Exhaust muffler comprising a catalytic converter

Details Exhaust muffler comprising a catalytic converter Exhaust muffler comprising a catalytic converter

2001-04-06

2002-05-28

Denion, Thomas (Department: 3748)

Power plants

Internal combustion engine with treatment or handling of...

By means producing a chemical reaction of a component of the...

C060S302000, C060S323000, C181S231000, C181S222000, C181S240000, C181S272000, C181S258000

Reexamination Certificate

active

06393835

ABSTRACT:

FIELD OF THE INVENTION
The invention relates to an exhaust-gas muffler on an internal combustion engine in a handheld work apparatus such as a motor chain saw or the like.
BACKGROUND OF THE INVENTION
Such an exhaust-gas muffler is known from WO 97/01023. An inner wall partitions the inner space of the muffler housing into an inlet end chamber and an outlet end chamber. The partition wall is configured as a double wall and carries a catalytic coating. On the inner wall, the partition wall, which lies transverse to the entering exhaust-gas flow, is provided with a plurality of inlet openings in order to conduct the exhaust gas intensely swirled into the intermediate space of the partition wall. The catalytic treatment takes place in this intermediate space. The exhaust-gas flow can enter via only one outlet opening into the outlet end chamber and flow from there out of the exhaust-gas outlet into the atmosphere.
For an exhaust-gas conductance of this kind, the catalytic converter has to be configured for the throughflow of the entire quantity of the exhaust-gas flow. In this connection, care must be taken that the gas counterpressure which builds up does not become too high so that it leads to power deterioration of the internal combustion engine. Here, it is especially to be considered that such exhaust-gas mufflers are regularly flange connected to two-stroke engines, especially slit-controlled two-stroke engines, which react with sensitivity to changes in the exhaust-gas path as to their power characteristic.
SUMMARY OF THE INVENTION
It is an object of the invention to improve an exhaust-gas muffler of the kind described above so that an adequate catalytic treatment of the exhaust gas in ensured at a low gas counterpressure.
The exhaust-gas flow, which flows into the muffler housing, is subdivided into component quantities. Only one of the component quantities is guided over the catalytic converting element and, after catalytic treatment, is joined to the previously branched-off component quantity. In this way, on the one hand, the catalytic converting element can be configured as to its structural size such that only a slight gas counterpressure is built up while there is an adequate catalytic treatment of the component flow. Furthermore, a reduction of the temperature level of the treated exhaust gas is possible because of the mixing of the treated exhaust-gas flow with the untreated exhaust-gas flow so that the exiting exhaust-gas flow lies in an acceptable temperature range notwithstanding the catalytic treatment of the energy rich exhaust gases of a two-stroke engine.
To split up the exhaust-gas flow, at least one conducting wall, which projects into the exhaust-gas flow, connects to the exhaust-gas inlet. In a preferred embodiment, the conducting wall is configured as an inlet pipe in whose pipe wall a plurality of outlet openings is introduced in the manner of a showerhead. Only a part of the outflow openings of the showerhead open into a catalytic converting element which is preferably carried by the inlet pipe. The catalytic converting element can comprise a housing pot which is itself made of a catalytic converting material or in which a catalytically effective material is accommodated, for example, an unordered weft or the like.
In another advantageous embodiment, two conducting walls, which lie approximately parallel to each other, delimit an inlet shaft into which the exhaust-gas inlet opens directly. At least one of the conducting walls carries a catalytic converting coating or comprises a catalytic converting material whereby the catalytic converting element is formed necessary for treating the exhaust gas. The conducting walls preferably define the legs of a U-shaped bracket whose base leg has an inlet opening coincident to the exhaust-gas inlet. The U-shaped bracket lies clamped between the bases of the housing shells.


REFERENCES:
patent: 4867270 (1989-09-01), Wissmann et al.
patent: 4890690 (1990-01-01), Fischer et al.
patent: 5139107 (1992-08-01), Nagai
patent: 5338903 (1994-08-01), Winberg
patent: 5440083 (1995-08-01), Masuda
patent: 5521339 (1996-05-01), Despant et al.
patent: 5738184 (1998-04-01), Masuda et al.
patent: 5857327 (1999-01-01), Sato et al.

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