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;
• a condenser connected to the compressor through a refrigerant line, and configured to condense the refrigerant;
• a first expansion valve connected to the condenser through the refrigerant line;
• an evaporator connected to the first expansion valve and the compressor through the refrigerant line, the evaporator configured to evaporate the refrigerant supplied from the refrigerant line;
• a connection line including:
• a first end connected to the refrigerant line between the condenser and the first expansion valve, and
• a second end connected to the refrigerant line between the compressor and the evaporator;
• a chiller provided on the connection line the chiller configured to exchange heat between the refrigerant introduced through the connection line and a coolant to adjust a temperature of the coolant;
• a second expansion valve provided on the connection line at an upstream end of the chiller;
• and
• a gas injection device provided on the refrigerant line between the condenser and the first expansion valve, the gas injection device configured to selectively expand the refrigerant supplied from the condenser and flow the refrigerant expanded by the gas injection device and selectively supply a partial refrigerant among the refrigerant supplied from the condenser to the compressor so as to increase a flow rate of the refrigerant circulating through the refrigerant line,
• wherein a flow direction of the refrigerant is controlled through operation of the gas injection device based on at least one mode for controlling a temperature of a vehicle interior.