Method and configuration for cleaning an exhaust-gas flow flowing in an exhaust system of a gasoline engine

Abstract

A method and a configuration are provided for cleaning exhaust gas in an exhaust gas system flowing from a gasoline engine. An air/fuel mixture is preferably supplied to the gasoline engine by direct injection. In order to provide improved cleaning, the exhaust gas flows successively in the exhaust gas system through at least one honeycomb body with a catalytically active coating, preferably a three-way coating, and a particle filter with a coating storing at least one pollutant component, in particular hydrocarbon, carbon monoxide and/or nitrogen oxide, at least from time to time. In addition to collecting soot particles, in particular the particle filter advantageously carries out supplementary oxidation of residual hydrocarbons as well as carbon monoxide during a cold start phase, and supplementary reduction of residual nitrogen oxides when the gasoline engine is operated under load.

We claim:  
     
         1 . A method for cleaning an exhaust-gas flow, which comprises: 
 supplying an air/fuel mixture to a gasoline engine;    conducting an exhaust-gas flow generated by the gasoline engine through an exhaust system; and    successively conducting the exhaust-gas flow in the exhaust system through at least one honeycomb body having a catalytically active coating, and a particle filter having a coating storing at least one pollutant component at least from time to time.    
     
     
         2 . The method according to  claim 1 , which further comprises supplying the air/fuel mixture to the gasoline engine by direct injection.  
     
     
         3 . The method according to  claim 1 , which further comprises providing the catalytically active coating as a three-way coating.  
     
     
         4 . The method according to  claim 1 , which further comprises carrying out the step of storing the at least one pollutant component as at least one substance from the group consisting of hydrocarbon, carbon monoxide and nitrogen oxide.  
     
     
         5 . The method according to  claim 1 , which further comprises feeding a rich air/fuel mixture to the gasoline engine, and storing residual HC and CO not converted in the honeycomb body, with the coating of the particle filter.  
     
     
         6 . The method according to  claim 1 , which further comprises feeding a lean air/fuel mixture to the gasoline engine, and storing residual NO x  not converted in the honeycomb body, with the coating of the particle filter.  
     
     
         7 . The method according to  claim 1 , which further comprises feeding a reducing agent to the particle filter as a function of a residual NO x  concentration in the exhaust gas downstream of the honeycomb body.  
     
     
         8 . The method according to  claim 7 , which further comprises selecting the reducing agent as ammonia.  
     
     
         9 . The method according to  claim 7 , which further comprises carrying out the step of feeding the reducing agent continuously.  
     
     
         10 . The method according to  claim 7 , which further comprises carrying out the step of feeding the reducing agent in intervals.  
     
     
         11 . The method according to  claim 10 , which further comprises carrying out the step of feeding the reducing agent in intervals as a function of quantities of residual NO x  stored in the particle filter.  
     
     
         12 . The method according to  claim 1 , which further comprises feeding an oxidizing agent to the particle filter as a function of a residual HC—CO concentration in the exhaust gas downstream of the honeycomb body.  
     
     
         13 . The method according to  claim 12 , which further comprises feeding oxygen to the particle filter as the oxidizing agent.  
     
     
         14 . The method according to  claim 1 , which further comprises storing oxygen with the coating of the particle filter, at least from time to time.  
     
     
         15 . The method according to  claim 1 , which further comprises measuring at least one residual pollutant component not converted in the honeycomb body, with at least one measuring probe disposed between the honeycomb body and the particle filter.  
     
     
         16 . The method according to  claim 15 , which further comprises carrying out the measuring step with at least one measuring probe respectively measuring each of hydrocarbon, carbon monoxide and nitrogen oxide as a residual pollutant component.  
     
     
         17 . The method according to  claim 1 , which further comprises regenerating the particle filter by burning particles.  
     
     
         18 . The method according to  claim 17 , which further comprises triggering the particle burning step by at least one of engine heat and exothermic reactions in the honeycomb body.  
     
     
         19 . The method according to  claim 17 , which further comprises triggering the particle burning step at predeterminable intervals.  
     
     
         20 . A configuration for cleaning an exhaust-gas flow, comprising: 
 a gasoline engine receiving an air/fuel mixture and generating the exhaust-gas flow;    an exhaust system conducting the exhaust-gas flow from said gasoline engine in a flow direction;    at least one honeycomb body disposed in said exhaust system, said at least one honeycomb body having a catalytically active coating; and    a particle filter disposed in said exhaust system downstream of said at least one honeycomb body in said flow direction, said particle filter having a coating storing at least one pollutant component at least from time to time.    
     
     
         21 . The configuration according to  claim 20 , wherein said gasoline engine receives the air/fuel mixture by direct injection.  
     
     
         22 . The configuration according to  claim 20 , wherein said at least one honeycomb body is a three-way catalytic converter.  
     
     
         23 . The configuration according to  claim 20 , wherein the at least one pollutant component stored by said coating is selected from the group consisting of hydrocarbon, carbon monoxide and nitrogen oxide.  
     
     
         24 . The configuration according to  claim 20 , wherein said gasoline engine receives a rich air/fuel mixture, and said coating of said particle filter stores hydrocarbon and carbon monoxide not converted in said at least one honeycomb body.  
     
     
         25 . The configuration according to  claim 20 , wherein said gasoline engine is fed a lean air/fuel mixture, and said coating of said particle filter stores nitrogen oxides not converted in said at least one honeycomb body.  
     
     
         26 . The configuration according to  claim 20 , including a reducing-agent reservoir, and at least one reducing-agent line feeding a reducing agent from said reducing-agent reservoir to said particle filter, as a function of a residual NO x  concentration in the exhaust gas downstream of said at least one honeycomb body.  
     
     
         27 . The configuration according to  claim 26 , wherein the reducing agent is ammonia.  
     
     
         28 . The configuration according to  claim 26 , wherein said reducing-agent line ends at said particle filter.  
     
     
         29 . The configuration according to  claim 28 , wherein said particle filter has an integrated distribution device connected to said reducing-agent line.  
     
     
         30 . The configuration according to  claim 20 , wherein said particle filter receives an oxidizing agent as a function of a residual HC—CO concentration in the exhaust gas downstream of said at least one honeycomb body.  
     
     
         31 . The configuration according to  claim 30 , wherein the oxidizing agent is oxygen.  
     
     
         32 . The configuration according to  claim 20 , wherein said coating of said particle filter stores oxygen, at least from time to time.  
     
     
         33 . The configuration according to  claim 20 , including at least one measuring probe disposed between said at least one honeycomb body and said particle filter, for measuring at least one residual pollutant component not converted in said at least one honeycomb body.  
     
     
         34 . The configuration according to  claim 33 , wherein said at least one measuring probe includes at least one measuring probe respectively measuring each of hydrocarbon, carbon monoxide and nitrogen oxide as residual pollutant components.  
     
     
         35 . The configuration according to  claim 20 , wherein said particle filter is to be regenerated by a process triggered by at least one of engine heat and exothermic reactions in said at least one honeycomb body.  
     
     
         36 . The configuration according to  claim 35 , wherein said particle filter is to be regenerated at predeterminable intervals.  
     
     
         37 . The configuration according to  claim 20 , wherein said at least one honeycomb body at least has partial regions forming said particle filter.