Apparatus for purifying and controlling exhaust gases

Abstract

A system having an NO x adsorption catalyst in an exhaust gas flow channel of the internal combustion engine, and adsorbing and capturing NO x in an oxidative atmosphere of an exhaust gas during lean burn running and then producing a reductive atmosphere thereby regenerating the adsorption catalyst, wherein a reduction treatment of NO x is carried out based on an estimated NO x purification rate and the NO x purification rate in the lean burn exhaust gas of the internal combustion engine is always maintained at or about a predetermined level thereby decreasing the amount of exhaust gas discharged.

What is claimed is:  
     
         1 . An exhaust gas purification apparatus for use in an internal combustion engine in which an NO x  adsorption catalyst for chemically adsorbing NO x  in a state where the amount of an oxidizing agent is larger than the amount of a reducing agent and catalytically reducing NO x  adsorbed on the catalyst in a state where the amount of the reducing agent, is equal to or larger than the amount of the oxidizing agent in a redox stoichiometric relation between each of components in an exhaust gas is disposed in an exhaust gas flow channel, and which produces a state where the amount of the oxidizing agent is larger than the amount of the reducing agent in a redox stoichiometric relation between each of components to chemically adsorb NO x  on the adsorption catalyst and then produces a state where the amount of the reducing agent is equal to or larger than the amount of the oxidizing agent to catalytically react and reduce NO x  adsorbed on the catalyst with the reducing agent into non-toxic N 2 , wherein the apparatus has a control unit for estimating the NO x  purification rate based on the amount of NO x  discharged from the internal combustion engine and the running state of the engine, and carrying out a reducing treatment for NO x  adsorbed on the NO x  adsorption catalyst when the estimated NO x  purification rate is lowered to a predetermined value.  
     
     
         2 . An exhaust gas purification and control apparatus for use in an internal combustion engine in which an NO x  adsorption catalyst for chemically adsorbing NO x  in a state where the amount of an oxidizing agent is larger than the amount of a reducing agent and catalytically reducing NO x  adsorbed on the catalyst in a state where the amount of the reducing agent is equal to or larger than the amount of the oxidizing agent, in a redox stoichiometric relation between each of components in an exhaust gas is disposed in an exhaust gas flow channel, and which produces a state where the amount of the oxidizing agent is larger than the amount of the reducing agent in a redox stoichiometric relation between each of components to chemically adsorb NO x  on the adsorption catalyst and then produces a state where the amount of the reducing agent is equal to or larger than the amount of the oxidizing agent and catalytically reacting NO x  adsorbed on the catalyst with the reducing agent and reduce the same into non-toxic N 2 , wherein the NO x  purification rate is estimated based on the amount of NO x  discharged from the internal combustion engine and the running state of the engine, and a reducing treatment is conducted for NO x  adsorbed on the NO x  adsorption catalyst when the estimated NO x  purification rate is lowered to a predetermined value.  
     
     
         3 . An exhaust gas purification apparatus for use in an internal combustion engine in which an NO x  catalyst for capturing NO x  discharged from an internal combustion engine and reducing a portion of the captured NO x  into N 2  during lean burn running and reducing NO x  captured as it is during lean burn running into N 2  when an air/fuel ratio of the internal combustion engine is set to a theoretical air/fuel ratio or a stoichiometrical ratio is disposed in an exhaust gas flow channel, wherein 
 the apparatus has a control unit for estimating the NO x  purification rate based on the amount of NO x  discharged from the internal combustion engine and the running state of the engine, and carrying out a reducing treatment for NO x  captured on the NO x  catalyst when the estimated NO x  purification rate is lowered to a predetermined value.    
     
     
         4 . A control apparatus for exhaust purification for use in an internal combustion engine in which an NO x  catalyst for capturing NO x  discharged from an internal combustion engine and reducing a portion of the captured NO x  into N 2  during lean burn running and reducing NO x  captured as it is during lean burn running into N 2  when an air/fuel ratio of the internal combustion engine is set to a theoretical air/fuel ratio or a stoichiometrical ratio is disposed in an exhaust gas flow channel, wherein 
 the NO x  purification rate is estimated based on the amount of NO x  discharged from the internal combustion engine and the running state of the engine, and a reducing treatment is conducted for NO x  captured on the NO x  catalyst when the estimated NO x  purification rate is lowered to a predetermined value.    
     
     
         5 . An exhaust gas purification apparatus for use in an internal combustion engine as defined in  claim 2 , wherein the NO x  purification rate of the NO x  adsorption catalyst is estimated, as a method of estimating the NO x  purification rate based on the amount of NO x  discharged from the internal combustion engine and the running state of the engine, based on one or more of amounts of states selected from the amount of NO x  adsorbed on the NO x  adsorption catalyst, the temperature of the exhaust gas, the temperature of the adsorption catalyst, the poisoning amount of sulfur, the running distance of the vehicle, the degree of degradation of the catalyst, the air/fuel ratio, the concentration of the unburnt hydrocarbons, the NO x  concentration before the catalyst, the period of time for the lean burn running having lapsed from the change over from the stoichiometrical (theoretical air/fuel ratio) or fuel rich running to lean burn running, the number of rotation of the internal combustion engine, the load on the engine, the amount of intake air, and the amount of the exhaust gas.  
     
     
         6 . An exhaust gas purification apparatus for use in an internal combustion engine as defined in  claim 4 , wherein the NO x  purification rate of the NO x  adsorption catalyst is estimated, as a method of estimating the NO x  purification rate based on the amount of NO x  discharged from the internal combustion engine and the running state of the engine, based on one or more of amounts of states selected from the amount of NO x  captured on the NO x  adsorption catalyst, the temperature of the exhaust gas, the temperature of the adsorption catalyst, the poisoning amount of sulfur, the running distance of the vehicle, the degree of degradation of the catalyst, the air/fuel ratio, the concentration of the unburnt hydrocarbons, the NO x  concentration before the catalyst, the period of time for the lean burn running having lapsed from the change over from the stoichiometrical (theoretical air/fuel ratio) or fuel rich running to lean burn running, the number of rotation of the internal combustion engine, the load on the engine, the amount of intake air, and the amount of the exhaust gas.