Acoustics – Sound-modifying means – Muffler – fluid conducting type
Reexamination Certificate
2000-07-14
2001-11-13
Donels, Jeffrey (Department: 2837)
Acoustics
Sound-modifying means
Muffler, fluid conducting type
C181S256000
Reexamination Certificate
active
06315076
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to a catalytic converter for cleaning exhaust gas, including a converter housing and at least one honeycomb body disposed therein and containing layers of sheet metal having catalytically active material. The converter is disposed on a dividing wall of a muffler housing for a small engine, the dividing wall has at least one opening, and the housing has an upper housing component and a lower housing component.
As environmental consciousness has become stronger and exhaust gas regulations relating to the exhaust gases of internal combustion engines have become stricter, a need has arisen to provide catalytic exhaust gas cleaning in small engines. Small engines are understood below to be internal-combustion engines with an engine capacity of less than 200 cm
3
, in particular less than 50 cm
3
. Such engines are found, in particular, in lawnmowers, power saws, transportable power packs, two-wheeled vehicles and such applications. In particular, in power saws, lawnmowers and other garden implements driven by internal-combustion engines, someone using such an implement is frequently located directly in the region of the exhaust gases of the small engine over a relatively long period of time. Catalytic exhaust gas cleaning is particularly important for that reason.
European Patent 0 470 113 B1 discloses a metallic catalytic converter carrier body which is suitable in particular for attachment in the dividing wall of a muffler housing. However, the construction and type of configuration of that catalytic converter carrier body are not very well suited to many muffler configurations. In addition, the manufacture thereof involves a certain degree of complexity.
The exhaust gas which enters a muffler near to the engine is, as a rule, already at a high temperature of, for example, over 600° C. As a result of exothermal reactions in the catalytic converter, its temperature may also rise considerably, for example to 1000° C. German Published, Non-Prosecuted Patent Application DE 38 29 668 A1, corresponding to U.S. Pat. No. 4,867,270, discloses a protection mechanism for an exhaust gas muffler for two-stroke engines, in particular for portable implements such as power saws or the like, having a housing, a catalytic converter and an exhaust gas end pipe. The catalytic converter is disposed in a hollow body which is provided in the muffler housing with spacing on all sides and has an output with a tapering cross section in the direction of flow of the treated exhaust gas that leads the treated exhaust gas out of the housing. The mechanical structure of that exhaust gas muffler is very complex and requires a specifically constructed adaptation of the catalytic converter for the respective purpose of use. Furthermore, the exhaust gas muffler has a large volume.
The above-described configurations for the catalytic exhaust gas cleaning of small engines additionally require specially fabricated honeycomb bodies. The manufacture, catalytic coating and installation of those honeycomb bodies require a relatively large number of working steps and are therefore relatively expensive in comparison with equipment provided with a small engine. For that reason, the provision of a catalytic converter for a small engine is frequently dispensed with.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a catalytic converter for a muffler of a small engine, which overcomes the herein afore-mentioned disadvantages of the heretofore-known devices of this general type, which is very cost-effective to manufacture, which requires the smallest possible changes to already existing small engines and their emission systems and which nevertheless catalytically removes a considerable portion of noxious substance from exhaust gas without, however, generating unacceptably high temperatures at outer surfaces of the emission system. With the foregoing and other objects in view here is provided, in accordance with the invention, in a small engine muffler housing including an upper housing component, a lower housing component and a dividing wall having at least one opening formed therein, a catalytic converter disposed on the dividing wall for cleaning exhaust gas, comprising at least one honeycomb body containing layers of sheet metal having catalytically active material; and a converter housing in which the at least one honeycomb body is disposed, the converter housing spaced apart from the muffler housing and fixed to the dividing wall, and the converter housing having a substantially half-shell shape for conducting an exhaust gas flow parallel to the dividing wall successively through the honeycomb body and through the at least one opening.
The exhaust gas which is to be cleaned flows, in a manner known per se, into a housing component of the muffler housing and from there out through the opening provided in the dividing wall into the converter housing in which there are located the layers of sheet metal that are coated with catalytic material and which are configured as a honeycomb body. The inverse flow, firstly through the converter housing and then through the opening in the dividing wall, is possible.
Since the converter housing of the catalytic converter according to the invention does not bear against the muffler housing, heating of the muffler housing by the catalytic converter is reduced or even avoided.
Since the converter housing of the catalytic converter according to the invention can be attached to the dividing wall of the muffler housing, a particularly simple and therefore cost-effective adaptation of the catalytic converter according to the invention to existing emission systems is possible. In fact, the converter merely has to be mounted on the dividing wall without any need for changes to the upper and/or lower housing component of the muffler housing. The catalytic converter and dividing wall can thus be prefabricated together and introduced into the usual process for fabricating the muffler.
In accordance with another feature of the invention, the converter housing has at least one side wall, one end wall, and a free space in the converter housing in the region of the end wall, the free space communicating with the opening in the dividing wall. This makes it possible to construct the catalytic converter as a separate component which a manufacturer of catalytic converters can supply as an assembly to a manufacturer of mufflers. The latter can then mount the catalytic converter according to the invention in a muffler housing.
In accordance with a further feature of the invention, the dividing wall of the muffler simultaneously forms a bottom wall of the converter housing. As a result, easier fabrication of a muffler which is equipped with the catalytic converter is made possible, since the converter and the dividing wall are constructed as one component which simply then has to be introduced between the lower and the upper housing components of the muffler housing and attached.
In accordance with an added feature of the invention, the layers of sheet metal which are provided for the honeycomb body can be squeezed, with plastic deformation, into the converter housing. As a result, a configuration of the catalytic converter according to the invention is obtained which is particularly simple in terms of production technology.
In accordance with an additional feature of the invention, there is provided a casing disposed around the honeycomb body. The casing serves as a support element for the individual layers of sheet metal of the honeycomb body so that the layers can be prefabricated and introduced into the casing before the casing is placed in the honeycomb body. The honeycomb body and the converter housing are thus constructed as separate components which can be connected to one another in a particularly simple way. The casing does not need to enclose the entire outer surface of the honeycomb body as long as it simply ensures that the honeycomb body holds together.
In accordance with yet another f
Bruck Rolf
Konieczny Jörg-Roman
Donels Jeffrey
Emitec Gesellschaft fur Emissionstechnologie mbH
Greenberg Laurence A.
Lerner Herbert L.
Lockett Kim
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