DE4240012A1 - Vehicle exhaust gas cleaning system - Google Patents

Abstract

Exhaust gas cleaning system for a combustion engine in which the gas is led first through an adsorber (3) which contains a zeolite or is formed as a catalytic converter, and then through a catalytic converter (5).A burner (9) with a separate air supply (11) and a fuel supply (10) is positioned between the adsorber and the converter (5) in order to heat the converter, which alternatively can be heated by an electrical resistance heater remote from the adsorber.

Description

The invention relates to an exhaust gas purification device an internal combustion engine with a catalytic converter ter as well as an upstream of it, esp especially a zeolite-containing adsorber.

Such an exhaust gas purification device is in DE 39 28 760 C2. The adsorber, which in particular Zeolite base is built, serves in the Start phase of the internal combustion engine in which the catalytic converter cal exhaust gas converter not yet its operating temperature has reached and is therefore not yet effective, exhaust gas Store or adsorb pollutants. When used The use of zeolite is the adsorption of hydrocarbons fen particularly effective. With increasing warming of the Exhaust system or the adsorber are attached to it released pollutants / hydrocarbons and can then at least theoretically in the downstream catalytic converter, which then also its Be should have reached the operating temperature, harmless be made. In fact, it has been shown that starting from a cold start of the internal combustion engine the heating of the entire engine exhaust gas the adsorption capacity of a zeolite adsorber rather  subsides as a catalytic converter is able to Successfully convert hydrocarbons. The means that the coal initially stored in the adsorber Hydrogen / pollutants are also released again even before the catalytic converter un these pollutants can cause harm. The short-term storage of the Hydrocarbons starting from a cold start The internal combustion engine thus remains essentially inactive sam, because in total no relief for the environment takes place, but only the pollutants at a late can be expelled at a later point in time.

It is the task of the before to show remedial measures lying invention.

To solve this problem is a heater for the catalytic converter provided by the adsorber is sufficiently far apart. Advantageous training and Developments describe the subclaims.

According to the invention, a heating device is provided which after a cold start of the internal combustion engine, too cold exhaust system or the likewise cold catalytic Bring the converter to its operating temperature faster can. This ensures that when the adsor Above all, especially zeolite adsorbers, which were initially released pollutants / hydrocarbons, the catalytic converter successfully removes these pollutants can convert. The arrangement should be chosen so that heating of the adsorber through the heating device is excluded, d. H. the heater should be sufficiently far from the adsorber. Next An electrically heated catalyst can also be used between the adsorber and a conventional monolithic catalyst sator a burner may be provided. Such are Burners that have a catalytic converter faster bring its operating temperature, known per se, however  are these converters in the known prior art always arranged directly downstream of the internal combustion engine. Would you now with a generic exhaust gas cleaning device with a catalytic converter and a this upstream adsorber also a burner directly downstream of the internal combustion engine and thus upstream arrange the adsorber, the efficiency would be one such exhaust gas cleaning device even worse tert because the adsorber only for an even shorter Period than without a burner would be able to remove pollutants capture and save. In contrast, the The present invention recognized that with the proposal NEN burner arrangement or heater arrangement on the one hand the adsorber / zeolite adsorber its known Retains effectiveness, and that on the other hand with the conclusion of Adsorption function of the downstream catalytic con is already effective, d. H. is able to successfully convert the emitted exhaust gas pollutants.

A burner can be installed directly in the burner's exhaust system engine between the adsorber and the converter be arranged. However, if it is outside the exhaust system arranged, the burner advantageously provides Continuous operation of the internal combustion engine is not a flow restrictor The burner has it next to your own Fuel supply also has its own combustion air supply supply, so an optimal burner operation can be on easy way to set. Own fuel supply for the burner is otherwise required, since in Be rich of the burner a flammable mixture, u. a. best hydrocarbons must be present. If but the burner an adsorber, which u. a. Hydrocarbon separates substances from the exhaust gas flow, downstream is, of course, those for the successful Chen operation required hydrocarbons can be fed separately again. Lies - like he already did  thinks - the burner outside the actual exhaust gas location, so the heating or heating of the Kon verters over the burner exhaust gases. These are becoming downstream of the adsorber and upstream of the converter in the exhaust system initiated. Downstream of the muzzle this burner exhaust gas or directly upstream of the converter can be related to catalytic exhaust Cleaning devices known Lambda probe arranged his. This proposed installation location enables despite the supply of particularly stoichiometric Burner exhaust the catalytic converter, in particular 3-way catalytic converter with "stoichiometric exhaust gas" open and thus an optimal reduction of stick to achieve oxides. The concept of "stoichiometric Exhaust gas "is to be interpreted so that the Brennma machine using the signals of the lambda probe is operated such a mixture that the burning engine exhaust and the burner exhaust such Exhaust gas mixture result as if the internal combustion engine at stopped burner with stoichiometric mixture would be driven.

The principle sketch attached and explained below shows a preferred exemplary embodiment of the invention. With the reference numeral 1 is a spark-ignited, in be warm operating condition in wide map areas with sto chiometric mixture operated internal combustion engine be. The exhaust gases pass through an exhaust manifold 2 into an adsorber 3 , which contains a zeolite. The exhaust system connected to the adsorber 3 , designated in its entirety by 4 , comprises, among other things, a catalytic converter 5 and a silencer 6 . The internal combustion engine exhaust gases reach the surroundings via the end pipe 7 .

Downstream of the adsorber 3 and upstream of the converter 5 , exhaust gases from a burner 9 can reach the exhaust system 4 via a burner tube 8 . The mouth of the Bren nerrohres 8 in the exhaust system 4 is sufficiently far from the adsorber 3 to prevent the adsorber 3 from being heated by hot burner gases. The burner 9 is seen with its own fuel supply 10 and its own combustion air supply 11 (blower) ver. Also provided is a lambda probe 12 projecting downstream of the mouth of the burner tube 8 into the exhaust system 4 , the signals of which are taken into account in the dimensioning of the combustible mixture supplied to the internal combustion engine.

If the cold internal combustion engine 1 is started, the exhaust system 4 is still cold, ie the catalytic converter 5 does not yet have its operating temperature of at least 300 ° C., from which it is able to convert harmful exhaust gas components. When the internal combustion engine 1 starts, the burner 9 is started up at the same time, ie it is supplied with combustion air and fuel and ignited. The hot burner exhaust gases released in the process reach the exhaust gas system 4 via the burner tube 8 and thus bring about an increased or accelerated heating of the converter 5 .

As long as the adsorber 3 filled with a zeolite, through which the internal combustion engine exhaust gases flow, is still colder than approx. 200 ° C.-250 ° C., 3 hydrocarbons contained in the internal combustion engine exhaust gases can be stored in this adsorber . In a first period of time after a cold start of the internal combustion engine, no hydrocarbons get into the environment thanks to the adsorber 3 . However, if the temperature of the adsorber 3 is approximately 250 ° C.-300 ° C., the adsorber 3 releases the hydrocarbons initially stored. At this time, thanks to the operation of the burner 9, however, the converter 5 has already reached its operating temperature and is now able to successfully not only the hydrocarbons emitted continuously by the internal combustion engine 1 , but also the hydrocarbons initially stored in the adsorber and now released to convert. Of course, now that the catalytic converter 5 has reached its operating temperature, the burner 9 can also be switched off.

In that a lambda probe 12 , with which the oxygen content in the exhaust gas flow can be determined, is arranged directly upstream of the converter 5 and downstream of the mouth of the burner tube 8 , on the one hand it is ensured that this lambda probe 12 after a cold start of the internal combustion engine 1 it briefly reaches its operating temperature, which is also desirable in view of successful pollutant conversion in the catalytic converter 5 . On the other hand, the lambda probe 12 measures the total exhaust gas flow at the proposed location, which results from the internal combustion engine exhaust gas and the burner exhaust gas. This makes it possible to operate the internal combustion engine 1 during the warm-up phase with a substoichiometric mixture and yet because of the supply of combustion air 11 in the catalytic converter 5 to have an exhaust gas which essentially corresponds to a stoichiometric mixture, so that nitrogen oxides are also present in the converter can be successfully converted.

In a further embodiment of the invention, the converter 5 is a structural unit composed of a conventional monolithic exhaust gas catalytic converter and a metal catalytic converter connected upstream thereof, which can be heated by an electrical resistance heater. Here, the catalytic converter - as known per se - is electrically heated and is therefore also able to convert pollutants effectively when the adsorber 3 releases these stored pollutants due to its heating. It must only be ensured that the adsorber 3 is sufficiently far from the heating device, ie from the electrocatalyst, so that the adsorber does not experience any additional heating through this heating device. Of course, when using an electric heating device, no burner 9 including its peripheral devices 8 , 10 , 11 is required. It may be advisable to arrange the lambda probe 12 directly downstream of the internal combustion engine 1 and upstream of the adsorber 3 . However, this and other details can also be designed otherwise without departing from the content of the claims.

Claims (4)

1. Exhaust gas purification device of an internal combustion engine ( 1 ) with a catalytic converter ( 5 ) and an upstream of the same, in particular a zeolite-containing adsorber ( 3 ), characterized by a sufficiently spaced from the adsorber ( 3 ) heating device for the catalytic converter. 2. Exhaust gas purification device according to claim 1, characterized in that the heating device is designed as an electrical resistance heater and is integrated in the converter ( 5 ). 3. Exhaust gas purification device according to claim 1, characterized in that the heating device as a between the adsorber ( 3 ) and the converter ( 5 ) provided with its own fuel supply ( 10 ) provided burner ( 9 ) for heating the converter ( 5 ) and / or the exhaust gas flow is formed. 4. Exhaust gas purification device according to claim 3, characterized by at least one of the following features:

• - The burner ( 9 ) has its own combustion air supply ( 11 )
• - The burner ( 9 ) is arranged outside the exhaust system ( 4 ) connecting the adsorber ( 3 ) to the converter ( 5 )
• - The burner exhaust gases come downstream of the adsorber ( 3 ) and upstream of the converter ( 5 ) via a burner tube ( 8 ) in the exhaust system ( 4 )
• - A lambda probe ( 12 ) measures the exhaust gas composition upstream of the converter ( 5 ) and downstream of the burner ( 9 ).