Exhaust gas purification device

An electronic control unit for an internal-combustion engine having a particulate filter disposed in an exhaust system of the engine for trapping particulates contained in the exhaust gas, said electric control unit being programmed to:

• determine a cleaning timing to remove the particulates trapped by the particulate filter;
• reduce an intake air amount to be taken into the internal-combustion engine in response to the determination of the cleaning timing;
• maintain combustion in the engine in a desired condition in response to the reduction of the intake air amount;
• and
• heat the particulate filter to clean the particulate filter;
• wherein said electronic control unit is programmed to supply unburned fuel into the exhaust gas when a predetermined time elapses after the particulate filter started heating.

A method for purifying an exhaust gas for an internal-combustion engine having a particulate filter disposed in an exhaust system of the engine for trapping particulates contained in the exhaust gas, comprising the step of:

• determining a cleaning timing to remove the particulates trapped by the particulate filter;
• reducing an intake air amount to be taken into the internal-combustion engine in response to the determination of the cleaning timing;
• maintaining combustion in the engine in a desired condition in response to the reduction of the intake air amount;
• and
• heating the particulate filter to clean the particulate filter;
• wherein the unburned fuel is supplied to the exhaust gas when a predetermined time elapses after the particulate filter started heating.