Heat pump system for vehicle and method of controlling the same

A method of controlling a heat pump system for a vehicle, comprising:

• a first step of receiving various sensor values of the vehicle and calculating a target discharge temperature;
• a second step of determining whether the air-conditioning mode or the heat pump mode is selected according to the target discharge temperature or a passenger's selection;
• a third step of calculating a deviation between the target discharge temperature and an air discharge temperature of the interior of the vehicle, when the heat pump mode is selected as the determination result of the second step;
• a fourth step of calculating the number of revolutions of a compressor by the deviation of the third step;
• a fifth step of determining whether or not the number of revolutions of the compressor is less than the number of the maximum revolutions of the compressor;
• a sixth step of variably controlling the compressor by the number of revolutions of the compressor according to the deviation calculated in the fourth step, if the number of revolutions of the compressor is less than the number of the maximum revolutions of the compressor as the determination result of the fifth step;
• a seventh step of determining whether or not the target discharge temperature is higher than the air discharge temperature of the interior of the vehicle, if the number of revolutions of the compressor is not less than the number of the maximum revolutions of the compressor as the determination result of the fifth step;
• and
• an eighth step of controlling the operation of an electric heater while keeping the operation of the compressor, if target discharge temperature is higher than the air discharge temperature of the interior of the vehicle as the determination result of the seventh step,
• wherein the number of the maximum revolutions of the compressor is the minimum value out of the number of the maximum revolutions of the compressor according to factors of outdoor air temperature, refrigerant pressure, vehicle speed, air volume of a blower, the number of revolutions of a cooling fan of an exterior heat exchanger, and the ON-OFF states of a driving source.