EP1760279B1 - Silencer for an exhaust system - Google Patents

Description

The present invention relates to a silencer for an exhaust system of an internal combustion engine, in particular of a motor vehicle.

Typically, a muffler comprises a housing having at least one exhaust inlet and at least one exhaust outlet. In this case, tubes can protrude into the housing on the inlet side and outlet side, it being fundamentally possible to provide at least two tubes on the inlet side or outlet side which lead into or out of the housing parallel to one another. In the case of silencers, there is generally the problem that the flow through the silencer takes place against a flow resistance which generates a pressure increase in the exhaust system upstream of the silencer. This increase in pressure can significantly affect their performance and efficiency in certain operating conditions of the internal combustion engine. Therefore, it is possible in principle to be able to open and lock at least one of the parallel tubes as required by means of a corresponding control device. At low speeds or at low load of the internal combustion engine is the switchable tube closed, while it opens at higher speed or greater load. By adding this switchable tube, the flow resistance of the muffler can be considerably reduced. However, it has been shown that this switching process can be accompanied by an additional noise emission into the environment, since the attenuation of the muffler is basically optimized with regard to operating conditions with low exhaust gas flow.

Out DE 197 43 446 A1 It is known, the exhaust system of the internal combustion engine, at least in a section of double-flow, so form with two separate, parallel-flow exhaust pipes. In each of these exhaust pipes then a separate muffler is arranged. The two silencers have different damping characteristics, so they are tuned to different frequencies or frequency ranges. Furthermore, one of the exhaust pipes can be opened and closed by means of a control flap. With a small exhaust gas flow, the switchable exhaust pipe is blocked, so that only one silencer flows through. For large exhaust gas flows, the switchable exhaust pipe is open so that both mufflers are flowed through.

The present invention is concerned with the problem of providing a muffler of the type mentioned, an improved embodiment, which is characterized by an improved damping effect and by an inexpensive manufacturability.

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

The invention is based on the general idea to acoustically couple a switchable tube of the muffler with a damper system, in such a way that the damper system is active on the one hand with the tube open and closed, so unfolds its respective damping effect, and on the other hand with another open pipe Damping characteristic than when the tube is closed. By this construction, the switchable tube forms a component of an effective damper system even when closed, which changes its damping characteristic when opening the tube, but remains active. Particularly advantageous is the fact that with the help of a control device on the one hand the flow resistance of the muffler is controllable and on the other hand, the damping characteristic of the muffler can be varied. In this case, the damper system connected to the switchable tube can be designed to be particularly advantageous in such a way that it damps the interfering or the most disturbing frequencies or frequency ranges in both switching states.

The damper system has a volume that is acoustically coupled to the at least one switchable tube, so in addition to the volume of the switchable tube is available. This extra volume can be used to realize different Damper types are used, such as a Helmholtz resonator or a λ / 4 resonator or a reflection chamber. This volume can preferably be used for damping relatively low frequencies or frequency ranges.

Other important features and advantages of the invention will become apparent from the dependent claims, from the drawings and from the associated figure description with reference to the drawings.

It is understood that the features mentioned above and those yet to be explained below can be used not only in the particular combination given, but also in other combinations or in isolation, without departing from the scope of the present invention.

Preferred embodiments of the invention are illustrated in the drawings and will be described in more detail in the following description, wherein like reference numerals refer to the same or similar or functionally identical components.

Fig. 1 bis 6

jeweils eine stark vereinfachte, schaltplanartige Prinzipdarstellung eines Schalldämpfers, bei unterschiedlichen Ausführungsformen.

Show, in each case schematically,

Fig. 1 to 6

in each case a greatly simplified, schematic diagram-like representation of a muffler, in different embodiments.

According to the Fig. 1 to 6 a muffler 1 according to the invention comprises a housing 2 with at least one exhaust gas inlet 3 and at least one exhaust gas outlet 4, 5. The muffler 1 is provided for installation in an exhaust system, not shown here, of an internal combustion engine, also not shown, wherein the internal combustion engine is preferably arranged in a motor vehicle. In the present example, the housing 2 has only a single exhaust inlet 3, while it has two separate exhaust gas outlets 4, 5. The housing 2 is equipped on its inlet side or on its outlet side with at least two tubes 6, 7. In the embodiments shown, in each case exactly two tubes 6, 7 are provided, which are also arranged on the outlet side as an example and are thus assigned in each case to one of the exhaust gas outlets 4, 5. In principle, however, another embodiment is possible in which the two tubes 6, 7 are arranged on the inlet side.

In the embodiments shown here, the two tubes 6, 7 led out of the housing 2 separately. It is in principle possible that the two tubes 6, 7 are brought together outside the housing 2 to form a common tube. At inlet-side tubes 6, 7 they can branch off from the housing 2 from a common pipe. Likewise, it is basically possible that the two inlet-side or outlet-side tubes 6, 7 are still combined within the housing 2 to form a common tube or branch off from a common tube.

One of these tubes 6, 7, here the lower tube 7, is permanently open. In contrast, the other tube 6, here the upper tube 6, designed controllable or switchable. For this purpose, a control device 8 is provided, with the aid of which the controllable tube 6 can be opened and closed, that is, at least switchable between an open state and a closed state. In the closed state of the switchable tube 6, the exhaust gases flow through the operation of the muffler 1 exclusively the permanently open tube 7. Accordingly, the exhaust gases flow z. B. via an inlet pipe 9 through the exhaust gas inlet 3 into the housing 2 and via the permanently open pipe 7 through the associated exhaust gas outlet 5 out of the housing 2 out. The exhaust gas flow is symbolized by arrows, which are drawn by a solid line. In the open state of the switchable tube 6, the exhaust gases can also flow out of the housing 2 via the switchable tube 6 through the associated exhaust gas outlet 4, which is symbolized by an arrow drawn with a broken line.

The control device 8 may for example have a flap 10 which is arranged in the switchable tube 6 and cooperates with a drive 11. In this case, the control device 8 as in the embodiments of Fig. 1 and 3 to 6 be arranged outside the housing 2. Likewise, the control device 8 as in the embodiment according to Fig. 2 be arranged within the housing 2. The controller 8 may be passive or active. The passive control device 8 controls the controllable tube 6 preferably in Dependence of the prevailing exhaust pressure. The drive 11 may then be formed for example by a return spring, which biases the flap 10 in its closed position. With sufficient exhaust pressure, the flap 10 is pressed and so the controllable tube 6 is opened. In contrast, an active control device 8 can control the controllable tube 6 as a function of operating parameters of the internal combustion engine, in particular as a function of the speed and / or load of the internal combustion engine. For example, the control device 8 closes the controllable tube 6 at low load or in a lower speed range. At higher load or at a larger speed range then the controllable tube 6 is opened.

According to the invention, the switchable tube 6 is acoustically coupled to a damper system 12. This damper system 12 is designed so that it is active in both open and closed switchable tube 6, but has 6 dependent switching characteristics of the switching state of the switchable tube. This means that the damper system 12 has a different damping characteristic when the switchable tube 6 is open than when the switchable tube 6 is closed. The different damping characteristics are characterized by the damping of different frequencies or frequency ranges. The damper system 12 thus attenuates other frequencies or frequency ranges when the switchable tube 6 is closed than when the controllable tube 6 is open. Particularly advantageous here is a design of the damper system 12, in which the damper system 12 targeted interference frequencies or interference frequency ranges attenuated, which arise when switching the switchable tube 6, so by the changed flow through the muffler 1. With appropriate coordination, the transition within the noise during the switching of the switchable tube 6 can be smoothed, whereby a sudden noise change is avoided or at least greatly attenuated.

The housing 2 includes a first chamber 13, through which both tubes 6, 7 are passed. Furthermore, a second chamber 14 is formed in the housing 2, in which the two tubes 6, 7 have their open ends 15, 16. Furthermore, the second chamber 14 communicates with the exhaust gas inlet 3.

In the embodiment according to Fig. 2 only these two chambers 13, 14 are provided, which are separated by a partition 17, in particular gas-tight. In contrast, in the embodiments of the Fig. 1 and 3 to 6 In addition, a third chamber 18 is provided, which is arranged between the two other chambers 13, 14 and through which the two tubes 6, 7 are passed. The third chamber 18 is separated from the first chamber 13 by a partition 19, in particular gas-tight. Furthermore, the third chamber 18 is separated from the second chamber 14 by a partition wall 20, in particular gas-tight. The permanently open tube 7 is acoustically coupled to the third chamber 18. The acoustic coupling is in this case for example by means of a perforation 21 of the wall of the permanently open tube 7 realized within the third chamber 18. The third chamber 18 serves as a reflection chamber and may optionally be filled with a suitable damper material. In another embodiment, instead of a perforation 21, an opening in the wall or an interruption of the permanently open tube 7 may be provided to form the reflection damper. Furthermore, the third chamber 18 can also serve as resonance volume for a Helmholtz resonator; the permanently open pipe 7 is then equipped with a corresponding branch pipe.

According to the Fig. 1 to 6 the damper system 12 has a volume 22 and 23, respectively, which is acoustically coupled to the switchable tube 6. This volume 22, 23 is added to the volume of the switchable tube 6 and is used to achieve the desired damping effect.

At the in Fig. 1 In the embodiment shown, the volume of the damper system 12 comprises a tube volume 22 of a branch pipe 24 and a chamber volume 23 of the first chamber 13. The branch pipe 24 branches off from the switchable pipe 6 in such a way that it opens inside the first chamber 13. The branch pipe 24 communicates on the one hand with the switchable pipe 6 and on the other hand with the first chamber 13. In this embodiment, the damper system 12 with closed switchable pipe 6 comprises a Helmholtz resonator whose resonance chamber is formed by the first chamber 13 and the resonator neck through the branch pipe 24 and the reaching from the open end 15 to a branch point 25 section the switchable tube 6 is formed. The damping effect of a Helmholtz resonator results on the one hand from the volume of the resonance chamber and on the other hand from the volume of the resonator neck. The volume of the resonator neck is itself determined by the neck length and the neck cross section. The effective at closed switchable tube 6 neck length is simplified here indicated by double arrows, namely by an arrow L1, which represents the length of the portion of the controllable tube 6 from the open end 15 to the branching point 25, and by an arrow L2, the length of the Branch pipe 24 represents. The active at the closed switchable tube 6 neck length is thus the sum of the two individual neck lengths L1 + L2.

Furthermore, in the case of a closed switchable tube 6, a λ / 4 resonator is formed therein whose resonator length extends from the open end 15 of the switchable tube 6 to the closure point of the switchable tube 6, that is to the flap 10. This resonator length thus corresponds to the sum of the two individual neck lengths L1 + L3, where L3 is the distance between the branching point 25 and the closure point, ie the flap 10. Thus, when the switchable tube 6 is closed, the damper system 12 additionally comprises said λ / 4 resonator.

With open switchable tube 6, however, only the length L2 of the branch pipe 24 is active, as a result of which the resonance behavior of the Helmholtz resonator changes significantly, namely in the direction of higher frequencies. Furthermore, is open switchable tube 6 of the aforementioned λ / 4 resonator inactive.

In the Fig. 2 The embodiment shown differs from that in FIG Fig. 1 shown embodiment only in that the branch pipe 24 is closed at its end remote from the switchable tube 6 end by a bottom 26. However, the damper system 12 can not build a Helmholtz resonator more by this measure; Rather, a λ / 4 resonator is realized in this embodiment. When the switchable tube 6 is closed, the effective length of the λ / 4 resonator is defined by the tube length from the open end 15 of the switchable tube 6 to the bottom 26, that is, by the sum of the lengths L1 + L2. In contrast, reduces the effective length of the λ / 4 resonator with open switchable tube 6 to the length L2 of the branch pipe 24. Again, the damping effect shifts thus in the direction of higher frequencies. In addition, here comes with closed switchable tube 6, the additional λ / 4 resonator whose resonator length is determined by the distance of the open end 15 of the flap 10, that is, by the sum of the lengths L1 + L3. When the switchable tube 6 is open, this additional λ / 4 resonator is eliminated. Thus, in this embodiment, the damper system 12 basically comprises two λ / 4 resonators, one of which is active only when the switchable tube 6 is closed, while the other is active even with the switchable tube 6 open, but then has a shorter resonator length.

Optionally, it is also possible in this embodiment to provide the branch pipe 24 and / or the bottom 26 with a leak, so that in principle a communicating connection between the switchable pipe 6 and the first chamber 13 is present. This leakage can increase the bandwidth of the damping effect of the λ / 4 resonator.

At the in Fig. 2 In the embodiment shown, the volume of the damper system 12 is thus formed exclusively by the tube volume 22 of the branch pipe 24. On the chamber volume 23 can be dispensed with for the damper system 12 of the switchable tube 6 and can be used as an example for the permanently open tube 7 associated with the reflection damper. Accordingly, in this embodiment, the permanently open tube 7 communicates with the first chamber 13 via its perforation 21. The first chamber 13 may optionally be filled with suitable damper material in this embodiment. In another embodiment, instead of the perforation 21, an opening in the wall or an interruption of the permanently open tube 7 may be provided to form the reflection damper. Furthermore, the first chamber 13 can then serve as a resonance volume for a Helmholtz resonator; the permanently open pipe 7 is then equipped with a corresponding branch pipe.

At the in Fig. 3 shown embodiment, the branch pipe 24 is at its end remote from the switchable tube 6 with a pinhole 27 provided. This results for the damper system 12, a λ / 4 resonator with a relatively broadband damping effect. At the same time, the chamber volume 23 can basically serve as resonance volume for a Helmholtz resonator. When the switchable tube 6 is closed, the effective length of the λ / 4 resonator is given by the sum of the individual lengths L1 + L2 and for the Helmholtz resonator by the sum of the individual lengths L1 + L2. In addition, the further λ / 4 resonator is also active here when the switchable tube 6 is closed, whose resonator length is formed by the sum of the individual lengths L1 + L3. When the switchable tube 6 is open, the active lengths are reduced, namely to the single length L2 for the λ / 4 resonator and also to the single length L2 for the Helmholtz resonator. At the same time, the further λ / 4 resonator is deactivated when the switchable tube 6 is open. In this embodiment, the volume of the damper system 12 is formed by both the tube volume 22 and the chamber volume 23.

It is clear that two or more such branch pipes 24 may be provided with or without bottom 26 or pinhole 27, which differ in particular by different pipe cross-sections and / or pipe lengths and communicate in particular with the same or different chambers.

In the embodiments of the 4 to 6 the volume of the damper system 12 comprises only the chamber volume 23 of the first chamber 13. A branch pipe 24 and thus a pipe volume 22 is not provided in these embodiments. Nevertheless, the switchable tube 6 communicates with the first chamber 13. For this purpose, the switchable tube 6 in accordance with the embodiment Fig. 4 an opening 28, in the embodiment according to Fig. 5 a perforation 29 and in the embodiment according to Fig. 6 an interruption 30 on. For the closed state of the switchable tube 6, this results for the damper system 12 each have a Helmholtz resonator whose neck length is formed by the single length L1, ie by the extending from the open end 15 to the "branching" 25 section of the switchable tube. 6 The branch point 25 in this case corresponds to the point at which the communication between the first chamber 13 and the switchable tube 6, and may also be referred to as a connection point 25.

In addition, in principle, the λ / 4 resonators can be active here in the closed state of the switchable tube 6, whose effective length is determined by the sum of the individual lengths L1 + L3.

In the open state of the switchable tube 6, the neck length of the Helmholtz resonator reduces approximately to the value zero. As a result, there is then a reflection chamber, which has a different damping characteristic than the Helmholtz resonator.

It is noteworthy that in all embodiments, the branch point 25 and the junction 25 between the switchable tube 6 and the first chamber 13 and the branch pipe 24 from the open end 15 of the switchable tube 6 is spaced. Furthermore, said connection point 25 is arranged between the open end 15 and the actuator, ie the flap 10 of the control device 8. This ensures that the sound to be damped reaches in any case up to the additional volume 22, 23 of the damper system 12.

The described Helmholtz resonators and the described λ / 4 resonators and combinations of Helmholtz resonator and λ / 4 resonator have in common that they are not flowed through during operation of the exhaust gases of the exhaust gas flow. The resonators mentioned are thus shunt resonators. In contrast, the resonators, which operate with a reflection chamber, are arranged in the main circuit, that flows through in the operation of the exhaust gases of the exhaust gas flow.

In the embodiments of the Fig. 1 to 3 the damper system 12 is designed such that it has at least one such shunt resonator both when the switchable tube 6 is closed and when the tube 6 is open. In the embodiment according to Fig. 1 this is a Helmholtz resonator, in the embodiment according to Fig. 2 around a λ / 4 resonator and in the embodiment according to Fig. 3 to a combination of a Helmholtz resonator and a λ / 4-resonator. By opening or closing the switchable tube 6, the respective shunt resonator remains active, but changes its damping characteristic.

In contrast, the damper system 12 in the embodiments of the 4 to 6 Although in principle also at least one shunt resonator, this is only active when the switchable tube 6 is closed. When the switchable tube 6 is open, the resonance chamber of the respective Helmholtz resonator is transformed into a reflection chamber. The reflection muffler that worked with it flows through, ie it is arranged in the main circuit. In that regard, in these embodiments, the damping principle is changed by the switching operation of the switchable tube 6, while in the embodiments of the Fig. 1 to 3 the damping principle remains the same in both switching states of the switchable tube 6.

It is clear that the configurations and arrangements of the chambers 13, 14, 18 and the tubes 6, 7, 9 shown here are only exemplary in principle, so that other configurations and arrangements are also possible. For example, the two tubes 6 and 7 need not have their free ends 15, 16 in the same chamber; Also, the inlet pipe 9 does not have to open in the same chamber we the other pipes 6, 7. For example, the inlet pipe 9 open into the middle chamber 18, in which case the associated partition 20 is designed gas-permeable. It is also possible that, for example, the permanently open pipe 7 its open End 16 in the middle chamber 18, wherein the permanently open tube 7 may be bent to achieve a particularly large tube length passed through the second chamber 14.

Claims (15)

1. A muffler for an exhaust gas system of an internal combustion engine, in particular a motor vehicle,

   - having a housing (2) which has at least one exhaust inlet (3) and at least one exhaust outlet (4, 5) and at least two pipes (6, 7) on the inlet or outlet ends, at least one pipe being switchable at least between an open state and a closed state by means of a control device (8) and being acoustically coupled to a silencer system (12) such that the silencer system (12) is active when the pipe (6) is opened and when the pipe (6) is closed and it has a different damping characteristic when the pipe (6) is opened than when it is closed,

   - wherein the silencer system (12) has a volume (22, 23) that is acoustically coupled to the at least one switchable pipe (6),

   characterized in

   - that the volume comprises at least one pipe volume (22) of at least one branching pipe (24) that branches off from and communicates with at least one switchable pipe (6),

   - that the volume comprises a chamber volume (23) of a first chamber (13) of the housing (2) through which the at least one switchable pipe (6) passes and which communicates with the at least one switchable pipe (6),

   - that the at least one branching pipe (24) communicates with the first chamber (13) of the housing (2).
2. The muffler according to Claim 1, characterized in that
   the at least one branching pipe (24) has a perforated plate (27) on its remote end from the at least one switchable pipe (6).
3. The muffler according to Claim 1 or 2, characterized in that
   the communicating connection between the at least one switchable pipe (6) and the at least one branching pipe (24) and/or the first chamber (13) is at a distance from an open end (15) of the at least one switchable pipe (6) arranged in the housing (2).
4. The muffler according to any one of Claims 1 to 3, characterized in that
   of the at least two pipes (6, 7) at the intake or exhaust ends, at least one is permanently open.
5. The muffler according to Claim 4, characterized in that
   at least one permanently open pipe (7) passes through the first chamber (13).
6. The muffler according to any one of Claims 1 to 5, characterized in that
   the at least two pipes (6, 7) on the intake or exhaust ends have their open ends (15, 16) in a second chamber (14) of the housing (2) that communicates with the at least one exhaust intake (3) or the at least one exhaust outlet (4, 5).
7. The muffler according at least to Claim 4, characterized in that
   the at least one permanently open pipe (7) passes through a third chamber (18) and is acoustically coupled to it.
8. The muffler according to Claim 7, characterized in that
   the at least one switchable pipe (6) passes through the third chamber (18).
9. The muffler according to Claim 7 or 8, characterized in that
   the third chamber (18) is separated from the first chamber (13) by a partition (19) and/or from the second chamber (14) by another partition (20).
10. The muffler according to any one of Claims 1 to 7, characterized in that

    - the control device (8) has at least one valve (10) arranged in the at least one switchable pipe (6) and inside or outside the housing (2), and/or

    - the control device (8) controls the at least one switchable pipe (6) passively as a function of the exhaust gas pressure or actively as a function of the rotational speed and/or load of the internal combustion engine.
11. The muffler according to any one of Claims 1 to 10, characterized in that
    the silencer system (12) is designed so that interfering frequencies, which occur in switching the at least one switchable pipe (6) due to a change in the flow through the muffler (1), are dampened.
12. The muffler according to any one of Claims 1 to 11, characterized in that
    the silencer system (12) comprises a bypass resonator when the switchable pipe (6) is opened and when it is closed.
13. The muffler according to Claim 12, characterized in that
    the bypass resonator is a Helmholtz resonator or a λ/4 resonator or a combination of a Helmholtz resonator and a λ/4 resonator when the switchable pipe (6) is opened and when it is closed.
14. The muffler according to any one of Claims 1 to 13, characterized in that
    when the switchable pipe (6) is closed, the silencer system (12) comprises a λ/4 resonator, its resonator length corresponding to the distance from the open end (15) of the switchable pipe (6) to the closure of the switchable pipe (6).
15. The muffler according to any one of Claims 1 to 14, characterized in that
    the two pipes (6, 7) branch off from a common pipe or are brought together to form a common pipe inside or outside of the housing (2).

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