HEAT PUMP SYSTEM FOR VEHICLE

The present invention relates to a heat pump system for a vehicle which can enhance heating performance of a plug-in hybrid vehicle by heating engine coolant necessary for heating using a refrigerant cycle. The heat pump system for a vehicle includes: an evaporator disposed inside an air-conditioning case to exchange heat between air and refrigerant; a heater core disposed inside the air-conditioning case to exchange heat between air and coolant; a first coolant line connecting an engine with the heater core so that the coolant is circulated; a first refrigerant circulation loop which circulates a compressor for compressing and discharging the refrigerant, an air-cooled condenser for exchanging heat between the refrigerant and air, a first expansion means for expanding the refrigerant, and the evaporator in a cooling mode; and a second refrigerant circulation loop which circulates the compressor, a water-cooled heat exchanger for exchanging heat between the refrigerant and the coolant, a second expansion means for expanding the refrigerant, and the air-cooled condenser in a heating mode. The water-cooled heat exchanger is disposed in the first coolant line between the engine and the heater core to exchange heat between the refrigerant of high temperature and high pressure passing through the compressor and the coolant of the first coolant line.