Exhaust purifying apparatus for internal combustion engine

An exhaust purifying apparatus for an internal combustion engine, comprising:

• an exhaust purifying mechanism that is located in an exhaust passage of the internal combustion engine, wherein the exhaust purifying mechanism traps particulate matter in exhaust gas;
• a fuel adding device for adding fuel to exhaust gas that passes through the exhaust purifying mechanism, to increase the temperature of the exhaust purifying mechanism so as to burn particulate matter;
• a detecting section that detects a pressure difference between a section upstream and a section downstream of the exhaust purifying mechanism;
• a first comparing section, wherein, when the fuel adding device is continuously adding fuel to exhaust gas, the first determining section compares an estimated accumulation amount of particular matter in the exhaust purifying mechanism with a threshold value;
• a second comparing section, wherein, when the fuel adding device is continuously adding fuel to exhaust gas, the second comparing section compares the pressure difference that is detected by the detecting section with a pressure difference reference value;
• and
• a setting section, wherein, when the first determining section determines that the estimated accumulation amount of particular matter becomes equal to or less than the threshold value and the second comparing section determines that the pressure difference exceeds the pressure difference reference value, the setting section switches the manner of adding fuel of the fuel adding device from the continuous fuel addition to intermittent fuel addition such that the temperature distribution of the exhaust purifying mechanism is suppressed from being uneven,
• wherein the threshold value is a value for determining that the intermittent fuel addition does not cause abrupt burning of particulate matter, and the pressure difference reference value is a value for determining that the continuous fuel addition does not cause sufficient burning of particulate matter.