Internal combustion engine exhaust gas control system and control method of internal combustion engine exhaust gas control system

A control method of an internal combustion engine exhaust gas control system, which is applied to a hybrid vehicle that is powered by an internal combustion engine and an electric motor, comprising:

• decreasing an opening amount of an exhaust throttle valve, provided downstream of an exhaust gas control catalyst, to a target opening amount if it is determined that warm-up control of the internal combustion engine is to be executed;
• calculating a target exhaust gas temperature by adding a reference temperature difference to a detected exhaust gas control catalyst temperature;
• calculating a target injection quantity of fuel necessary to raise the temperature of exhaust gas flowing into the exhaust gas control catalyst to the target exhaust gas temperature when the opening amount of the exhaust throttle valve has been decreased to the target opening amount;
• setting the fuel injection quantity to the target injection quantity;
• adjusting assist torque generated by the electric motor so that the sum of torque generated by the internal combustion engine and the assist torque generated by the electric motor substantially equals a required torque;
• and
• reducing an increase amount of the fuel injection quantity as the target opening amount of the exhaust throttle valve is reduced.

An internal combustion engine exhaust gas control system, which is applied to a hybrid vehicle that is powered by an internal combustion engine and an electric motor, the internal combustion engine exhaust gas control system comprising:

• an exhaust gas control catalyst provided in an exhaust passage of the internal combustion engine;
• an exhaust throttle valve, provided downstream of the exhaust gas control catalyst, that changes a sectional area of the exhaust passage;
• an electronic control unit;
• a memory, the memory storing instructions that when executed cause the electronic control unit to perform as:
• a first catalyst warm-up device that warms up the exhaust gas control catalyst by increasing a fuel injection quantity in the internal combustion engine;
• an assist amount adjusting device that adjusts assist torque generated by the electric motor such that the sum of engine torque, after the fuel injection quantity has been increased, and the assist torque is substantially equal to a required torque;
• and
• a second catalyst warm-up device that warms up the exhaust gas control catalyst by decreasing an opening amount of the exhaust throttle valve;
• and
• a catalyst temperature sensor that detects the temperature of the exhaust gas control catalyst,
• wherein:
• when the opening amount of the exhaust throttle valve is reduced to a target opening amount, the first catalyst warm-up device increases the fuel injection quantity to increase a temperature of exhaust gas flowing into the exhaust gas control catalyst to a target exhaust gas temperature such that the target exhaust gas temperature is increased gradually and the fuel injection quantity is increased gradually in accordance with an increase in the temperature of the exhaust gas control catalyst, the target exhaust gas temperature being set higher than the detected exhaust gas control catalyst temperature, and
• an increase amount of the fuel injection quantity is reduced as the target opening amount of the exhaust throttle valve is reduced.