| 摘要 |
PROBLEM TO BE SOLVED: To provide a refrigeration cycle employing refrigerant having a low critical point such as carbon dioxide CO2, in which the size, weight and costs of an expansion valve are reduced when an electric expansion unit is employed by preventing the size of a driving coil from increasing, the expansion valve can follow up abrupt variation of high pressure and each component in the cycle is protected by preventing abnormal rise of high pressure while facilitating pressure withstanding design. SOLUTION: The expansion unit 5 in a refrigeration cycle is provided with a pressure reduction regulating valve 10 for controlling the conducting state between a high pressure side passage part 12 and a low pressure side passage part 13 by regulating the position of a valve disc 17 through control of an exciting current being fed to a driving coil 20, and a relief valve 11 for relieving the pressure of refrigerant from the high pressure side passage part 12 to the low pressure side passage part 13 when the pressure of the refrigerant at the high pressure side passage part 12 exceeds a specified level.
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