Apparatus for deterioration diagnosis of an oxidizing catalyst

Abstract

An unburned fuel supply section performs temperature rise control to supply fuel to an oxidizing catalyst disposed upstream of an exhaust purification device to cause temperature rise of the exhaust purification device using heat generated in oxidation reaction of fuel on the catalyst. During the temperature rise control, an actual cumulative fuel quantity calculation section obtains actual cumulative fuel quantity by accumulating the amount of fuel supplied to the catalyst. A theoretical cumulative fuel quantity calculation section calculates fuel supply quantity required for temperature rise of the exhaust purification device on the premise that oxidation performance of the catalyst is not deteriorated, and obtains theoretical cumulative fuel quantity by accumulating the calculated fuel supply quantity. After the temperature rise control ends, a deterioration determination section determines whether the catalyst is deteriorated, on the basis of the ratio between the actual cumulative fuel quantity and the theoretical cumulative fuel quantity.

1 . An apparatus for deterioration diagnosis of an oxidizing catalyst, comprising:
 an exhaust purification device disposed in an exhaust passage of an engine for purifying exhaust from the engine;   an oxidizing catalyst disposed upstream of the exhaust purification device;   unburned fuel supply means for, when temperature rise of the exhaust purification device is required, performing temperature rise control to supply unburned fuel to the oxidizing catalyst to cause temperature rise of the exhaust purification device using heat generated in oxidation reaction of unburned fuel on the oxidizing catalyst;   actual cumulative fuel quantity calculation means for obtaining actual cumulative fuel quantity by successively accumulating the amount of unburned fuel supplied to the oxidizing catalyst by the unburned fuel supply means during the temperature rise control;   theoretical cumulative fuel quantity calculation means for calculating fuel supply quantity required for temperature rise of the exhaust purification device, on the premise that oxidation performance of the oxidizing catalyst is not deteriorated, and obtaining theoretical cumulative fuel quantity by successively accumulating the calculated fuel supply quantity during the temperature rise control; and   deterioration determination means for determining whether or not the oxidizing catalyst is deteriorated, on the basis of the ratio between the actual cumulative fuel quantity obtained by the actual cumulative fuel quantity quantity obtained by the actual cumulative fuel quantity calculation means and the theoretical cumulative fuel quantity obtained by the theoretical cumulative fuel quantity calculation means, after the temperature rise control ends.   
     
     
         2 . The apparatus for deterioration diagnosis of an oxidizing catalyst according to  claim 1 , wherein
 the unburned fuel supply means performs the temperature rise control to restore exhaust purification function of the exhaust purification device.   
     
     
         3 . The apparatus for deterioration diagnosis of an oxidizing catalyst according to  claim 2 , wherein
 the exhaust purification device is a filter for trapping particulate matter emitted from the engine, and   the unburned fuel supply means performs the temperature rise control to burn off the particulate matter trapped by the filter.   
     
     
         4 . The apparatus for deterioration diagnosis of an oxidizing catalyst according to  claim 2 , wherein
 the exhaust purification device is a NOx catalyst for converting NOx emitted from the engine, and   the unburned fuel supply means performs the temperature rise control to restore exhaust purification function of the NOx catalyst.   
     
     
         5 . The apparatus for deterioration diagnosis of an oxidizing catalyst according to  claim 4 , wherein
 the unburned fuel supply means performs the temperature rise control to perform SOx purge of the NOx catalyst.   
     
     
         6 . The apparatus for deterioration diagnosis of an oxidizing catalyst according to  claim 1 , wherein
 the unburned fuel supply means supplies unburned fuel to the oxidizing catalyst by performing post-injection in expansion stroke or exhaust stroke after main injection to the engine, and   the actual cumulative fuel quantity calculation means obtains the actual cumulative fuel quantity by successively accumulating the amount of unburned fuel supplied to the oxidizing catalyst by the post-injection.   
     
     
         7 . The apparatus for deterioration diagnosis of an oxidizing catalyst according to  claim 1 , wherein
 the unburned fuel supply means supplies unburned fuel to the oxidizing catalyst by injecting fuel through a fuel injection valve fitted to the exhaust passage, and   the actual cumulative fuel quantity calculation means obtains the actual cumulative fuel quantity by successively accumulating the amount of unburned fuel supplied to the oxidizing catalyst by injection through the fuel injection valve fitted to the exhaust passage.   
     
     
         8 . The apparatus for deterioration diagnosis of an oxidizing catalyst according to  claim 1 , wherein
 the theoretical cumulative fuel quantity calculation means obtains the theoretical cumulative fuel quantity by successively accumulating fuel supply quantity calculated on the basis of inlet temperature of the oxidizing catalyst and intake air flow rate of the engine.   
     
     
         9 . The apparatus for deterioration diagnosis of an oxidizing catalyst according to  claim 1 , wherein
 the deterioration determination means determines that the oxidizing catalyst is deteriorated, when the ratio between the actual cumulative fuel quantity and the theoretical cumulative fuel quantity exceeds a first threshold value and the actual cumulative fuel quantity exceeds a second threshold value.