JPH07117307B2 - Cryogenic cooling device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cryogenic cooling device, and in particular, a cryogenic liquefied refrigerant generated in a cryogenic refrigerator is supplied to an object to be cooled via a liquefied gas tank. The present invention relates to a cryogenic cooling device.

[Conventional technology]

Hereinafter, the case of liquid helium as the cryogenic liquefied refrigerant will be described as an example.

FIG. 2 is a block diagram showing the configuration of a conventional cryogenic cooling device. In FIG. 2, 1 is a compressor, 2 is a helium refrigerator, 3 is a high pressure helium line, 4 is a low pressure helium line, 5 is a medium pressure tank, 6 is a high pressure helium line pressure control valve, and 7 is a low pressure helium line pressure. Control valve, 8 liquid helium tank, 9 first liquid helium supply pipe, 10 first
Gas helium return pipe, 11 cryostat, 12 cooled object such as superconducting magnet, 13 second liquid helium supply pipe, 14 second gas helium return pipe, 15 liquid helium supply valve, 20 heater , 21 is a superconducting liquid level gauge, and 22 is a liquid level control calculator.

Next, the operation of the conventional helium refrigeration system configured as described above will be described. The high-pressure helium compressed by the compressor 1 is supplied to the helium refrigerator 2 through the high-pressure helium line 3 and part of it becomes liquid helium and is sent to the liquid helium tank 8 through the first liquid helium supply pipe 9. The liquid helium in the liquid helium tank 8 is the second liquid helium supply pipe.
It passes through 13 and is sent to the cryostat 11 to cool the cooled object 12. The gas evaporated by cooling the cooled object is the second
After returning to the helium refrigerator 2 through the gas helium return pipe 14 of FIG.
Return to. The liquid helium required for the cryostat 11 is adjusted by the liquid helium supply valve 15. Liquid helium in the liquid helium tank 8 is detected by the superconducting liquid level gauge 21, and the liquid level control calculator 22 outputs a control output to the heater 20. The pressures of the high-pressure helium line 3 and the low-pressure helium line 4 are kept constant via the medium-pressure tank 5 by the high-pressure helium line pressure control valve 6 and the low-pressure helium line pressure control valve 7.

A related device of this type is, for example, JP-A-57-108557.

[Problems to be solved by the invention]

In the conventional cryogenic cooling device having the above-described configuration and operation, since the heater 20 is controlled only by the liquid level of the liquid helium tank 8, if the amount of liquid helium held in the cryostat 11 increases, the medium pressure tank 5 There is a case where the pressure of is abnormally reduced, the pressure of the low-pressure helium line 4 cannot be adjusted, and the operation of the cryogenic cooling device must be stopped.

An object of the present invention is to maintain the pressure of the room temperature refrigerant gas in the intermediate pressure tank at a pressure that does not hinder the pressure control of the low pressure refrigerant gas returned from the cryogenic refrigerator to the compressor, thereby performing the operation operation. It is to provide a cryogenic cooling device that can be smoothly and easily operated.

[Means for solving problems]

The above-mentioned object is a cryogenic refrigerator that produces a cryogenic liquefied refrigerant, a compressor that circulates a refrigerant gas to the cryogenic refrigerator, a medium pressure tank for holding a refrigerant gas at room temperature, and the cryogenic refrigerator. A liquefied gas tank holding the generated cryogenic liquefied refrigerant, an object to be cooled by the cryogenic liquefied refrigerant from the liquefied gas tank, and a liquefied gas heating for heating and evaporating the cryogenic liquefied gas in the liquefied gas tank A device, a control calculator for calculating a direction for controlling the amount of cryogenic liquefied refrigerant held in the liquefied gas tank to a constant amount, and a pressure of the room temperature refrigerant gas in the medium pressure tank to a constant pressure. A comparison calculation for performing a comparison calculation of another control calculation unit that performs calculation of the direction and a calculation output value from the other control calculation unit and a calculation output value from the control calculation unit, and selectively outputting to the liquefied gas heating device. It is achieved by including a container.

[Action]

A predetermined amount of cryogenic liquefied refrigerant gas is contained in the liquefied gas tank, even if the operation output value of the control arithmetic unit for controlling the holding amount in the liquefied gas tank is not in the direction of operating the liquefied gas heating device, If the pressure in the medium pressure tank drops, the calculation output value from another control calculation unit that controls the pressure in the medium pressure tank to a constant pressure enters the comparison calculation unit, and this calculation output value enters the liquefied gas heating device. Since the cryogenic liquefied refrigerant gas in the liquefied gas tank is evaporated, the pressure of the room temperature cooling gas in the medium pressure tank is adjusted to a pressure that does not hinder the pressure control of the low pressure refrigerant gas returned from the cryogenic refrigerator to the compressor. Can hold

〔Example〕

The cryogenic liquefied refrigerant in the liquefied gas tank is mainly consumed during precooling and liquid storage of the object to be cooled. Therefore, it is necessary to hold the maximum amount of cryogenic liquefied refrigerant in the liquefied gas tank at the start of precooling of the object to be cooled, but after reaching a steady state, the cryogenic liquefied refrigerant held in the liquefied gas tank is the maximum amount. Since it is not necessary to exist, it is possible to change the set value of the holding amount control, for example, the liquid level control. However, since the amount of refrigerant gas held in the device is not always constant, the liquid level control set value to be changed and set is not always constant. It is possible to increase the capacity of the medium-pressure tank so that there is no problem even if the maximum amount of cryogenic liquefied refrigerant is held in the liquefied gas tank and the cryostat at the same time. In the case of helium, room temperature gas helium has a volume of about 700 times that of liquid helium), and the amount of hold refrigerant gas in the device is not always constant, so the problem cannot be solved.

In order to solve the above problems, the liquid level control performs a control calculation with the maximum hold amount of the liquefied gas tank as the set value, and the pressure of the medium pressure tank is the pressure of the low pressure refrigerant gas flowing through the low pressure gas helium line. Perform pressure control calculation (for example, increase the heater input when the medium pressure tank pressure drops) so as to maintain the pressure at which control is not hindered, and compare the control output of the above liquid level control calculation and pressure control calculation. Do, for example,
It can be solved by selecting the one that increases the heater input.

An embodiment of the present invention will be described below with reference to FIG.

In FIG. 1, 22 'is a liquid helium tank 8 which is a liquefied gas tank.
A liquid level control calculator, which is a control calculator for performing a calculation in a direction for controlling the amount of liquid helium, which is a cryogenic liquefied refrigerant, to be controlled to a constant amount, and 30 is a room temperature refrigerant gas in the intermediate pressure tank 5. Another control calculator that calculates the pressure of the room temperature helium gas in a direction to control it to a constant pressure, 31 compares the calculation output value from the liquid level control calculator 22 'with the calculation output value from the pressure control calculator 30. It is a comparison calculator that performs a calculation and selectively outputs it to the heater 20, which is a liquefied gas heating device. In FIG. 1, the same devices and the like as those in FIG. 2 are denoted by the same reference numerals and the description thereof will be omitted.

In FIG. 1, more specifically, the liquid level control calculator 22 'is
Similar to the conventional cryogenic cooling device shown in the figure, when the liquid helium holding amount in the liquid helium tank 8 increases, the control calculation in the direction of increasing the input of the heater 20 is performed. On the other hand, the pressure control calculator 30 increases the input of the heater 20 when the pressure of the intermediate pressure tank 5 is decreased so that the pressure of the intermediate pressure tank 5 is maintained at a value not hindering the pressure control of the low pressure helium line 4. The calculation of the direction to be performed is performed. With the control output of the above liquid level control calculator 22,
The control output of the pressure control computing unit 30 is input to the comparison computing unit 31, and the comparison computing unit 31 selects the one in which the input of the heater 20 increases and outputs it to the heater 20.

In this embodiment, the following effects can be obtained.

(1) Since the pressure of the room temperature helium gas in the medium pressure tank can be maintained at a pressure that does not hinder the pressure control of the low pressure helium gas returned from the helium refrigerator to the compressor, the operation can be smoothly and easily performed. .

(2) Since it is not necessary to uselessly evaporate the liquid helium by the heater until the maximum amount of liquid helium is held in the liquid helium tank, it is possible to reduce power consumption in the compressor and reduce operating costs.

(3) Since a certain amount or more of liquid helium is not automatically held in the liquid helium tank, it is possible to make the components of the device have an appropriate capacity.

〔The invention's effect〕

As described above, the present invention can maintain the pressure of the room temperature refrigerant gas in the medium pressure tank at a pressure that does not hinder the pressure control of the low pressure refrigerant gas returned from the cryogenic refrigerator to the compressor, so that the operation can be performed. The effect is that it can be performed smoothly and easily.

[Brief description of drawings]

FIG. 1 is a structural block diagram showing an embodiment of a cryogenic cooling device according to the present invention, and FIG. 2 is a structural block diagram of a conventional cryogenic cooling device. 1 ... Compressor, 2 ... Helium refrigerator, 5 ... Medium pressure tank, 8 ... Liquid helium tank, 12 ... Cooled object, 20 ... Heater, 22 '... Liquid level control calculator, 30 ...... Pressure control calculator, 31 …… Comparison calculator

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kawamura Adult 794 Higashi Toyoi, Kudamatsu City, Yamaguchi Prefecture Inside the Kasado Plant, Hitachi Ltd. (56) Reference JP-A-57-108557 (JP, A) JP Flat 1-121660 (JP, A)

Claims (1)

[Claims] 1. A cryogenic refrigerator for producing a cryogenic liquefied refrigerant, a compressor for circulating a refrigerant gas to the cryogenic refrigerator, a hollow tank for holding a refrigerant gas at room temperature, and the cryogenic refrigerator. A liquefied gas tank holding the generated cryogenic liquefied refrigerant, an object to be cooled by the cryogenic liquefied refrigerant from the liquefied gas tank, and a liquefied gas heating for heating and evaporating the cryogenic liquefied gas in the liquefied gas tank A device, a control calculator for calculating a direction for controlling the amount of cryogenic liquefied refrigerant held in the liquefied gas tank to a constant amount, and a pressure of the room temperature refrigerant gas in the medium pressure tank to a constant pressure. A comparison calculation for performing a comparison calculation of another control calculation unit that performs calculation of the direction and a calculation output value from the other control calculation unit and a calculation output value from the control calculation unit, and selectively outputting to the liquefied gas heating device. And a cryogenic cooling device characterized by comprising: .