US Patent 9562712 Vehicular air-conditioning unit

The heating capacity particularly at low outside air temperatures in a vehicular air-conditioning unit that heats the vehicle interior by heat pump operation of a refrigerant circuit using a compressor is improved. During heating, a refrigerant discharged from a compressor 2 releases heat in a radiator 4 into the vehicle interior, and the refrigerant decompressed after the heat release in the radiator evaporates in at least one of an external heat exchanger 7 and a ventilation heat exchanger 24. During cooling, the refrigerant discharged from the compressor releases heat in the external heat exchanger, and the refrigerant decompressed after the heat release in the external heat exchanger evaporates in an internal heat exchanger 9 to absorb heat from the vehicle interior. The vehicular air-conditioning unit includes a hot gas cycle circuit 31 for decompressing a part of the refrigerant discharged from the compressor, and causing the decompressed part of the refrigerant to flow through the internal heat exchanger to release heat into the vehicle interior.