US Patent 10183554 Vehicular air conditioning device

An air conditioning refrigerant circuit (6) includes an engine-driven compressor (7) and an electric compressor (11), which are arranged in parallel. When the engine is running, the engine-driven compressor (7) is used. When the engine stops, e.g., when idling stops, the electric compressor (11) is used. At the startup of the engine by a manual operation such as ignition by a key, the engine-driven compressor (7) is kept at rest and instead, the electric compressor (11) is operated for a predetermined time. After the predetermined time, the engine-driven compressor (7) is operated. In this way, the oil recovery to the electric compressor is promoted.