HEAT PUMP SYSTEM FOR VEHICLE AND ITS CONTROL METHOD

摘要

PURPOSE: A heat pump system for vehicles and a control method thereof are provided to control the defrosting of the system by using the refrigerant pressure in an entrance of an outdoor heat exchanger and differences of outdoor temperature of the vehicle and the refrigerant temperature in an exit and detecting the frosting of the outdoor heat exchanger. CONSTITUTION: A heat pump system for vehicles comprises a first bypass line (R1) and a control unit. The first bypass line connects a refrigerant circulation line (R) in an entrance of a first expansion unit (140) and a refrigerant circulation line in an exit of an evaporator (160). The first bypass line makes a refrigerant circulating the refrigerant circulation line selectively bypass the first expansion unit and the evaporator. The control unit controls the system as it is determined to generate the defrost in an outdoor heat exchanger (130) when the difference value of outdoor temperatures of the vehicle and refrigerant temperatures in an exit of the outdoor heat exchanger is greater than a predetermined temperature and the refrigerant pressure of an entrance of the outdoor heat exchanger is lower than a reference value in a heat pump mode.