FREEZING CYCLE

PROBLEM TO BE SOLVED: To prevent vibration and noise from occurring upon a valve being opened and closed, and improve the stability of control over an entire load region used. SOLUTION: A freezing cycle comprises a compressor for forcedly feeding a refrigerant, a radiator for radiating the heat of the refrigerant compressed by the compressor, a high pressure control valve 10 for reducing the pressure of the refrigerant by adjusting the pressure of a high pressure line and flow the same to a low pressure line, an evaporator for evaporating the refrigerant reduced in the pressure thereof with the high pressure control valve, and a relief valve 11 for releasing the refrigerant from the high pressure line to the low pressure line when the high pressure line exceeds set pressure. In the freezing cycle, there is further provided all closing prevention means for preventing the high pressure control valve 10 and the relief valve 11 from becoming an all closed state.