Cryogenic refrigerator and control method therefor

Abstract

A cryogenic refrigerator (10) which generates a cryogenic temperature by compressing and expanding a working gas in a closed loop (11). The cryogenic refrigerator comprises a bypass line (22) allowing a high-pressure portion and a low-pressure portion to communicate with each other, a gas storage tank (24) located midway in the bypass line and having pressure regulation valves (23a, 23b) on the high-pressure side and the low-pressure side, respectively, and a pressure control unit (26) controlling the pressure regulation valves. The pressure control unit (26) controls the pressure regulation valves (23a, 23b) so that the pressure in the gas storage tank (24) is equal to the pressure in the closed loop at room temperature and in a stopped state and so that the pressure in the gas storage tank (24) is between the pressures in the high-pressure portion and in the low-pressure portion and is close to the pressure in the low-pressure portion in an operating state.

Description

BACKGROUND OF THE INVENTION[0001]1. Technical Field of the Invention[0002]The present invention relates to a cryogenic refrigerator having a cooling capacity of cooling a cooled object up to cryogenic temperatures and a control method therefor.[0003]2. Description of the Related Art[0004]A cryogenic refrigerator (for example, a Brayton cycle refrigerator or an Ericsson cycle refrigerator) is used to cool down high temperature superconducting (HTS) equipment (for example, a superconducting transmission cable, a superconducting transformer, a superconducting motor, a superconducting coil for storing superconducting power, a large accelerator, a nuclear fusion test facility, MHD power generation, a superconducting coil, or the like).[0005]For example, in the case of using the cryogenic refrigerator for cooling the high temperature superconducting equipment, the lowest temperature is 65K, 40K, 30K, 20K, or the like, though it depends on the type and application of a superconducting wire...

AI Technical Summary

Benefits of technology

[0032]Therefore, the capacity of the gas storage tank is set so that the pressure in the gas storage tank is able to be maintained at a predetermined reference pressure or lower level at room temperature in the stopped state and so that the pressure in the high-pressure portion is able to be maintained at a predetermined operating pressure level in the operating state in which the cryogenic temperature is generated, thereby enabling the cryogenic refriger

Problems solved by technology

While the working gases (helium, neon, and the like) for use in the foregoing cryogenic refrigerator have extremely low liquefaction temperatures and therefore are excellent in preventing liquefaction in the inside of an expander, there is a problem that the working gases are very expensive.

In this case, discharging the working gas to the outside causes a great loss of the expensive working gas, and bleeding the working gas to the pres

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