Exhaust system for an internal combustion engine and method for operating the exhaust system

Abstract

An exhaust system is provided for an internal combustion engine having at least a first and a second cylinder, wherein the first cylinder is assigned a first exhaust gas pipe and the second cylinder is assigned a second exhaust gas pipe. The first exhaust gas pipe is assigned a first muffler, and the second exhaust gas pipe is assigned a second muffler. A first damping pipe branches off from the first exhaust gas pipe upstream of a first shut-off element. The damping pipe firstly opens into a first reflection chamber and is subsequently led through the first muffler and opens into the second exhaust gas manifold downstream of a second shut-off element. A second damping pipe branches off from the second exhaust gas pipe upstream of a second shut-off element. The second damping pipe firstly opens into a second reflection chamber and is subsequently led through the second muffler and opens into the first exhaust gas pipe downstream of the first shut-off element.

Claims

1. An exhaust system for an internal combustion engine having at least a first and a second cylinder, the exhaust system comprising: a first exhaust pipe assigned to the first cylinder; a second exhaust pipe assigned to the second cylinder; a first muffler assigned to the first exhaust pipe; a second muffler assigned to the second exhaust pipe; a first damping pipe branching off of the first exhaust pipe upstream of a first shut-off element in the first exhaust pipe; a second damping pipe branching off of the second exhaust pipe upstream of a second shut-off element in the second exhaust pipe, wherein the first damping pipe leads first into a first reflection chamber and subsequently extends through the first muffler and leads into the second exhaust pipe downstream of the second shut-off element in a portion of the second exhaust pipe located in a fourth reflection chamber, the second damping pipe leads first into a second reflection chamber and subsequently extends through the second muffler and leads into the first exhaust pipe downstream of the first shut-off element in a portion of the first exhaust pipe located in a third reflection chamber, the first exhaust pipe is connected in an exhaust-gas-carrying manner, by way of perforations in the second exhaust pipe, with the third reflection chamber, and the second exhaust pipe is connected in an exhaust-gas-carrying manner by way of perforations in the first exhaust pipe, with the fourth reflection chamber.

2. The exhaust system according to claim 1, wherein at least one of the first and the third reflection chambers are connected with one another in an exhaust-gas-carrying manner and the second and the fourth reflection chambers are connected with one another in an exhaust-gas-carrying manner.

3. The exhaust system according to claim 1, wherein at least one of the first and the third reflection chambers are connected with one another in an exhaust-gas-carrying manner and the second and the fourth reflection chambers are connected with one another in an exhaust-gas-carrying manner.

4. The exhaust system according to claim 1, further comprising a common housing in which the first and the second mufflers are arranged.

5. The exhaust system according to claim 4, wherein the first and the second reflection chambers are arranged in the common housing.

6. The exhaust system according to claim 5, wherein the third and the fourth reflection chambers are arranged in the common housing.

7. The exhaust system according to claim 4, wherein the third and the fourth reflection chambers are arranged in the common housing.

8. A method of operating an exhaust system for an internal combustion engine having at least a first and a second cylinder, the method comprising the acts of: providing a first exhaust pipe assigned to the first cylinder; providing a second exhaust pipe assigned to the second cylinder; providing a first muffler assigned to the first exhaust pipe; providing a second muffler assigned to the second exhaust pipe; providing a first damping pipe branching off of the first exhaust pipe upstream of a first shut-off element in the first exhaust pipe; providing a second damping pipe branching off of the second exhaust pipe upstream of a second shut-off element in the second exhaust pipe, wherein the first damping pipe leads first into a first reflection chamber and subsequently extends through the first muffler and leads into the second exhaust pipe downstream of the second shut-off element in a portion of the second exhaust pipe located in a fourth reflection chamber, the second damping pipe first leads into a second reflection chamber and subsequently extends through the second muffler and leads into the first exhaust pipe downstream of the first shut-off element in a portion of the first exhaust pipe located in a third reflection chamber, the first exhaust pipe is connected in an exhaust-gas-carrying manner, by way of perforations in the second exhaust pipe, with the third reflection chamber, and the second exhaust pipe is connected in an exhaust-gas-carrying manner by way of perforations in the first exhaust pipe, with the fourth reflection chamber; and opening the first and the second shut-off elements for minimal muffling.

9. The method according to claim 8, further comprising the act of: opening the first shut-off element and closing the second shut-off element for medium muffling.

10. The method according to claim 9, further comprising the act of: closing the first and the second shut-off elements for maximum muffling.

11. The method according to claim 8, further comprising the act of: closing the first and the second shut-off elements for maximum muffling.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic view of an exhaust system according to an embodiment of the invention;

(2) FIG. 2 is a view of the exhaust system according to the embodiment of the invention with two closed shut-off elements;

(3) FIG. 3 is a view of the exhaust system according to the embodiment of the invention with two opened shut-off elements;

(4) FIG. 4 is a view of the exhaust system according to the embodiment of the invention with one closed and on opened shut-off element.

DETAILED DESCRIPTION OF THE DRAWINGS

(5) FIG. 1 illustrates an end section of an exhaust system 1 for an internal-combustion engine (not shown) having at least a first and a second cylinder (also not shown). The first and the second cylinder are also representative of cylinder groups of the internal-combustion engine. For example, in the case of a six-cylinder internal-combustion engine, cylinders 1 to 3 represent cylinder group 1, and cylinders 4 to 6 represent cylinder group 2. A first exhaust pipe 2 is assigned to the first cylinder, and a second exhaust pipe 3 is assigned to the second cylinder. Furthermore, a first muffler 4 is assigned to the first exhaust pipe 2, and a second muffler 5 is assigned to the second exhaust pipe 3.

(6) According to an embodiment of the invention, a first damping pipe 2 branches off the first exhaust pipe 2 upstream of a first shut-off element 6. This first damping pipe 2 first leads out into a first reflection chamber 7 and subsequently extends through the first muffler 4 and again leads into the second exhaust pipe 3 downstream of a second shut-off element 8. Furthermore, a second damping pipe 3 branches off the second exhaust pipe 3 upstream of a second shut-off element 8, which damping pipe 3 first leads into a second reflection chamber 9 and subsequently extends through the second muffler 5 and leads into the first exhaust pipe 2 downstream of the first shut-off element 6. Flow directions of the exhaust gases, which are indicated by arrows, are illustrated in FIGS. 2 to 4.

(7) As known from the state of the art, the first damping pipe 2 and the second damping pipe 3 have perforations in the volume of the first muffler 4 and in the volume of the second muffler 5, for the output of sound emissions into the mufflers 4, 5 for the frequency-selective damping of the sound pressure level. In FIGS. 2 to 4, the damping effect is symbolically illustrated by broken lines in the area of the perforations.

(8) In the present embodiment, the first and the second shut-off elements 6, 8 are exhaust flaps; in other embodiments, they may, for example, be rolls.

(9) Furthermore, a third reflection chamber 10 is assigned to the first exhaust pipe 2 downstream of the first shut-off element 6, and a fourth reflection chamber 11 is assigned to the second exhaust pipe 3 downstream of the second shut-off element 8. In another embodiment, one reflection chamber 10, 11 may be absent.

(10) The first exhaust pipe 2 is preferably connected by way of perforations 12 in an exhaust-gas-carrying manner with the third reflection chamber 10 and/or the second exhaust pipe 3 is connected by way of perforations 12 in an exhaust-gas-carrying manner with the fourth reflection chamber 11. In a further embodiment, the first and the third reflection chamber 7, 10 and/or the second and the fourth reflection chamber 9, 11 may be mutually connected in an exhaust-gas-carrying manner, for example, by way of an additional perforation. These measures permit a further acoustic optimization.

(11) Particularly preferably, the first and the second muffler 4, 5 are arranged in a common housing 13, whereby manufacturing costs can be saved.

(12) In another particularly preferred embodiment, the first and the second reflection chamber 7, 9 are also arranged in the housing 13. The most costs are saved when also the third and the fourth reflection chamber 10, 11 are arranged in the housing 13.

(13) In another further embodiment, the first and the second reflection chambers 7, 9 may also be designed as resonator chambers.

(14) In a further embodiment, the third and the fourth reflection chambers 10. 11 may also be designed as absorption chambers. The respective further development of a reflection chamber, of a resonator chamber or absorption chamber will not be explained in detail in the following, since they are sufficiently defined in conventional textbooks.

(15) As a result of the symmetrical construction of the entire exhaust system 1, particularly the manufacturing costs can be reduced, because the identical-part principle can be applied to a large extent. Thus, for example, the Y-branching pipes (transition area from the exhaust pipe to the damping pipe), the damping pipes 2, 3, the shut-off elements 6, 8, the tailpipe branchings, the reflection chambers 7, 9, 10, 11, the mufflers 4, 5 and the exhaust pipes 2, 3 may be designed as identical parts. In a particularly advantageous fashion, the mufflers 4, 5, and the reflection chambers 7, 9, 19, 11 can be cost-effectively accommodated in a single common housing 13.

(16) Assembly tools can also be saved for the production as a result of the identical parts for the exhaust system 1. This leads to a clear reduction of tool costs.

(17) FIGS. 2 to 4, in which the same reference symbols as in FIG. 1 apply to identical components, show the same exhaust system as in FIG. 1 again, but for three different operating conditions. As mentioned above, exhaust gas flow directions are schematically illustrated by arrows.

(18) FIG. 2 illustrates the exhaust system 1 with a setting for a first operating method, in which the first and the second shut-off elements 6, 8 are closed. By means of this setting, maximal muffling is achieved for the exhaust system 1.

(19) FIG. 3 illustrates the exhaust system 1 according to the invention with a setting for a second operating method, in which the first and the second shut-off elements are open. By means of this setting, minimal muffling is achieved for the exhaust system 1.

(20) FIG. 4 illustrates the exhaust system 1 according to the invention with a setting for a third operating method, in which the first shut-off element 6 is closed and the second shut-off element 8 is open. By means of this setting, medium muffling is achieved for the exhaust system 1.

(21) The exhaust system 1 according to the invention has a very advantageous construction with respect to the exhaust gas backpressure. By means of the construction according to the invention, one or both shut-off elements 6, 8 may also be closed simultaneously with any significant rise of the exhaust gas backpressure. In contrast to conventional exhaust systems, a minimal or hardly measurable throttling (raising of the exhaust gas backpressure) takes place when shut-off elements 6, 8, such as exhaust gas flaps, are open, because the entire exhaust gas is utilizedfrom the damping pipe volume to the end of the exhaust system 1. As a result of a slightly changed construction, the shut-off elements 6, 8 can also be switched in a time-staggered manner, in order to improve a subjective hearing impression during the switching phase. By means of the staggered switching-over of the two shut-off elements 6, 8, level jumps that are too conspicuous can be advantageously reduced.

(22) The very low exhaust gas backpressure of the exhaust system 1 caused by the further development according to the invention has a very positive effect on the performance and dynamics (response behavior of the internal-combustion engine). For slight acoustic adaptations, the volumes of the first muffler 4 and of the second muffler 5 may also be changed later. In addition, one or more possibly required resonator chambers 10, 11, also constructed as reflection chambers, can also be integrated in a simple manner without large expenditures into the exhaust system while symmetry is maintained.

(23) Because of the arrangement of the first and the second adjusting elements 6, 8 in the first and in the second exhaust pipes 2, 3 in the flow direction of the exhaust gas in front of the exhaust gas tailpipe, a switching operation can practically not be heard by persons on the outside.

LIST OF REFERENCE NUMBERS

(24) 1. Exhaust system 2. First exhaust pipe 2 First damping pipe 3. Second exhaust pipe 3 Second damping pipe 4. First muffler 5. Second muffler 6. First shut-off element 7. First reflection chamber (resonator chamber) 8. Second shut-off element 9. Second reflection chamber (resonator chamber) 10. Third reflection chamber (absorption chamber 11. Fourth reflection chamber (absorption chamber) 12. Perforations 13. Housing

(25) The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.