Particulate Matter Remaining Amount Estimating Method for Particulate Filter and Particulate Filter Regenerating Method

Abstract

Every time a specified period of time is counted during execution of filter regeneration control, a PM remaining amount every time that the specified period of time passes is estimated by subtracting the product of the specified period of time, a PM removal rate per unit time, and a PM remaining amount at the point when the specified period of time started to be counted from the PM remaining amount at the point when the specified period of time started to be counted. As a result, the PM remaining amount during execution of filter regeneration control which oxidizes and removes particulate matter that has accumulated on a particulate filter is estimated with greater accuracy.

1 . A method for estimating an amount of particulate matter remaining on a particulate filter, which is provided in an exhaust passage of an internal combustion engine and traps particulate matter in exhaust gas, comprising: 
 executing a filter regeneration control which oxidizes and removes the particulate matter that has accumulated on the particulate filter by raising the temperature of the particulate filter; and    estimating the remaining amount of the particulate matter accumulated on the particulate filter is estimated based on a particulate matter removal rate per unit time during execution of the filter regeneration control, a particulate matter accumulation amount on the particulate filter at the start of execution of the filter regeneration control, and the time elapsed from the start of execution of the filter regeneration control.    
   
   
       2 . The method for estimating an amount of particulate matter remaining on a particulate filter according to  claim 1 , further comprising: 
 starting to count the elapsed time at the start of execution of the filter regeneration control;    every time a specified period of time is counted in the elapsed time, subtracting the product of the specified period of time, the particulate matter removal rate per unit time, and a remaining amount of the particulate matter at the point when the specified period of time started to be counted, from the remaining amount of particulate matter at the point when the specified period of time started to be counted; and    estimating the remaining amount of particulate matter every time the specified period of time passes according to the subtraction calculation.    
   
   
       3 . The method for estimating an amount of particulate matter remaining on a particulate filter according to  claim 1 , wherein the particulate matter removal rate per unit time is set to be a higher value the greater the flow rate of exhaust gas flowing into the particulate filter.  
   
   
       4 . The method for estimating an amount of particulate matter remaining on a particulate filter according to  claim 1 , wherein the particulate matter removal rate per unit time is set to be a higher value the higher an oxygen concentration of exhaust gas flowing into the particulate filter.  
   
   
       5 . The method for estimating an amount of particulate matter remaining on a particulate filter according to  claim 1 , wherein the particulate matter removal rate per unit time is set to be a higher value the higher the temperature of the particulate filter.  
   
   
       6 . A method for regenerating a particulate filter, comprising: 
 calculating, according to the method for estimating an amount of particulate matter remaining on a particulate filter according to  claim 3 , a remaining amount of particulate matter at the point an operating state of the internal combustion engine changes, when the operating state of the internal combustion engine changes during execution of the filter regeneration control;    calculating a duration of the filter regeneration control necessary to oxidize and remove remaining particulate matter based on the calculated remaining amount of particulate matter and the particulate matter removal rate per unit time set in accordance with the operating state of the internal combustion engine after the operating state of the internal combustion engine changed; and    stopping the filter regeneration control when the duration is equal to, or greater than, a predetermined duration.    
   
   
       7 . A method for regenerating a particulate filter, comprising: 
 calculating, according to the method for estimating an amount of particulate matter remaining on a particulate filter according to  claim 4 , a remaining amount of particulate matter at the point an operating state of the internal combustion engine changes, when the operating state of the internal combustion engine changes during execution of the filter regeneration control;    calculating a duration of the filter regeneration control necessary to oxidize and remove remaining particulate matter based on the calculated remaining amount of particulate matter and the particulate matter removal rate per unit time set in accordance with the operating state of the internal combustion engine after the operating state of the internal combustion engine changed; and    stopping the filter regeneration control when the duration is equal to, or greater than, a predetermined duration.    
   
   
       8 . A method for regenerating a particulate filter, comprising: 
 calculating, according to the method for estimating an amount of particulate matter remaining on a particulate filter according to  claim 5 , a remaining amount of particulate matter at the point an operating state of the internal combustion engine changes, when the operating state of the internal combustion engine changes during execution of the filter regeneration control;    calculating a duration of the filter regeneration control necessary to oxidize and remove remaining particulate matter based on the calculated remaining amount of particulate matter and the particulate matter removal rate per unit time set in accordance with the operating state of the internal combustion engine after the operating state of the internal combustion engine changed; and    stopping the filter regeneration control when the duration is equal to, or greater than, a predetermined duration.