Fuel supply control method applied to exhaust gas control apparatus for internal combustion engine and exhaust gas control apparatus to which the method is applied

An exhaust gas control apparatus for an internal combustion engine, comprising:

• an exhaust gas control portion provided in an exhaust passage of an internal combustion engine;
• a fuel supply portion that supplies fuel to a portion upstream of the exhaust gas control portion;
• and
• a fuel supply control portion that operates the fuel supply portion such that a cycle formed by combining a fuel supply period in which fuel is supplied from the fuel supply portion and a fuel supply stopped period in which fuel is not supplied is repeatedly performed in order to control a temperature of the exhaust gas control portion to a target temperature, wherein
• the fuel supply period:
• i) comprises a plurality of fuel pulses, ii) begins at a first point in time when the temperature of the exhaust gas control portion is below the target temperature, and iii) ends at a second point in time, following the first point in time, when the temperature of the exhaust gas control portion is above the target temperature, wherein
• the temperature of the exhaust gas control portion continuously increases from the first point in time to the second point in time, and
• the fuel supply control portion comprises:
• a temperature-based required fuel supply amount calculating portion that calculates a fuel supply amount that is required to control the temperature of the exhaust gas control portion to the target temperature;
• an estimated fuel supply amount calculating portion that calculates a fuel supply amount that is required to maintain an air-fuel ratio in the exhaust gas control portion at a target air-fuel ratio during a predetermined period;
• a fuel supply stopped period calculating portion that calculates a length of the cycle based on the fuel supply amount calculated by the temperature-based required fuel supply amount calculating portion and the fuel supply amount calculated by the estimated fuel supply amount calculating portion, and that calculates a length of the fuel supply stopped period in the cycle by subtracting a length of the predetermined period, as a length of the fuel supply period, from the calculated length of the cycle;
• and
• a fuel supply timing control portion that controls whether fuel supply by the fuel supply portion is performed in each cycle such that a half of the calculated fuel supply stopped period is set, as a pre-supply fuel supply stopped period, before the fuel supply period.

An exhaust gas control apparatus for an internal combustion engine, comprising:

• an exhaust gas control portion provided in an exhaust passage of an internal combustion engine;
• a fuel supply portion that supplies fuel to a portion upstream of the exhaust gas control portion;
• and
• a fuel supply control portion that operates the fuel supply portion such that a cycle formed by combining a fuel supply period in which fuel is supplied from the fuel supply portion and a fuel supply stopped period in which fuel is not supplied is repeatedly performed in order to control a temperature of the exhaust gas control portion to a target temperature, wherein
• the fuel supply period:
• i) comprises a plurality of fuel pulses, ii) begins at a first point in time when the temperature of the exhaust gas control portion is below the target temperature, and iii) ends at a second point in time, following the first point in time, when the temperature of the exhaust gas control portion is above the target temperature, wherein
• the temperature of the exhaust gas control portion continuously increases from the first point in time to the second point in time, and
• the fuel supply control portion comprises:
• a temperature-based required fuel supply amount calculating portion that calculates a fuel supply amount that is required to control the temperature of the exhaust gas control portion to the target temperature;
• an estimated fuel supply amount calculating portion that calculates a fuel supply amount that is required to maintain an air-fuel ratio in the exhaust gas control portion at a target air-fuel ratio during a predetermined period;
• a fuel supply stopped period calculating portion that calculates a length of the cycle based on the fuel supply amount calculated by the temperature-based required fuel supply amount calculating portion and the fuel supply amount calculated by the estimated fuel supply amount calculating portion, and that calculates a length of the fuel supply stopped period in the cycle by subtracting a length of the predetermined period, as a length of the fuel supply period, from the calculated length of the cycle;
• and
• a fuel supply timing control portion that controls whether fuel supply by the fuel supply portion is performed in each cycle such that a half of the fuel supply period is set, as a pre-supply-stop fuel supply period, before the fuel supply stopped period.