Exhaust system having variable exhaust gas paths

Abstract

An exhaust system for internal combustion engines has an exhaust tract, which has at least one first flow path and a second flow path for an exhaust gas stream. The first and the second flow path extend fluidically separated from each other from a pre-silencer to at least one end silencer. Depending on the rotational speed of the engine, the first flow path can be continuously closed by way of a controllable flap, wherein the exhaust gas stream is guided through the second flow path when the flap is closed.

Claims

1. An exhaust system for an internal combustion engine, comprising: an exhaust tract having a first flow path and a second flow path for an exhaust gas stream; a controllable flap; a pre-silencer configured to receive the exhaust gas stream upstream of the first and second flow paths; an end silencer; and a separating element arranged perpendicular to a flow direction of the exhaust gas stream in the end silencer such that the separating element defines a first upstream section and a second downstream section adjacent to an outlet of the end silencer, the separating element being configured to seal the first upstream section relative to the second downstream section, wherein the pre-silencer and the end silencer are spaced apart from one another by a portion of the exhaust tract not within a housing in which the first and second flow paths extend parallel to one another, the first and the second flow paths extend fluidically separated from each other from the pre-silencer to the end silencer, the second flow path ends in the first upstream section of the end silencer such that the exhaust gas stream from the second flow path enters the first flow path, the first upstream section is sized to provide a flow diameter area that is at least twice the size of a flow diameter area of the second flow path, and the first flow path is continually closable via the controllable flap as a function of engine speed, with the exhaust gas stream flowing through the second flow path when the controllable flap is closed.

2. The exhaust system according to claim 1, wherein a flow diameter area of the first flow path is larger than the flow diameter area of the second flow path.

3. The exhaust system according to claim 1, wherein the first and the second flow paths extend side-by-side in a parallel arrangement.

4. The exhaust system according to claim 1, wherein: the first flow path extends inside the second flow path in a coaxial arrangement, and a space between an outer wall of the exhaust tract containing the first flow path and an inner wall of the exhaust tract containing the second flow path forms the flow diameter area of the second flow path.

5. The exhaust system according to claim 1, wherein: the first and the second flow paths extend into the end silencer, and the first flow path penetrates the end silencer completely in a flow direction up to the outlet of the end silencer.

6. The exhaust system according to claim 1, wherein the first flow path is fluidically connected to the first upstream section in the end silencer by a perforated wall defining the first flow path within the end silencer.

7. The exhaust system according to claim 1, further comprising: an insulator arranged in the second downstream section and surrounding the first flow path.

8. An engine system, comprising: an internal combustion engine; an exhaust tract having a first flow path and a second flow path for an exhaust gas stream; a pre-silencer; an end silencer; a first flow path for exhaust gas; a second flow path for the exhaust gas; a controllable flap configured to open and close the first flow path as a function of engine speed; and a separating element arranged perpendicular to a flow direction of the exhaust gas stream in the end silencer such that the separating element defines a first upstream section and a second downstream section adjacent to an outlet of the end silencer, the separating element being configured to seal the first upstream section relative to the second downstream section, wherein the pre-silencer and the end silencer are spaced apart from one another by a portion of the exhaust tract not within a housing in which the first and second flow paths extend parallel to one another, the first and the second flow paths extend fluidically separated from each other from the pre-silencer to the end silencer, the second flow path ends in the first upstream section of the end silencer such that the exhaust gas stream from the second flow path enters the first flow path, the first upstream section is sized to provide a flow diameter area that is at least twice the size of a flow diameter area of the second flow path, and the exhaust gas flows through the second flow path when the controllable flap closes the first flow path.

9. The engine exhaust system according to claim 8, wherein the first and second flow paths are arranged side-by-side parallel to one another.

10. The engine exhaust system according to claim 8, wherein the first and second flow paths are arranged concentrically coaxially with respect to one another.

11. A motorcycle, comprising: an internal combustion engine; an exhaust system for the internal combustion engine, the exhaust system comprising: an exhaust tract having a first flow path and a second flow path for an exhaust gas stream; a controllable flap; a pre-silencer configured to receive the exhaust gas stream upstream of the first and second flow paths; an end silencer; and a separating element arranged perpendicular to a flow direction of the exhaust gas stream in the end silencer such that the separating element defines a first upstream section and a second downstream section adjacent to an outlet of the end silencer, the separating element being configured to seal the first upstream section relative to the second downstream section, wherein the pre-silencer and the end silencer are spaced apart from one another by a portion of the exhaust tract not within a housing in which the first and second flow paths extend parallel to one another, the first and the second flow paths extend fluidically separated from each other from the pre-silencer to the end silencer, the second flow path ends in the first upstream section of the end silencer such that the exhaust gas stream from the second flow path enters the first flow path, the first upstream section is sized to provide a flow diameter area that is at least twice the size of a flow diameter area of the second flow path, and the first flow path is continually closable via the controllable flap as a function of engine speed, with the exhaust gas stream flowing through the second flow path when the controllable flap is closed.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows an exhaust system with a parallel first and second flow path connected to a pre-silencer;

(2) FIG. 2 shows the continuation of the exhaust system in FIG. 1 (area of the end silencer);

(3) FIG. 3 shows an alternate embodiment of the exhaust system with a coaxial first and second flow path.

(4) FIG. 4 schematically shows an embodiment of a motorcycle with an exhaust system in accordance with the present invention.

(5) In all views, identical reference symbols refer to identical parts.

DETAILED DESCRIPTION OF THE DRAWINGS

(6) FIG. 1 shows a partially cut, perspective representation of an exhaust system 1 in a first embodiment having separate first and second flow paths 3, 4. Each flow path 3, 4 is developed as a pipe. The second flow path 4 is formed by a thinner pipe with a lesser flow diameter area relative to the pipe of the first flow path 3. Both flow paths 3, 4 extend from within the pre-silencer 20 and end in the end silencer 6 (see FIG. 2). Inside the first flow path 3 is a flap 5, which is controllable in a conventional fashion, by which the flow area of the first flow path 3 can be closed continuously as a function of speed and/or load. When the flap 5 is closed, the exhaust gas stream flows from the pre-silencer 20 essentially exclusively through the second flow path 4 to the end silencer 6. It goes without saying that the flap 5 does not completely seal off the first flow path 3, however, the restriction is sufficient for the significant portion of the exhaust gas stream to be guided through the second flow path 4. Via holes 21 and/or a perforation of the external walls, the two flow paths 3, 4 are fluidically connected to each other in the pre-silencer 20. In doing so, the pre-silencer 20 essentially acts as reflection silencer.

(7) In the end silencer 6 according to FIG. 2, the first flow path 3 extends in the exhaust gas flow direction completely to the outlet 7. The second flow path 4 ends in a chamber 8, which provides a flow diameter area that is instantly enlarged relative to the second flow path 4. The enlarged flow diameter area is obtained in that the end silencer 6 has a diameter that is greater than the sum of the diameters of the first and second flow paths 3, 4, and the chamber 8 is developed by the space in the end silencer 6 which extends in an extension of the second flow path 4 and about the first flow path 3. Furthermore, in the embodiment shown, the diameter enlarges toward the outlet 7. Inside of the end silencer 6, the second flow path 4 is fluidically connected to the chamber 8 via a completely perforated development of the first flow path 3 (pipe). After the instant expansion of the exhaust gas of the second flow path 4 in the chamber 8, the exhaust gas flows via the perforation into the first flow path 3 and to the outlet 7. The end silencer 6 is divided in the direction of flow of the exhaust gas by a separating wall 9, so that an upstream first section 10 and a downstream second section 11 adjacent to the outlet 7, is developed. In the embodiment shown, the first section 10, when viewed in the direction of flow, is twice as long as the second section 11. In the downstream second section 11, insulation wool is provided, which surrounds the first flow path 3 and reduces the formation of noise at the outlet. The size of the chamber 8 can be determined by the position of the separating wall 9. The FIG. 2 arrangement is schematically shown in FIG. 4 with an engine 25 upstream of a pre-silencer 20 in a motorcycle 30.

(8) FIG. 3 shows a second embodiment of the exhaust system 1 in a perspective representation. The first and second flow paths 3, 4 are developed as concentric coaxial pipes, so that the second flow path 4 surrounds the first flow path 3 in a spaced apart fashion and the space between the first and second flow paths 3, 4 forms the flow diameter area of the second flow path 4. As with the embodiment in FIG. 1, the first and second flow paths 3, 4 are connected to the pre-silencer 20, with the exhaust gas stream from the pre-silencer 20 being led to both flow paths 3, 4 depending on the position of the flap 5. In the embodiment shown, the flow area of the first flow path 3 can be closed by way of the flap 5, as in FIG. 1. The exhaust gas then essentially flows exclusively via the second flow path 4 into the end silencer 6, in which the chamber 8 connects to the second flow path 4. The operating principle of the instant diameter enlargement in the end silencer 6 is identical to FIG. 1 except that the pipes of the flow paths 3, 4 do not extend side by side, but coaxially inside each other.

(9) In both embodiments, the flap control is not shown. To that end, known solutions from the prior art can be employed.

(10) The invention is not limited to the preferred exemplary embodiments described above. Rather, a number of variants are contemplated, which take advantage of the described solution even if the embodiments are principally different in type. For example, instead of a reflection silencer, it is also possible to use an absorption silencer as the end silencer, or the two single paths can end in two separate end silencers so that, for example, the power path extends on the left side and the acoustic path extends on the right side of the motorcycle.

(11) 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.