Catalyst deterioration determination device and method, and engine control unit

Abstract

A catalyst deterioration determination device capable of determining whether or not fuel is high-sulfur fuel containing much sulfur content, and properly determining whether a catalyst is deteriorated while suppressing the frequency of execution of control for recovering the catalyst from the poisoned state to the minimum. The device determines whether or not a catalyst which purifies exhaust gases exhausted from an internal combustion engine is deteriorated based on the capacity of the catalyst for purifying exhaust gases. If it is determined that the catalyst is deteriorated, first sulfur elimination control is executed for eliminating sulfur content accumulated in the catalyst. Further, when the first sulfur elimination control is terminated, the deterioration determination of the catalyst is executed. Then, when it is determined by the deterioration determination that the catalyst is not deteriorated, it is determined that the fuel is high-sulfur fuel containing lots of sulfur content.

1 . A catalyst deterioration determination device that determines deterioration of a catalyst disposed in an exhaust passage of an internal combustion engine, for purifying exhaust gases exhausted from the engine, comprising:
 first deterioration-determining means for determining whether or not the catalyst is deteriorated based on a capacity of the catalyst for purifying exhaust gases;   first sulfur elimination control-executing means for executing first sulfur elimination control for eliminating sulfur content accumulated in the catalyst, when it is determined by said first deterioration-determining means that the catalyst is deteriorated;   second deterioration-determining means for determining whether or not the catalyst is deteriorated, when the first sulfur elimination control is terminated; and   high sulfur-determining means for determining that the fuel is high-sulfur fuel containing lots of sulfur content, when it is determined by said second deterioration-determining means that the catalyst is not deteriorated.   
   
   
       2 . A catalyst deterioration determination device as claimed in  claim 1 , further comprising deterioration determination-inhibiting means for inhibiting the deterioration determination of the catalyst by said first deterioration-determining means, when it is determined by said high sulfur-determining means that the fuel is high-sulfur fuel. 
   
   
       3 . A catalyst deterioration determination device as claimed in  claim 2 , further comprising fuel consumption-calculating means for calculating consumption of fuel, and
 wherein said deterioration determination-inhibiting means inhibits the deterioration determination, when the calculated fuel consumption reaches a first predetermined threshold.   
   
   
       4 . A catalyst deterioration determination device as claimed in  claim 2 , further comprising fuel consumption-determining means for determining whether or not the fuel which is determined as high-sulfur fuel is consumed; and
 deterioration determination-restarting means for restarting the deterioration determination of the catalyst by said first deterioration-determining means, when it is determined by said fuel consumption-determining means that the fuel is consumed during inhibition of the deterioration determination of the catalyst.   
   
   
       5 . A catalyst deterioration determination device as claimed in  claim 4 , wherein said fuel consumption-determining means determines that the fuel is consumed when the fuel consumption reaches a second predetermined threshold which is larger than the first predetermined threshold. 
   
   
       6 . A catalyst deterioration determination device as claimed in  claim 4 , further comprising refueling determining means for determining whether or not refueling is performed, and
 wherein said fuel consumption-determining means determines that fuel is consumed when it is determined by said refueling determining means that refueling is performed.   
   
   
       7 . A catalyst deterioration determination device as claimed in  claim 4 , wherein the first sulfur elimination control is executed prior to restarting the deterioration determination of the catalyst by said deterioration determination-restarting means. 
   
   
       8 . A catalyst deterioration determination device as claimed in  claim 1 , further comprising second sulfur elimination control-executing means for executing second sulfur elimination control separately from the first sulfur elimination control, for eliminating sulfur content accumulated in the catalyst in accordance with progress of operation of the engine, and
 wherein a time period over which the first sulfur elimination control is executed is longer than a time period over which the second sulfur elimination control is executed.   
   
   
       9 . A catalyst deterioration determination device as claimed in  claim 1 , further comprising second sulfur elimination control-executing means for executing second sulfur elimination control separately from the first sulfur elimination control, for eliminating sulfur content accumulated in the catalyst in accordance with progress of operation of the engine, and
 wherein said first and second sulfur elimination control-executing means control the exhaust gases flowing into the catalyst to a reduction atmosphere, and   wherein a degree of reduction of the exhaust gases is controlled to a higher value during execution of the first sulfur elimination control, than during execution of the second sulfur elimination control.   
   
   
       10 . A catalyst deterioration determination device as claimed in  claim 1 , further comprising second sulfur elimination control-executing means for executing second sulfur elimination control separately from the first sulfur elimination control, for eliminating sulfur content accumulated in the catalyst in accordance with progress of operation of the engine, and
 wherein temperature of the catalyst is controlled to a higher value during execution of the first sulfur elimination control, than during execution of the second sulfur elimination control.   
   
   
       11 . A catalyst deterioration determination device as claimed in  claim 8 , further comprising second sulfur elimination control period-setting means for setting a repetition period at which the second sulfur elimination control is executed to a short time period, when it is determined by said high sulfur-determining means that the fuel is high-sulfur fuel. 
   
   
       12 . A catalyst deterioration determination device as claimed in  claim 1 , wherein the catalyst is configured to trap NOx in exhaust gases under the oxidation atmosphere,
 the catalyst deterioration determination device further comprising:   reduction control means for executing reduction control for controlling exhaust gases flowing into the catalyst to the reduction atmosphere to reduce the NOx trapped by the catalyst, and   reduction control repetition period-setting means for setting a repetition period at which the reduction control is executed to a short time period, when it is determined by said high sulfur-determining means that the fuel is high-sulfur fuel.   
   
   
       13 . A method of determining deterioration of a catalyst disposed in an exhaust passage of an internal combustion engine, for purifying exhaust gases exhausted from the engine, comprising:
 executing first deterioration determination for determining whether or not the catalyst is deteriorated, based on a capacity of the catalyst for purifying exhaust gases;   executing first sulfur elimination control for eliminating sulfur content accumulated in the catalyst, when it is determined by the first deterioration determination that the catalyst is deteriorated;   executing second deterioration determination for determining whether or not the catalyst is deteriorated, when the first sulfur elimination control is terminated; and   determining that the fuel is high-sulfur fuel containing lots of sulfur content, when it is determined by the second deterioration determination that the catalyst is not deteriorated.   
   
   
       14 . A method as claimed in  claim 13 , further comprising inhibiting the first deterioration determination of the catalyst, when it is determined that the fuel is high-sulfur fuel. 
   
   
       15 . A method as claimed in  claim 14 , further comprising calculating consumption of fuel, and
 wherein said inhibiting includes inhibiting the first deterioration determination, when the calculated fuel consumption reaches a first predetermined threshold.   
   
   
       16 . A method as claimed in  claim 14 , further comprising determining whether or not the fuel which is determined as high-sulfur fuel is consumed; and
 restarting the first deterioration determination, when it is determined by said fuel consumption determining that the fuel is consumed during inhibition of the deterioration determination of the catalyst.   
   
   
       17 . A method as claimed in  claim 16 , wherein said fuel consumption determining includes determining that the fuel is consumed when the fuel consumption reaches a second predetermined threshold which is larger than the first predetermined threshold. 
   
   
       18 . A method as claimed in  claim 16 , further comprising determining whether or not refueling is performed, and
 wherein said fuel consumption determining includes determining that fuel is consumed when it is determined by said refueling determining that refueling is performed.   
   
   
       19 . A method as claimed in  claim 16 , wherein the first sulfur elimination control is executed prior to restarting the first deterioration determination of the catalyst. 
   
   
       20 . A method as claimed in  claim 13 , further comprising executing second sulfur elimination control separately from the first sulfur elimination control, for eliminating sulfur content accumulated in the catalyst in accordance with progress of operation of the engine, and
 wherein a time period over which the first sulfur elimination control is executed is longer than a time period over which the second sulfur elimination control is executed.   
   
   
       21 . A method as claimed in  claim 13 , further comprising executing second sulfur elimination control separately from the first sulfur elimination control, for eliminating sulfur content accumulated in the catalyst in accordance with progress of operation of the engine, and
 wherein said first and second sulfur elimination controls control the exhaust gases flowing into the catalyst to a reduction atmosphere, and   wherein a degree of reduction of the exhaust gases is controlled to a higher value during execution of the first sulfur elimination control, than during execution of the second sulfur elimination control.   
   
   
       22 . A method as claimed in  claim 13 , further comprising executing second sulfur elimination control separately from the first sulfur elimination control, for eliminating sulfur content accumulated in the catalyst in accordance with progress of operation of the engine, and
 wherein temperature of the catalyst is controlled to a higher value during execution of the first sulfur elimination control, than during execution of the second sulfur elimination control.   
   
   
       23 . A method as claimed in  claim 20 , further comprising setting a repetition period at which the second sulfur elimination control is executed to a short time period, when it is determined that the fuel is high-sulfur fuel. 
   
   
       24 . A method as claimed in  claim 13 , wherein the catalyst is configured to trap NOx in exhaust gases under the oxidation atmosphere,
 the method further comprising:   executing reduction control for controlling exhaust gases flowing into the catalyst to the reduction atmosphere to reduce the NOx trapped by the catalyst, and   setting a repetition period at which the reduction control is executed to a short time period, when it is determined that the fuel is high-sulfur fuel.   
   
   
       25 . An engine control unit including a control program for causing a computer to execute a method of determining deterioration of a catalyst disposed in an exhaust passage of an internal combustion engine, for purifying exhaust gases exhausted from the engine,
 wherein the method comprises:   executing first deterioration determination for determining whether or not the catalyst is deteriorated, based on a capacity of the catalyst for purifying exhaust gases;   executing first sulfur elimination control for eliminating sulfur content accumulated in the catalyst, when it is determined the first deterioration determination that the catalyst is deteriorated;   executing second deterioration determination for determining whether or not the catalyst is deteriorated, when the first sulfur elimination control is terminated; and   determining that the fuel is high-sulfur fuel containing lots of sulfur content, when it is determined by the second deterioration determination that the catalyst is not deteriorated.   
   
   
       26 . An engine control unit as claimed in  claim 25 , wherein the method further comprises inhibiting the first deterioration determination of the catalyst, when it is determined that the fuel is high-sulfur fuel. 
   
   
       27 . An engine control unit as claimed in  claim 26 , wherein the method further comprises calculating consumption of fuel, and
 wherein said inhibiting includes inhibiting the first deterioration determination, when the calculated fuel consumption reaches a first predetermined threshold.   
   
   
       28 . An engine control unit as claimed in  claim 26 , wherein the method further comprises:
 determining whether or not the fuel which is determined as high-sulfur fuel is consumed; and   restarting the first deterioration determination, when it is determined by said fuel consumption determining that the fuel is consumed during inhibition of the deterioration determination of the catalyst.   
   
   
       29 . An engine control unit as claimed in  claim 28 , wherein said fuel consumption determining includes determining that the fuel is consumed when the fuel consumption reaches a second predetermined threshold which is larger than the first predetermined threshold. 
   
   
       30 . An engine control unit as claimed in  claim 28 , wherein the method further comprises determining
 whether or not refueling is performed, and wherein said fuel consumption determining includes determining that fuel is consumed when it is determined by said refueling determining that refueling is performed.   
   
   
       31 . An engine control unit as claimed in  claim 28 , wherein the first sulfur elimination control is executed prior to restarting the first deterioration determination of the catalyst. 
   
   
       32 . An engine control unit as claimed in  claim 25 , wherein the method further comprises executing second sulfur elimination control separately from the first sulfur elimination control, for eliminating sulfur content accumulated in the catalyst in accordance with progress of operation of the engine, and
 wherein a time period over which the first sulfur elimination control is executed is longer than a time period over which the second sulfur elimination control is executed.   
   
   
       33 . An engine control unit as claimed in  claim 25 , wherein the method further comprises executing second sulfur elimination control separately from the first sulfur elimination control, for eliminating sulfur content accumulated in the catalyst in accordance with progress of operation of the engine, and
 wherein said first and second sulfur elimination controls control the exhaust gases flowing into the catalyst to a reduction atmosphere, and   wherein a degree of reduction of the exhaust gases is controlled to a higher value during execution of the first sulfur elimination control, than during execution of the second sulfur elimination control.   
   
   
       34 . An engine control unit as claimed in  claim 25 , wherein the method further comprises executing second sulfur elimination control separately from the first sulfur elimination control, for eliminating sulfur content accumulated in the catalyst in accordance with progress of operation of the engine, and
 wherein temperature of the catalyst is controlled to a higher value during execution of the first sulfur elimination control, than during execution of the second sulfur elimination control.   
   
   
       35 . An engine control unit as claimed in  claim 32 , wherein the method further comprises setting a repetition period at which the second sulfur elimination control is executed to a short time period, when it is determined that the fuel is high-sulfur fuel. 
   
   
       36 . An engine control unit as claimed in  claim 25 , wherein the catalyst is configured to trap NOx in exhaust gases under the oxidation atmosphere,
 wherein the method further comprises:   executing reduction control for controlling exhaust gases flowing into the catalyst to the reduction atmosphere to reduce the NOx trapped by the catalyst, and   setting a repetition period at which the reduction control is executed to a short time period, when it is determined that the fuel is high-sulfur fuel.