Trouble diagnosis device for exhaust gas purification system and trouble diagnosis method for exhaust gas purification system

Abstract

There are provided a trouble diagnosis device and a trouble diagnosis method for an exhaust gas purification system in which the presence or absence of a trouble of the exhaust gas purification system such as abnormality of a control system for the exhaust gas purification system, catalyst deterioration or the like can be determined with high precision, and the reliability of the exhaust gas purification system can be enhanced. The device includes upstream-side NO x flow rate calculating means, downstream-side NO x flow rate calculating means, reduction condition determining means for determining whether at least one condition for performing normal reduction of NO x is satisfied, upstream-side NO x flow amount calculating means for integrating the upstream-side NO x flow amount to calculate the amount of NO x passing through the upstream side of the catalyst within a predetermined time when the condition concerned is determined to be satisfied, downstream-side NO x amount calculating means for integrating the downstream-side NO x flow amount to calculate the amount of NO x passing through the downstream side of the catalyst within a predetermined time when the condition concerned is determined to be satisfied, and trouble determining means for comparing the upstream-side NO x amount and the downstream-side NO x amount to determine whether the exhaust gas purification system operates normally.

1 - 7 . (canceled) 
   
   
       8 . A trouble diagnosis device for an exhaust gas purification system for passing exhaust gas discharged from an internal combustion engine through NO x  catalyst to reduce NO x  contained in the exhaust gas, the trouble diagnosis device comprising:
 upstream-side NO x  flow rate calculating means for calculating the flow amount of upstream-side NO x  flow amount per unit time at an upstream side of the NO x  catalyst;   downstream-side NO x  flow rate calculating means for calculating a downstream-side NO x  flow amount per unit time at a downstream side of the NO x  catalyst;   reduction condition determining means for determining whether at least one condition for performing normal reduction of NO x  is satisfied;   upstream-side NO x  flow amount calculating means for integrating the upstream-side NO x  flow amount to calculate the amount of upstream-side NO x  passing through the upstream side of the NO x  catalyst within a predetermined time when a condition concerned is determined to be satisfied;   downstream-side NO x  amount calculating means for integrating the downstream-side NO x  flow amount to calculate the amount of downstream-side NO x  passing through the downstream side of the NO x  catalyst within a predetermined time when the condition concerned is determined to he satisfied; and   trouble determining means for comparing the upstream-side NO x  amount and the downstream-side NO x  amount to determine whether the exhaust gas purification system operates normally.   
   
   
       9 . The trouble diagnosis device for the exhaust gas purification system according to  claim 8 ,
 wherein the upstream-side NO x  amount calculating means and the downstream-side NO x  amount calculating means store integration values which have been obtained till now when integration of the NO x  flow amount is interrupted, and resume the integration from the stored integration values when the condition concerned is satisfied again.   
   
   
       10 . The trouble diagnosis device for the exhaust gas purification system according to  claim 8 ,
 wherein the upstream-side NO x  amount calculating means and the downstream-side NO x  amount calculating means store integration values which have been obtained till now when integration of the NO x  is interrupted, and reset the integration values when the condition concerned is not satisfied again within a predetermined time.   
   
   
       11 . The trouble diagnosis device for the exhaust gas purification system according to  claim 9 ,
 wherein the upstream-side NO x  amount calculating means and the downstream-side NO x  amount calculating means store the integration values which have been obtained till now when the integration of the NO x  is interrupted, and reset the integration values when the condition concerned is not satisfied again within a predetermined time.   
   
   
       12 . The trouble diagnosis device for the exhaust gas purification system according to  claims 9 , wherein the trouble determining means finishes the integration of the upstream-side NO x  flow amount and the downstream-sidle NO x  flow amount when the upstream-side NO x  amount reaches a predetermined value, and compares the upstream-side NO x  amount and the downstream-side NO x  amount. 
   
   
       13 . The trouble diagnosis device for the exhaust gas purification system according to  claims 10 , wherein the trouble determining means finishes the integration of the upstream-side NO x  flow amount and the downstream-side NO x  flow amount when the upstream-side NO x  amount reaches a predetermined value, and compares the upstream-side NO x  amount and the downstream-side NO x  amount. 
   
   
       14 . The trouble diagnosis device for the exhaust gas purification system according to  claim 8 ,
 wherein the trouble determining means compares the ratio between the upstream-side NO x  amount and the downstream-side NO x  amount with a threshold value which is determined in accordance with a condition under which reduction of NO x  is normally performed for determination.   
   
   
       15 . The trouble diagnosis device for the exhaust gas purification system according to  claim 9 ,
 wherein the trouble determining means compares the ratio between the upstream-side NO x  amount and the downstream-side NO x  amount with a threshold value which is determined in accordance with a condition under which reduction of NO x  is normally performed for determination.   
   
   
       16 . The trouble diagnosis device for the exhaust gas purification system according to  claim 10 ,
 wherein the trouble determining means compares the ratio between the upstream-side NO x  amount and the downstream-side NO x  amount with a threshold value which is determined in accordance with a condition under which reduction of NO x  is normally performed for determination.   
   
   
       17 . The trouble diagnosis device for the exhaust gas purification system according to  claim 8 ,
 wherein the upstream-side NO x  flow rate calculating means performs its calculation on a basis of an NO x  concentration discharged from the internal combustion engine which is calculated from an operation state of the internal combustion engine.   
   
   
       18 . The trouble diagnosis device for the exhaust gas purification system according to  claim 9 ,
 wherein the upstream-side NO x  flow rate calculating means performs its calculation on a basis of an NO x  concentration discharged from the internal combustion engine which is calculated from an operation state of the internal combustion engine.   
   
   
       19 . The trouble diagnosis device for the exhaust gas purification system according to  claim 10 ,
 wherein the upstream-side NO x  flow rate calculating means performs its calculation on a basis of an NO x  concentration discharged from the internal combustion engine which is calculated from an operation state of the internal combustion engine.   
   
   
       20 . A trouble diagnosis method for an exhaust gas purification system for diagnosing the presence or absence of a trouble of an exhaust gas purification system in which exhaust gas discharged from an internal combustion engine is passed through NO x  catalyst to reduce NO x  contained in the exhaust gas, the method comprising:
 calculating all upstream-side NO x  flow amount and a downstream-side NO x  flow amount per unit time at upstream and downstream sides of the NO x  catalyst;   determining whether at least one condition under which the reduction of NO x  is normally performed is satisfied or not;   integrating the upstream-side NO x  flow amount and the downstream-side NO x  flow amount when a condition concerned is satisfied, and calculating an upstream-side NO x  amount and the downstream-side NO x  amount passing through the upstream side and the downstream side of the NO x  catalyst within a predetermined time; and   comparing the upstream-side NO x  amount with the downstream-side NO x  amount to determine whether the exhaust gas purification system operates normally.