VEHICLE AIR-CONDITIONING DEVICE, AND REFRIGERANT LEAKAGE DIAGNOSIS METHOD FOR VEHICLE AIR-CONDITIONING DEVICE

In a vehicle air-conditioning device, refrigerant leakage is diagnosed precisely without any restrictions from an operating condition of the air-conditioning device. When the operating condition of the vehicle air-conditioning device is stable, a threshold value Th for determination of refrigerant leakage is set based on an outlet pressure Pd and an inlet pressure Ps of a compressor. Furthermore, a volume flow Gr in that refrigerant pipe running from a condenser to an expansion valve through which the refrigerant circulates in a liquid state is detected. When it is determined that the volume flow Gr exceeds the threshold value Th for determination of refrigerant leakage, a diagnosis result (alarm) indicating that the refrigerant leaks is output.