranged on the sheet metal strip 28.

(23) Following these preparatory steps, the sheet metal strip 28 is rolled up in the winding direction W, starting with the radially innermost layer 14.

(24) The roll produced in this way is calibrated to its final shape and size in a calibrating device 36, for example by punches 38 traveling radially inwards and acting on the outer layer 18. This calibrating device 36 can be integrated into the production device 25, so that the rolled-up sheet metal strip 28 does not need to be transferred to another device. The fixing in the final shape is effected by inductive heating of the brazing material, so that the respective neighboring layers are brazed to each other at the fixing points 24. The induction device 40 is integrated in the calibrating device 36, for example, the induction brazing being performed as long as the punches 38 are still in the final position of calibration.

(25) After completion, the component 10 is removed from the production device 25. The production device 25 is then available for the production of a further component 10.

(26) All production steps can be carried out in succession in one single production device 25.

(27) It is, of course, possible to carry out the step of structuring with a wave form prior to the application of brazing material or the incorporation of openings, or later.

(28) A plurality of structured layers 16 may also be provided. It is possible to form all existing layers as structured layers or to design one or more of the layers as flat layers, i.e. without selectively reshaping such layer(s) to achieve a structuring.

(29) The number of layers corresponds to the number of revolutions of the sheet metal strip 28 in the winding direction W, a revolution of 360 degrees in the winding direction W being required to generate a complete layer.

(30) The wave form selected in this embodiment is essentially composed of sections extending in a straight line, which adjoin each other in bends forming the wave crests 20 and the wave troughs 22. In the wave crests 20 and the wave troughs 22, the adjacent sections may form angles between 30 degrees and 120 degrees, for example.

(31) It would be conceivable to form the wave structure from a simple zigzag structure in which respective bends are only provided in the wave crests 20 and in the wave troughs 22.

(32) In the example shown here, however, the flank between each wave crest 20 and each wave trough 22 has a further bend 42 provided thereon, where the material of the structured layer 16 projects outward, that is, toward the radially outermost layer 18. These bends 42 are positioned freely in the air gap L formed between the radially innermost layer 14 and the radially outermost layer 18.

(33) Owing to the additional bends 42, the structured layer 16 does not extend linearly between the wave crests 20 and the wave troughs 22. This results in an increased elasticity, which improves the overall stability of the double-walled pipe 12.

(34) FIG. 3 illustrates a component according to a second embodiment of the invention.

(35) Here, the double-walled pipe 12 is produced by winding up a stack of two structured layers 16a, 16b, which are placed on top of each other as is illustrated in FIG. 4.

(36) Each of the structured layers 16a, 16b here has a sinusoidal shape with the same period and the same amplitude. Of course, a different wave form could also be selected, which does not correspond to a mathematically exact sine, but also extends periodically and without any sharp bends, that is, discontinuities in the gradient.

(37) The two structured layers 16a, 16b are shifted relative to each other such that they touch each other away from the wave crests 20 and the wave troughs 22, in this case by a phase of about π/4. At these locations, the fixing points 24 are provided. The fixing points 24 are thus located in the region of a zero crossing 44 of the structured layer 16b or between the zero crossing 44 and the wave trough 22 of the structured layer 16a, for example.

(38) In this case, a plurality of respective air gaps L are formed between the neighboring fixing points 24.

(39) In a variant of the embodiment just described, two further layers 14, 18 which are flat, that is, unstructured, are provided on either side of the two structured layers 16a, 16b, forming the radially innermost layer 14 and the radially outermost layer 18 in the finished double-walled pipe 12 as in the first embodiment. In this case, a further air gap L is then formed between the layer 14 and the layer 18.

(40) With the difference that the sheet metal strips 28′ are stacked on top of each other and positioned accordingly before the rolling-up process, the production can take place in the production device 25 shown in FIG. 4, as described for the first embodiment.

(41) In this case, a plurality of supply rolls 26 are provided, for example, from which the individual sheet metal strips 28, 28′ are fed to a stacking area in which the individual layers 14, 16a, 16b, 18 are stacked on top of each other in the desired order after structuring in the embossing tool 34, if desired. Of course, some or all layers 14, 16a, 16b, 18 may also be fabricated from blanks from a single supply roll 26, if required.

(42) Rather than placing all of the layers 14, 16a, 16b, 18 on top of each other to form a stack before rolling them up, it would also be conceivable, by analogy with the first embodiment, to provide a single, elongated sheet metal strip which includes the individual layers 14, 16a, 16b, 18 linearly adjoining each other with the appropriate lengths, the layers assuming their desired positions after being rolled up in the winding direction W. In this case, too, the brazing material for the fixing points 24 may be applied prior to stacking the individual layers on top of each other and prior to rolling them up, and fixing of the individual layers 14, 16a, 16b, 18 to one another may be obtained by inductive heating after the rolling-up process.

(43) Stacking the individual layers 14, 16, 18 before rolling them up would also be possible in the first embodiment.

(44) In addition, rather than the basic wave form shown in the first embodiment, a sinusoidal shape or a sine-like shape as used in the second embodiment may, of course, also be used there.

(45) Generally, it is conceivable to provide only one single structured layer 16, 16a, 16b or any desired number of radially superposed structured layers 16, 16a, 16b. Likewise, the radially innermost layer and/or the radially outermost layer may generally have a flat design.

(46) The wave forms shown have been chosen by way of example only. Of course, any suitable wave form that preferably does not extend linearly between wave crests and wave troughs can be employed in a component according to the invention for an exhaust system.