HEAT PUMP SYSTEM FOR A VEHICLE

A heat pump system for a vehicle, capable of improving cooling and heating performance, includes a gas injection device selectively operable in an air conditioning mode of the vehicle interior to increase the flow rate of the refrigerant. The heat pump system is capable of preventing the performance of cooling the vehicle interior from deteriorating, by preventing the temperature of the refrigerant discharged from the compressor from becoming excessively high, when the external temperature is high, or when a refrigerant having a high critical pressure and critical temperature is applied.