Vehicle system and method of heating soot filter by using the same

A method of heating a soot filter by using a vehicle system which includes an engine which burns an air-fuel mixture to generate energy and discharges exhaust gas generated during combustion of the air-fuel mixture, a hybrid starter and generator (HSG) which generates electricity by starting the engine or by using energy generated in the engine, the soot filter which collects particulate matters (soot) included in exhaust gas, and a control unit which control the operations of the engine and the HSG, the method comprising:

• when the engine is operated, determining whether the quantity of soot collected in the soot filter is equal to or larger than a predetermined quantity;
• when a quantity of soot collected in the soot filter is equal to or larger than the predetermined quantity, determining whether a temperature of the soot filter is lower than a first temperature;
• when the temperature of the soot filter is lower than the first temperature, increasing a load of the HSG by a first load;
• when the temperature of the soot filter is equal to or higher than the first temperature, determining whether the temperature of the soot filter is lower than a second temperature;
• when the temperature of the soot filter is lower than the second temperature, increasing a load of the HSG by a second load which is smaller than the first load;
• and
• returning to the determining of whether the temperature of the soot filter is lower than the first temperature.