EP3311009B1 - Exhaust system - Google Patents

Description

The present invention relates to an exhaust system for a vehicle having an internal combustion engine, with a Helmholtz resonator and two exhaust pipes extending in the direction of the resonator, according to the preamble of claim 1.

Exhaust systems for multi-cylinder, powerful internal combustion engines are usually provided with two separate exhaust pipes, for example, emanating from a respective cylinder bank of a V-engine or, for example, each of two or three cylinders of a multi-cylinder in-line engine.

The configuration with separate exhaust pipes has the advantage over a single exhaust pipe with a large single cross-section, that it is easier to lay for the sake of the available space in a vehicle and still provides sufficiently large cross-sections to the exhaust pipe.

In the exhaust pipes in addition to a common or separate exhaust catalysts other components for reducing the combustion-related noise emissions of the engine are installed, such as front silencer, middle silencer or rear silencer and finally, the exhaust pipes also have respective tailpipes or Abgasauslassmündungen.

It is also already known, in the housing of the rear silencer or connected to a branch line with the rear silencer specifically tuned Helmholtz resonators or λ / 4 provide attenuator, which are each tuned to a speed range of the engine, in which the internal combustion engine to conspicuous, the Comfort specifications for the vehicle not corresponding drone frequencies tends. With these, the noise emissions of the internal combustion engine influencing facilities intended targeted the muzzle level at the exhaust outlet or the exhaust gas outlet ports are reduced.

Based on DE 200 03 666 U1 a multi-stage Helmholtz resonator has become known in which the resonator volume can be increased or decreased via a switchable flap provided in the resonator housing, whereby a sound level reduction of two different main frequencies can be achieved.

Based on DE 100 84 870 T1 For example, an exhaust system for a vehicle has been disclosed, which has a silencer which is coupled via a branch line to a Helmholtz resonator, which is formed by a separate resonator housing, which is arranged on the vehicle underbody and the exhaust gas is not flowed through and formed from a polymer is.

It is also already known to provide switchable exhaust valves in the exhaust system, which further reduce the noise emissions with the flap closed by a consequent reduction of the exhaust gas flowable through the cross section of the exhaust pipes, said measures but regularly increase the pressure prevailing in the exhaust system exhaust back pressure and thus deteriorate the experience of the driver of the vehicle responsiveness of the engine and increase the fuel consumption of the engine due to the exhaust gas to be provided by the engine against the high exhaust backpressure.

Based on GB 2 161 215 A is an exhaust system for a vehicle with an internal combustion engine, with a Helmholtz resonator and two extending in the direction of the resonator exhaust pipes, wherein the resonator has two neck openings to a resonator volume (4) and a respective neck opening is coupled to a respective exhaust pipe.

Finally, that describes US 2010/0043398 A1 an exhaust system with a flap control in the exhaust system for noise reduction.

Proceeding from this, the present invention, the object of providing an exhaust system for a vehicle with an internal combustion engine to create, which allows a reduction in the noise emissions of the engine, but without generating a high exhaust back pressure. It is also intended to provide a method for operating an exhaust system of an internal combustion engine.

To solve this problem with regard to the exhaust system, the invention has the features specified in claim 1. Advantageous embodiments thereof are described in the further claims.

In addition, the invention has the features specified in claim 12 with respect to the method.

The invention provides an exhaust system for a vehicle with an internal combustion engine, with a Helmholtz resonator and two extending in the direction of the resonator exhaust pipes, wherein the resonator has two neck openings to a resonator volume and a respective neck opening is coupled to an exhaust pipe, wherein the resonator is tuned for damping a dominant engine order and each exhaust pipe in the flow direction of the exhaust pipes downstream of the resonator at least two exhaust gas outlet and at least one respective exhaust outlet port is provided with an exhaust valve, by means of the exhaust gas outlet port is reversibly closed.

The invention takes into account the cramped space available on a vehicle for silencing regularly and sees instead of the use of the silencer volume for integration of damping components that allow sound absorption by the reflection method or absorption method, the formation of a Helmholtz resonator in a possible silencer volume exploiting housing before, wherein the resonator volume is coupled by means of a respective neck opening with a respective exhaust pipe of the twin-flow exhaust system.

The exhaust system accordingly has two exhaust pipes, which are provided for the conduction of exhaust gas from the internal combustion engine in the direction of the Abgasauslassmündungen and each exhaust pipe is coupled by means of a respective neck opening or branch line with the resonator volume of the Helmholtz resonator housing forming the Helmholtz resonator is tuned to attenuate at least one engine order specific to the engine. In this case, the engine order may be the one which delivers the greatest contribution to the orifice level in terms of absolute value, so that the resonator can be tuned to the frequency which contributes the highest absolute sound pressure level to a measured orifice level. For example, the resonator can be tuned exactly to the frequency that gives the highest level in a type approval approval drive.

This orifice level may thus be, for example, the orifice level relevant to a vehicle type approval of the vehicle during an approval run, which is then reduced by the resonator to an allowable measured sound pressure level without the need for sound attenuation devices operating according to the reflection or absorption techniques. Due to the lack of sound damping devices that operate on the reflection method or the absorption process, also eliminates the disadvantage of increasing the exhaust backpressure in the exhaust system.

It is provided according to a development of the invention that the resonator a housing having the resonator volume, which is formed separately from other component housings of the exhaust system and the housing is arranged at a distance from the rear region of the vehicle. By means of this configuration it is achieved that as much resonator volume as possible is used within the installation space available for silencing measures on the vehicle and the resonator housing is mounted at a great distance from the rear area of the vehicle, whereby a component having a rigid structure, namely For noise reduction required housing is removed from the area of the rear structure of the vehicle and damaged in a damage to the rear of the vehicle by the rigid component no longer adjacent components on the vehicle by the rigid component.

It is also provided according to a development of the invention that the exhaust system has a respective, arranged in the region between the exhaust pipe and the resonator volume flap, which is designed for at least partially releasing and / or closing the respective neck opening. With these flaps arranged adjacent to the resonator volume, the Helmholtz resonator can be turned on or off, so it is possible to influence the sound level at the exhaust outlet of the exhaust pipes, it is also possible by only partially releasing the neck openings variable the attenuation level of the resonator adjust. It does not change the resonance frequency of the damping, but only the degree of damping according to the opening angle of the flaps or resonator flaps.

The opening and / or closing of the flaps can be done, for example, selective or selective gangstufsel or driving mode selective, the flaps can be opened, for example, in a certain speed range of the vehicle, so that the Helmholtz resonator reduces the muzzle level, while the flaps in another speed range of the vehicle or for example, are closed in a sport driving mode of the vehicle and therefore the muzzle level is higher.

It is provided according to the invention that each exhaust pipe in the flow direction of the exhaust pipes downstream of the resonator at least two Abgasauslaßmündungen and at least one respective exhaust outlet port is provided with an exhaust valve, by means of the exhaust gas outlet opening is reversibly closed.

In other words, this means that a respective exhaust pipe has two exhaust gas outlet openings, ie four exhaust gas outlet openings are provided in the case of two exhaust pipes, wherein in each case an exhaust gas outlet orifice of an exhaust gas outlet orifice pair is provided with an exhaust flap which can be controlled separately from the resonator flaps.

By means of the exhaust flap, the respective exhaust outlet can be closed, whereby further influencing the noise emissions of the vehicle is possible, it can be counteracted with the exhaust valves, for example, while driving the comfort of the vehicle-reducing noise emissions that may occur, for example, in overrun operation of the vehicle. The fact that the exhaust valves are controlled independently of the resonator, an impact on the noise emissions of the vehicle over a wide range of applications is possible.

It is also provided according to a development of the invention that the common cross section of the exhaust gas outlet openings per exhaust pipe is the same size as the cross section of the relevant exhaust pipe. In other words, this means that the sum cross section of the exhaust gas outlet openings of an exhaust pipe is larger than the cross section of this exhaust pipe. In this way, it is achieved that the flow resistance which occurs in the region of the exhaust gas outlet openings and which counteracts the exhaust gas flow is not greater than the flow resistance in the exhaust pipe, as is the case with known exhaust systems.

As a result, it is also possible to achieve a reduction in the exhaust emissions, since the internal combustion engine does not have to provide increased exhaust work for discharging the exhaust gases at high exhaust counterpressure. The in known exhaust systems For reducing the noise emissions necessary reduction of the flow cross-section of the exhaust gas outlet can thus be omitted in the exhaust system according to the invention.

According to a development of the invention, it is also provided that the exhaust system has a device for the common control of the arranged between the resonator volume and the respective exhaust pipe flap. This device can be part of the engine control and control both resonator flaps together, whereby the cost of providing signal lines or Ansteuerleitungen is reduced to the Resonatorklappen the vehicle.

It is also provided according to a development of the invention that the exhaust system comprises a device for the common control of the arranged in a respective exhaust outlet port exhaust flap. This device may also be part of the engine control and control the exhaust valves together, which in turn reduces the number of signal lines or control lines to the exhaust valves on the vehicle.

It is also provided according to a development of the invention that the exhaust system has a provided in the flow direction of the exhaust pipes downstream of the resonator means for sound damping. This device for soundproofing may be, for example, a rear muffler which receives the outlet orifice of the respective exhaust pipe and with which the vehicle-specific sound spectrum can be influenced.

According to a development of the invention, it is also provided that the resonator volume is divided by means of a partition in at least two sub-volumes. The sub-volumes can also be controlled by means of a passage passing through the partition - for example by means of a flap closing or releasing the passage - whereby the possibility is created to dampen a further engine order in addition to the dominant engine order.

It is also provided according to a development of the invention that the resonator has a housing body formed from a plastic material, whereby a reduction in the intrinsic mass of the resonator can be achieved.

Finally, according to a further development of the invention, it is also provided that the exhaust system has a further neck opening extending from the respective exhaust pipe to the resonator volume and at least one of the existing neck openings is provided with a flap for at least partially releasing and / or closing the respective neck opening , This creates a configuration with which, in addition to a frequency to be damped, a second frequency can be damped. With a closed flap, the resonator attenuates a first frequency by means of the still existing and permanently open neck opening, and with the flap open the resonator also damps the second frequency. The two frequencies may be interfering frequencies in the sense of buzzing or droning or even to such a disturbing frequency and the other frequency then by a frequency that is to be reduced to admission or the like in terms of level.

The neck opening continuously opened in the direction of the resonator volume per exhaust line generates a bypass line with which the first interfering frequency is permanently damped, while the second disturbing frequency can be selectively damped or not dampened by releasing or closing the further neck opening.

Finally, according to the invention, a method for operating an exhaust system of an internal combustion engine of a vehicle is provided, as has been described above and the exhaust system is provided with an exhaust valve in an exhaust outlet, wherein provided by the method that the exhaust valve in overrun operation of the vehicle is closed. As a result, special disturbing frequencies in the overrun mode of the vehicle can be eliminated.

• Fig. 1 eine schematische Darstellung einer nicht in den Schutzbereich der Ansprüche fallenden Variante einer Abgasanlage mit zwei Abgasleitungen und vier Abgasauslassmündungen und einem Helmholtz-Resonator;
• Fig. 2 eine Darstellung ähnlich derjenigen nach Fig. 1 einer nicht in den Schutzbereich der Ansprüche fallenden Variante mit einem zusätzlichen Nachschalldämpfer pro Abgasstrang der Abgasanlage;
• Fig. 3 eine Darstellung ähnlich derjenigen nach Fig. 1 mit einer schaltbaren Abgasklappe in einer Abgasauslassmündung pro Abgasstrang;
• Fig. 4 eine Darstellung ähnlich derjenigen nach Fig. 3 mit einem zusätzlichen Nachschalldämpfer pro Abgasstrang der Abgasanlage;
• Fig. 5 eine Darstellung ähnlich derjenigen nach Fig. 1 einer nicht in den Schutzbereich der Ansprüche fallenden Variante mit einer Resonatorklappe pro Halsöffnung;
• Fig. 6 eine Darstellung ähnlich derjenigen nach Fig. 5 einer nicht in den Schutzbereich der Ansprüche fallenden Variante mit einem zusätzlichen Nachschalldämpfer pro Abgasstrang der Abgasanlage;
• Fig. 7 eine Darstellung ähnlich derjenigen nach Fig. 6 mit einer zusätzlichen Abgasklappe in einer Abgasauslassmündung pro Abgasstrang der Abgasanlage;
• Fig. 8 eine Darstellung ähnlich derjenigen nach Fig. 7 mit einem zusätzlichen Nachschalldämpfer pro Abgasstrang der Abgasanlage;
• Fig. 9 eine Darstellung einer Anordnung ähnlich derjenigen nach Fig. 8 mit einer weiteren Halsöffnung in Richtung zum Resonatorvolumen von der jeweiligen Abgasleitung ausgehend zusätzlich zu der mit einer Resonatorklappe schaltbaren Halsöffnung pro Abgasleitung;
• Fig. 10 eine Darstellung einer Anordnung ähnlich derjenigen nach Fig. 6 einer nicht in den Schutzbereich der Ansprüche fallenden Variante, die sich dahingehend unterscheidet, dass pro Abgasstrangseite nur eine Abgasauslassmündung vorgesehen ist;
• Fig. 11 eine Darstellung einer Anordnung ähnlich derjenigen nach Fig. 9 einer nicht in den Schutzbereich der Ansprüche fallenden Variante, aber ohne Abgasklappe im Bereich der Abgasauslassmündung; und
• Fig. 12 eine Darstellung einer Anordnung ähnlich derjenigen nach Fig. 5 einer nicht in den Schutzbereich der Ansprüche fallenden Variante, wiederum mit nur einer Abgasauslassmündung pro Abgasstrangseite.
• Fig. 1 der Zeichnung zeigt eine schematische Darstellung einer zweiflutigen Abgasanlage 1 mit Helmholtz-Resonator 2.

The invention will be explained in more detail below with reference to the drawing. This shows in:

• Fig. 1 a schematic representation of a not falling within the scope of the claims variant of an exhaust system with two exhaust pipes and four Abgasauslassmündungen and a Helmholtz resonator;
• Fig. 2 a representation similar to that after Fig. 1 a variant not falling within the scope of the claims with an additional rear silencer per exhaust system of the exhaust system;
• Fig. 3 a representation similar to that after Fig. 1 with a switchable exhaust flap in an exhaust outlet port per exhaust line;
• Fig. 4 a representation similar to that after Fig. 3 with an additional rear silencer per exhaust system of the exhaust system;
• Fig. 5 a representation similar to that after Fig. 1 a variant not falling within the scope of the claims with a resonator flap per neck opening;
• Fig. 6 a representation similar to that after Fig. 5 a variant not falling within the scope of the claims with an additional rear silencer per exhaust system of the exhaust system;
• Fig. 7 a representation similar to that after Fig. 6 with an additional exhaust flap in an exhaust outlet port per exhaust line of the exhaust system;
• Fig. 8 a representation similar to that after Fig. 7 with an additional rear silencer per exhaust system of the exhaust system;
• Fig. 9 a representation of an arrangement similar to that after Fig. 8 with another neck opening in the direction of the resonator volume of the respective exhaust pipe starting in addition to the switchable with a resonator flap neck opening per exhaust pipe;
• Fig. 10 a representation of an arrangement similar to that after Fig. 6 a variant not falling within the scope of the claims, which differs in that only one exhaust outlet port is provided per exhaust-gas side;
• Fig. 11 a representation of an arrangement similar to that after Fig. 9 a variant not falling within the scope of the claims, but without exhaust flap in the region of the exhaust outlet port; and
• Fig. 12 a representation of an arrangement similar to that after Fig. 5 a variant not falling within the scope of the claims, again with only one exhaust outlet port per exhaust gas line side.
• Fig. 1 The drawing shows a schematic representation of a twin-flow exhaust system 1 with Helmholtz resonator. 2

The dual-flow exhaust system 1 has two exhaust pipes 3 with a in the region between the two exhaust pipes 3, which emanate from a non-illustrated internal combustion engine of a vehicle, not shown, arranged resonator 4, which forms a resonator 5 of the Helmholtz resonator 2.

The resonator housing 4 has two extending in the direction of the exhaust pipes 3 branch lines 6, which form neck openings 7 of the Helmholtz resonator 2.

The resonator housing 4 is not flowed through by the exhaust gas, so that it is not acted upon by the hot exhaust gas with a resonator 2 passing through the heat flow during operation of the exhaust system 1 and therefore can be made of a plastic material.

The tuning of the Helmholtz resonator 2 takes place via a design of the resonator volume adapted to the respective internal combustion engine, the length of the resonator neck, that is to say the length of the branch line 6, and the diameter of the resonator neck. As a result of this tuning, the resonator 2 is designed for the frequency which has the highest sound pressure level in terms of magnitude of a muzzle level measured, for example, during a test drive or registration run of the vehicle.

This can be done, for example, by carrying out a test run with the vehicle without a Helmholtz resonator and by examining the orifice level measured in a test track for the frequency which produces the highest sound pressure level during the test run. By appropriate tuning of the Helmholtz resonator to this frequency, this frequency can then be correspondingly reduced in a test drive with a Helmholtz resonator, without the need for sound damping devices that operate according to the reflection method, absorption method or resonance method.

At the in Fig. 1 The exhaust system 1 according to the invention is not limited to this number of Abgasauslassmündungen, but for example, each exhaust pipe 3 may have only one exhaust outlet 8, as for example in the variants of Exhaust system after 10 to FIG. 12 the drawing is the case.

Fig. 2 The drawing shows a modified variant of the exhaust system 1 with a rear silencer 9 per exhaust gas side. With the rear silencer 9 can be influenced by the user of the vehicle acoustically perceptible sound, for example in the direction of a sporty or enriched with low frequencies sound.

Fig. 3 The drawing shows an embodiment of an exhaust system 1, in which two exhaust gas outlet openings 8 each with a reversibly closable exhaust flap 10 are provided. The exhaust valve 10 can be controlled via a device, not shown, for opening and closing the exhaust outlet 8. The device can be implemented for example by the engine control of the internal combustion engine, not shown, which outputs to an actuator of the exhaust valve 10, a control signal for closing the exhaust valve 10 when the vehicle and thus the internal combustion engine goes into a pushing state. By then closed exhaust valve 10, the emission is prevented by perceived as droning frequencies.

Fig. 4 shows a further modified embodiment of the exhaust system 1 with two exhaust valves 10, one of which is provided at a Abgasauslaßmündung 8 and one provided per exhaust gas side rear muffler 9. With the rear muffler 9, the sound of the engine can be influenced, as mentioned above has been.

Fig. 5 The drawing shows a variant of the exhaust system 1 with two exhaust pipes 3 and a switched between the exhaust pipes 3 Helmholtz resonator 2, as with reference to Fig. 1 the drawing has already been explained.

Unlike the variant after Fig. 1 can the Helmholtz resonator 2 after Fig. 5 the drawing are switched, so be switched in terms of its damping function in a damping and a non-damping state. For this purpose, the neck openings 7 are changeable with a flap or resonator flap 11 arranged in the region of a respective neck opening 7 such that the neck openings 7 can be blocked or closed or opened.

When the resonator flaps 11 are blocked by means of an actuation of the resonator flaps 11, the damping effect of the resonator 2 is canceled and in the case of an actuation of the resonator flaps 11 open or continuous neck openings 7, the resonator 2 performs the attenuation function described above.

In all embodiments of the exhaust system 1 with resonator flaps 11, it is also provided according to the present invention that the resonator flaps 11 can not only digitally opened or closed, but can also occupy angular positions between the open state and the closed state, whereby the degree of attenuation of the resonator. 2 can be set variably. The change in the degree of opening of the resonator flaps 11 does not change the resonant frequency of the damping but only the degree of attenuation in accordance with the set opening angle of the resonator flaps 11.

Fig. 6 The drawing shows a variant of an exhaust system 1 with controllable or controllable Resonatorklappen 11, as they have just been described and a rear silencer 9 per exhaust gas side, with which the sound of the exhaust system can be designed.

Fig. 7 The drawing shows an embodiment of an exhaust system 1 with controllable or controllable resonator flaps 11 and additional exhaust flaps 10 in the region of two Abgasauslassmündungen 8. As has already been explained above, thus influencing the sound pattern of the internal combustion engine by turning on or off the resonator 2 and the Damping, for example, be changed during the coasting operation of the vehicle by the exhaust valves 10 are controlled by, for example, the engine control to close the corresponding exhaust outlet 8.

A further reduction in the sound level emitted by the exhaust system 1 can be achieved by significantly reducing the exhaust gas passage diameter of the exhaust gas outlet opening 8 without the exhaust valve 10 relative to the diameter of the exhaust pipe 3, so that the sound pattern of the internal combustion engine can be varied within a wide adjustment range ,

Fig. 8 The drawing shows an embodiment of an exhaust system 1 similar to that after Fig. 7 with additionally provided per exhaust gas side, downstream of the resonator 2 arranged rear silencer 9 to influence the sound of the engine.

Fig. 9 The drawing shows a further modified embodiment of an exhaust system 1, in addition to two first, controllable by means of two Resonatorklappen 11 neck openings 7, two more neck openings 12 are provided per exhaust pipe 3, a neck opening 12, the one between the respective exhaust pipe. 3 and the resonator 4 arranged branch line 13 is formed.

This embodiment provides a switchable or controllable resonator 2 which also performs the function of a basic resonator. The term "base resonator" is understood to mean a resonator tuned to a first frequency-the base frequency-for the damping of which it is designed. The base frequency is determined inter alia by the opening diameter of the neck opening 12, so that the in Fig. 9 The resonator shown in the drawing always attenuates the base frequency, since the branch lines 13 are constantly open.

By way of example, the base frequency may be a frequency which dominates a sound level to be maintained during a test drive or certification run and which is therefore permanently damped. When the exhaust flaps 11 are opened, the resonator can also attenuate a second disturbing frequency. The branch lines 13 and the resonator flaps 11 can be matched in terms of their length and the common cross-section to a required damping frequency, which may also be, for example, the damping frequency required for the registration drive or a second perceived as disturbing in a particular driving mode frequency.

10 to FIG. 12 The drawing shows variants of exhaust systems with two exhaust pipes 3 and a respective resonator 2, each with only one orifice or exhaust outlet 8th

The in Fig. 10 The resonator 2 shown in the drawing has two controllable or controllable resonator flaps 11, the function of which in conjunction with Fig. 5 the drawing explained resonator flaps 11 corresponds.

Fig. 11 The drawing shows a variant of an exhaust system 1 similar to those after Fig. 9 with additional neck openings 12, which are always open, and resonator flaps 11. While the in Fig. 9 the drawing shown exhaust system also has two exhaust valves 10 at two Abgasauslassmündungen 8, which are provided for example for the damping of Dröhnfrequenzen in overrun mode of the vehicle, has in Fig. 11 The drawing shown exhaust gas system as well as the exhaust system after Fig. 9 the drawing two rear silencer 9, but not the exhaust valves 10th

In the Fig. 11 The exhaust system shown in the drawing is, for example, provided for arrangement on an internal combustion engine, which generates no disturbing Dröhnfrequenzen in overrun, so that the exhaust valves 11 can be omitted for cost reduction.

Finally shows Fig. 12 the drawing an exhaust system with two exhaust pipes 3 and a resonator on the flaps 11 controllable or controllable resonator 2, so that also in this embodiment, the degree of damping of the resonator 2 according to the opening angle of the resonator flaps 11 can be changed. To reduce costs compared to in Fig. 10 the drawing shown exhaust system has in Fig. 12 the exhaust system shown in the drawing but no rear silencer 9 per exhaust gas side, as this in the embodiment according to Fig. 10 the drawing is shown.

Although in the embodiments of the exhaust system shown in the figures next to the respective Helmholtz resonator no further muffler housing are shown, may be arranged in the respective exhaust system, for example, a further sound damping device in the form of a center muffler in the area in front of the Helmholtz resonator.

In the respective embodiment with exhaust valves in the exhaust outlet port, the exhaust flap takes over the damping of disturbing frequencies, especially in overrun mode of the engine, in an embodiment with additional resonator flaps, the sound level at the exhaust gas outlet can be changed in many areas, and thus the acoustics of the exhaust system can be particularly affected in that a resonator which is at least partially opened by the opening of the resonator flaps assumes the function of a cross-talk station, so that a distinctly different sound pattern is produced, in particular in an internal combustion engine in V-arrangement, than in an exhaust system without a cross-talk station.

A resonator provided with additional neck openings which are always open can also be used for damping a disturbing frequency arising when the resonator flaps are closed.

Since the resonator is not flowed through by hot exhaust gas, it can for example be made of a plastic material, resulting in a significant reduction in the dead weight of the resonator. The use of plastic or, for example, a carbon fiber reinforced plastic, the resonator can be adapted to the geometry of the underbody of the vehicle and thereby also shifted from the rear of the vehicle towards the center of the vehicle, thereby improving the crash behavior of the vehicle.

With regard to features of the invention which are not explained in greater detail above, reference is expressly made to the claims and the drawings, moreover.

LIST OF REFERENCE NUMBERS

1.

exhaust system

Second

Helmholtz resonator

Third

flues

4th

resonator

5th

resonator

6th

branch lines

7th

neck opening

8th.

Abgasauslassmündung

9th

silencer

10th

exhaust flap

11th

Flap, resonator flap

12th

neck opening

13th

branch line

Claims (12)

1. An exhaust system for a vehicle having an internal combustion engine, with a Helmholtz resonator (2) and two exhaust lines (3) extending in the direction of the resonator, wherein the resonator (2) has two neck openings (7) to a resonator volume (4) and one neck opening (7) in each case is coupled to one exhaust line (3) in each case, characterised in that the resonator (2) is tuned to damp a dominating engine order and each exhaust line (3) in the direction of throughflow of the exhaust lines (3) has at least two exhaust outlet openings (8) downstream from the resonator (2), and at least one respective exhaust outlet opening (8) is provided with an exhaust flap (10) by means of which the exhaust outlet opening (8) is reversibly closable.
2. An exhaust system according to Claim 1, characterised in that the resonator (2) has a housing (4) containing the resonator volume (5) which is formed separately from other component housings of the exhaust system (1), and the housing (4) is arranged at a distance from the rear region of the vehicle.
3. An exhaust system according to Claim 1 or Claim 2, characterised by a respective flap (11) arranged in the region between the exhaust line (3) and the resonator volume (5), which flap is designed to at least partially open and/or close the respective neck opening (7).
4. An exhaust system according to one of the preceding claims, characterised in that the common cross-section of the exhaust outlet openings (8) per exhaust line (3) is equal to or greater than the cross-section of the exhaust line (3).
5. An exhaust system according to one of Claims 3 to 4, characterised by a means for joint actuation of the flap (11) arranged between the resonator volume (5) and the respective exhaust line (3).
6. An exhaust system according to one of the preceding claims, characterised by a means for joint actuation of the exhaust flap (10) arranged in a respective outlet opening (8).
7. An exhaust system according to one of the preceding claims, characterised by a means for silencing (9) provided in the direction of throughflow through the exhaust lines (3) downstream from the resonator (2).
8. An exhaust system according to one of the preceding claims, characterised in that the resonator volume (5) is subdivided into at least two partial volumes by means of a partition.
9. An exhaust system according to Claim 8, characterised in that the partition has a passage connecting the partial volumes.
10. An exhaust system according to one of the preceding claims, characterised in that the resonator (2) has a housing body (4) formed of a plastics material.
11. An exhaust system according to one of the preceding claims, characterised by a further neck opening (12) in each case extending from the respective exhaust line (3) to the resonator volume (5), with at least one of the neck openings (7) per exhaust line (3) being provided with a flap (11) for at least partially opening and/or closing the respective neck opening (7).
12. A method for operating an exhaust system (1) of an internal combustion engine of a vehicle according to one of the preceding claims and the exhaust system (1) is provided with an exhaust flap (10) in an exhaust outlet opening (8), characterised in that the exhaust flap (10) is closed during coasting operation of the vehicle.

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