Silencer

Abstract

A silencer for an exhaust system of an internal combustion engine comprises at least one silencer component (30) with a perforation (42) in a wall (40) of the silencer component (30) comprising a plurality of flow openings (44), wherein the flow openings (44) are permeable in a flow direction (S) from an upstream side (54) of the wall (40) to a downstream side (58) of the wall (40), wherein at least in part of the flow openings (44), preferably all flow openings (44), the perforation (42) provides a flow opening flow cross-section (D) in the flow direction (S).

Description

[0001] The present invention relates to a silencer which can be used, for example, in an exhaust system of an internal combustion engine to dampen noises generated during operation of the internal combustion engine.

[0002] Such silencers, which can be used in exhaust systems of internal combustion engines, generally comprise an outer wall enclosing a silencer interior. Within the silencer interior, the exhaust gas emitted by an internal combustion engine is guided through one or more exhaust guide pipes, each of which provides silencer components. Furthermore, one or more partition walls, each of which provides silencer components, can be provided within the silencer interior, which partition walls, for example, separate silencer chambers that perform different functions.

[0003] In order to bring different volume regions in the silencer interior into flow connection with one another in such a silencer, perforations with a plurality of generally comparatively small and closely spaced flow openings can be formed in one or more silencer components, for example, one or more exhaust guide pipes and / or one or more partition walls. The flow openings of such a perforation serve to allow the direct passage of exhaust gas and are not intended, for example, when configured in a partition wall, to accommodate exhaust guide pipes in order to connect them to such a partition wall and to also guide the exhaust gas guided through such an exhaust guide pipe through the partition wall.Through such flow openings of a perforation, exhaust gas can flow, for example, from the volume formed inside an exhaust gas guide pipe into the volume surrounding the exhaust gas guide pipe, or exhaust gas can flow from one of two chambers separated by a partition wall into the other of the two chambers separated by this partition wall if such a perforation is formed in the partition wall.

[0004] A silencer according to the preamble of claim 1 is known from DE 196 39 079 A1.

[0005] It is the object of the present invention to provide a silencer for an exhaust system of an internal combustion engine, which achieves improved flow guidance with improved sound damping behavior.

[0006] According to the invention, this object is achieved by a silencer for an exhaust system of an internal combustion engine, comprising at least one silencer component with a perforation comprising a plurality of through-flow openings in a wall of the silencer component, wherein the through-flow openings can be flowed through in a direction from an upstream side of the wall to a downstream side of the wall, wherein at least in some of the through-flow openings, preferably all of the through-flow openings, the through-flow opening flow cross-section of the perforation decreases in the flow direction to provide a through-flow opening flow guide surface.

[0007] In order to efficiently avoid flow turbulence in the area of ​​the through-flow openings, an inclination angle of the through-flow opening flow guide surfaces with respect to an opening center axis in the area of ​​an outlet end of a respective through-flow opening is in the range of 5° to 15°.

[0008] By providing flow guide surfaces at flow openings in muffler components whose flow cross-sections decrease in the direction of flow, the exhaust gas emitted by an internal combustion engine, for example, is directed from the area of ​​larger flow cross-section to the area of ​​smaller flow cross-section of a respective flow opening. This reduces turbulence in the exhaust flow in the area of ​​the flow openings, which contributes both to a reduction in flow resistance and to a reduction in noise when flowing through such a perforation.

[0009] For optimized flow guidance, the flow opening flow cross-section can decrease degressively in the flow direction.

[0010] This can be achieved, for example, by reducing the flow cross-section of the through-flow opening with a rounded cross-sectional change profile. To avoid the formation of turbulence, a design in which the flow cross-section of the through-flow opening decreases with a substantially edge-free cross-sectional change profile is particularly advantageous.

[0011] In order to avoid the formation of turbulences when connecting a respective flow-through opening flow guide surface to the upstream side of the wall of the silencer component, it is proposed that the flow-through opening flow guide surface connects to the upstream side of the wall essentially without edges.

[0012] The flow opening flow cross section may, for example, decrease in a first flow opening opening length range corresponding to a wall thickness of the wall between the upstream side of the wall and the downstream side of the wall.

[0013] A more pronounced flow-guiding property of the flow-through openings can be achieved, for example, by providing, in association with at least some of the flow-through openings, preferably all of the flow-through openings, a flow-through projection projecting downstream beyond the downstream side of the wall and surrounding a respective flow-through opening in a second flow-through opening length range in a ring-like manner. In at least some of the flow-through projections, preferably all of the flow-through projections, the flow-through opening flow cross-section of each flow-through opening surrounded by one of the flow-through projections can decrease in the second flow-through opening length range.

[0014] In order to achieve the degressive decrease of the flow opening flow cross section, the flow opening flow cross section can decrease more in the first flow opening opening length range than in the second flow opening opening length range.

[0015] The at least one silencer component can, for example, be designed as an exhaust gas guide pipe. If a silencer is provided with multiple exhaust gas guide pipes, such a perforation with the structure of the flow openings designed according to the invention can be provided only in one or some of the exhaust gas guide pipes or in each exhaust gas guide pipe. Alternatively or additionally, the at least one silencer component can be designed as a partition wall separating two silencer chambers from one another. Here, too, if a silencer is provided with multiple partition walls, a perforation with the structure of the flow openings designed according to the invention can be provided in one or some of the partition walls or in each partition wall.

[0016] The invention further relates to an exhaust system for an internal combustion engine, comprising at least one silencer constructed according to the invention.

[0017] Furthermore, the invention relates to a method for producing a silencer with the structure described above, which is characterized by: that the at least one silencer component is constructed with metal material, and that passages are formed in the wall of the silencer component to provide the flow-through opening flow guide surfaces, or that the at least one silencer component is designed as a plastic molded part, and that the flow-through opening flow guide surfaces are molded onto the wall of the silencer component.

[0018] The present invention is described in detail below with reference to the accompanying figures. They show: Fig. 1 a silencer of an exhaust system of an internal combustion engine with a partially open silencer housing; Fig. 2 a perspective view of a silencer component, for example of the silencer of the Fig. 1 usable exhaust pipe; Fig. 3 a perspective view of a silencer component, for example the silencer of the Fig. 1 insertable partition wall; Fig. 4 a partial longitudinal sectional view of a silencer component, for example the silencer of the Fig. 1 insertable exhaust pipe; Fig. 5 an enlarged view of detail V in Fig. 4 ; Fig. 6one of the Fig. 5 corresponding representation of an alternative design of a silencer component.

[0019] In Fig. 1 A silencer, generally designated 10, of an exhaust system 12 for an internal combustion engine is shown by way of example. The silencer 10 comprises a silencer housing 14, which in the illustrated example comprises a substantially cylindrical peripheral wall 16 and two end walls 18, 20 provided at its axial ends. A partition wall 22 is provided inside the silencer housing 14, which divides the interior space 24 of the silencer into two chambers 26, 28.

[0020] In the chamber 26, an exhaust pipe 32 providing a silencer component 30 extends between the end wall 18 and the partition wall 22. The exhaust pipe 32 can be closed off by the partition wall 22 in its end region adjoining the partition wall 22, or can, as in the case of the Figur 3 illustrated partition wall 22, in its axial end region adjoining the partition wall 22, be open to an opening 34 formed in the partition wall 22, for example with a passage, and thus to the chamber 28.

[0021] An exhaust pipe 36 extending into the chamber 24 provides a further silencer component 30, which is open in its end region adjoining the partition wall 22 to the chamber 26 via an opening 38 formed, for example, by a passage in the partition wall 22. For example, the exhaust pipe 32 can provide an inlet pipe of the silencer 10 or connect to it in the region of the end wall 18. The exhaust pipe 36 can provide an outlet pipe of the silencer 10 or connect to it in the region of the end wall 20. In the case of the Fig. 1 If, in the silencer 10 shown as an example, the exhaust pipe 32 is closed off in its end region adjoining the partition wall 22 by the partition wall 22, the exhaust gas A entering the silencer via the exhaust pipe 12 passes through the perforation 42 into the chamber 26 and from the chamber 26 into the exhaust pipe 36, via which the exhaust gas A leaves the silencer 10. The chamber 28 can act as a resonator chamber for sound dampening. If the exhaust pipe 32 is designed with the partition wall 22 as shown in Fig. 3 shown, open to the chamber 28 via the opening 34 in the partition wall 22, exhaust gas A entering the exhaust guide pipe 32 can enter the exhaust guide pipe 36 via the perforation 42 in the exhaust guide pipe 32 and the chamber 26 as well as via the chamber 28 and the perforation 42 in the exhaust guide pipe 36 and exit from the silencer 10 via this.

[0022] It should be noted that with reference to the Fig. 1 Only an exemplary construction of a very simply structured silencer 10 is explained with regard to the essential system areas of such a silencer. Of course, several chambers can be formed in the silencer housing of such a silencer, separated from one another by respective partition walls, and more than the two exhaust pipes shown can be provided in order to guide the exhaust gas flowing through the silencer in a defined manner through the silencer and the chambers formed therein.

[0023] The Fig. 2 illustrates, for example, with reference to the exhaust pipe 32 providing a silencer component 30, that a perforation, generally designated 42, with a plurality of flow openings 44 can be formed in a wall 40 of the exhaust pipe 36 or in the partition wall 22. Fig. 3 illustrated perforation 42 can be formed with a plurality of comparatively small and closely spaced flow openings 44 through which the exhaust gas flowing through the silencer 10 can flow.

[0024] The structure of the perforation 42 or the flow openings 44 thereof is described below with reference to the Fig. 4 and 5explained in detail. It should be noted that a perforation with such structured flow openings can be provided both in a wall of a silencer component designed as an exhaust pipe and in a wall of a silencer component designed as a partition wall.

[0025] These figures show, for example, using the exhaust guide pipe 32 providing a silencer component 30, how the structure of the flow openings 44 is coordinated with the flow guidance in the silencer 10. In particular, it can be seen that in the exhaust guide pipe 32, the exhaust gas A emitted by an internal combustion engine and flowing in the exhaust system 12 towards the silencer 10 enters a volume 48 delimited by the wall 40 of the exhaust guide pipe 32 and can flow into the chamber 26 through the perforation 42 formed in the wall 44 or, in the example shown, the flow openings 44 thereof. In the region of each of the flow openings 44, the exhaust gas A flows essentially in a flow direction S from the volume 48 into the chamber 26, which can approximately correspond to an extension direction of an opening center axis O of the flow openings 44.Taking into account the fact that the exhaust gas A basically flows in the direction of a pipe longitudinal axis R through the volume 48 in the exhaust gas guide pipe 32, the flow direction S can be set in the direction of the pipe longitudinal axis R with respect to the direction of extension of the opening center axis O of a respective flow opening 44.

[0026] One recognizes in Fig. 5 that preferably each of the flow openings 44 is formed in such a way that in the flow direction S or in the direction of the opening center axis O a Fig. 5 The flow cross-section D, illustrated by the opening diameter, decreases in the flow direction S and, with the cross-sectional change profile, provides a respective through-flow opening flow guide surface 50. In the example shown, the through-flow opening flow guide surface 50 formed in the region of each through-flow opening 44 adjoins an upstream side 54 of the wall 40, which provides an inner surface 52 of the exhaust gas guide pipe 32, essentially without an edge-like or step-like transition and provides a fundamentally rounded, edge-free cross-sectional change profile.

[0027] In the area of ​​preferably each throughflow opening 44, a throughflow projection 60 is formed, projecting in the downstream direction beyond a downstream side 58 of the wall 40 of the exhaust guide pipe 32, which provides an outer circumferential surface 56. If the exhaust guide pipe 32 is constructed as a metal component, for example, from sheet metal, the throughflow projections 60 can be formed as passages in the area of ​​the throughflow openings 44 by using appropriate forming tools during the forming of a metal blank. If the exhaust guide pipe 32 is manufactured as a plastic molded part, for example in a die-casting or deep-drawing process, the throughflow projections 60 can be molded onto the exhaust guide pipe 32 during the die-casting process by using appropriate molds.

[0028] By providing the flow-through projections 60, the flow-through openings 44 are formed with two flow-through opening length ranges L 1 , L 2 that follow one another in the flow direction S. The first flow-through opening length range L 1 essentially corresponds to that extension section of a respective flow-through opening 44 that corresponds to the wall thickness W of the wall 40 of the exhaust gas guide pipe 32. The second flow-through opening length range L 2 that then follows in the flow direction S corresponds to that extension section in which a respective flow-through projection 60 protrudes outward beyond the downstream side 58 of the wall 40.

[0029] In the illustrated embodiment, in which a respective through-flow opening flow guide surface 50 is rounded in the flow direction S and thus the through-flow opening flow cross-section D, i.e. for example the diameter in the case of a circular design of the through-flow openings 44, decreases degressively in the flow direction S, i.e. essentially in the direction of the opening center axis O, the through-flow opening flow cross-section D changes more strongly in the first through-flow opening opening length range L 1 than in the second through-flow opening opening length range L 2 .Since the through-flow opening cross-section D changes, i.e. decreases, over the entire extension area of ​​a respective through-flow opening 44 in the flow direction S, a comparatively large radius of curvature for the through-flow opening flow guide surface 50 can be provided by providing the through-flow projections 60 and the resulting greater extension length of a respective through-flow opening 44 in the flow direction S compared to the wall thickness W, so that the exhaust gas A flowing through the volume 48 and flowing approximately radially outwards in the flow direction S through the through-flow openings 44 with respect to the longitudinal axis R of the exhaust gas guide pipe 32 is guided into the through-flow openings 44 comparatively gently and without the creation of significant turbulence.Thus, when exhaust gas A passes through the perforation 42, a significantly reduced flow resistance can be achieved compared to, for example, a sharp-edged transition from the upstream side 54 to the flow openings 44, and the risk of noise being generated by turbulence in this transition area can be significantly reduced.

[0030] In Fig. 5 It can be seen from a tangent line T that, due to the provision of the flow projections 60 in association with the flow openings 44 of the perforation 42, the flow opening flow guide surface 50, which extends curvedly in the flow direction S or in the direction of the opening center axis O of a respective flow opening 44, is almost parallel to the opening center axis O in the region of an outlet end 46 of a respective flow opening 44 or is inclined at a comparatively small angle in the range of 5°-15°. This supports the reduction of turbulence in the exhaust gas flow, particularly in the region of the outlet ends 46 of the flow openings 44.

[0031] An alternative embodiment of a silencer component 30 is shown in Fig. 6 for example, using an alternative embodiment of the exhaust gas guide pipe 32. In this embodiment, no flow projections protruding beyond the downstream side 58 are provided on the wall 40 of the exhaust gas guide pipe 32. This means that the extension length of the flow openings 44 in the flow direction S essentially corresponds to the extension length of the first flow opening length regions L 1 corresponding to the wall thickness W of the wall 40. Even with such an embodiment, the flow openings 44 can be provided with a flow opening flow cross section D decreasing in the flow direction S and the flow opening flow guide surfaces 50, for example, rounded. This can be clearly seen in the comparison of the Fig. 5 und 6 that with essentially the same course, i.e. cross-sectional change profile, of the flow-through opening flow guide surfaces 50 in the first flow-through opening length range L 1, the tangent line T at the outlet end 46 of a respective flow-through opening 44 in the embodiment according to Fig. 6 is more strongly angled with respect to the opening center axis O than in the case of the design of the Fig. 5 .

[0032] The Fig. 6 The variant of a silencer component 30 shown can be provided particularly advantageously if it is produced as a plastic molded part, for example in a die-casting process, in which the through-flow openings 44 and the flow-through opening flow guide surfaces 50 bordering them are produced by appropriate shaping of the molded parts of a casting mold.

[0033] It should be noted that the principles of the present invention can also be applied if the throughflow openings 44 are provided with a fundamentally different structure. For example, these could be designed as slot-like openings through which the exhaust gas A flows and which are delimited by respective throughflow opening flow guide surfaces 50. It can also be provided that the radius of curvature of the throughflow opening flow guide surfaces 50 changes. For example, this radius of curvature could be larger in the area adjacent to the upstream side 54 than in the area adjacent to the downstream side 58 or in the second throughflow opening length ranges L 2 formed in a respective throughflow extension 60.

[0034] It should also be noted that, depending on the flow direction, in a tubular design of a silencer component, the flow openings can also be provided to introduce exhaust gas into the volume delimited by a wall of the tubular exhaust guide component. In this case, the upstream side of the wall of such a tubular silencer component forms the outer peripheral surface, while the downstream side provides the inner peripheral surface and, for example, flow projections are then designed to protrude radially inward. It should also be noted that the flow openings of such a perforation can be arranged in a different pattern than that shown in the figures, and that not all openings of such a perforation need to be the same size.Accordingly, flow projections provided for example in association with flow openings of such a perforation having different cross-sections can also have different extension lengths in the flow direction. For example, the flow projections can have a greater extension length when associated with larger flow openings than when associated with smaller flow openings.

[0035] In a further alternative embodiment, the decreasing flow cross-section could also be achieved by designing the flow-through opening flow guide surfaces with a substantially truncated cone-like structure or by designing several successive sections with a substantially truncated cone-like structure in the flow direction, in order to also achieve a degressive decrease in the flow cross-section of the flow-through openings in the flow direction. However, due to the turbulence that inevitably arises in the region of edge-like transitions, the rounded structure of the flow-through opening flow guide surfaces in the flow direction, as shown in the figures, is preferred.

Claims

1. A muffler for an exhaust system of an internal combustion engine, comprising at least one muffler component (30) with a perforation (42) comprising a plurality of through-flow openings (44) in a wall (40) of the muffler component (30), wherein the through-flow openings (44) can be flowed through in a flow direction (S) in the direction from an upstream side (54) of the wall (40) to a downstream side (58) of the wall (40), wherein, at least in the case of some of the through-flow openings (44) of the perforation (42), a through-flow opening flow cross section (D) decreases degressively in the flow direction (S) in order to provide a through-flow opening flow-guiding surface (50), characterized in that an angle of inclination of the through-flow opening flow-guiding surfaces (50) with respect to an opening center axis (O) is in a range of from 5° to 15° in the region of an outlet end (46) of a respective through-flow opening (44).

2. The muffler as claimed in claim 1, characterized in that in the case of all through-flow openings (44) of the perforation (42), the through-flow opening flow cross section (D) decreases degressively in the flow direction (S) in order to provide the through-flow opening flow-guiding surface (50).

3. The muffler as claimed in claim 1 or 2, characterized in that the through-flow opening flow cross section (D) decreases with a rounded cross-section change profile (D), or / and in that the through-flow opening flow cross section decreases with a substantially edge-free cross-section change profile.

4. The muffler as claimed in any of claims 1-3, characterized in that the through-flow opening flow-guiding surface (50) adjoins the upstream side (54) of the wall (40) substantially without edges.

5. The muffler as claimed in any of claims 1-4, characterized in that the through-flow opening flow cross section (D) decreases in a first through-flow opening opening-length region (L1) corresponding to a wall thickness (W) of the wall (40) between the upstream side (54) of the wall (40) and the downstream side (58) of the wall (40).

6. The muffler as claimed in any of claims 1-5, characterized in that, in association with at least some of the through-flow openings (44), preferably all of the through-flow openings (44), a through-flow extension (60) is provided which projects in the downstream direction beyond the downstream side (58) of the wall (40) and annularly surrounds a respective through-flow opening (44) in a second through-flow opening opening-length region (L2).

7. The muffler as claimed in claim 6, characterized in that, in the case of at least some of the through-flow extensions (60), preferably all of the through-flow extensions (60), the through-flow opening flow cross section (D) of each through-flow opening (44) surrounded by one of the through-flow extensions (60) decreases in the second through-flow opening opening-length region (L2).

8. The muffler as claimed in claim 5 and claim 7, characterized in that the through-flow opening flow cross section (D) decreases to a greater extent in the first through-flow opening opening-length region (L1) than in the second through-flow opening opening-length region (L2).

9. The muffler as claimed in any of claims 1-8, characterized in that the at least one muffler component (30) is designed as an exhaust gas conduit pipe (32, 34), or / and in that the at least one muffler component (30) is designed as a partition wall (22) which separates two muffler chambers (26, 28) from one another.

10. An exhaust system for an internal combustion engine, comprising at least one muffler (10) as claimed in any of claims 1-9.

11. A method for producing a muffler (10) as claimed in any of claims 1-9, characterized in that - the at least one muffler component (30) is constructed with metal material, and rim holes are formed in the wall (40) of the muffler component (30) in order to provide the through-flow opening flow-guiding surfaces (50), or - the at least one muffler component (30) is designed as a plastic molding, and the through-flow opening flow-guiding surfaces (50) are molded onto the wall of the muffler component (30).

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