Power plants – Internal combustion engine with treatment or handling of... – By means producing a chemical reaction of a component of the...
Reexamination Certificate
2000-05-31
2002-06-04
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...
C060S280000, C422S177000
Reexamination Certificate
active
06397588
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a catalytic converter for purifying the exhaust gas of a combustion engine with a supercharger based on the exhaust turbocharger principle and to an exhaust gas purification system with a catalytic converter for such an engine.
In the case of catalytic converters of this type, it is desirable to arrange a catalyst carrier body of the converter as close as possible to the exhaust outlet of the engine, in order to ensure an adequate light-off temperature, which is required for the catalytic conversion and treatment of the exhaust gas, in every operating state of the engine. Catalytic converters for engines with superchargers, hereafter also referred to as an exhaust turbocharger, have the problem that the temperature of the exhaust gas is additionally reduced by the energy removal for compressing combustion air in comparison with engines without an exhaust turbocharger. Specifically in the case of diesel engines, in which the temperatures of the exhaust gas are in any case relatively low (exhaust-gas temperatures when idling approximately 100-200° C., under full load approximately 550-750° C. at the outlet), this leads to a deterioration in the overall degree of conversion of the exhaust gas purification system and exhaust gas can increasingly be emitted in an untreated form. In other words, increased pollutant emission can occur with these engines.
Recently, the statutory regulations concerning exhaust emission limit values (for example the EU exhaust regulations stages 2 and 3) have become increasingly stringent, so that there is a considerable and increasing need for a further reduction in the pollutant emissions of engines. Extensive efforts have recently been undertaken in this respect to optimize further existing, conventional catalyst systems for engines, in order to achieve effective emission control in all operating states and with every type of engine, including in the critical cold-starting phase of the engine.
By way of example, international PCT publication WO 99/11911 describes a catalyst carrier assembly which has at least one catalyst carrier body which can be arranged with a flange-like fastening section between a cylinder head and an exhaust manifold. A disadvantage of that catalyst support assembly, which is also referred to as a cylinder head catalyst, is that the catalyst carrier bodies must be adapted to different cylinder head dimensions and forms of manifold, respectively corresponding to the specific conditions. This makes cost-effective production virtually impossible. What is more, a separate catalyst carrier body is required for each cylinder. With these cylinder head catalysts, difficulties also arise because of the at times very high exhaust rates at an individual cylinder head outlet.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a catalytic converter for combustion engines with an exhaust turbocharger, which overcomes the above-mentioned disadvantages of the heretofore-known devices and methods of this general type and which is of a simple design, permits efficient conversion even at low exhaust-gas temperatures, and can be produced in a simple way.
With the foregoing and other objects in view there is provided, in accordance with the invention, a catalytic converter for cleaning exhaust gas of an internal combustion engine with an exhaust turbocharger. The internal combustion engine has an exhaust pipe with a connecting joint and a supercharger for compressing a combustion air on the principle of an exhaust turbocharger. The catalytic converter comprises:
a catalyst carrier body formed with a multiplicity of flow channels;
a tubular jacket encasing the catalyst carrier body;
the catalyst carrier body being adapted to being fitted into the connecting joint in the exhaust pipe ahead of the supercharger in a flow direction of the exhaust gas; and
a retaining element for fastening the catalyst carrier body in the connecting joint.
In other words, the catalytic converter according to the invention has a catalyst carrier body which is adapted for being fitted into a connecting joint of the exhaust pipe ahead of the supercharger, i.e. upstream of the exhaust turbocharger in the exhaust gas flow direction. As a result, it is possible with the catalytic converter according to the invention even to treat exhaust gases which, ahead of the exhaust turbocharger, are still at a temperature level above the catalytic reaction temperature but, after the exhaust turbocharger, would be at too low a temperature to allow them to be catalytically treated. This is so because, with the invention, at least part of the exhaust gas is treated ahead of the exhaust turbocharger. With the catalytic converter according to the invention, it is consequently possible to further reduce the fraction of untreated exhaust gas, which in the case of engines with an exhaust turbocharger leads to poorer emission values.
Furthermore, the catalytic converter according to the invention can be produced equally well for a large number of engine types, without regard to special designs of cylinder heads of the combustion engine or geometries of the exhaust manifold. It can be fitted into the corresponding section of the exhaust pipe. This is achieved in particular by the catalyst carrier body being adapted for being fitted into a connecting joint of the exhaust pipe that lies between the combustion engine and the supercharger, i.e. which lies upstream of the exhaust turbocharger in the direction of flow of the exhaust gas.
The operating mode of the exhaust turbocharger arranged downstream in the direction of flow is not hindered at all, or scarcely at all, by the catalyst carrier body, since the latter is adapted for being fitted there. The adaptation of the catalyst carrier body takes place for example by adapting its form, its length, its number of flow channels per unit area of the cross section or other catalytic converter parameters.
Also provided is a retaining element for fastening the catalyst carrier body in the connecting joint. The advantage of such a retaining element is that an additional housing for the catalyst carrier body is not necessary. The retaining element allows fitting inside the exhaust pipe. The catalytic converter can consequently be fitted at this in any case already spatially restricted location between the combustion engine and the exhaust turbocharger, indeed with very simple means.
In accordance with an added feature of the invention, the retaining element is a collar-type bead formed on the tubular jacket or a collar formed on an end section of the tubular jacket.
The bead on the jacket allows the catalytic converter to be inserted into any desired tail-pipe end section and fastened within the exhaust pipe like a pocket. The collar-like bead is advantageous in particular as a retaining element if the catalytic converter is fastened at a flange-like connecting joint of two tail-pipe sections. The two tail-pipe sections may in such a case be connected by means of conventional pipe clips, the bead being clamped in between the two flange-like end sections of the tail-pipe ends.
The crimped collar on the tubular jacket allows the catalytic converter to be inserted into the exhaust pipe like a pocket, but in this case the catalyst carrier body and/or the tubular jacket merely protrude(s) in one direction into the exhaust pipe. In this way, the catalytic converter can also be fitted into a connecting joint of the exhaust pipe which has devices in the direction of flow preventing elements from being arranged within the exhaust pipe in this direction. For example, this may be the case if a relatively long catalytic converter according to the invention is to be arranged in the proximity of the exhaust turbocharger.
In accordance with an additional feature of the invention, the tubular jacket of the catalyst carrier body is an intermediate section of the exhaust pipe and the tubular jacket has a fastening element at each of its ends, for connecting to adjacent s
Brück Rolf
Konieczny Jörg-Roman
Denion Thomas
Emitec Gesellschaft fur Emissionstechnologie mbH
Greenberg Laurence A.
Mayback Gregory L.
Nguyen Tu M.
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