Exhaust purification system, control apparatus and control method therefor

Abstract

An exhaust gas purification control apparatus for an internal combustion engine instructs an exhaust fuel valve to inject additive fuel when a diesel particulate filter is to be regenerated, and determines that both the exhaust fuel valve and an oxidation catalyst are normal if an exhaust temperature rises. If the exhaust temperature does not rise, the control apparatus instructs an engine fuel valve to inject additive fuel as a post-injection. If the exhaust temperature does not rise, the control apparatus determines that the oxidation catalyst is abnormal. If the exhaust temperature rises, the control apparatus determines that the oxidation catalyst is normal but the exhaust fuel valve is abnormal.

1 . An exhaust purification control apparatus for an internal combustion engine having an exhaust fuel valve, an oxidation catalyst and an exhaust purification device in an exhaust passage thereof, the exhaust fuel valve being for supplying additive fuel into the exhaust passage and the oxidation catalyst being provided upstream the exhaust purification device so that the additive fuel supplied from the exhaust fuel valve raises exhaust temperature by oxidation reaction, the exhaust purification control apparatus comprising:
 temperature determination means configured to determine a catalyst exhaust temperature in the oxidation catalyst based on an output signal of a temperature sensor provided in the exhaust passage;   fuel control means configured to control a first addition of fuel from the exhaust fuel valve into the exhaust passage and a second addition of fuel supplied from an engine fuel valve as a post-injection of the engine fuel valve; and   abnormality check means configured to check whether the oxidation catalyst or the exhaust fuel valve is abnormal based on the catalyst exhaust temperatures determined when the fuel control means has instructed the first addition of fuel and the second addition of fuel, respectively.   
   
   
       2 . The exhaust purification control apparatus according to  claim 1 , wherein:
 the fuel control means is configured to instruct the second addition of fuel as the post-injection when the catalyst exhaust temperature, which is determined when the first addition of fuel by the exhaust fuel valve is instructed, is lower than a first predetermined temperature;   the abnormality check means is configured to determine that the oxidation catalyst and the exhaust fuel valve are normal, when the catalyst exhaust temperature becomes greater than the first predetermined temperature in response to the first addition of fuel;   the abnormality check means is configured to determine that the oxidation catalyst is abnormal, when the catalyst exhaust temperature is less than a second predetermined temperature in response to the second addition of fuel, which is instructed when the catalyst exhaust temperature is less than the first predetermined temperature; and   the abnormality check means is configured to determine that the oxidation catalyst is normal and the exhaust fuel valve is abnormal, when the catalyst exhaust temperature becomes greater than the second predetermined temperature in response to the second addition of fuel.   
   
   
       3 . The exhaust purification control apparatus according to  claim 1 , wherein:
 the fuel control means is configured to instruct the first addition of fuel by the exhaust fuel valve when the catalyst exhaust temperature, which is determined when the second addition of fuel by the engine fuel valve is instructed, becomes greater than a second predetermined temperature;   the abnormality check means is configured to determine that the oxidation catalyst is normal, when the catalyst exhaust temperature becomes greater than the second predetermined temperature in response to the second addition of fuel;   the abnormality check means is configured to determine that the exhaust fuel valve is normal, when the catalyst exhaust temperature becomes greater than a first predetermined temperature in response to the first addition of fuel, which is instructed when the catalyst exhaust temperature is greater than the second predetermined temperature in response to the second addition of fuel; and   the abnormality check means determines that the exhaust fuel valve is abnormal, when the catalyst exhaust temperature is less than the first predetermined temperature in response to the first addition of fuel.   
   
   
       4 . The exhaust purification control apparatus according to  claim 1 , wherein the exhaust purification device includes a particulate filter. 
   
   
       5 . An exhaust purification system for an internal combustion engine having an exhaust passage comprising:
 an exhaust fuel valve provided in the exhaust passage for supplying additive fuel into the exhaust passage;   an oxidation catalyst provided in the exhaust passage for causing oxidation reaction of the additive fuel;   a temperature sensor for outputting a signal corresponding to an exhaust temperature in the oxidation catalyst;   an exhaust purification device provided downstream the oxidation catalyst for purifying harmful components in emissions exhausted from the internal combustion engine; and   an exhaust purification control apparatus according to  claim 1 .   
   
   
       6 . A control method for an exhaust purification system for an internal combustion engine having an exhaust passage comprising an engine fuel valve provided on the engine for supplying fuel into the engine, an exhaust fuel valve provided in the exhaust passage for supplying additive fuel into the exhaust passage, an oxidation catalyst provided in the exhaust passage for causing oxidation reaction of fuel in exhaust gas of the engine, and an exhaust purification device provided downstream the oxidation catalyst for purifying exhaust gas of the engine, the control method comprising:
 instructing the exhaust fuel valve and the engine fuel valve to supply first additive fuel into the exhaust passage and second additive fuel into the engine, respectively, at different timings, the second additive fuel being supplied into the engine in an exhaust stroke of the engine;   checking whether temperature in the oxidation catalyst has risen in response to each instruction of supply of the first additive fuel and the second additive fuel; and   determining which one of the exhaust fuel valve and the oxidation catalyst is abnormal based on check results of temperatures in the oxidation catalyst.   
   
   
       7 . The control method according to  claim 6 , wherein:
 the checking compares the temperature in the oxidation catalyst with a first predetermined temperature and a second predetermined temperature when the supply of the first additive fuel and the second additive fuel are instructed, respectively; and   the first predetermined temperature is higher than the second predetermined temperature.