JPH05312425A - Cryogenic freezer machine - Google Patents

Abstract

PURPOSE:To provide a cold heat accumulative type cryogenic freezer machine capable of substantially improving an actual freezing capability. CONSTITUTION:A cold heat generating unit 12 assembled in a final stage of a GM freezer passes high pressure herium gas into a cold heat accumulation chamber 35 in cooperation with a reciprocating movement of a displacer 32 and the gas is cooled, thereafter the gas is fed into an expansion chamber 31 and expanded there, the cold herium gas is passed again through the cold heat accumulation chamber 35 and this cold heat accumulating operation is repeated and heat is absorbed through either the head wall of the cylinder 29 or the circumferential wall 51 near the head wall. The cylinder 29 is set such that a ratio of L/D is 4 to 10, with a length L extending from the part 51 applied for heat absorption to a substantial opening part and its inner diameter D.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cryogenic refrigerator,
In particular, a pole comprising an expansion chamber formed of a cylinder and a displacer having a cold storage chamber, and one or more cold generation units connected to absorb heat through the head wall of the cylinder or the peripheral wall near the head wall. Low temperature refrigerator.

[0002]

There are various types of cryogenic refrigerators. Among these, there is a cold storage type cryogenic refrigerator typified by Gifford McMahon refrigerator (hereinafter abbreviated as GM refrigerator). This regenerator type cryogenic refrigerator, for example, a GM refrigerator, usually has a cylinder and a displacer that is reciprocally arranged in the cylinder to form an expansion chamber and has a regenerator therein. A cold generation unit including a seal device provided between the displacer and the cylinder was connected in one or more stages, and high-pressure helium gas was passed through a cool storage chamber to be cooled in association with the reciprocating movement of the displacer. After that, it is guided to the expansion chamber to be expanded, and the helium gas cooled by this expansion is repeatedly passed through the cold storage chamber to repeat the operation of storing cold, and heat is absorbed through the head wall of the cylinder or the peripheral wall near the head wall. ..

However, in the conventional cryogenic refrigerator configured as described above, the total refrigeration loss is subtracted from the ideal refrigerating capacity because the entire structure of the cold generating unit is not sufficiently considered. There was a problem that the actual refrigerating capacity was still low and the application was limited due to this. Further, in the conventional cryogenic refrigerator, a cylinder formed of stainless steel or the like having a poor thermal conductivity is used in order to suppress heat intrusion through the cylinder constituting wall. Then, an endothermic stage made of copper or the like is soldered to the outer surface of the portion of the cylinder that is used for endothermic heat absorption, and heat is absorbed through this endothermic stage. For this reason,
There is a large thermal resistance between the outer surface of the heat absorption stage and the inner surface of the portion of the cylinder wall that is used for heat absorption, and this thermal resistance causes a large temperature difference between the two surfaces, which is also a factor that reduces the actual refrigeration capacity. Was becoming.

[0004]

As described above, the conventional cryogenic refrigerator has a problem that the actual refrigerating capacity is low because the entire structure of the cold generating unit is not sufficiently considered. there were. Therefore, an object of the present invention is to provide a cryogenic refrigerator having a structure capable of significantly improving the actual refrigerating capacity.

[0005]

In order to achieve the above object, in the cryogenic refrigerator according to the first aspect of the present invention, the length and inner diameter of the cylinder are modified. That is, this first
In the cylinder incorporated in the cryogenic refrigerator according to the invention, the ratio L / D of the length L from the portion used for heat absorption to the substantial opening of the cylinder to the inner diameter D of the cylinder is 4 or more and 10
It is set below.

Further, in order to achieve the above object, in the cryogenic refrigerator according to the second aspect of the present invention, the material constituting the cylinder is devised. That is, in the cylinder incorporated in the cryogenic refrigerator according to the second aspect of the present invention, the portion used for absorbing heat is formed of one kind selected from copper, copper alloy, aluminum and aluminum alloy, and the remaining portion. Is formed of a dissimilar metal joint structure formed of one kind selected from stainless steel, titanium, and titanium alloys.

[0007]

In the cryogenic refrigerator according to the first aspect of the invention, the L / D is set to 4 or more, so the refrigeration loss can be greatly reduced. Moreover, since L / D is set to 10 or less, it is possible to suppress the decrease in the ideal refrigerating capacity, and in the end,
A large actual freezing capacity can be obtained.

Further, in the cryogenic refrigerator according to the second aspect of the present invention, since the portion of the cylinder constituting wall for absorbing heat is formed of a material having a high thermal conductivity, the portion for absorbing heat is The temperature difference between the inner and outer surfaces can be made sufficiently small, and as a result, a large actual refrigerating capacity can be obtained.

[0009]

Embodiments will be described below with reference to the drawings. FIG. 1 shows a regenerator type cryogenic refrigerator according to an embodiment of the present invention, which is a GM refrigerator in which two cold generation units are connected in series.

This GM refrigerator is roughly divided into a cold head 1 and a refrigerant gas introduction / exhaust system 2 for introducing a refrigerant gas into the cold head 1 and discharging a refrigerant gas from the cold head 1. Has been done.

The cold head 1 includes a first cold-generating unit 11, a second cold-generating unit 12 connected in series to the first cold-generating unit 11, and a first cold-generating unit 12 of these.
And a motor 13 for commonly driving the movable parts of the second cold generation units 11 and 12.

The first cold-generating unit 11 includes a cylinder 21 made of thin stainless steel or the like, and a displacer 23 that is reciprocally housed in the cylinder 21 and forms an expansion chamber 22 with the cylinder 21. It is composed of a seal device 24 that seals a gap existing between the displacer 23 and the cylinder 21.

The displacer 23 has a piston 25 formed of a heat insulating material such as phenol resin, a cold storage chamber 26 formed by a fluid passage axially penetrating the piston 25, and a cold storage chamber 26 filled with the cold storage chamber 26. The regenerator material 27 is made of copper mesh or the like.

On the other hand, the second cold-generating unit 12 is formed with a diameter smaller than that of the cylinder 21 of the first cold-generating unit 11 and is coaxially connected to the cylinder 21 via the head wall 28 of the cylinder 21. And a displacer 32 which is connected to the lower end of the displacer 23 in the figure through a connecting mechanism 30 and is reciprocally housed in a cylinder 29 to form an expansion chamber 31 with the displacer 32. And cylinder 29
And a sealing device 33 that seals a gap existing between the and.

The displacer 32 has a piston 34 formed of a heat insulating material such as phenol resin, a cold storage chamber 35 formed by a fluid passage axially penetrating the piston 34, and a cold storage chamber 35 filled with the cold storage chamber 35. The regenerator material 36 is composed of a plurality of lead balls or a plurality of spheres or blocks having a composition of Er ₃ Ni.

The upper end of the displacer 23 in the figure is connected to the rotary shaft of the motor 13 via a connecting rod 37, a Scotch yoke or a crank shaft 38. Therefore, when the motor 13 rotates, the displacers 23 and 32 integrally reciprocate in the direction indicated by the solid arrow 39 in the figure in synchronization with this rotation.

A refrigerant gas inlet 40 and an outlet 41 are provided at an upper position in the drawing on the peripheral wall of the cylinder 21, and the inlet 40 and the outlet 41 are connected to the refrigerant gas guide / discharge system 2. There is.

The refrigerant gas guide / exhaust system 2 includes cylinders 21 and 2.
A system that circulates helium gas in a path that reciprocates in 9 is constituted, and a low pressure valve 42, a compressor 43,
It is connected to the inlet 40 via a high pressure valve 44. That is, in the refrigerant gas guide / discharge system 2, low-pressure (about 5 atm) helium gas is compressed by the compressor 43 into high-pressure (about 18 atm).
m) and send it into the cylinders 21 and 29. The low pressure valve 42 and the high pressure valve 44 are the displacers 23, 3
The opening / closing control is performed in the relationship described later in relation to the reciprocating motion of 2.

In this GM refrigerator, the portion that produces cold, that is, the portion that is used for absorbing heat, is the head wall of the cylinder 21 in the first cold-generating unit 11 and the portion 45 in the vicinity thereof, and the second cold-generating unit. Head wall 46 of the cylinder 29 in 12. In this example, a heat absorbing cylinder 47 made of copper or the like is fixed to the outer surface of the portion 45 via a solder layer. The heat absorbing cylinder 47 is thermally connected to the first object 48 to be cooled. On the other hand, the head wall 46 of the cylinder 29 has a second object 49 to be cooled.
Is thermally connected to. Of course, only the head wall 46 may be thermally connected to the object to be cooled depending on the purpose. Here, the structure of the cylinder 29 incorporated in the second cold generation unit 12 will be described.

As shown in FIG. 2 (a), the cylinder 29 is made of stainless steel having a poor thermal conductivity, up to the vicinity of the head wall 46, that is, a portion 50 other than the portion for absorbing heat. .. The head wall 46 and its vicinity, that is, the portion 51 used for absorbing heat, is made of copper, copper alloy,
It is made of a good heat conductive material such as aluminum or aluminum alloy. The portion 50 and the portion 51 are joined by electron beam welding, friction joining, or the like.
That is, the cylinder 29 is formed in a dissimilar metal joint structure. As shown in FIG. 2B, a plurality of grooves 52 for increasing the heat exchange area are formed in the axial direction on the inner peripheral surface of the portion 51.

The cylinder 29 is further formed in the following dimensional relationship. That is, the length from the portion 51 used for heat absorption to the substantial opening position of the cylinder 29 (more accurately, the lower end position of the sealing device 33 in the figure when the displacer 32 is located at the top dead center). To L
And the inner diameter of the cylinder 29 is D, the ratio L /
D is 4 or more and 10 or less, and is set to 6 in this example. Next, the operation of the refrigerator configured as described above will be described.

When the motor 13 starts rotating, the displacers 23 and 32 reciprocate between the bottom dead center and the top dead center. When the displacers 23 and 32 are at the bottom dead center, the high pressure valve 44 is opened and the high pressure helium gas is supplied to the cold head 1.
Flows in. Next, the displacers 23 and 32 move to the top dead center. As described above, the seal devices 24 and 33 are mounted between the outer peripheral surface of the displacer 23 and the inner peripheral surface of the cylinder 21, and between the outer peripheral surface of the displacer 32 and the inner peripheral surface of the cylinder 29, respectively. Therefore, when the displacers 23 and 32 move toward the top dead center,
The high-pressure helium gas flows into the expansion chamber 22 and the expansion chamber 31 through the regenerator chamber 26 formed in the displacer 23 and the regenerator chamber 35 formed in the displacer 32. With this flow, the high-pressure helium gas is stored in the regenerator material 2.
The high pressure helium gas flowing into the expansion chamber 22 is cooled to the 30K level, and the high pressure helium gas flowing into the expansion chamber 31 is cooled to the 4K level.

Here, the high pressure valve 44 is closed and the low pressure valve 42 is opened. When the low pressure valve 42 is opened in this way, the high pressure helium gas in the expansion chamber 22 and the expansion chamber 31 expands to generate cold, and heat is absorbed in the portion 45 of the cylinder 21 and the portion 51 of the cylinder 29. Then, when the displacers 23 and 32 move to the bottom dead center again, the helium gas in the expansion chamber 22 and the expansion chamber 31 is removed accordingly. The expanded helium gas cools the regenerator materials 27, 36 while passing through the regenerator chambers 26, 35, and is discharged at normal temperature. Hereinafter, the cycle described above is repeated to perform the refrigerating operation.

As described above, in this embodiment, the ratio L / D between the length L of the cylinder 29 and the inner diameter D of the second cold generation unit 12 is set to 6. Therefore, the actual refrigerating capacity can be greatly improved. That is, the actual refrigerating capacity of the GM refrigerator is the ideal refrigerating capacity determined by the expansion / compression cycle minus the total refrigerating loss such as heat penetration and cold storage loss.

The ideal refrigerating capacity is obtained by multiplying the expansion volume determined by the inner diameter D of the cylinder and the moving stroke of the displacer by the pressure difference between the high pressure helium gas and the low pressure helium gas, and correcting this value with a coefficient determined by the physical properties of the helium gas. Is required by doing. When the length L from the portion of the cylinder that is used for heat absorption to the substantial opening of the cylinder is increased and the axial length of the displacer is increased, the pressure loss increases as the flow resistance increases. That is, as shown in FIG. 3, the pressure loss also increases as L / D increases. Thus, as the pressure loss increases,
Since the pressure on the high pressure side becomes lower than the target value and the pressure on the low pressure side becomes higher than the target value and the pressure difference decreases, the ideal refrigeration capacity decreases. Therefore, to increase the ideal refrigerating capacity, L / D should be reduced.

Most heat intrusions are conduction losses through the cylinder and displacer, and shuttle losses that accompany the reciprocating movement of the displacer. These heat intrusions are proportional to the axial temperature gradient of the cylinder wall. This temperature gradient is created in the portion from the portion used for heat absorption of the cylinder to the substantial opening, that is, in the range of the length L described above. Therefore, if the length L of the above-mentioned portion of the cylinder is increased, the temperature gradient can be reduced and heat intrusion can be reduced.

On the other hand, the cold storage loss greatly depends on the ratio between the amount of gas processed and the heat capacity of the cold storage material. Generally, when the amount of regenerator material is increased, the regenerator loss is reduced accordingly. It is known that the loss can be made almost zero when the ratio is made larger than a certain value. When the length L of the above-mentioned portion of the cylinder is lengthened, the displacer can be lengthened in the axial direction, so that the amount of regenerator material can be increased and the regenerator loss can be reduced. I can say.

As described above, the L / D can be reduced to increase the ideal refrigerating capacity, and the L / D can be increased as shown in FIG. 4 to reduce the total refrigerating loss. It has the opposite relationship.

As described above, the actual refrigeration capacity is the ideal refrigeration capacity minus the total refrigeration loss. FIG. 5 shows the relationship between the actual refrigerating capacity and L / D capable of maintaining the portion of the cylinder used for heat absorption at 4.2K. As can be seen from this figure, when L / D is less than 4, the total refrigeration loss increases sharply and the actual refrigeration capacity sharply decreases. Also, L / D is 10
If it exceeds, the ideal refrigerating capacity is deteriorated and the actual refrigerating capacity is drastically decreased. Therefore, the L / D is preferably 4 or more and 10 or less, and when it is set to 6 as in this embodiment, almost the maximum actual refrigerating capacity can be exhibited.

Further, in the cylinder 29 of the second cold-generating unit 12 in this embodiment, the portion 51 for absorbing heat is formed of a good heat conductive material such as copper, copper alloy, aluminum, aluminum alloy, Since the other portion 50 is formed of stainless steel having poor thermal conductivity, the actual refrigerating capacity can be further improved.

In other words, with the above-mentioned structure, since the portion 51 can be directly connected to the object to be cooled as an endothermic stage to absorb heat, a special endothermic stage fixed by solder or the like as in the prior art. Unlike, part 5
The temperature difference between the inner and outer surfaces of No. 1 can be reduced, and as a result, the actual refrigerating capacity can be improved.

FIG. 6 shows the relationship between the temperature of the surface that actually absorbs heat from the object to be cooled and the refrigerating capacity. In the figure, S ₁ shows an example in the case of using a cylinder formed in a dissimilar metal joint structure as in the present embodiment, and S ₂ shows an outer surface of a portion of the conventional cylinder, that is, a cylinder made of stainless steel, which is used for heat absorption. Shows an example in which a copper endothermic stage is fixed via a solder layer. From this figure, it is understood that the cylinder having the dissimilar metal joint structure is effective in improving the actual refrigerating capacity.

The present invention is not limited to the above embodiment. That is, the above-described embodiment is an example in which the present invention is applied to a GM refrigerator, but the present invention can be applied to all regenerators having a reciprocating displacer and a regenerator. Further, in the above-described embodiment, the L / D relationship and the dissimilar metal joining structure are adopted only for the cylinder of the second cold-generating unit, but these relationships are also applied to the first cold-generating unit. Good. Further, although the portion of the cylinder other than the portion used for absorbing heat is formed of stainless steel, it may be formed of titanium or a titanium alloy instead of stainless steel.

FIG. 7 shows an SIS (Superconductor Insulator Superconductor) incorporating the GM refrigerator shown in FIG.
) The receiver is shown. The SIS receiver is for observing weak radio waves (millimeter wave, submillimeter wave) from space, and SIS operates at liquid helium temperature (4.2K).
Requires a refrigerator to cool the mixer.

In the figure, 1 indicates the cold head of the GM refrigerator, 11 indicates the first cold generation unit,
Reference numeral 12 indicates a second cold generation unit. The second cold generation unit 12 is located in the vacuum container 61.
A heat shield 62 is arranged in the vacuum container 61,
The heat shield 62 is cooled to 30K by the heat absorbing portion of the first cold generation unit 12. Second cold unit 1
4K on the outer surface of the head wall 46 of the cylinder 29 in 2
A heat absorbing plate 63 to be cooled is attached below, and a SIS mixer 64 is attached to the heat absorbing plate 63. An observation window 65 is provided on the wall of the vacuum container 61.
The radio waves arriving at 5 are collected by the horn 66 and enter the SIS mixer 64. In the figure, 67 is an isolator, 68 is an amplifier, and 69 is a waveguide.

In the SIS receiver configured as described above,
The size and weight can be reduced to about 1/3 as compared with a conventional GM refrigerator combined with the JT system for cooling. The pre-cooling time is 4.5 hours and the operating temperature is 3.4.
K, power consumption is 3.3 kw.

[0037]

As described above, according to the present invention,
The actual freezing capacity can be increased and the range of use can be expanded.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of a main part of a GM refrigerator according to an embodiment of the present invention.

FIG. 2 (a) is a local sectional view of a cylinder incorporated in a second cold-generating unit of the refrigerator, and (b) is a sectional view taken along the line AA in (a).

FIG. 3 is a diagram showing a relationship between a pressure loss, a cylinder length L and a cylinder inner diameter D.

FIG. 4 is a diagram showing a relationship between a refrigeration loss and a cylinder length L and a cylinder inner diameter D.

FIG. 5 is a diagram showing a relationship between a refrigerating capacity and a cylinder length L and a cylinder inner diameter D.

FIG. 6 is a diagram showing a relationship between a refrigerating capacity and a temperature of an endothermic portion in comparison with a conventional example.

FIG. 7 is a perspective view showing a partially cutaway SIS receiver incorporating a GM refrigerator according to an embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Cold head 2 ... Refrigerant gas guide / exhaust system 11 ... 1st cold generation unit 12 ... 2nd cold generation unit 21, 29 ... Cylinder 22, 31 ... Expansion chamber 23, 32 ... Displacer 24, 33 ... Sealing device 25 , 34 ... Piston 26, 35 ... Regenerator 27, 36 ... Regenerator material 45, 51 ... Part used for absorbing heat 47 ... Endothermic cylinder 48, 49 ... Object to be cooled

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Katsunori Araoka 1 Komukai Toshiba-cho, Sachi-ku, Kawasaki-shi, Kanagawa Inside the Toshiba Research Laboratories (72) Inventor Shigeki Monma Komu-Toshiba-cho, Kawasaki-shi, Kanagawa No. 1 Incorporated company Toshiba Research Institute

Claims (3)

[Claims] Claim: What is claimed is: 1. A cylinder, a displacer that is reciprocally arranged in the cylinder to form an expansion chamber, and a displacer having a regenerator therein, and a displacer provided between the displacer and the cylinder. At least one stage of a cold generation unit including a sealing device is provided, and high-pressure gas is passed through the cold storage chamber to be cooled in association with the reciprocating movement of the displacer, and is then introduced into the expansion chamber to be expanded. In the cryogenic refrigerator configured to absorb heat through the peripheral wall near the head wall or the head wall of the cylinder while repeating the operation of re-cooling the cooled gas through the cold storage chamber, at least one of the cylinders, If the ratio L / D of the length L from the portion used for heat absorption to the substantial opening of the cylinder and the inner diameter D of the cylinder is 4 or more, 0 cryocooler, characterized in that it is set below. 2. A cylinder and a displacer that is reciprocally arranged in the cylinder to form an expansion chamber and has a cool storage chamber therein; and a displacer provided between the displacer and the cylinder. At least one stage of a cold generation unit including a sealing device is provided, and high-pressure gas is passed through the cold storage chamber to be cooled in association with the reciprocating movement of the displacer, and is then introduced into the expansion chamber to be expanded. In the cryogenic refrigerator configured to absorb heat through the peripheral wall near the head wall or the head wall of the cylinder while repeating the operation of re-cooling the cooled gas through the cold storage chamber, at least one of the cylinders, The portion used for heat absorption is formed of one kind selected from copper, copper alloy, aluminum and aluminum alloy, and the rest Part stainless steel, titanium,
A cryogenic refrigerator characterized by being formed in a dissimilar metal joint structure formed of one selected from titanium alloys. 3. The cylinder formed in the dissimilar metal joint structure has a ratio L / D of a length L from a portion used for absorbing heat to a substantial opening of the cylinder to an inner diameter D of the cylinder. The cryogenic refrigerator according to claim 2, wherein the temperature is set to 10 or less.