Patent Application
20080053747
Preferred exemplary embodiments of the invention are depicted in the drawings and explained in greater detail in the following description, where the same reference numerals refer to the same or similar or functionally identical components.
According to
In the second space 7, the antinoise generator 3 is situated, whereby it consists of at least one vibration-generating diaphragm drive 9 and a diaphragm 10 emitting these vibrations. The antinoise generator 3 is arranged in the second space 7 in such a way that it can act upon the first space 5 with antinoise through the wall opening 8. It is conceivable here that the diaphragm 10 of the antinoise generator 3 may tightly seal the wall opening 8. It is also conceivable for the diaphragm 10 of the antinoise generator 3 to be part of the partition 6 and to be manufactured together with it, for example.
During operation of the active muffler 1, the antinoise generator 3 generates sound signals which preferably eliminate the sound waves emitted by the exhaust gas flowing in the pipe 4. This may be accomplished, for example, by a phase-shifted emission of antinoise signals which cover the interfering signals generated by the exhaust gas flowing through the exhaust pipe 4 so that the latter are eliminated.
Since the exhaust gas system 2 can reach relatively high operating temperatures during operation, and furthermore, the diaphragm drive 9 also generates heat during operation, there may be high thermal stresses which have a negative effect on the lifetime of the antinoise generator 3. To counteract this and thus be able to prolong the lifetime of the antinoise generator 3, the latter should preferably be cooled. In the inventive approach, such cooling is achieved by the fact that the diaphragm drive 9 of the antinoise generator 3 is coupled via at least one coupling element 11 to an outside wall 13 of the muffler 1, which is in contact with the environment 12, in such a way as to conduct heat and reduce noise. The heat-conducting and noise reduction coupling element 11 then achieves a heat transfer from the diaphragm drive via the coupling element 11 into the outside wall 13 of the muffler 1 from which the heat can be dissipated into the environment 12. The outside wall 13 thus acts as a cooling surface for the diaphragm drive 9.
The sound-suppressing design of the coupling element 11, however, prevents any transfer of sound from the antinoise generator 3 to the outside wall 13 and emission therefrom into the environment 12. The coupling element 11 may be made of a heat-conducting and at the same time noise reduction material, e.g., in the form of a tough substance such as a heat-conducting paste or a layer of an elastic material having a good thermal conductivity. In addition to an increased thermal conduction, such a substance and/or such a material fulfills a tolerance equalizing function, which is necessary for the manufacture of the muffler 1 because there must always be a gap between the diaphragm drive 9 and the outside wall 13, although it should be as small as possible. The diaphragm drive 9 may be a conventional magnetic coil, for example. Another important property of the coupling element 11 is a certain mechanical elasticity which prevents a transfer of sound waves from the diaphragm drive 9 via the coupling element 11 into the outside wall 13. This prevents the outside wall 13 from functioning as a sound-emitting diaphragm, thereby destroying the noise reduction effect of the antinoise generator 3. The coupling element 11 usually has a thickness of approx. 0.1 mm to approx. 5 mm.
To be able to further increase the heat transfer between the outside wall 13 and the diaphragm drive 9 of the antinoise generator 3 via the coupling element 11 and thus be able to achieve a further improvement in the cooling of the diaphragm drive 9, the outside wall 13 of the muffler 1 which is in contact with the environment 12 is designed so that there can be an increased heat transfer with the environment 12. This is achieved, for example, through special heat transfer elements 14 or through a suitable design of the surface of the outside wall 13. A suitably shaped surface may have a highly fissured structure so that the surface area is increased and thus the cooling effect is supported. Examples of possible heat transfer elements 14 include ribs, flanging and wind deflector plates which also increase the surface area of the outside wall 13 or also generate a specific air flow which additionally supports the cooling effect. It may be assumed here that the outside wall 13 of the muffler 1 is usually arranged beneath the motor vehicle and therefore is exposed to the relative wind in driving during operation of the motor vehicle.
In general, the thermal conductivity elements 14 may be designed as flanging or ribs, for example, as described above and may have either a straight line or curved shape.
The coupling between the antinoise generator 3 and the outside wall 13 by the coupling element 11 also produces a reinforcement of the outside wall 13, so that it radiates outward much less antinoise that is produced by antinoise generator 3. Without any mechanical contact between the outside wall 13 and the diaphragm drive 9, the outside wall 13 would radiate much more structure-borne sound due to the high sound pressure level generated by the antinoise generator 3, so that to be able to counteract this, the sheet metal thickness of the outside wall 13 would have to be increased significantly, which would in turn result in a greater weight and a higher cost as well as a higher thermal inertia and would therefore have a negative effect on the dissipation of heat by the diaphragm drive 9.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2006 042 224.4 | Sep 2006 | DE | national |
