Apparatus and method for diagnosing deterioration of catalyst, and catalytic converter apparatus for exhaust emission of engine

Abstract

An apparatus for diagnosing deterioration of a catalyst for an internal combustion engine, having a first catalyst and a second catalyst and provided with sensors for detecting a particular exhaust component before and after the first catalyst, wherein a relationship between a deterioration property involved in clarification of an exhaust gas of the internal combustion engine by a combination of the first catalyst and the second catalyst and a deterioration property of the first catalyst are determined previously; a deterioration degree of the first catalyst is calculated according to outputs from the sensors disposed before and after the first catalyst; deterioration of the first catalyst is judged according to the deterioration degree; and deterioration of the second catalyst is judged according to the deterioration degree of the first catalyst.

1 . An apparatus for diagnosing deterioration of a catalyst for an internal combustion engine, having a first catalyst and a second catalyst and provided with sensors for detecting a particular exhaust component before and after the first catalyst, wherein: 
 a relationship between a deterioration property involved in clarification of an exhaust gas of the internal combustion engine by a combination of the first catalyst and the second catalyst and a deterioration property of the first catalyst are determined previously;    a deterioration degree of the first catalyst is calculated according to outputs from the sensors disposed before and after the first catalyst;    deterioration of the first catalyst is judged according to the deterioration degree; and    deterioration of the second catalyst is judged according to the deterioration degree of the first catalyst.    
   
   
       2 . The apparatus for diagnosing deterioration of a catalyst for an internal combustion engine according to  claim 1 , wherein a volume of a space between the first catalyst and the second catalyst is added to elements contributing to the deterioration of the second catalyst when a relationship of the first catalyst to the deterioration property due to the combination of the first catalyst and the second catalyst is derived.  
   
   
       3 . The apparatus for diagnosing deterioration of a catalyst for an internal combustion engine according to  claim 1 , wherein the sensors for detecting the particular exhaust component are O 2  sensors which output a binary output for the presence or not of oxygen contained in the exhaust gas.  
   
   
       4 . The apparatus for diagnosing deterioration of a catalyst for an internal combustion engine according to  claim 2 , wherein the sensors for detecting the particular exhaust component are O 2  sensors which output a binary output for the presence or not of oxygen contained in the exhaust gas.  
   
   
       5 . The apparatus for diagnosing deterioration of a catalyst for an internal combustion engine according to  claim 1 , wherein the sensors for detecting the particular exhaust component are sensors which output a signal corresponding to an oxygen density or a fuel concentration contained in the exhaust gas.  
   
   
       6 . The apparatus for diagnosing deterioration of a catalyst for an internal combustion engine according to  claim 2 , wherein the sensors for detecting the particular exhaust component are sensors which output a signal corresponding to an oxygen density or a fuel concentration contained in the exhaust gas.  
   
   
       7 . A method for diagnosing deterioration of a catalyst for an internal combustion engine, having a first catalyst and a second catalyst and provided with sensors for detecting a particular exhaust component before and after the first catalyst, comprising: 
 determining previously a relationship between a deterioration property involved in clarification of an exhaust gas from the internal combustion engine by a combination of the first catalyst and the second catalyst and a deterioration property of the first catalyst;    calculating a deterioration degree of the first catalyst according to outputs from the sensors disposed before and after the first catalyst;    judging deterioration of the first catalyst according to the deterioration degree; and    judging deterioration of the second catalyst according to the deterioration degree of the first catalyst.    
   
   
       8 . A catalytic converter apparatus for exhaust emission disposed in an exhaust gas passage of an internal combustion engine, the apparatus having a first catalyst and a second catalyst, and a volume of the first catalyst disposed on the upper stream side of an exhaust gas flow in the exhaust gas passage is smaller than that of the second catalyst disposed on the down stream side.  
   
   
       9 . The catalytic converter apparatus according to  claim 8 , wherein a proportion of a volume of the first catalyst to that of the second catalyst is determined to be smaller according to a proportion of an unburnt gas conversion efficiency of a combination of the first catalyst and the second catalyst when they are new to an unburnt gas conversion efficiency at the time when an emission level is judged as ineffective.  
   
   
       10 . The catalytic converter apparatus according to  claim 8 , wherein the first catalyst and the second catalyst are stored in one and the same housing.  
   
   
       11 . The catalytic converter apparatus according to  claim 9 , wherein the first catalyst and the second catalyst are stored in one and the same housing.