| 摘要 |
PROBLEM TO BE SOLVED: To carry out proper defrosting not to bring cooling trouble in a shed, so as to prevent a problem wherein that a motor-driven expansion valve is stored inside a cold gas duct for facilitating repair and inspection to be exposed to the cold gas, in the motor-driven expansion valve used sometimes as a decompression device, wherein frost is thereby deposited in the periphery of the motor-driven expansion valve to disturb the cold gas flowing the duct, and wherein proper cold gas circulation is not executed to bring the cooling trouble in the shed, in a refrigeration unit circulated with carbon dioxide as a refrigerant. SOLUTION: A refrigerant circuit is constituted to evaporate the carbon dioxide refrigerant compressed at two stages by a compressor in an evaporator (cooler) for cooling the cooling shed through the motor-driven expansion valve after heat-radiated in a heat radiator, so as to be fed back to the first stage compression part of the compressor, the motor-driven expansion valve is stepping motor type one for opening and closing a refrigerant passage by a driving valve, based on a pulse signal electrified in a coil, and a heating mode is provided to bring the motor-driven expansion valve into a heating condition with heat generation in the coil, although the driving valve is not operated. COPYRIGHT: (C)2007,JPO&INPIT
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