Exhaust gas purifying filter, system of regenerating gasoline particulate filter, and method thereof

A system for regenerating a particulate filter that is mounted on an exhaust pipe of a gasoline engine, the system comprising:

• a three-way catalyst device disposed on the exhaust pipe, and adapted to oxidize or reduce exhaust gas exhausted from the gasoline engine;
• an ammonia storage catalyst unit mounted on the exhaust pipe downstream of the three-way catalyst device, and adapted to (a) absorb ammonia generated in the three-way catalyst device when a temperature of the ammonia storage catalyst unit is lower than a predetermined temperature, (b) release the absorbed ammonia when the temperature of the ammonia storage catalyst unit is higher than or equal to the predetermined temperature, and (c) generate nitrogen oxide from the released ammonia;
• a particulate filter disposed near the ammonia storage catalyst unit, and adapted to trap particulate matter contained in the exhaust gas and to regenerate the trapped particulate matter by using the nitrogen oxide generated from the ammonia storage catalyst unit;
• and
• a control portion adapted to control an air-fuel ratio of an air-fuel mixture flowing into the gasoline engine,
• wherein the control portion is adapted to create a lean atmosphere when a pressure difference of the particulate filter is larger than or equal to a predetermined pressure difference.

A method for regenerating a particulate filter that comprises an ammonia storage catalyst unit adapted to absorb or release ammonia contained in exhaust gas depending on a temperature of the ammonia storage catalyst unit, and a particulate filter adapted to trap particulate matter contained in the exhaust gas, the method comprising:

• absorbing ammonia contained in the exhaust gas;
• comparing a pressure difference of the particulate filter to a predetermined pressure difference;
• creating a lean atmosphere when the pressure difference of the particulate filter is larger than or equal to the predetermined pressure difference;
• releasing the ammonia from the ammonia storage catalyst unit;
• generating nitrogen oxide from the released ammonia;
• and
• regenerating the particulate filter using the generated nitrogen oxide.