Particulate matter trap filter regeneration temperature control for internal combustion engine

Abstract

An internal combustion engine ( 1 ) comprises a fuel injector ( 9 ), a filter ( 13 ) which traps particulate matter in exhaust gas, and a catalyst ( 14 ) which oxidizes unburnt fuel or carbon monoxide in the exhaust gas on the upstream side of the filter ( 13 ). When regeneration of the filter ( 13 ) is required, a controller ( 21 ) determines a post-injection fuel injection timing and a post-injection fuel injection amount of the fuel injector ( 9 ) on the basis of an upstream exhaust gas temperature (Texh) and a catalyst temperature (Tcat) (S 16 , S 17 , S 19 , S 20 , S 22 , S 23 , S 25 , S 26 , S 28 ), thereby optimizing the regeneration temperature condition of the filter ( 13 ).

1 . A filter regeneration temperature control device for an internal combustion engine, the engine comprising a fuel injector, an exhaust passage, a filter which traps particulate matter in exhaust gas in the exhaust passage, and a catalyst which promotes oxidation of unburnt fuel or carbon monoxide in the exhaust gas in the exhaust passage on an upstream side of the filter, the device comprising:
 a sensor which detects an upstream exhaust gas temperature in the exhaust passage upstream of the catalyst;   a sensor which detects any one of a downstream exhaust gas temperature in the exhaust passage downstream of the catalyst and a temperature of the filter, as a catalyst temperature of the catalyst; and   a programmable controller programmed to:
 determine if regeneration of the filter is required; 
 determine a post-injection fuel injection timing and a post-injection fuel injection amount on the basis of the upstream exhaust gas temperature and the catalyst temperature when regeneration of the filter is required; and 
 control the fuel injector to perform a post-injection fuel injection corresponding to the post-injection fuel injection timing and the post-injection fuel injection amount. 
   
   
   
       2 . The filter regeneration temperature control device as defined in  claim 1 , wherein the controller is further programmed to:
 control the fuel injector, when regeneration of the filter is required, to perform a post-injection fuel injection on the basis of a basic post-injection fuel injection timing and a basic post-injection fuel injection amount; and   determine the fuel injection timing and the fuel injection amount by applying correction to the basic post-injection fuel injection timing and the basic post-injection fuel injection amount on the basis of the upstream exhaust gas temperature and the catalyst temperature detected after an immediately preceding post-injection fuel injection.   
   
   
       3 . The filter regeneration temperature control device as defined in  claim 2 , further comprising a sensor which detects an engine rotation speed of the internal combustion engine and a sensor which detects an engine load of the internal combustion engine, wherein the controller is further programmed to set the basic post-injection fuel injection timing to a more advanced value and the basic post-injection fuel injection amount to a larger value as the engine load decreases and the engine rotation speed decreases. 
   
   
       4 . The filter regeneration temperature control device as defined in  claim 2 , wherein the controller is further programmed to:
 compare the upstream exhaust gas temperature with a predetermined target upstream exhaust gas temperature;   apply retard-correction to the basic post-injection fuel injection timing or decrease-correction to the basic post-injection fuel injection amount to determine the post-injection fuel injection timing and the post-injection fuel injection amount, when the upstream exhaust gas temperature is higher than the target upstream exhaust gas temperature; and   apply advance-correction to the basic post-injection fuel injection timing or increase-correction to the basic post-injection fuel injection amount to determine the post-injection fuel injection timing and the post-injection fuel injection amount, when the upstream exhaust gas temperature is lower than the target upstream exhaust gas temperature.   
   
   
       5 . The filter regeneration temperature control device as defined in  claim 2 , wherein the controller is further programmed to:
 compare the catalyst temperature with a predetermined target catalyst temperature;   apply advance-correction to the basic post-injection fuel injection timing or decrease-correction to the basic post-injection fuel injection amount to determine the post-injection fuel injection timing and the post-injection fuel injection amount, when the catalyst temperature is higher than the target catalyst temperature; and   apply retard-correction to the basic post-injection fuel injection timing or increase-correction to the basic post-injection fuel injection amount to determine the post-injection fuel injection timing and the post-injection fuel injection amount, when the catalyst temperature is lower than the target catalyst temperature.   
   
   
       6 . The filter regeneration temperature control device as defined in  claim 2 , wherein the controller is further programmed to:
 apply retard-correction to the basic post-injection fuel injection timing while not applying correction to the basic post-injection fuel injection amount to determine the post-injection fuel injection timing and the post-injection fuel injection amount in a first region in which the upstream exhaust gas temperature is higher than a predetermined target upstream exhaust gas temperature and the catalyst temperature is lower than a predetermined target catalyst temperature;   apply increase-correction to the basic post-injection fuel injection amount while not applying correction to the basic post-injection fuel injection timing to determine the post-injection fuel injection timing and the post-injection fuel injection amount in a second region in which the upstream exhaust gas temperature is lower than the target upstream exhaust gas temperature and the catalyst temperature is lower than a predetermined target catalyst temperature;   apply advance-correction to the basic post-injection fuel injection timing while not applying correction to the basic post-injection fuel injection amount to determine the post-injection fuel injection timing and the post-injection fuel injection amount in a third region in which the upstream exhaust gas temperature is lower than the target upstream exhaust gas temperature and the catalyst temperature is higher than the target catalyst temperature; and   apply decrease-correction to the basic post-injection fuel injection amount while not applying correction to the basic post-injection fuel injection timing to determine the post-injection fuel injection timing and the post-injection fuel injection amount in a fourth region in which the upstream exhaust gas temperature is higher than the target upstream exhaust gas temperature and the catalyst temperature is higher than the target catalyst temperature.   
   
   
       7 . The filter regeneration temperature control device as defined in  claim 1 , wherein the controller is further programmed to:
 determine if regeneration of the filter is complete; and   control the fuel injector to stop the post-injection fuel injection, when regeneration of the filter is complete.   
   
   
       8 . The filter regeneration temperature control device as defined in  claim 1 , wherein the catalyst comprises an oxidation catalyst or a three-way catalyst. 
   
   
       9 . A filter regeneration temperature control device for an internal combustion engine, the engine comprising a fuel injector, an exhaust passage, a filter which traps particulate matter in exhaust gas in the exhaust passage, and a catalyst which promotes oxidation of unburnt fuel or carbon monoxide in the exhaust gas in the exhaust passage on an upstream side of the filter, the device comprising:
 means for detecting an upstream exhaust gas temperature in the exhaust passage upstream of the catalyst;   means for detecting any one of a downstream exhaust gas temperature in the exhaust passage downstream of the catalyst and a temperature of the filter, as a catalyst temperature of the catalyst;   means) for determining if regeneration of the filter is required;   means for determining a post-injection fuel injection timing and a post-injection fuel injection amount on the basis of the upstream exhaust gas temperature and the catalyst temperature when regeneration of the filter is required; and   means for controlling the fuel injector to perform a post-injection fuel injection corresponding to the post-injection fuel injection timing and the post-injection fuel injection amount.   
   
   
       10 . A filter regeneration temperature control method for an internal combustion engine, the engine comprising a fuel injector, an exhaust passage, a filter which traps particulate matter in exhaust gas in the exhaust passage, and a catalyst which promotes oxidation of unburnt fuel or carbon monoxide in the exhaust gas in the exhaust passage on an upstream side of the filter, the method comprising:
 detecting an upstream exhaust gas temperature in the exhaust passage upstream of the catalyst;   detecting any one of a downstream exhaust gas temperature in the exhaust passage downstream of the catalyst and a temperature of the filter, as a catalyst temperature of the catalyst;   determining if regeneration of the filter is required;   determining a post-injection fuel injection timing and a post-injection fuel injection amount on the basis of the upstream exhaust gas temperature and the catalyst temperature when regeneration of the filter is required; and   controlling the fuel injector to perform a post-injection fuel injection corresponding to the post-injection fuel injection timing and the post-injection fuel injection amount.