Heat pump system for a vehicle

A heat pump system for a vehicle, the heat pump system comprising:

• a compressor configured to compress a refrigerant;
• an HVAC module having an internal condenser and an evaporator connected to the compressor through a refrigerant line;
• an external heat-exchanger connected to the internal condenser through the refrigerant line, the external heat-exchanger being configured to condense or evaporate the refrigerant by heat-exchanging with air;
• a first expansion valve provided on the refrigerant line between the external heat-exchanger and the evaporator;
• an accumulator provided on the refrigerant line between the evaporator and the compressor;
• a first connection line having a first end connected to the accumulator;
• a chiller provided on the first connection line, the chiller being configured to heat-exchange the refrigerant introduced through the first connection line with a coolant to adjust a temperature of the coolant;
• a second expansion valve provided on the refrigerant line between the external heat-exchanger and the first expansion valve, the second expansion valve connected to a second end of the first connection line;
• a gas injection device connected to the refrigerant line between the internal condenser and the external heat-exchanger, the gas injection device being configured to selectively expand the refrigerant supplied from the internal condenser or the external heat-exchanger and configured to flow the refrigerant expanded by the gas injection device, the gas injection device being configured to selectively supply a partial refrigerant among the refrigerant supplied from the internal condenser or the external heat-exchanger to the compressor to increase a flow rate of the refrigerant circulating through the refrigerant line;
• and
• a second connection line having a first end connected to the refrigerant line between the compressor and the internal condenser,
• wherein a flow direction of the refrigerant is controlled depending on at least one mode of the heat pump system for a temperature control of a vehicle interior.