Silencer for an exhaust system

Abstract

Silencer for an exhaust system of an internal combustion engine, - with a housing (2) in which an expansion chamber (6) is formed, - with an inlet pipe (7) leading exhaust gas into the housing (2), which has an end section (8) in the housing (2) which has an outlet opening (9) in the expansion chamber (6), - with a main outlet pipe (10) leading exhaust gas out of the housing (2), which has an initial section (11) in the housing (2) which projects into the end section (8) of the inlet pipe (7), - with a gap (14) formed in an overlap region (13) between the end section (8) of the inlet pipe (7) and the initial section (11) of the main outlet pipe (10), which gap forms a bypass in the end section (8) of the inlet pipe (7) bypassing the initial section (11) of the main outlet pipe (10), through which exhaust gas can flow from the inlet pipe (7) into the expansion chamber (6), - with a secondary outlet pipe (15) leading exhaust gas out of the housing (2) and having an inlet opening (16) in the expansion chamber (6), - wherein the end section (8) of the inlet pipe (7) and the initial section (11) of the main outlet pipe (10) are designed to be straight, characterized in that - that an axial length (17) of the overlap region (13) is at least twice as large as a diameter (18) of the end section (8) of the inlet pipe (7).

Description

[0001] The present invention relates to a muffler for an exhaust system of an internal combustion engine, preferably of a road vehicle, in particular a passenger car. The invention also relates to an exhaust system for an internal combustion engine equipped with such a muffler.

[0002] In sporty passenger cars, especially sports cars, there is often a need for acoustic feedback on the current operating status of the vehicle or its internal combustion engine. This need is particularly evident during acceleration, i.e., at upper partial loads and at full engine load. Therefore, comparatively low sound attenuation is desired under these operating conditions. At the same time, the lowest possible exhaust backpressure in the muffler for the exhaust gas flow is desired under these operating conditions in order to be able to access as much power from the internal combustion engine as possible to propel the vehicle. On the other hand, there is a need to achieve the most efficient acoustic attenuation possible under low partial loads of the internal combustion engine, particularly when idling.Since there is a lot of excess power in this operating range of the internal combustion engine, a relatively high back pressure in the muffler can be accepted.

[0003] To enable a muffler to meet these opposing requirements, it is possible, as shown, for example, in DE 10 2005 041 692 A1, to implement two exhaust paths in the muffler, one of which can be controlled by a control device, while the other is generally uncontrolled. At full load, the controllable exhaust path is opened, reducing exhaust backpressure. With appropriate routing of this controlled exhaust path, reduced sound attenuation can also be achieved. At low power, however, the controllable exhaust path is blocked, so that the exhaust gas flows only through the uncontrolled path, where it is efficiently attenuated.The problem with such systems, however, is that even at full load, a comparatively efficient acoustic coupling of the controllable, open exhaust path with the acoustic damping means of the silencer is provided, so that a certain degree of sound damping is still achieved even at full load.

[0004] From JP 2005 - 256 736 A a silencer is known in which an inlet pipe and an outlet pipe are inserted into one another in a silencer housing in such a way that an annular channel is created which creates a non-flow acoustic connection to the interior of the silencer housing in order to form a Helmholtz resonator whose resonance chamber is formed by the interior and whose throat is formed by the annular channel.

[0005] A generic silencer is known from DE 41 40 429 A1 and comprises a housing in which an expansion chamber is formed, an inlet pipe leading exhaust gas into the housing, which has an end section in the housing which has an outlet opening in the expansion chamber, a main outlet pipe leading exhaust gas out of the housing, which has an initial section in the housing which projects into the end section of the inlet pipe, a gap formed in an overlap region between the end section of the inlet pipe and the initial section of the main outlet pipe, which gap forms a bypass in the end section of the inlet pipe which bypasses the initial section of the main outlet pipe and through which exhaust gas can flow from the inlet pipe into the expansion chamber, and a secondary outlet pipe leading exhaust gas out of the housing, which secondary outlet pipe has an inlet opening in the expansion chamber.In addition, in the known silencer, the end section of the inlet pipe and the initial section of the main outlet pipe are designed in a straight line.

[0006] The present invention addresses the problem of providing an improved embodiment for a silencer of the type described above, which is characterized in particular in that an acoustic coupling of an exhaust gas path active at full load with sound damping means of the silencer is reduced.

[0007] This problem is solved according to the invention by the subject matter of the independent claim. Advantageous embodiments are the subject matter of the dependent claims.

[0008] The invention is based on the general idea of ​​forming an overlap region between an inlet pipe and a main outlet pipe, in which the inlet pipe and main outlet pipe are inserted into one another in such a way that a bypass is formed in this overlap region between the inlet pipe and outlet pipe, through which exhaust gas can flow from the inlet pipe past the main outlet pipe into an expansion chamber. A secondary outlet pipe, through which exhaust gas can flow out of the expansion chamber, also opens into this expansion chamber. The pipe-in-pipe arrangement proposed according to the invention ensures that the inlet pipe and the main outlet pipe act like a continuous exhaust pipe for part of the exhaust gas flow, which is largely decoupled from the sound-damping means of the silencer, whereby low sound attenuation and low exhaust backpressure can be achieved for this part of the exhaust gas flow.The remaining exhaust flow, however, flows through the bypass into the expansion chamber and out of the muffler through the secondary outlet pipe. The expansion chamber effectively dampens this portion of the exhaust flow.

[0009] An expansion chamber is generally characterized by a free space into which airborne sound can propagate. In principle, sound-absorbing material can be placed in an expansion chamber, just like in an absorption chamber. However, such an expansion chamber is not completely filled with sound-absorbing material. Rather, a free space must remain within the expansion chamber into which airborne sound can expand, e.g., through a bypass or a perforation.

[0010] Furthermore, it has been shown that such an overlap region, in which an initial section of the main outlet pipe extends into an end section of the inlet pipe, improves the use of the main outlet pipe as a resonance pipe, for example, in the form of a λ / 4 pipe or a λ / 2 pipe, since particularly efficient vibration excitation can be achieved in the overlap region. In this case, the main outlet pipe can be inserted into the inlet pipe as deeply as necessary to achieve optimal vibration excitation in the main outlet pipe.

[0011] According to a first solution according to the invention, in which the end section of the inlet pipe and the initial section of the main outlet pipe are designed to be rectilinear, the axial length of the overlap region, with which the main outlet pipe extends into the inlet pipe, is at least twice the diameter of the end section of the inlet pipe. As a result, a predetermined flow, which, for example, has a predetermined flow resistance, is realized in a gap formed radially between the end section of the inlet pipe and the initial section of the main outlet pipe, which forms the aforementioned bypass.

[0012] In particular, the axial length of the overlap region may be at least three times or at least four times the diameter of the end portion of the inlet pipe.

[0013] According to a particularly advantageous embodiment, the flow-through cross-sections and / or the flow resistances of the main outlet pipe, secondary outlet pipe, and gap can be coordinated such that 40% to 60% of the exhaust gas flow supplied via the inlet pipe is discharged through the main outlet pipe. A flow split of approximately 50:50 between the main outlet pipe and the secondary outlet pipe is preferred. It has been shown that with such a flow split, for example, a control device for controlling the flow through the main outlet pipe can be dispensed with. Accordingly, the effort required to manufacture such a silencer is reduced. In this case, the main outlet pipe and secondary outlet pipe are uncontrolled, and exhaust gas constantly flows through them during operation of the silencer.

[0014] According to a second solution according to the invention, the flow-through cross-section of the gap in the overlap region is, on average, approximately the same size as the flow-through cross-section of the main outlet pipe. With a homogeneous flow in the inlet pipe upstream of the overlap region, such a ratio of the flow-through cross-sections of the main outlet pipe and the gap results in the exhaust gas flow being split approximately equally between the main outlet pipe and the secondary outlet pipe.

[0015] In another advantageous embodiment, the housing can be cylindrical and equipped with a shell and two end plates. The inlet pipe is expediently passed through the shell. The main outlet pipe is expediently passed through one end plate.

[0016] The secondary outlet pipe is expediently routed through the other end plate. This allows the muffler to be implemented, in particular, as a transverse muffler, which, when installed, is arranged transversely to a vehicle's longitudinal axis with respect to its longitudinal center axis. The outlet pipes exiting the housing at opposite axial ends can form two tailpipes of the exhaust system or lead to two tailpipes. Alternatively, the main outlet pipe and secondary outlet pipe can also exit the housing through the same end plate. It is also conceivable to implement the housing in a shell construction.

[0017] It can be advantageous to provide the inlet pipe with no perforation. This ensures efficient flow guidance to the main outlet pipe. Additionally or alternatively, the main outlet pipe can be imperforate. This measure also results in efficient flow guidance within the main outlet pipe. Additionally or alternatively, the secondary outlet pipe can be imperforate. This measure also ultimately results in particularly efficient flow guidance in the secondary outlet pipe. If all three of the aforementioned pipes in the housing are imperforate, the housing advantageously contains only the expansion chamber.

[0018] According to a third solution according to the invention, the main outlet pipe has a perforation in the expansion chamber. This ensures that airborne sound entrained in the exhaust stream can escape through the perforation of the main outlet pipe into the expansion chamber, thereby achieving a certain degree of damping. Additionally or alternatively, the inlet pipe can have a perforation in the overlap area, creating an acoustic coupling to a space surrounding the overlap area.

[0019] In another advantageous embodiment, at least one additional chamber can be formed in the housing. The inlet pipe and / or the secondary outlet pipe can have a perforation in at least one such additional chamber. As a result, the respective additional chamber is acoustically connected via the respective perforation and can serve to dampen the entrained airborne sound. For example, the inlet pipe can have a perforation in the overlap area.

[0020] According to a particularly advantageous embodiment, two further chambers can be formed in the housing, namely a first further chamber which is axially adjacent to the expansion chamber, and a second further chamber which is axially adjacent to the first further chamber on a side facing away from the expansion chamber. It can now be expediently provided that the auxiliary outlet pipe has a perforation in the second further chamber. As a result, the second further chamber is acoustically coupled via the perforation of the auxiliary outlet pipe. The second further chamber can, for example, be designed as an absorption chamber filled with sound-absorbing material. It is also conceivable to design the second further chamber as an expansion chamber.

[0021] According to an advantageous development, the first additional chamber can be designed as an absorption chamber filled with sound-absorbing material. The first additional chamber can be separated from the expansion chamber by a first partition wall and from the second additional chamber by a second partition wall. The partition walls are arranged axially between the end plates and are axially spaced from these and from one another. The acoustic connection of the first additional chamber acting as an absorption chamber can be realized via a perforation in the inlet pipe or via a perforation in the secondary outlet pipe or via a perforation in the first partition wall or via a perforation in the second partition wall. It is also conceivable to achieve the acoustic coupling through a combination of the above perforations.An embodiment is conceivable in which the first partition wall and the second partition wall are imperforate, while the secondary outlet pipe has a perforation in the first additional chamber. It is also conceivable for the inlet pipe to pass through the first partition wall and be imperforate in the first additional chamber.

[0022] In a preferred embodiment, the first partition wall can be perforated, so that the first additional chamber is acoustically coupled to the expansion chamber. If the second partition wall is unperforated, the acoustic coupling of the first additional chamber to the expansion chamber occurs through the first partition wall. Alternatively, the second partition wall can also be perforated, so that the first additional chamber is acoustically coupled to the expansion chamber and to the second additional chamber.

[0023] In an alternative embodiment, however, the first partition wall is imperforate, while the second partition wall is perforated, so that the acoustic connection between the first additional chamber and the second additional chamber is established through the second partition wall. Furthermore, the inlet pipe and secondary outlet pipe in the first additional chamber are imperforate, while the secondary outlet pipe in the second additional chamber has a perforation. In this case, the second additional chamber is expediently designed as an expansion chamber, so that airborne sound can reach the perforated second partition wall through a free space in the expansion chamber.

[0024] A preferred embodiment results when an absorption chamber adjoins the expansion chamber and a resonance chamber adjoins the absorption chamber. The absorption chamber can be acoustically connected to the expansion chamber by a perforation in the first partition. Likewise, the inlet pipe can have a perforation in the overlap area located in the absorption chamber. The resonance chamber can be acoustically connected to the expansion chamber via a connecting pipe, wherein the connecting pipe penetrates both partitions. The second partition is expediently unperforated. The secondary outlet pipe and the main outlet pipe are expediently unperforated in this embodiment.

[0025] However, an embodiment is particularly advantageous in which two further chambers are formed in the housing, namely a first further chamber which is axially connected to the expansion chamber via a first partition wall, and a second further chamber which is axially connected to the first further chamber on a side facing away from the expansion chamber via a second partition wall, wherein the first further chamber is designed as an absorption chamber which is filled with a sound-absorbing material and which is acoustically coupled to the expansion chamber by the perforated first partition wall, and wherein the second further chamber is designed as a resonator chamber which is separated from the first further chamber by means of the imperforate second partition wall and which is acoustically connected to the secondary outlet pipe or to the expansion chamber via a resonator pipe.Thus, broadband damping can be realized by means of expansion, absorption and resonance via the secondary path.

[0026] The main exhaust line and the secondary exhaust line are expediently arranged parallel to each other within the housing. The pipes are expediently arranged within the housing such that, during operation of the internal combustion engine, the exhaust gas in the expansion chamber must be deflected 180° from an outlet opening of the gap in order to enter the secondary exhaust pipe through the inlet opening of the secondary exhaust pipe. If both outlet pipes exit the housing through the same end plate, the inlet opening of the secondary exhaust pipe and the outlet opening of the gap are expediently arranged such that the flow in the expansion chamber must be deflected twice by 180° in order to reach the inlet opening of the secondary exhaust pipe from the outlet opening of the gap.

[0027] The main outlet pipe is expediently supported radially on the inlet pipe in the overlap region in order to reduce relative movements between the inlet pipe and the main outlet pipe. For this purpose, the main outlet pipe can be supported on the inlet pipe via several webs that are distributed in the circumferential direction of the main outlet pipe and bridge the gap. Additionally or alternatively, it can be provided that the main outlet pipe is supported on the inlet pipe via at least one perforated ring that extends in the circumferential direction of the main outlet pipe and fills the gap. In both cases, significant stabilization is achieved, which can be implemented comparatively inexpensively.

[0028] Furthermore, the main outlet pipe can be supported by a perforated intermediate floor located in the expansion chamber and supported on the housing. This measure also stabilizes the position of the main outlet pipe within the housing. The perforated intermediate floor does not create any acoustic separation within the expansion chamber, thus maintaining the chamber as a single unit.

[0029] According to an advantageous development, the main exhaust pipe can be controlled with regard to the flow of exhaust gas through it by means of a control device. This control device can be coupled to the main exhaust pipe inside the housing or outside thereof. This control device can in particular be designed such that it opens the main exhaust pipe at least when the internal combustion engine is at full load and that it closes the main exhaust pipe at least when the internal combustion engine is at low partial load. Control devices are also conceivable in which one, several or any number of intermediate positions can be realized. The control device can be configured such that it operates actively, i.e. is equipped with an actuator, or such that it operates passively and is therefore only adjusted by displacement forces of the flow.A semi-active design of the control device is also conceivable, which, for example, operates with a pressure cell and is controlled by the pressure prevailing in the inlet pipe and / or in the expansion chamber and / or in the initial area of ​​the main outlet pipe.

[0030] Further important features and advantages of the invention emerge from the subclaims, from the drawing and from the associated description of the figures based on the drawing.

[0031] It is understood that the features mentioned above and those to be explained below can be used not only in the combination specified in each case, but also in other combinations or on their own, without departing from the scope of the present invention.

[0032] Preferred embodiments of the invention are illustrated in the drawing and are explained in more detail in the following description.

[0033] The only Fig. 1 shows a highly simplified, circuit diagram-like schematic diagram of a silencer.

[0034] Accordingly Fig. 1, a muffler 1, which is intended for an exhaust system of an internal combustion engine, comprises a housing 2, which is preferably cylindrical in design and accordingly has a cylindrical casing 3 and, at each of its axial ends, an end plate, namely a first end plate 4 and a second end plate 5. The exhaust system or the internal combustion engine is expediently arranged in a road vehicle. This is preferably a passenger car, in particular a sports car.

[0035] An expansion chamber 6 is formed in the housing 2. It is characterized by a free space into which exhaust gas or the airborne sound entrained therein can expand. Sound-absorbing material can optionally be arranged in the expansion chamber 6 outside this free space, e.g., along boundary walls.

[0036] The silencer 1 is equipped with an inlet pipe 7, which has an end section 8 in the housing 2, with which the inlet pipe 7 ends in the expansion chamber 6. For this purpose, the end section 8 has an outlet opening 9 in the expansion chamber 6. Furthermore, the silencer 1 is equipped with a main outlet pipe 10, which has a starting section 11 in the housing 2. This starting section 11 is inserted into the end section 8 of the inlet pipe 7 and ends inside the inlet pipe 7. Accordingly, the starting section 11 is in Fig. 1 only shown with a broken line. The initial section 11 has an inlet opening 12 within the inlet pipe 7. Since the initial section 11 of the main outlet pipe 10 projects into the end section 8 of the inlet pipe 7, an overlap region 13 is formed between the end section 8 and the initial section 11, which overlap region 13 Fig. 1 is indicated by a curly bracket. In this overlap area 13, a gap 14 is formed radially between the end section 8 and the beginning section 11. This gap 14, in turn, forms a bypass that bypasses the beginning section 11 within the end section 8. Thus, exhaust gas from the inlet pipe 7 can flow through the gap 14 past the outside of the beginning section 11 into the expansion chamber 6. Finally, the silencer 1 also has a secondary connection pipe 15, which has an inlet opening 16 in the expansion chamber 6.

[0037] The end section 8 of the inlet pipe 7 and the initial section 11 of the main outlet pipe 10 expediently extend in a straight line, so that the overlap region 13 is also straight. The initial section 11 extends axially into the end section 8 so far that the overlap region 13 has an axial length 17, which in the example shown is approximately four times as large as a diameter 18 of the inlet pipe 7 in the end section 8. The insertion depth or the length 17 of the overlap region 13 can be used to optimize a resonance effect in the main outlet pipe 10, which can be used to specifically dampen a certain frequency of the sound transported in the exhaust gas.

[0038] The flow-through cross sections or flow resistances of the main outlet line 10, the secondary outlet line 15 and the gap 14 are expediently matched to one another such that, at least at partial load and / or full load of the internal combustion engine, a predetermined division of an exhaust gas flow 19 supplied via the inlet pipe 7 into a main partial flow 20 discharged through the main outlet pipe 10 and a secondary partial flow 21 discharged through the secondary outlet pipe 15 is established. The supplied total flow 19, the main partial flow 20 and the secondary partial flow 21 are in Fig. 1 by arrows. Preferably, the total flow 19 is divided into the main flow 20 and the secondary flow 21 in a ratio ranging from 40:60 to 60:40. A ratio of approximately 50:50 is particularly advantageous.

[0039] In order to achieve this division of the total flow 19 into the main partial flow 20 and the secondary partial flow 21, it can be provided that a flow-through cross-section of the gap 14 in the overlap region 13 is selected to be on average approximately the same size as a flow-through cross-section of the main outlet pipe 10 in the initial section 11. Accordingly, the flow-through cross-sections of the gap 14 and initial section 11 are each approximately half the size of the flow-through cross-section of the inlet pipe 7 immediately upstream of the inlet opening 12 of the main outlet pipe 10.

[0040] Although in Fig. 1 shows a concentric arrangement of starting section 11 and end section 8, which leads to a gap 14 that runs completely around the starting section 11 in a ring shape, basically any eccentric arrangement can be selected. In particular, it is also conceivable for the starting section 11 to touch the end section 8 in a line. It is also conceivable for the end section 8 and starting section 11 to have a common wall section that is limited in the circumferential direction of the overlap region 13. The gap 14 can also have different geometries depending on the cross-sectional geometry of the starting section 11 and end section 8 in the overlap region 13. It can, for example, be annular or C-shaped for round pipe cross-sections and U-shaped or I-shaped for angular, preferably rectangular, pipe cross-sections.

[0041] In the preferred embodiment shown here with a cylindrical housing 2, the inlet pipe 7 passes through the casing 3, while the outlet pipes 10 and 15 pass through the end plates 4, 5. Specifically, the main outlet pipe 10 passes through the first end plate 4, while the secondary outlet pipe 15 passes through the second end plate 5. Alternatively, both outlet pipes 10, 15 can pass through the same end plate 4 or 5.

[0042] Furthermore, in the embodiment shown here, two further chambers are formed in the housing 2, namely a first further chamber 22 and a second further chamber 23. The first further chamber 22 is axially connected to the expansion chamber 6. The second further chamber 23 is axially connected to the first further chamber 22 on a side facing away from the expansion chamber 6. The axial direction is defined by a longitudinal central axis 24 of the cylindrical housing 2. The first further chamber 22 is separated from the expansion chamber 6 by means of a first partition wall 25 and from the second further chamber 23 by means of a second partition wall 26. An embodiment is preferred in which the first further chamber 22 is designed as an absorption chamber and is filled with a sound-absorbing material 27. The first further chamber 22 is expediently completely filled with sound-absorbing material 27. Furthermore, the first partition wall 25 is preferably perforated.The first additional chamber 22 is thus acoustically connected to the expansion chamber 6. The first partition wall 25 is penetrated by the inlet pipe 7 and the secondary outlet pipe 15. The second partition wall 26 is preferably designed to be imperforate. The second additional chamber 23 can preferably be designed as an expansion chamber, as an absorption chamber, or as a resonance chamber. Furthermore, an embodiment is preferred in which the inlet pipe 7 and the main outlet pipe 10 are imperforate. In contrast, the secondary outlet pipe 15 in the second additional chamber 23 can be provided with a perforation 28, whereby the second additional chamber 23 is acoustically coupled to the secondary outlet pipe 15. The secondary outlet pipe 15 can be imperforate in the first additional chamber 22 or have a further perforation, not shown here. In conjunction with the perforation 28, the second additional chamber 23 forms a further expansion chamber.

[0043] Instead of the perforation 28 shown, a resonator tube 29, indicated by a dashed line, can also be provided on the secondary outlet pipe 15. This resonator tube, in conjunction with the free volume of the second additional chamber 23, forms a Helmholtz resonator. The second additional chamber 23 is then a resonance or resonator chamber.

[0044] Preferably, a resonator tube 32 can also be used to acoustically connect the expansion chamber 6 to the second additional chamber 23, in order to form such a Helmholtz resonator. In this case, too, the second additional chamber 23 is a resonator chamber. The resonator tube 32 penetrates the perforated first partition wall 25 and the imperforate second partition wall 26, as well as the first additional chamber 22, which in this case serves as an absorption chamber. Furthermore, in this case, the secondary outlet tube 15 and the inlet tube 7 are each imperforate, at least in the second additional chamber 23.

[0045] Alternatively, it is also conceivable to provide, in addition to the perforation 28, a connecting pipe 30 which Fig. 1 is also indicated only by a dashed line. This connecting pipe 30 then interacts with the free volume of the first additional chamber 22 as a Helmholtz resonator. In this case, it may be expedient to design the second additional chamber 23, which is acoustically connected to the secondary outlet line 15 via the perforation 28, as an absorption chamber, which is then filled with sound-absorbing material 27.

[0046] In Fig. 1 also shows a control device 31, with the aid of which the exhaust gas can flow through the main outlet pipe 10. In particular, this allows the division of the total flow 19 into the main partial flow 20 and the secondary partial flow 21 to be varied. For example, when the internal combustion engine is at full load, the control device 31 can open the main outlet pipe 10, so that a comparatively large main partial flow 20 is created. In a lower partial load range, however, the control device 31 can block the main outlet pipe 10, so that a comparatively large secondary partial flow 21 is created, which in the extreme case corresponds to the total flow 19. In the example shown, this optional control device 31 is arranged outside the housing 2. In another embodiment, the control device 31 can also be arranged on the housing 2 or in the housing 2.

[0047] According to Fig.1, it is also provided that the main outlet pipe 10 is supported radially on the inlet pipe 7 in the overlap region 13. In the example shown, this is achieved in the region of the inlet opening 12 of the main outlet pipe 10 by means of several webs 33 that support the main outlet pipe 10 on the inlet pipe 7, which are distributed in the circumferential direction of the main outlet pipe 10 and arranged at a distance from one another, and which each bridge the gap 14. Furthermore, in the example, in the region of the outlet opening 9 of the inlet pipe 7, a perforated ring 34 is provided, via which the main outlet pipe 10 is supported on the inlet pipe 7, which extends in the circumferential direction of the main outlet pipe 10 and fills the gap 14. Finally, it is additionally or alternatively provided that the main outlet pipe 10 is supported on a perforated intermediate floor 35 which is arranged in the expansion chamber 6 and supported on the housing 2.

[0048] In the overlap area 13, a tube-in-tube arrangement of inlet pipe 7 and main outlet pipe 10 is thus created, which enables virtually uninterrupted flow through the housing 2 when the main outlet pipe 10 is open. This tube-in-tube arrangement thus creates a main exhaust gas path through the housing 3. If, in addition, the inlet pipe 7 and the main outlet pipe 10 are unperforated and, in particular, the end section 8 and the initial section 11 are also unperforated in the overlap area 13, only a very low acoustic coupling with the acoustic damping means of the silencer 1 occurs via this quasi-continuous pipe. In particular, only a comparatively small volume of the silencer 1 is coupled to this main path.These acoustic damping means are, for example, as explained above, the expansion chamber 6, the first additional chamber 22, and the second additional chamber 23, which can optionally serve as an expansion chamber, an absorption chamber, or a resonance chamber of a Helmholtz resonator. When the main outlet pipe 10 is open, the airborne sound entrained in the overall flow 19 can exit the silencer 1 through the main outlet pipe 10 largely undamped along the main exhaust path, providing the driver with the desired acoustic feedback. If, however, the main outlet pipe 10 is blocked, the airborne sound entrained in the overall flow 19 is forced to follow the secondary exhaust path through the secondary outlet pipe 15, whereby all of the provided damping means are active and accordingly effect efficient damping of the entrained airborne sound.Furthermore, the pipe-in-pipe arrangement allows the coupling of the main outlet pipe 10, which acts as a resonance pipe, to be optimized.

Claims

[1] Silencer for an exhaust system of an internal combustion engine, - with a housing (2) in which an expansion chamber (6) is formed, - with an inlet pipe (7) leading exhaust gas into the housing (2), which has an end section (8) in the housing (2) which has an outlet opening (9) in the expansion chamber (6), - with a main outlet pipe (10) leading exhaust gas out of the housing (2), which has an initial section (11) in the housing (2) which projects into the end section (8) of the inlet pipe (7), - with a gap (14) formed in an overlap region (13) between the end section (8) of the inlet pipe (7) and the initial section (11) of the main outlet pipe (10), which gap forms a bypass in the end section (8) of the inlet pipe (7) bypassing the initial section (11) of the main outlet pipe (10), through which exhaust gas can flow from the inlet pipe (7) into the expansion chamber (6), - with a secondary outlet pipe (15) leading exhaust gas out of the housing (2) and having an inlet opening (16) in the expansion chamber (6), - wherein the end section (8) of the inlet pipe (7) and the initial section (11) of the main outlet pipe (10) are designed to be straight, characterized by , - that an axial length (17) of the overlap region (13) is at least twice as large as a diameter (18) of the end section (8) of the inlet pipe (7). [2] Silencer according to claim 1, characterized by that the flow-through cross-sections and / or the flow resistances of the main outlet pipe (10), secondary outlet pipe (15) and gap (14) are coordinated with one another in such a way that, at partial load of the internal combustion engine, 40% to 60% of the exhaust gas flow (19) supplied via the inlet pipe (7) is discharged through the main outlet pipe (10). [3] Silencer for an exhaust system of an internal combustion engine, - with a housing (2) in which an expansion chamber (6) is formed, - with an inlet pipe (7) leading exhaust gas into the housing (2), which has an end section (8) in the housing (2) which has an outlet opening (9) in the expansion chamber (6), - with a main outlet pipe (10) leading exhaust gas out of the housing (2), which has an initial section (11) in the housing (2) which projects into the end section (8) of the inlet pipe (7), - with a gap (14) formed in an overlap region (13) between the end section (8) of the inlet pipe (7) and the initial section (11) of the main outlet pipe (10), which gap forms a bypass in the end section (8) of the inlet pipe (7) bypassing the initial section (11) of the main outlet pipe (10), through which exhaust gas can flow from the inlet pipe (7) into the expansion chamber (6), - with a secondary outlet pipe (15) leading exhaust gas out of the housing (2) and having an inlet opening (16) in the expansion chamber (6), characterized by , - that in the overlapping area (13) a flow-through cross-section of the gap (14) is on average approximately the same size as a flow-through cross-section of the main outlet pipe (10). [4] Silencer according to one of claims 1 to 3, characterized by , - that the housing (2) is cylindrical and has a shell (3) and two end plates (4, 5), - that the inlet pipe (7) passes through the casing (3), - that the main outlet pipe (10) passes through one end plate (4), - that the secondary outlet pipe (15) passes through the other end plate (5). [5] Silencer according to one of claims 1 to 4, characterized by , - that the inlet pipe (7) is unperforated, and / or - that the main outlet pipe (10) is unperforated, and / or - that the secondary outlet pipe (15) is unperforated. [6] Silencer for an exhaust system of an internal combustion engine, - with a housing (2) in which an expansion chamber (6) is formed, - with an inlet pipe (7) leading exhaust gas into the housing (2), which has an end section (8) in the housing (2) which has an outlet opening (9) in the expansion chamber (6), - with a main outlet pipe (10) leading exhaust gas out of the housing (2), which has an initial section (11) in the housing (2) which projects into the end section (8) of the inlet pipe (7), - with a gap (14) formed in an overlap region (13) between the end section (8) of the inlet pipe (7) and the initial section (11) of the main outlet pipe (10), which gap forms a bypass in the end section (8) of the inlet pipe (7) bypassing the initial section (11) of the main outlet pipe (10), through which exhaust gas can flow from the inlet pipe (7) into the expansion chamber (6), - with a secondary outlet pipe (15) leading exhaust gas out of the housing (2) and having an inlet opening (16) in the expansion chamber (6), characterized by , - that the inlet pipe (7) has a perforation in the overlap area (13). [7] Silencer according to one of claims 1 to 6, characterized by , - that at least one further chamber (22, 23) is formed in the housing (2), - that the inlet pipe (7) and / or the secondary outlet pipe (15) has / have a perforation (28) at least in such a further chamber (22, 23). [8] Silencer according to one of claims 1 to 7, characterized by , - that two further chambers (22, 23) are formed in the housing (2), namely a first further chamber (22) which is axially connected to the expansion chamber (6) via a first partition wall (25), and a second further chamber (23) which is axially connected to the first further chamber (22) on a side facing away from the expansion chamber (6) via a second partition wall (26), - that the first further chamber (22) is designed as an absorption chamber which is filled with a sound-absorbing material (27) and which is acoustically coupled to the expansion chamber (6) via the perforated first partition wall (25), - that the second further chamber (23) is designed as a resonator chamber which is separated from the first further chamber (22) by the imperforate second partition wall (26) and which is acoustically connected to the secondary outlet pipe (15) or to the expansion chamber (6) via a resonator pipe (29; 32). [9] Silencer according to one of claims 1 to 8, characterized by that the main outlet pipe (10) is supported radially on the inlet pipe (7) in the overlap area (13). [10] Silencer according to claim 9, characterized by that the main outlet pipe (10) is supported on the inlet pipe (7) via a plurality of webs (33) which are distributed in the circumferential direction of the main outlet pipe (10) and bridge the gap (14). [11] Silencer according to claim 9 or 10, characterized bythat the main outlet pipe (10) is supported on the inlet pipe (7) via at least one perforated ring (34) which extends in the circumferential direction of the main outlet pipe (10) and fills the gap (14). [12] Silencer according to one of claims 1 to 11, characterized by that the main outlet pipe (10) is supported on a perforated intermediate floor (35) which is arranged in the expansion chamber (6) and supported on the housing (2). [13] Silencer according to one of claims 1 to 12, characterized by that the main outlet pipe (10) is controlled with regard to the flow of exhaust gas by means of a control device (31) which opens the main outlet pipe (10) at least at full load of the internal combustion engine and blocks the main outlet pipe (10) at least at low partial load. [14] Exhaust system for an internal combustion engine, in particular of a motor vehicle, with an exhaust line which leads from at least one exhaust manifold to at least one tailpipe and in which at least one silencer (1) according to one of claims 1 to 13 is arranged.

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