JPS61197962A - Small-sized cryogenic refrigerator - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a small-sized cryogenic refrigeration system that uses magnetic refrigeration and is applicable to cryopumps, He liquefaction equipment, and the like.

L Prior Art j A conventional small cryogenic refrigeration system has a piston-shaped displacer slidably fitted in a cylinder, and by repeatedly operating the displacer, the distance between the displacer and the low-temperature end of the cylinder is established. l formed between! ! i
It is common that the volume of the It chamber is increased or decreased, and the expansion and contraction of the expansion chamber sequentially expands the waste to run a predetermined refrigeration cycle. is the temperature limit at which heat can be pumped.

Therefore, in order to realize an extremely low temperature of about the liquid helium temperature (4.2K), a combination with a freezing means that can pump heat from 4K to 20K is required.

As one of the refrigeration means to be combined with the small refrigerator of such a gas cycle, the use of an m-air refrigerator that uses a magnetic refrigeration material (a material whose entropy change characteristics differ depending on the strength of the magnetic field at extremely low temperatures) was devised. ing. That is,
In this magnetic refrigerator, when the magnetic refrigeration material undergoes a repeating cycle of demagnetization and excitation, during demagnetization the temperature decreases due to adiabatic demagnetization and heat is absorbed as the end C1 increases, and during excitation the temperature decreases due to adiabatic excitation. It can act as a heat pump, dissipating heat as the entropy decreases as the temperature rises, and recent research has demonstrated that it can be used to pump heat from 4K to 20K.

Therefore, the currently proposed cryogenic refrigeration equipment that utilizes this magnetic refrigerator consists of the above-mentioned small-sized cass cycle refrigerator and magnetic refrigerator, each of which is constructed independently, and the two are connected as appropriate. They are connected with a thermal anchor to pump heat from the magnetic refrigerator back to room temperature. Specifically, the cold head of the gas refrigerator and the magnetic refrigeration material of the magnetic refrigerator are thermally connected through metal heat conduction or He gas heat transfer. However, if the two are constructed separately and combined in this way, the mechanism will inevitably be complicated, and the overall size of the device will inevitably increase. Since the heat intrusion is not 11fin, the cold caused by heat transfer loss is 7! l! There is a problem in that the capacity margin F is also large.

[Problems to be Solved by the Invention] The present invention has been made by focusing on the above-mentioned problems, and combines a gas refrigerator and a magnetic refrigerator to
As a refrigeration system that can realize extremely low temperatures below the EG&C temperature, it is possible to solve the above problems at the same time, that is, the overall size of the system has been made smaller, and a gas refrigerator and a magnetic refrigerator have been developed. The purpose of the present invention is to provide a new cryogenic refrigeration device in which the heat transfer mechanism between the two is easily constructed, there is little heat transfer loss, and improvement in refrigeration performance can be expected.

Measures to solve the L problem 1 The present invention aims to achieve such an objective.

The outer wall of the final stage expansion chamber on the extremely low temperature side is formed of a magnetic refrigeration material, and the end face of the piston member facing the inner surface of the magnetic refrigeration material and expanding and contracting the expansion chamber is connected to the exhaust T of the expansion chamber.
a reciprocating refrigerator configured to come into contact with the inner surface of the magnetic refrigeration material at every step; and a magnetic field variable means for variably applying a magnetic field to the magnetic refrigeration material; The magnetic refrigeration material is characterized in that it is energized when the piston member approaches, and demagnetized when the piston member moves away.

[Function] With this configuration, regardless of the type of reciprocating gas refrigerator or the type of refrigeration cycle operated by it, the magnetic refrigeration material forming the outer wall of the final stage expansion chamber is compatible with the piston member. A thermal cycle similar to a reverse Carnot cycle is carried out by using the contact and separation of the magnetic refrigerating material as a thermal switch, which absorbs heat from the low temperature region around the two magnetic refrigerating materials and radiates this heat directly to the piston member of the gas refrigerator. That is, the magnetic refrigeration material, which also serves as the outer wall of the expansion chamber, is excited when the piston member approaches, so at this time, it is first adiabatically excited and heated up, and then the piston member comes into contact with its inner surface. When the two come into contact, heat is applied to the piston member due to thermal conduction, and the piston member is isothermally excited. Also, when the piston member separates, it is demagnetized, so at this time, the magnetic refrigeration material is first adiabatically demagnetized and cooled, and then the #A
When the temperature drops to the temperature of the surrounding cryogenic region, heat is taken away from the surrounding area and the temperature becomes isothermal. The heat pumped out in such a cycle is then pumped out to the room temperature side in the refrigeration cycle of the reciprocating gas refrigerator.

〔Example] Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

1 and 2 are diagrams showing a schematic configuration of a cryogenic apparatus according to the present invention, in which a reciprocating gas refrigerator 1 is arranged on the upper normal temperature side and a magnetic refrigerator 2 is arranged on the lower cryogenic temperature side. This is what happens.

The reciprocating gas-cooled cylinder is a movable shell type recently developed and proposed by the present inventor, and the figure shows this type of two-stage type. So, first of all, let's talk about the JI of this gas refrigerator 1! To briefly explain about i, in this one, each stage has internal regenerators 3b, 4b, and regenerators 3b, 4.
5. A cylindrical u moving cylinder that surrounds b and can slide in all directions on its axis. A cylindrical casing 6 surrounds the shell 5 with external regenerators 3a and 4a interposed therebetween, and a member facing the movable shell 5 inside and outside at the lower end of each stage. In the volumetric space created between the
, 8a. To explain more specifically, first stage R4i internal regenerator 3b is connected by a communication pipe IO which also serves as a gas inflow/outflow member into the movable shell 5. The second internal regenerator 4b is supported by the base 9 at the end, and the second internal regenerator 4b is supported by the inner regenerator 3 of the first stage.
b, and are each positioned and fixed.

Further, the first and second stage external regenerators 3a and 4a are each firmly supported by the casing 6, and are positioned and fixed together with the casing 6 supported by the base 9. It goes without saying that each of the above regenerators has gas permeability,
This is to exchange heat with the circulating gas. moreover,
The L1 pivoting shell 5 has an imaginary part at the L end of the base 9gA, through which the communicating pipe 10 passes airtight from the lid part, and chambers 11b and 11a are formed inside and outside the upper end thereof. Then, inside the movable shell 5, gas can be sucked and discharged from the inflow/outflow boat 12 provided on the base 9 through the communication pipe 10 into the internal regenerator 3b of the first punch ( Gas is also filled into the chamber ttb), and gas can be sucked in and discharged from the outside of the movable shell 5 through an inlet/outlet bow 13 provided on the base 9 through a chatuba lla.

In the movable shell type gas refrigerator having such a configuration, in order to integrate the magnetic refrigeration 41!2 with the magnetic field variable means which will be described in detail in the cold section, for example, GGG (gadolium gallium A 51% refrigerating material 18 made of garnet 2) is provided. That is, this magnetic refrigeration material 18 is provided so as to form an outer wall at the end of the expansion chamber 8a in the final stage on the extremely low temperature side of the gas refrigerator, and in the case of the illustrated example, the lower end is open. A thick magnetic refrigerating material 18 is fitted into the opening of the casing 6 to airtightly seal the opening, and at the same time, its inner surface is exposed to the final stage expansion chamber 8a and its outer surface is connected to the outer pole. It is exposed to a low temperature atmosphere. In addition, at the lower end of the movable shell 5 facing the inner surface of the final stage expansion chamber 8a made of the magnetic refrigeration material 18, in order to increase the heat storage capacity of the lower end portion 19 of the shell, this portion is made of, for example, a thick heat storage material made of Pb.・It is made of parts. Specifically, in the illustrated example, a separate heat storage member 19 is fitted into the opening of the AR effect cylinder 5, which is open at the lower end, to airtightly close the opening. Note that this heat storage member 19
It must not have air permeability to the eye and body.1
For example, by drilling a gas inlet hole, the inner and outer expansion chambers 8b,
It is preferable to promote heat exchange with the gas in the aa as much as possible.

As described above, the magnetic refrigeration material 18 and the heat storage member 19 are arranged with the final stage expansion chamber 8a in between, and each time the expansion chambers 8a and 7a on the outside of the movable shell 5 are exhausted, Each time the part 19 approaches the magnetic refrigerating material 18 in the F& top and bottom, as shown in FIG.
Adjusts the reciprocating movement of the

An overview of the driving means of the T-motion Kusiel type refrigerator 1 configured as described above is as follows. ! ! An air supply system passage 15 and an exhaust system passage 16, which are connected to the discharge port and intake port of the compressor 14, respectively, are connected to the inflow/outflow port 12.13 provided in the base 9 on the end side via a timing pulp 17. hand! ,lノ#
By switching this valve 17, the intake and exhaust air necessary for mating is performed in the expansion chambers 7b, 8b, 7a, and 8a inside and outside the movable shell 5.
is designed to reciprocate visually depending on the suction gas pressure inside and outside. That is, the mouth motion shell 5 has a high r
When the upper gas is supplied to 4 people, 5 is urged downward due to the difference in the pressure receiving area between the low temperature side and the normal temperature side (specifically, the cross-sectional area of the communication pipe 10 at Nayampa Ilb).

On the other hand, when high-pressure gas is introduced to the outside of the
The cross-sectional area of the communicating pipe 10 at point (a) is biased northward. For each reciprocating movement of the movable shell 5, the inner expansion chamber 7b,
8b and the outer expansion chambers 7a, 8a are expanded and contracted with a half-cycle phase shift.

Next, the structure of the magnetic refrigerator 112 will be explained. This magnetic refrigerator 2 includes a magnetic refrigerating material 18 provided at the lower end of the gas refrigerator l which also serves as the outer wall of the final stage expansion chamber 8a, and a magnetic refrigerating material 18 provided at the lower end of the gas refrigerator l, 18 and magnetic field variable means 20 disposed around the magnetic field variable means 18. In this case, the magnetic field variable means 20 is formed by disposing a superconducting magnet 21 inside an annular movable case 20a having a liquid reservoir 20b for storing liquefied He, etc. (
The magnetic refrigerating material 18 can be excited or demagnetized at a predetermined timing by reciprocating up and down in synchronization with the switching of the timing valve 17 of the gas refrigerator l together with the moving case 20a. That is, when approaching the magnetic refrigeration material 18 of the movable shell 5, the superconducting mucket 21 is raised and the tl-magnetic refrigeration material 1
8 to make the magnetic refrigeration material 18 magnetized wJJ (the state shown in FIG. The superconducting magnet 2 is moved away from the magnetic refrigeration material 18 to demagnetize the magnetic refrigeration material 18 (the state shown in Fig. 2), and during this descent, the superconducting magnet 2
1 is immersed together with its case 20a in the liquefied gas 23 stored in the deyuwa 22 of the lower blade, and at this time the liquid reservoir 2
LHe and the like will be sequentially supplied to 0b. In FIG. 1, 24 is a gas liquefaction chamber, and 25 is a vacuum chamber surrounding the low temperature side of the magnetic refrigerator 2 and the gas refrigerator 1.

The operation of the refrigeration system having the above configuration will be explained using an example in which the refrigeration system is used for He liquefaction.

When the volume of the outer expansion chambers 7a, 8a of each stage is the maximum and the volume of the inner expansion chambers 7b, 8b is the minimum (the state shown in FIG. 2), the timing valve 17 is set to the B position, When the outside of the air supply system path 15 is communicated with the exhaust system path 16, the inside expansion chambers 7b, 8b are provided with coolers 3b, 4b.
High-pressure gas is introduced through the expansion chambers 7a, 8a without being pre-cooled, and gas cooled by adiabatic expansion is discharged from the outer expansion chambers 7a, 8a while cooling the regenerators 3a, 4a. Due to the unbalanced gas pressure acting on the movable shell 5 as described above, the movable shell 5 descends until the lower end 19 of the shell comes into contact with the inner surface of the magnetic refrigeration material 18 in the final stage expansion chamber 8a. Ru. On the other hand, at the same time as the timing valve 17 is changed to +j1, the superconducting magnet 21 rises from the liquid He below to a position close to the magnetic refrigeration material 18 and moves the magnetic refrigeration material 18 from the magnetic field strength B=0. A certain strength B=B,
It will be excited up to. At this time, as shown by I-II in FIG. 3, the &1 air refrigerating material 18 first raises its temperature by adiabatic excitation (isentropic change without exchange of heat with the outside), and then the lower end of the shell When the part 19 comes into contact with the inner surface of the magnetic refrigeration material 18 and the two come into surface contact, the magnetic refrigeration material 18 loses heat to the shell lower end 19 through contact heat conduction, so that the temperature of the shell lower end 19 increases to 15.
If so, the magnetic refrigerating material 18 is subjected to isothermal fertilization so as to maintain this temperature and drop it to 1l-III in FIG.

Next, in the state shown in FIG. 1 in which the shell lower end 19 is in contact with the inner surface of the magnetic refrigerating material 18, the volume of the external expansion chambers 7a and 8a of each stage is the minimum and the volume of the inner expansion chambers 7b and 8b is the maximum. When the timing valve 17 is set to the human position and the outside of the movable shell 5 is connected to the air supply line 15 and the inside thereof is connected to the exhaust line 16, the inner expansion chambers 7b and 8b are cooled by adiabatic expansion. The stored gas is discharged from the regenerators 3b and 4b while being cooled, and high-pressure gas is introduced from the outer expansion chambers 7a and 8a while being precooled through the regenerators W3a and 4a. movable shell 5
Due to the unbalance of the gas pressure acting on the gas pressure, the operating cylinder 5 rises again, and finally, as shown in FIG. reached the bottom dead center position. -At the same time as replacing the timing valve 17,
The superconducting magnet 21 then falls down from around the magnetic refrigeration material 18 and is immersed in the liquefied He 23 on the F side, so that the magnetic refrigeration material 18 is
The magnetic field strength B=Bl is demagnetized to B=0. At this time, as shown by ■-■ in Fig. 3, the magnetic refrigerating material 18 first lowers its temperature due to adiabatic extinction (i.e., no exchange of heat with the outside, etc.), and then the temperature When the LHe temperature drops to 4.2K, the magnetic refrigeration material 18 absorbs heat from the He gas in the surrounding gas liquefaction chamber 24 and liquefies it, while being isothermally demagnetized as shown at N-1 in FIG. That will happen.

Therefore, according to one or more cycles, the magnetic refrigeration material 18
operates a thermal cycle similar to the reverse Carnot cycle, and gas cooling is carried out from the gas liquefaction chamber 24 (4.2K) on the cryogenic side. ! [
It will play the role of a heat pump that pumps heat to the cold head (15K) of 1 (IV-T absorbs heat, and L
I- [radiate heat with 11). Moreover, the transfer of heat from this magnetic refrigeration material 18 to the gas refrigerator l is magnetic cooling 711! Material 18
The difference between the contact heat conduction between the shell and the lower end of the shell and the heat transfer when the shell is facing the opposite direction realizes an effective heat switch and is carried out efficiently. In this way, the heat pumped up to the cold head side by the magnetic refrigerating material 18 from the temperature level 4, 2 to the temperature level 15 through heat conduction to the shell F end 19 is transferred to the cold head side. It will be pumped out to the room temperature side by the refrigeration cycle of the refrigerator 1. Note that this gas refrigeration system consisting of a +i shell type is not limited to the Gifford-McMahon cycle as shown in the operation explanation, but can also be operated with other refrigeration cycles such as the Solvay cycle. good.

If the refrigeration equipment has such a configuration and function,
The following effects will be obtained.

Compared to the conventional structure in which a gas refrigerator and a magnetic refrigerator are configured independently and are thermally connected via a heat transfer member, 5Sl has a structure that allows both to be organically connected. Since they are integrally connected, it is possible to realize an extremely compact cryogenic refrigerator a, which has never been seen before, and has a refrigerating capacity from about the LHe temperature (4.2 K). Second, as described above, this device requires a separate heat transfer member to connect and separate the magnetic refrigeration material that forms the outer wall of the final stage expansion chamber of the gas refrigerator from the lower end of the shell. Since the heat switch directly transfers heat to the cold head side of the gas refrigerator, there is no need to complicate the mechanism due to the thermal connection required in the past. Since the risk of heat intrusion is also eliminated, the decrease in refrigeration efficiency due to heat transfer loss is also minimized.

Although one embodiment has been described above, the uninvented small-sized cryogenic refrigeration device is not limited to this, and can be modified and implemented in various ways. To give an example of this, first of all, the magnetic refrigeration material used in the present invention is not necessarily limited to the above-mentioned GGG, but can be broadly used as long as it is a material whose entropy or other characteristics change greatly depending on the strength of the magnetic field at extremely low temperatures. expected to be available.

In addition, in the embodiment, as the magnetic variable means, a superconducting magnet is moved relative to the magnetic refrigerating material at the fixed position, and the &1
Although the magnetic field strength of the air refrigeration material is changed, this may be done by turning ON/OFF the coil current of a *magnet disposed at a fixed position with respect to the magnetic refrigeration material to excite and demagnetize it.

1. Regarding the type of gas refrigerator used in the present invention, if it is basically a reciprocating type, the same procedure can be carried out.
It is considered to be fk. In other words, it is not necessarily limited to the case where it is combined with a movable shell type, but
Especially when the present invention is combined with a movable shell type gas refrigerator as in the embodiment, the utility value of the present invention can be further enhanced for the following reasons. In other words, this new model has a reciprocating displacer that incorporates a regenerator, which is common in the past.
With one round trip of the +jJ moving shell, the inner and outer expansion chambers are respectively l.
Not only does it run a cycle, effectively doubling its refrigeration capacity, but it also reciprocates a movable shell with a small inertial mass, so the internal space is filled with a regenerator to make the most of its volume. However, it does not cause problems such as vibration, and therefore it is the most compact gas refrigerator of this type with the same performance. In other words, this is very convenient for maximizing downsizing when combined with a magnetic refrigerator.

It goes without saying that this movable shell type is not limited to the two-stage type as in the case of the example, but can be increased or decreased to any number of stages as required. The constituent material of the lower end of the shell, which forms the end surface of the piston member that comes into contact with it.

A composite material may be used in which the surface in contact with the magnetic refrigeration material is made of a material that has good thermal conductivity and is lightweight. A fin may be provided at a portion in contact with.

(Effects of the Invention) Since the present invention has the following configuration, it can be constructed particularly small and compact as a small cryogenic refrigeration device used for freezing around the temperature of liquid helium. Furthermore, it has been possible to provide a device that has a simple structure and has a high refrigerating capacity without a decrease in efficiency due to heat transfer loss from the magnetic refrigerating material.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, and FIG. 1 is a cross-sectional view showing the schematic configuration of the refrigeration system according to the present invention, and FIG. It is a partial sectional view, and FIG. 3 is a temperature-entropy diagram showing the thermal cycle of this refrigeration apparatus. 1...Gas refrigerator 2--Magnetic refrigerator 3a, 4a life/external regenerator 3b, 4b...Kenuchi regenerator 5...Working movable shell (piston member) 6...Casing 7a, 8a・Meeting・Outside expansion chamber (8a*...Final 7b, 8
b...Inner expansion chamber Stage expansion chamber) 9...Bone base lO...e communication pipe 12.13...Inflow/outflow boat 15...Air supply system path 16@・Fist exhaust system path 17・φ・Timing pulp 18...-Magnetic refrigeration material

Claims (1)

[Claims] The outer wall of the final stage expansion chamber on the extremely low temperature side is formed of a magnetic refrigeration material, and the end surface of a piston member that faces the inner surface of the magnetic refrigeration material and expands and contracts the expansion chamber is made of magnetic refrigeration material every time the expansion chamber is evacuated. A reciprocating gas refrigerator configured to abut against an inner surface of a refrigerating material, and a magnetic field variable means for variably applying a magnetic field to the magnetic refrigerating material,
A small cryogenic refrigeration apparatus characterized in that the magnetic refrigeration material is energized when the piston member approaches, and demagnetized when the piston member moves away.