Site News  |   Monitor Keywords  |   Monitor Archive  |   Organizer  |   Account Info  |

Variable geometry muffler for an exhaust system of an internal combustion engine

The present invention relates to a variable geometry muffler for an exhaust system of an internal combustion engine.

An internal combustion engine is provided with an exhaust system, which has the function of introducing into the atmosphere the gases produced by the combustion limiting both the noise and the content of polluting substances. A modern exhaust system comprises at least one muffler comprising a tubular body, which typically displays an elliptical section and is provided with an inlet opening and an outlet opening. A labyrinth which determines a path for the exhaust gases from the inlet opening to the outlet opening is defined within the tubular body; such labyrinth is normally formed by diaphragms (or baffles) arranged transversally (i.e. perpendicularly to the longitudinal axis of the tubular body) to define chambers within the tubular body and by tubes which connect the chambers to each other.

In a traditional muffler, the counterpressure generated by the muffler (i.e. the loss of pressure determined in the exhaust gases by the passage through the muffler) grows exponentially according as the engine speed increases (i.e. as the average speed of the exhaust gases increases). Consequently, in order to avoid excessively high counterpressure values at high engine speeds, it is necessary to penalise noise attenuation at low engine speeds. However, it would be preferable if the counterpressure generated by the muffler were more constant at varying engine speeds so as obtain both a good noise attenuation at low engine speeds and a limited counterpressure at high engine speeds.

In order to have a more constant counterpressure generated by the muffler at the variation of the engine speed, it has been suggested the use of at least one bypass valve, which is controlled by pressure (i.e. is passive being without a motor member) and has the function of modifying the geometry of the muffler labyrinth according to the exhaust gas pressure (i.e. according to the engine speed). An example of a bypass valve is provided in patent application WO2005059327A1.

A known bypass valve displays a lid, which is coupled to a bypass opening obtained through a diaphragm of the muffler and is mobile from a closed position of the bypass opening to an opening position of the bypass opening by effect of the exhaust gas pressure and against the bias of a spring which tends to maintain the lid in the closed position. The most common solution provides that the lid is hinged onto the diaphragm of the muffler and is coupled to a torsional spring.

It has been observed that the known bypass valves display a limited reliability in time, because the sliding couplings of the known bypass valves (i.e. the hinging points of the lid and the turns of the spring) tend to get jammed or however to work in a different manner from that provided in the design step by effect of the incrustations formed by the exhaust gases.

It is the object of the present invention to provide a variable geometry muffler for an exhaust system of an internal combustion engine, which muffler is free from the above-described drawbacks, and specifically is easy and cost-effective to manufacture.

According to the present invention, a variable geometry muffler for an exhaust system of an internal combustion engine is provided as claimed in the attached claims.

The present invention will now be described with reference to the accompanying drawings, which illustrate some non-limitative examples of embodiment thereof, in which:

FIG. 1 is a schematic and perspective view of a muffler made according to the present invention;

FIG. 2 is a schematic view of an internal labyrinth of the muffler in FIG. 1;

FIG. 3 is a side section view of a bypass valve of the muffler in FIG. 1;

FIG. 4 is a schematic and perspective view of a different embodiment of the bypass valve in FIG. 3;

FIG. 5 is a schematic and perspective view of a further embodiment of the bypass valve in FIG. 3;

FIG. 6 is a side elevated view of the bypass valve in FIG. 5;

FIG. 7 is a perspective exploded view of the bypass valve in FIG. 5;