Method and device for regulating the fuel/air ratio of a combustion process

Abstract

A method for regulating the fuel/air ratio of a combustion process which is operated alternatingly with excess air and air deficiency, and having at least one catalyst volume in the exhaust gas of the combustion process which stores oxygen when there is excess oxygen in the exhaust gas and gives it off when there is oxygen deficiency, in which method the oxygen charges into the catalyst volume taking place when there is excess air, and the oxygen discharges from the catalyst volume taking place when there is air deficiency determined, and in which the fuel/air ratio is regulated in a first control loop such that the sum of the oxygen charges and oxygen discharges determined in a predefined interval takes on a predetermined value, wherein the combustion process is operated using oxygen excess or oxygen deficiency, respectively, at least until these appear at an oxygen-sensitive Nernst probe downstream from the catalyst volume.

What is claimed is:  
     
         1 . A method for regulating an fuel/air ratio of a combustion process which is operated alternatingly with excess air and air deficiency, and having at least one catalyst volume in an exhaust gas of a combustion process which stores oxygen when there is excess oxygen in the exhaust gas and gives the oxygen off when there is oxygen deficiency, comprising: 
 charging the oxygen into the catalyst volume when there is excess air;    discharging the oxygen from the catalyst volume when there is an air deficiency;    setting the fuel/air ratio in a first control loop such that a sum of the oxygen charges and the oxygen discharges determined in a predefined interval has a predetermined value; and    operating the combustion process on average using one of oxygen excess and oxygen deficiency, respectively, at least until the oxygen excess and the oxygen deficiency occur at an oxygen-sensitive Nernst probe downstream from the catalyst volume.    
     
     
         2 . The method according to  claim 1 , wherein the predetermined interval extends over a period in which the combustion process is operated once on average using oxygen excess and once on average using oxygen deficiency.  
     
     
         3 . The method according to  claim 1 , further comprising controlling a change between the oxygen excess and the oxygen deficiency during operation of the internal combustion engine such that a difference in the oxygen charges into the catalyst volume taking place during the excess air, and the oxygen discharges from the catalyst volume taking place during the air deficiency reaches a predetermined value.  
     
     
         4 . The method according to  claim 1 , further comprises using a variable which at least co-determines a fuel inflow to the internal combustion engine for a determination of the oxygen charges into the catalyst volume taking place during the air excess and the oxygen discharges from the catalyst volume taking place during the air deficiency.  
     
     
         5 . The method according to  claim 4 , further comprising forming the variable based on an intake air quantity calculated from measured variables and based on a fuel quantity metered into the air intake quantity.  
     
     
         6 . The method according to  claim 4 , further comprising forming the variable as a function of a signal of an exhaust gas probe situated upstream from the catalytic converter.  
     
     
         7 . The method according to  claim 6 , wherein the variable includes an input variable for a second control loop, in which the fuel/air ratio is regulated using a time constant that is smaller in comparison that in a first control loop.  
     
     
         8 . The method according to  claim 5 , further comprising changing a formation of the variable when the oxygen charges and the oxygen discharges deviate from each other.  
     
     
         9 . The method according to  claim 6 , further comprising changing a formation of the variable when the oxygen charges and the oxygen discharges deviate from each other.  
     
     
         10 . The method according to  claim 8 , wherein the change occurs such that the deviation becomes smaller.  
     
     
         11 . The method according to  claim 9 , further comprising forming the change as a function of an integral of the deviation.  
     
     
         12 . The method according to  claim 1 , further comprising predefining the fuel/air ratio by a superposed control loop.  
     
     
         13 . The method according to  claim 3 , further comprising determining a real zero value between the oxygen excess and the oxygen deficiency based upon the values of the oxygen charges and oxygen discharges determined.  
     
     
         14 . The method according to  claim 4 , further comprising determining a real zero value between the oxygen excess and the oxygen deficiency based upon the values of the oxygen charges and oxygen discharges determined.  
     
     
         15 . A control device configured to perform a method for regulating an fuel/air ratio of a combustion process which is operated alternatingly with excess air and air deficiency, and having at least one catalyst volume in an exhaust gas of a combustion process which stores oxygen when there is excess oxygen in the exhaust gas and gives the oxygen off when there is oxygen deficiency, the method including: 
 charging the oxygen into the catalyst volume when there is excess air;    discharging the oxygen from the catalyst volume when there is an air deficiency;    setting the fuel/air ratio in a first control loop such that a sum of the oxygen charges and the oxygen discharges determined in a predefined interval has a predetermined value; and    operating the combustion process on average using one of oxygen excess and oxygen deficiency, respectively, at least until the oxygen excess and the oxygen deficiency occur at an oxygen-sensitive Nernst probe downstream from the catalyst volume.    
     
     
         16 . The control device according to  claim 15 , wherein the predetermined interval extends over a period in which the combustion process is operated once on average using oxygen excess and once on average using oxygen deficiency.  
     
     
         17 . The control device according to  claim 15 , wherein the method further includes controlling a change between the oxygen excess and the oxygen deficiency during operation of the internal combustion engine such that a difference in the oxygen charges into the catalyst volume taking place during the excess air, and the oxygen discharges from the catalyst volume taking place during the air deficiency reaches a predetermined value.  
     
     
         18 . The control device according to  claim 15 , wherein the method further includes using a variable which at least co-determines a fuel inflow to the internal combustion engine for a determination of the oxygen charges into the catalyst volume taking place during the air excess and the oxygen discharges from the catalyst volume taking place during the air deficiency.  
     
     
         19 . The control device according to  claim 18 , wherein the method further includes forming the variable based on an intake air quantity calculated from measured variables and based on a fuel quantity metered into the air intake quantity.  
     
     
         20 . The control device according to  claim 18 , wherein the method further includes forming the variable as a function of a signal of an exhaust gas probe situated upstream from the catalytic converter.  
     
     
         21 . The control device according to  claim 20 , wherein the variable includes an input variable for a second control loop, in which the fuel/air ratio is regulated using a time constant that is smaller in comparison that in a first control loop.  
     
     
         22 . The control device according to  claim 19 , wherein the method further includes changing a formation of the variable when the oxygen charges and the oxygen discharges deviate from each other.  
     
     
         23 . The control device according to  claim 20 , wherein the method further includes changing a formation of the variable when the oxygen charges and the oxygen discharges deviate from each other.  
     
     
         24 . The control device according to  claim 22 , wherein the change occurs such that the deviation becomes smaller.  
     
     
         25 . The control device according to  claim 23 , wherein the method further includes forming the change as a function of an integral of the deviation.  
     
     
         26 . The control device according to  claim 15 , wherein the method further includes predefining the fuel/air ratio by a superposed control loop.  
     
     
         27 . The control device according to  claim 17 , wherein the method further includes determining a real zero value between the oxygen excess and the oxygen deficiency based upon the values of the oxygen charges and oxygen discharges determined.  
     
     
         28 . The control device according to  claim 18 , wherein the method further includes determining a real zero value between the oxygen excess and the oxygen deficiency based upon the values of the oxygen charges and oxygen discharges determined.