Exhaust emission control device

Abstract

An exhaust purification device incinerates particulates, collected by the DPF, always in an appropriate combustion state, thereby surely regenerating a DPF without melting down the DPF. An ECU of the device estimates the amount of the particulates collected by the DPF (S 6 ), selects a map according to whether the collection amount is appropriate or excessive (S 8 ), determines a target oxygen amount from a DPF temperature on the basis of the selected map (S 10 and S 12 ), and feedbacks the oxygen amount in exhaust gas to the target oxygen amount (S 20 ). Since the particulate collection amount is reflected in control of the oxygen amount, the particulates can be incinerated always in the appropriate combustion state regardless of the particulate collection amount.

1 . An exhaust purification device having a filter disposed in an exhaust passage of an internal combustion engine for collecting particulates contained in exhaust gas, and an oxygen supply amount-adjusting device capable of adjusting an oxygen amount supplied to the filter, comprising: 
 a temperature-estimating device for detecting or estimating a temperature of or near the filter,    wherein said oxygen supply amount-adjusting device adjusts the oxygen supply amount to a value between lower and upper regeneration limit oxygen amounts that are determined according to the filter temperature.    
     
     
         2 . The exhaust purification device according to  claim 1 , wherein said oxygen supply amount-adjusting device determines the oxygen supply amount from a residual oxygen amount in the exhaust gas, which corresponds to combustion state of the internal combustion engine.  
     
     
         3 . The exhaust purification device according to  claim 1 , wherein said oxygen supply amount-adjusting device determines an optimum oxygen amount between the lower and upper regeneration limit oxygen amounts according to the filter temperature and adjusts the oxygen supply amount to be equal to or close to the optimum oxygen amount.  
     
     
         4 . The exhaust purification device according to  claim 3 , wherein the optimum oxygen amount is set at a value near an intermediate value between the lower and upper regeneration limit oxygen amounts or a value closer to the lower regeneration limit oxygen amount than to the intermediate value.  
     
     
         5 . The exhaust purification device according to  claim 3 , wherein the optimum oxygen amount has a predetermined range between a first optimum oxygen amount and a second optimum oxygen amount larger than the first one, and 
 said oxygen supply amount-adjusting device determines the oxygen supply amount according to the residual oxygen amount in the exhaust gas, which corresponds to the combustion state of said internal combustion engine, and, if the oxygen supply amount is outside the predetermined range of the optimum oxygen amount, adjusts the oxygen supply amount to either the first or the second optimum oxygen amount, whichever is closer to the oxygen supply amount.    
     
     
         6 . The exhaust purification device according to  claim 3 , wherein said oxygen supply amount-adjusting device determines a first and a second residual oxygen amount in the exhaust gas, which correspond to the combustion states in which the internal combustion engine is operated at a lower limit air/fuel ratio and at an upper limit air/fuel ratio, respectively, compares the optimum oxygen amount to each of the first and second residual oxygen amounts, and adjusts the oxygen supply amount according to a result of the comparison.  
     
     
         7 . The exhaust purification device according to  claim 6 , wherein said oxygen supply amount-adjusting device adjusts the oxygen supply amount to the optimum oxygen amount when the optimum oxygen amount is between the first and second residual oxygen amounts.  
     
     
         8 . The exhaust purification device according to  claim 6 , wherein said oxygen supply amount-adjusting device adjusts the oxygen supply amount to either the first or the second residual oxygen amounts, whichever is closer to the optimum oxygen amount, if the optimum oxygen amount is not between the first and second residual oxygen amounts.  
     
     
         9 . The exhaust purification device according to claim  6 , wherein said oxygen supply amount-adjusting device adjusts the oxygen supply amount to either the lower or the upper regeneration limit oxygen amount, whichever is closer to the first or the second residual oxygen amount, if the optimum oxygen amount is not between the first and second residual oxygen amounts and if the first and the second residual oxygen amount are not between the lower and upper regeneration limit oxygen amounts.  
     
     
         10 . The exhaust purification device according to  claim 1 , wherein the lower regeneration limit oxygen amount has a predetermined range between a first lower regeneration limit oxygen amount and a second lower regeneration limit oxygen amount larger than the first one; 
 the upper regeneration limit oxygen amount has a predetermined range between a first upper regeneration limit oxygen amount and a second upper regeneration limit oxygen amount larger than the first one; and    said oxygen supply amount-adjusting device determines the oxygen supply amount from the residual oxygen amount in the exhaust gas which corresponds to the combustion state of the internal combustion engine, adjusts the oxygen supply amount to the first lower regeneration limit oxygen amount when the oxygen supply amount is smaller than the first lower regeneration limit oxygen amount, adjusts the oxygen supply amount to the second lower regeneration limit oxygen amount when the oxygen supply amount is within the predetermined range of the lower regeneration limit oxygen amount, adjusts the oxygen supply amount to the first upper regeneration limit oxygen amount when the oxygen supply amount is within the predetermined range of the upper regeneration limit oxygen amount, and adjusts the oxygen supply amount to the second upper regeneration limit oxygen amount when the oxygen supply amount is larger than the second upper regeneration limit oxygen amount.    
     
     
         11 . The exhaust purification device according to  claim 1 , wherein said oxygen supply amount-adjusting device estimates an amount of the particulates collected by the filter and sets the lower and upper regeneration limit oxygen amounts according to the estimated particulate collection amount and the filter temperature.  
     
     
         12 . The exhaust purification device according to  claim 1 , wherein said oxygen supply amount-adjusting device adjusts the oxygen supply amount when the estimated particulate collection amount is not smaller than a predetermined amount and when the internal combustion engine is in a predetermined operation state.  
     
     
         13 . The exhaust purification device according to  claim 1 , wherein said temperature-estimating device estimates the temperature of or near the filter based on a detection output of a temperature-detecting device for detecting the temperature of or near the filter and a change of the detection output.  
     
     
         14 . The exhaust purification device according to  claim 1 , wherein said filter can be regenerated through an oxidative reaction of an oxidation catalyst disposed in the filter or in the exhaust passage at a location upstream of the filter.