Method and apparatus for improved catalytic converter performance

Abstract

A method and apparatus for controlling the equivalence ratio in an internal combustion engine to improve catalytic converter performance including varying an equivalence ratio setpoint between a rich and a lean state periodically, and introducing a fuel enrichment pulse to the equivalence ratio that sweeps the equivalence ratio across stoichiometry.

1 . A method of controlling the equivalence ratio in an internal combustion engine to improve three way catalytic converter performance comprising: 
 varying an equivalence ratio setpoint between a rich and a lean state periodically;    introducing a fuel enrichment pulse in the internal combustion engine to the equivalence ratio that sweeps the equivalence ratio across stoichiometry to clean sulfur from the three way catalytic converter; and    wherein the fuel enrichment pulse is controlled to clean the CeO2 elements in the three way catalytic converter.    
   
   
       2 . The method of  claim 1  wherein the step of varying an equivalence ratio setpoint between a rich and a lean state characterized as a periodic function comprises varying the equivalence ratio between 0.9 and 1.1.  
   
   
       3 . The method of  claim 1  wherein the magnitude of the fuel enrichment pulse at least enriches the equivalence ratio by 0.1.  
   
   
       4 . The method of  claim 1  wherein the fuel enrichment pulse is added periodically based upon the rate of sulfur poisoning of the three way catalytic converter.  
   
   
       5 . The method of  claim 1  further comprising determining the equivalence ratio of the internal combustion engine using an oxygen sensor.  
   
   
       6 . The method of  claim 5  wherein said oxygen sensor generates a discrete signal.  
   
   
       7 . A method of controlling equivalence ratio in an internal combustion engine having a three way catalytic converter comprising: 
 dithering the equivalence ratio about an equivalence ratio setpoint;    controlling the equivalence ratio with an oxygen sensor;    periodically introducing a fuel enrichment pulse in the internal combustion engine to sweep the equivalence ratio across stoichiometry to remove sulfur from the three way catalytic converter;    wherein said fuel enrichment pulse is optimized to clean oxygen storage sites in said three way catalytic converter; and    wherein said oxygen sensor is a discrete switching oxygen sensor.    
   
   
       8 . cancelled  
   
   
       9 . The method of  claim 7  further comprising determining the equivalence ratio of the internal combustion engine using an oxygen sensor.  
   
   
       10 . The method of  claim 7  wherein said oxygen sensor generates a discrete signal.  
   
   
       11 . The method of  claim 10  wherein said oxygen sensor generates an analog signal.  
   
   
       12 . An engine control system for an internal combustion engine comprising: 
 a fuel injector for introducing fuel into the internal combustion engine;    a controller for controlling the amount of fuel injected into the internal combustion engine by said fuel injector;    an exhaust manifold coupled to said internal combustion engine;    a catalytic converter coupled to said exhaust manifold; and    wherein said controller dithers the equivalence ratio about stoichiometry and introduces a fuel enrichment pulse to periodically sweep the equivalence ratio across stoichiometry, said fuel enrichment pulse introduction based upon the rate of sulfur reaction with the catalytic converter.    
   
   
       13 . The system of  claim 12  wherein said internal combustion engine is an overhead valve engine.  
   
   
       14 . The system of  claim 12  wherein said internal combustion engine is an overhead cam engine.  
   
   
       15 . The system of  claim 12  wherein said internal combustion engine is a rotary engine.  
   
   
       16 . The system of  claim 12  wherein said catalytic converter is a three-way catalytic converter.  
   
   
       17 . The system of  claim 12  wherein said sulfur is removed from cerium molecules in the catalytic converter.