Evaluating method for no eliminating catalyst, an evaluating apparatus therefor, and an efficiency controlling method therefor

Abstract

In order to prevent a catalyst for an internal combustion engine from decreasing efficiency by deterioration after long time use of the catalyst, the decreased efficiency of the catalyst is determined, and the internal engine is controlled based on results of the determination so as to maintain high efficiency of the catalyst. The catalyst is installed in an exhaust pipe of the engine. Sensors for detecting conditions of exhaust gas both at upstream side and downstream side of the catalyst are provided, respectively. As for the sensor, for example, an oxygen sensor of which output varies stepwise at λ=1, or a sensor of which output varies in proportion to air-fuel ratio can be used. Detected values of the sensors are taken into a control unit, eliminating efficiency and deteriorating degree of the catalyst are estimated by comparison of the detected values, and the engine is controlled so that the eliminating efficiency becomes maximum. In accordance with the present invention, a preferable exhaust gas cleaning characteristics of the catalyst can be maintained because the decreased efficiency of the catalyst is determined exactly and the engine is controlled so as to prevent the catalyst from decreasing efficiency.

1 . An evaluating method for NO x  eliminating catalyst installed in an exhaust gas system of an internal combustion engine, including 
 NO x  eliminating catalyst for eliminating NO x  in exhaust gas, characterized in    evaluating said NO x  eliminating catalyst by comparing at least one of physical parameters of at least one of components in said exhaust gas at upstream side and at downstream side of said NO x  eliminating catalyst.    
   
   
       2 . An evaluating method for NO x  eliminating catalyst installed in an exhaust gas system of an internal combustion engine, including 
 NO x  eliminating catalyst for reducing NO x  in an oxidizing atmosphere, characterized in    evaluating said NO x  eliminating catalyst based on difference in at least one of physical parameters of at least one of components in exhaust gas at upstream side and at downstream side of said NO x  eliminating catalyst.    
   
   
       3 . An evaluating method for NO x  eliminating catalyst installed in an exhaust gas system of an internal combustion engine, including 
 NO x  eliminating catalyst for reducing NO x  in an oxidizing atmosphere, characterized in    evaluating said NO x  eliminating catalyst based on difference of    oxygen concentration in exhaust gas at upstream side of said NO x  eliminating catalyst and oxygen concentration in exhaust gas at downstream side of said NO x  eliminating catalyst which is changed by effects of said NO x  eliminating catalyst.    
   
   
       4 . An evaluating method for NO x  eliminating catalyst installed in an exhaust gas system of an internal combustion engine, including 
 NO x  eliminating catalyst for eliminating NO x  in exhaust gas, characterized in    evaluating said NO x  eliminating catalyst based on difference of at least one of physical parameters of at least one of components in said exhaust gas at upstream side and at downstream side of said NO x  eliminating catalyst    under a condition that said internal combustion engine is operated in a lean operating condition.    
   
   
       5 . An evaluating method for NO x  eliminating catalyst installed in an exhaust gas system of an internal combustion engine, including 
 NO x  eliminating catalyst for eliminating NO x  in exhaust gas, characterized in    evaluating said NO x  eliminating catalyst based on difference of at least one of physical parameters of at least one of components in said exhaust gas at upstream side and at downstream side of said NO x  eliminating catalyst    under a condition that said internal combustion engine is operated with a normal operating condition in a lean operating region.    
   
   
       6 . An evaluating method for NO x  eliminating catalyst installed in an exhaust gas system of an internal combustion engine, including 
 NO x  eliminating catalyst for eliminating NO x  in exhaust gas, characterized in    evaluating said NO x  eliminating catalyst based on difference of at least one of physical parameters of at least one of components in said exhaust gas at upstream side and at downstream side of said NO x  eliminating catalyst corresponding to an alteration in a air-fuel ratio in air-fuel mixture which is supplied to said internal combustion engine    under a condition that the air-fuel ratio is altered arbitrarily.    
   
   
       7 . An evaluating apparatus for NO x  eliminating catalyst comprising; 
 (a) a base body composed of an ion conductive solid electrolyte,    (b) platinum electrodes provided respectively at both surfaces of said base body holding said base body between;    (c) diffused resistors covering said platinum electrodes,    (d) an exhaust gas inlet path which flows exhaust gas at upstream side of the NO x  eliminating catalyst to one of said diffused resistors, and flows exhaust gas at downstream side of the NO x  eliminating catalyst to another one of said diffused resistors, and    (e) an output portion for supplying electric signals generated between said platinum electrodes to a postfixed evaluating means.    
   
   
       8 . An evaluating apparatus for NO x  eliminating catalyst comprising; 
 (a) a first base body composed of an ion conductive solid electrolyte,    (b) platinum electrodes provided respectively at both surfaces of said first base body holding said first base body between,    (c) a first diffused resistor covering one of said platinum electrodes at said first base body,    (d) a first exhaust gas inlet path which flows exhaust gas at upstream side of the NO x  eliminating catalyst to said first diffused resistors,    (e) a second base body composed of an ion conductive solid electrolyte,    (f) platinum electrodes provided respectively at both surfaces of said second base body holding said second base body between,    (g) a second diffused resistor covering one of said platinum electrodes at said second base body,    (h) a second exhaust gas inlet path which flows exhaust gas at downstream side of the NO x  eliminating catalyst to said second diffused resistors, and    (i) first and second output portions for supplying electric signals generated between said first platinum electrode at said first base body and said second platinum electrode at second base body to a postfixed evaluating means.    
   
   
       9 . An efficiency controlling method for NO x  eliminating catalyst installed in an exhaust gas system of an internal combustion engine, including 
 NO x  eliminating catalyst for eliminating NO x  in exhaust gas, characterized in    evaluating said NO x  eliminating catalyst, and    elevating temperature of said NO x  eliminating catalyst or/and    increasing an amount of hydrocarbon supplied to said NO x  eliminating catalyst when said NO x  eliminating catalyst is judged as deteriorated.