Patent Application
20120181106
The present application claims the benefit of German Patent Application No. 10 2011 001 554.8 filed Jan. 14, 2011, which is fully incorporated herein by reference.
Not applicable.
The present invention relates to an exhaust assembly for use with a combustion engine. Such an exhaust assembly is known from document DE 697 02 447 T2.
In the known exhaust assembly two separate combustion gas flow routes can be controlled to change the damping characteristic of the exhaust assembly. In this context, in particular a rotatably mounted valve can be employed as the control means, making it possible to selectively block or open the combustion gas flow routes in order to change the gas distribution in the two combustion gas flow routes. Thereby, the exhaust assembly is characterized in that the two combustion gas flow routes have a different damping characteristic. The first combustion gas flow route is characterized by damping means enabling muffling of the combustion gases being discharged by the exhaust assembly. The second combustion gas flow route, by contrast, is characterized in that no damping means at all or else only attenuated damping means are provided, so that combustion gases being discharged along the second combustion gas flow route are not muffled at all or are muffled in an attenuated fashion.
As a result, by controlling the control means, the user is provided with the option to selectively change the damping characteristic of the exhaust assembly. When the combustion gases are routed via the first combustion gas flow route, the combustion gases are muffled and noise emissions are correspondingly reduced. If the combustion gases, by contrast, are routed via the second combustion gas flow route, the combustion gases are discharged without being muffled while enabling a correspondingly enhanced performance of the combustion engine, and cause a higher noise level.
Said known exhaust assemblies are employed in particular in large-volume combustion engines of motorcycles. The users of such motorcycles preferably desire to have a maximum low-frequency noise characteristic reminiscent of a bubbling sound. Tests have now shown that the control means being required in exhaust assemblies of this generic type, which are frequently designed in the type of a valve flap, give rise to the generation of undesirable relatively high-frequency noise, whereas the desirable low-frequency parts are filtered out by the damping means in the first combustion gas flow route. As a result, the known exhaust assemblies of the control means for changing the damping characteristic thus have a noise characteristic which is widely criticized in respect of the frequency distribution.
Thus, it is an object of the present invention to suggest a novel exhaust assembly for use with a combustion engine, which has a damping characteristic that can be selectively changed while providing an enhanced noise characteristic.
This object is attained in one embodiment by an exhaust assembly having a first combustion gas flow route, a second combustion flow route, and a valve. The first combustion gas flow route includes at least one sound damper. The at least one sound damper is a high-frequency damper adapted to dampen primarily higher frequencies of the frequency spectrum being contained in the combustion gas. The second combustion gas flow route has substantially no sound damping, so that the first and second combustion gas flow routes have different damping characteristics. The valve is operable selectively by an operator and adapted to selectively divide an approximately constant stream of combustion gases from an engine over the first and second combustion gas flow routes, irrespective of the volume of the combustion gase.
The inventive exhaust assembly is based on the fundamental idea that the damping means of the first combustion gas flow route comprise a high-frequency damper, wherein said high-frequency damper is adapted to dampen primarily higher frequencies of the frequency spectrum being contained in the combustion gas. The term “high-frequency damper” thus is supposed to mean that the high-frequency damper is suitable for damping the relatively higher frequencies of the frequency spectrum being contained in the combustion gas. In fact it does not refer to the damping of high-frequency oscillations of the electromagnetic wave spectrum. The damping of said higher frequencies of the frequency spectrum being contained in the combustion gas significantly enhances the noise characteristic of the exhaust assembly, since the undesirable higher frequencies are eliminated, respectively reduced. By contrast, the high-frequency damper has no significant impact on the desirable lower frequencies of the frequency spectrum being contained in the combustion gas. The constructional design of the high-frequency damper of the inventive exhaust assembly is basically optional. However, here the high-frequency damper is preferably designed in the type of a closed sound-trapping chamber which is in communication with the first combustion gas flow route via sound passage openings. Said sound passage openings here are not part of the first combustion gas flow route and substantially are not passed through by the combustion gas. Instead, only the sound waves pass through the sound passage openings and are damped selectively in the closed sound-trapping chamber to the effect that primarily higher frequencies are eliminated or reduced. By contrast, the desirable lower frequencies are not impaired at all or else only very slightly by the closed sound-trapping chamber.
In order to enhance the desirable damping effect for damping the higher frequencies of the frequency spectrum being contained in the combustion gas, the sound-trapping chamber can be filled with a damping material, for instance damping wool.
A particularly simple and inexpensively producible embodiment of the inventive exhaust assembly can be obtained if the exhaust assembly has a gas-tight housing and a perforated inner tube which is placed at a distance therefrom. In this regard, the housing at one side thereof is closed around the inner tube and is connected to a combustion gas supply pipe via connecting means. Furthermore, valve means for completely or partially closing the inner tube are provided at a distance from the connecting means. When the valve means are opened, the combustion gas is enabled to uninterruptedly pass through the inner tube into the environment, so that the inner tube forms the second combustion gas flow route when the valve means are opened. When the valve means are closed, the combustion gas is prevented from being discharged through the inner tube and instead is deflected at the valve means. As a result, the combustion gas then initially passes through the inner tube and through perforation openings formed therein into a bypass which comprises the inner tube in a cylindrical fashion and is part of the first combustion gas flow route. From said bypass, the combustion gas is then enabled to flow back again through perforation openings into the inner tube, in order to be discharged therefrom into the environment, or else the combustion gas is directly discharged from the bypass into the environment. In the bypass being located downstream of the perforation openings of the inner tube, it is possible to optionally install damping means. On the inside of the housing, which as such forms the outside of the bypass for the first combustion gas flow route, it is possible to arrange sound passage openings of the cylindrically designed sound-trapping chamber. As a result, the combustion gas is then discharged through the bypass and thereby passes through the sound passage openings of the sound-trapping chamber which surrounds said bypass in a cylindrical fashion.
In the exhaust assembly having the inner tube and the valve means, it is particularly advantageous if the cylindrical sound-trapping chamber is formed by a gas-tight outer housing wall and a perforated inner sound passage wall. The perforations in the sound passage wall thereby are not required to be formed completely, but partial perforation of the sound passage wall in many cases is already sufficient.
In order to enhance the desirable damping effect for damping the higher frequencies of the frequency spectrum being contained in the combustion gas, according to a preferred alternative embodiment, provision can be made for a deflection element in the first combustion gas flow route, by means of which the flow route of the combustion gases along the perforated inner sound passage wall of the sound-trapping chamber is extended. By means of said extended flow path along the sound passage wall of the sound-trapping chamber, a correspondingly larger part of the sound waves is passed through the sound passage walls and is damped to a correspondingly higher extent.
In order to be able to eliminate, respectively reduce, the undesirable higher frequencies of the frequency spectrum being contained in the combustion gas even when said frequencies are produced during the discharge along the second combustion gas flow route, additional sound passage openings can also be provided between the second combustion gas flow route and the sound-trapping chamber. As a consequence, the sound-trapping chamber is capable of damping in combination the higher frequencies of the frequency spectrum being contained in the combustion gas both in the first combustion gas flow route and in the second combustion gas flow route.
In order to realize the combined damping of the higher frequencies both in the second combustion gas flow route and in the first combustion gas flow route, the additional sound passage openings can also be arranged in the common flow route which is jointly formed by the first and the second combustion gas flow route.
If an embodiment of the exhaust assembly is used which has an inner tube, said inner tube preferably can also have sound passage openings which are not part of the first combustion flow route and which substantially are not passed through by the combustion gas.
Two embodiments of the inventive exhaust assembly are schematically illustrated in the drawings and will be explained hereinafter by way of example.
In the drawings:
When the valve means 05 are closed, as is exemplarily shown in
The bypass duct 07 on the outside is limited by a perforated inner sound passage wall 10 which has a plurality of sound passage openings. By means of said sound passage openings in the sound passage wall 10, the bypass duct 07 of the first combustion gas flow route is connected to a cylindrical sound-trapping chamber 11 which is formed between the gas-tight outer housing wall 04 and the perforated inner sound passage wall 10. The higher frequencies generated in the bypass duct 07 of the first combustion gas flow route are strongly damped when passing through the sound passage openings in the sound passage wall 10. Damping wool 12, which is shown in
| Number | Date | Country | Kind |
|---|---|---|---|
| 20 2011 001 554.8 | Jan 2011 | DE | national |
