Problem detection apparatus and method in exhaust purifying apparatus

Abstract

An exhaust purifying apparatus is provided with a filter located in an exhaust path of an internal combustion engine and configured to collect particulates in exhaust gas. The exhaust purifying apparatus is also provided with a differential pressure sensor which detects the pressure difference generated between the upstream side and downstream side of the filter. The problem detection apparatus of the exhaust purifying apparatus is provided with a differential pressure calculation unit and a judgment unit. The differential pressure calculation unit calculates the pressure difference between the upstream and downstream sides of the filter based on the operating state of the internal combustion engine. The judgment unit calculates a difference P between an actual measurement value of the pressure difference and a calculation differential pressure value compares the difference P with a threshold value, and detects that the filter has a problem.

1 . A problem detection apparatus in an exhaust purifying apparatus having a filter which is provided in an exhaust path in an internal combustion engine, and collects particulates in exhaust gas, and a differential pressure sensor which detects a pressure difference generated between the upstream side and downstream side of the filter, the problem detection apparatus comprising:
 a differential pressure calculation means which calculates a value of a pressure difference between the upstream and downstream sides of the filter based on an operating state of the internal combustion engine; and   a judgment means which calculates a difference P between an actual measurement value of the pressure difference between the upstream side and downstream side of the filter detected by the differential pressure sensor and the calculation differential pressure value from the differential pressure value calculation means, compares the difference P with a threshold value, and detects that the filter has a problem.   
   
   
       2 . The problem detection apparatus in the exhaust purifying apparatus according to  claim 1 , wherein the judgment means has a first threshold value used for judging a clogging of the filter, and a second threshold value used for judgment a leak of the filter, and judges that the filter has a problem, when a value of the difference P exceeds the first threshold value, or when a value of the difference P exceeds the second threshold value. 
   
   
       3 . The problem detection apparatus in the exhaust purifying apparatus according to  claim 2 , wherein the first threshold value is calculated from an exhaust flow rate, and a clogging coefficient based on a soot calculation deposition value and ash calculation deposition value of the filter; and the second threshold value is calculated from an exhaust flow rate, and a leak coefficient based on a soot calculation deposition value and ash calculation deposition value of the filter. 
   
   
       4 . The problem detection apparatus in the exhaust purifying apparatus according to  claim 3 , wherein the differential pressure calculation means calculates a calculation differential pressure value based on a reference differential pressure value calculated from temperature and exhaust flow rate in the upstream side of the filter. 
   
   
       5 . The problem detection apparatus in the exhaust purifying apparatus according to any one of  claims 1  to  4 , wherein the judgment means has a decision means which decided that the filter is defective when the filter is judged defective and the judgment is continued for a predetermined time. 
   
   
       6 . A problem detection method in an exhaust purifying apparatus having a filter which is provided in an exhaust path in an internal combustion engine, and collects particulates in exhaust gas,
 wherein a differential pressure sensor for detecting a pressure difference between the upstream side and downstream side of the filter detects a pressure difference between the upstream side and downstream side of the filter;   a differential pressure calculation means for calculating a value of a pressure difference between the upstream side and downstream side of the filter based on an operating state of the internal combustion engine calculates a pressure difference between the upstream side and downstream side of the filter; and   a judgment means calculates a difference P between an actual measurement value of a pressure difference between the upstream side and downstream side of the filter detected by the differential pressure sensor and a calculation differential pressure value calculated by the differential pressure value calculation means, compares the difference P with a threshold value, and judges whether the filter has a problem.   
   
   
       7 . The problem detection method in the exhaust purifying apparatus according to  claim 6 , wherein the judgment means judges that the filter has a problem, when a value of the difference P exceeds the first threshold value, or when a value of the difference P exceeds the second threshold value. 
   
   
       8 . The problem detection method in the exhaust purifying apparatus according to  claim 7 , wherein the first threshold is a value calculated from an exhaust flow rate, and a clogging coefficient based on a soot calculation deposition value and ash calculation deposition value of the filter; and the second threshold value is a value calculated from an exhaust flow rate, and a leak coefficient based on a soot calculation deposition value and ash calculation deposition value of the filter. 
   
   
       9 . The problem detection method in the exhaust purifying apparatus according to  claim 8 , wherein the calculation differential pressure value calculated by the differential pressure calculation means is a value calculated based on a reference differential pressure value calculated from temperature and exhaust flow rate in the upstream side of the filter. 
   
   
       10 . The problem detection method in the exhaust purifying apparatus according to any one of  claims 6  to  9 , wherein the judgment means judges that the filter has a problem, when the filter is judged defective and the judgment is continued for a predetermined time.