JP2003056928A - Regenerative cryogenic refrigerating machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To raise operation characteristics without deteriorating refrigeration performance by preventing convection of a refrigerant gas between gaps of a cylinder and a displacer constituting a cold storage unit. SOLUTION: A regenerative cryogenic refrigerating machine produces cold by compressing the refrigerant gas by a compressor, and reciprocating the displacers 10 and 17 of the first stage cold storage unit 3 and the second stage cold storage unit 6. A material having a coefficient of heat shrinkage equal with or smaller than that of a material constituting the first and the second stage cylinders 9 and 16 is used to make the first and the second stage displacers 10 and 17. The displacers 10 and 17 are cold storage containers packed with a cold storage material, and are constituted of a fiber reinforced resin which expands as temperature is lowered. The cylinders 5 and 6 are made of a stainless steel.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a regenerator type cryogenic refrigerator which can be operated under a gravity condition for a long period of time without deteriorating refrigeration performance.

[0002]

2. Description of the Related Art A cold storage refrigerator comprises a compressor installed on the high temperature side, a regenerator connected to the compressor, and an expansion chamber provided below the regenerator. The refrigerant gas compressed by the compressor is heat-removed by a heat source such as cooling water in a high temperature environment, and then gradually cooled through a regenerator forming a temperature gradient and guided to an expansion chamber. .

The refrigerant gas in the expansion chamber expands to generate cold, and cools the object to be cooled through a cooling stage or the like provided on the lower surface of the expansion chamber. After that, this refrigerant gas again passes through the regenerator in the reverse direction, the temperature of the refrigerant gas itself rises while cooling the regenerator material, and is again guided to the compressor. The cold storage refrigerator is operated by the above refrigeration cycle.

By the way, Japanese Patent Laid-Open No. 11-257771 discloses that
A multi-stage regenerator type cryogenic refrigerator in which a plurality of regenerators and expansion chambers are connected in series and combined in order to further lower the cooling temperature is disclosed.

As shown in FIG. 8, among the regenerator type cryogenic refrigerators, a two-stage Gifford-McMahom (GM) refrigerator is known, and its outline will be described with reference to FIG. In FIG. 8, reference numeral 1 is a refrigerator drive unit, and a lower stage flange portion 2 of the refrigerator drive unit 1 is connected with a one-stage regenerator 3. A first-stage expansion chamber 4 is provided below the first-stage regenerator 3, a first-stage cooling stage 5 is attached to the lower surface of the first-stage expansion chamber 4, and a second-stage regenerator 6 is connected below the first-stage cooling stage 5. ing. A two-stage expansion chamber 7 is provided below the two-stage regenerator 6, and a two-stage cooling stage 8 is attached to the lower surface of the two-stage expansion chamber 7.

The first-stage regenerator 3 includes a first-stage cylinder 9 and the first-stage cylinder 9.
It consists of a first-stage displacer 10 that is vertically movable in a single-stage cylinder 9.
Built-in cold storage material 11.

An upper end plate 12 and a lower end plate 13 are provided at both upper and lower ends of the single-stage displacer 10, and refrigerant flow holes 14 are provided in the upper and lower end plates 12 and 13, respectively. A one-step seal 15 is provided between the lower surface of the upper end plate 12 and the inner surface of the one-step cylinder 9.

The two-stage regenerator 6 has a two-stage cylinder 16 and two
It is composed of a two-stage displacer 17 that is vertically inserted into a two-stage cylinder 16.
It has a built-in cold storage material 18. Reference numeral 19 is a two-stage seal and is provided above the two-stage regenerator material 18 and between the two-stage cylinder 16. Reference numeral 20 is a lower end plate for the two-stage regenerator, which has a refrigerant flow hole 14 in the center.

The first-stage displacer 10 and the second-stage displacer 17 are reciprocally moved up and down by the motor drive of the refrigerator drive unit 1, and intake and exhaust valves (not shown) are opened and closed at a predetermined timing in the same cycle as the reciprocating motion. And a compressor, and an intake pipe and an exhaust pipe connecting the cold head and the compressor.

Usually, the one-stage cooling stage 5 is often cooled to the liquid nitrogen temperature (77K) level, so that the one-stage regenerator 3 is made of steel such as copper, stainless steel, lead or the like, or a spherical one-stage regenerator material 11. I am using. In general, the two-stage cooling stage 8 is cooled to the level of 20K.
Lead (sphere) is used for. In recent years, for the purpose of cooling liquid helium temperature (4.2K) level, the two-stage regenerator material 18 is made of a magnetic material (Er ₃ N) having higher specific heat at this temperature level than lead.
Development of a cryogenic refrigerator using i) or the like has been made.

Here, a member having a low thermal conductivity such as stainless steel is usually used for the final stage cylinder, and a resin such as bakelite is used for the displacers 10 and 17 filled with the regenerator material. The displacers 10 and 17 reciprocate in the cylinders 9 and 16, and therefore the cylinders 9 and 16
There must be some clearance between the displacer and the displacer 10,17.

Since the above-mentioned gap is a dead volume which does not participate in the refrigeration cycle at all, it is preferable that the gap is as narrow as possible. Also, when the posture of the refrigerator is oriented in a direction other than the downward direction under gravity, the difference in temperature of the refrigerant gas is Due to the density difference due to, convection occurs in the gap, resulting in freezing loss. Therefore, it is preferable that the gap is narrow and short.

[0013]

However, in the structure of the conventional regenerator type cryogenic refrigerator, even if the above-mentioned gap is made as short as possible at room temperature, the stainless steel of the cylinders 9 and 16 and the displacer 10, at low temperature, There is a problem that the gap expands due to the difference in the thermal contraction rate between the 17 member and Bakelite. Therefore, it is recommended that the cylinder and the displacer use the same material with the same heat shrinkage rate.
When 0 and 17 are made of stainless steel, for example, friction occurs between the stainless steels, causing many troubles.

Further, as described above, the cylinders 9 and 16 and the displacers 10 and 17 are composed of members having the same heat shrinkage ratio,
If the gap formed by the inner diameters of the cylinders 9 and 16 and the outer diameters of the displacers 10 and 17 is configured to be small enough to prevent convection that causes heat intrusion or leakage from the high temperature side, for example, a refrigerator is cooled. During cold maintenance work to replace the refrigerator while it is in the open state, the cooler of the newly inserted refrigerator has no heat shrinkage because it is at room temperature, and the displacer becomes thicker than the inside diameter of the cooled cylinder. There is a problem that becomes difficult.

Further, when the cold head of the refrigerator is operated in a posture in which the cold side is not directed downward under gravity, convection occurs in the gap between the displacer and the cylinder at the final stage, and as a result, the cold side is cooled from the hot side. There is a problem that the inflow of heat to the side increases and the refrigeration performance deteriorates.

The present invention has been made to solve the above problems, and prevents heat convection generated between a cylinder and a displacer so that the refrigeration performance does not deteriorate in any posture operation, and cold maintenance is performed. Another object of the present invention is to provide a cryogenic refrigerator which is easy to operate, does not need to provide a seal portion at cryogenic temperatures which causes troubles, can operate stably for a long time, and has reliability.

[0017]

The invention according to claim 1 is
A compressor for compressing a refrigerant gas, a regenerator into which a refrigerant compressed by the compressor flows, and an expansion chamber provided on a low temperature side of the regenerator are provided, and the regenerator includes a cylinder and the cylinder. In a regenerator type cryogenic refrigerator having a displacer reciprocally inserted therein and having a regenerator therein, the displacer is a member having a heat shrinkage equal to or smaller than a heat shrinkage of a member constituting the cylinder. It is characterized by being constituted by.

According to a second aspect of the present invention, the regenerator has a plurality of stages, and the displacer in the regenerator at the final stage is formed of a member having a negative heat shrinkage rate than the displacer in the regenerator at the first stage. The mechanical seal portion between the cylinder and the displacer is provided with a portion having a small spring force and a short gap on the low temperature side.

According to a third aspect of the invention, in the cylinder,
A plurality of thick portions are provided to reduce the gap between the cylinder and the displacer. The invention according to claim 4 is characterized in that a plurality of coating portions are provided on the inner surface of the cylinder.

According to a fifth aspect of the present invention, a plurality of cool storage materials of different members are partitioned and filled in the displacer through a partition plate, and the partition plate is made of a member having the same heat shrinkage rate as the displacer. It is characterized by being configured.

The invention according to claim 6 comprises a compressor for compressing a refrigerant gas, a regenerator into which the refrigerant compressed by the compressor flows, and an expansion chamber provided on the low temperature side of the regenerator. In the regenerator type cryogenic refrigerator having a cylinder and a displacer that is reciprocally inserted into the cylinder and has a regenerator material therein, the regenerator has a plurality of stages, and a first stage regenerator The expansion chamber and a part of the final stage cylinder are connected to a pulse tube, the final stage regenerator has a replaceable cartridge type seal part, the cylinder is made of stainless steel, and the displacer is a fiber reinforced resin. It is characterized in that it is configured by.

According to the present invention, thermal convection does not occur in the gap between the displacer at the final stage and the cylinder. That is, in order to keep the gap between the displacer and the cylinder in cooling at a predetermined length or less, the material of the displacer should be the same as the thermal contraction rate of the cylinder, or
Alternatively, a small member is used. This prevents convection,
The refrigeration performance does not deteriorate in any posture, and the cryogenic section is not sealed, so that long-term operation can be achieved.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION A first embodiment of a cold storage type cryogenic refrigerator according to the present invention will be described with reference to FIG. Note that FIG.
In FIG. 8, those parts which are the same as those corresponding parts in FIG. 8 are designated by the same reference numerals, and a description of the overlapping parts will be omitted.

That is, in this embodiment, the displacer is reciprocated in the cylinder, and the intake air is synchronized with it.
The drive unit for periodically opening and closing the exhaust valve is the same as in the conventional GM refrigerator. As the material of the first-stage cylinder 9 and the second-stage cylinder 16, stainless steel having low heat conduction is used. 1-stage displacer 10 and 2-stage displacer
17 also functions as a container for filling the cold storage materials 11 and 18, and the refrigerant gas flows back and forth inside the container filled with the cold storage material.

At this time, the first-stage displacers 10 and 2
Outside of the step displacer 17 and each cylinder 9, 16
If there is a large amount of leak gas flowing in the gap formed between the inside and the inside, the amount of heat entering the low temperature end increases. for that reason,
As shown in FIG. 8, the amount of leak gas is reduced by the seal 19 that normally uses the pressing force of the spring. In the present embodiment, instead of the seal 19, the gap distance of the gap space is shortened so that the amount of leak gas can be reduced.

In order to shorten the gap distance, a member having a negative heat shrinkage ratio (such as fiber reinforced resin (DFRP)) is used as the member forming the two-stage displacer 17 (it expands as the temperature becomes lower). The thermal shrinkage determines the outer diameter at room temperature so that the gap between the two-stage cylinder 16 and the two-stage displacer 17 in the final cooled state is obtained.

In this case, the outer diameter of the two-stage displacer 17 at room temperature is made smaller than the inner diameter of the two-stage cylinder 16 when cooled (in the case of stainless steel, it is smaller than the inner diameter at room temperature). Is also possible. For example, the DFRP
Is capable of arbitrarily selecting the heat shrinkage ratio in the radial direction depending on the angle of the wound fiber, and therefore the diameter and the heat shrinkage ratio are two independent parameters, and two different conditions can be satisfied. .

That is, the first and second stage cylinders 9, 16
Under the condition that both the first and second stage displacers 10, 17 are at low temperature, the gap between the first and second stage cylinders 9, 16 and the first and second stage displacers 10, 17 is short, and Under the condition that only the two-stage cylinders 9 and 16 are cooled, the first-stage and second-stage displacers 10,
It is also possible for 17 to be insertable into the cylinders 9, 16.

Further, in the present embodiment, since the gap interval is short during cooling, it is possible to suppress the amount of leak, but during the precooling from room temperature, the gap interval becomes long, so the precooling capacity is improved. It may decrease. In this case, by supplementarily providing a mechanical seal mechanism,
It is possible to prevent a decrease in capacity during precooling.

Next, a second embodiment of the cold storage type cryogenic refrigerator according to the present invention will be described with reference to FIG. 8 in FIG.
The same parts as those in FIG. This embodiment is different from the first embodiment in that the material of the two-stage displacer 17 of the two-stage regenerator 6 used is a member having a negative heat shrinkage such as DFRP. Since the mechanical seal and the mechanical seal need to be effective only during precooling, the two-stage seal with a small spring force 19
a is provided. According to the present embodiment, since the two-stage seal 19a has a small spring force, the surface pressure of the seal surface is small, and heat generation due to friction during low temperature cooling can be reduced.

In the first and second embodiments,
Although the two-stage GM refrigerator has been described, it can be applied to a one-stage GM refrigerator or a three-stage GM refrigerator. One-stage
In the case of the GM refrigerator, since the first-stage seal 15 is installed at the room temperature part, the temperature of the cylinder and the displacer is constant on the high temperature side, and the gap interval can be controlled regardless of the heat shrinkage rate. .

However, since the gap distance increases toward the low temperature side, the amount of leak can be reduced by providing a member that shortens the gap distance on the low temperature side. Further, also in the three-stage GM refrigerator, the present embodiment can be applied to the two-stage regenerator, the three-stage regenerator, or both.

Next, a third embodiment of the regenerator type cryogenic refrigerator according to the present invention will be described with reference to FIG. 8 in FIG.
The same parts as those in FIG. This embodiment is a two-stage cylinder of the two-stage regenerator 6.
The gap between 16 and the two-stage displacer 17 is not made small, but in order to shorten the gap between the two-stage cylinder 16 and the two-stage displacer 17 in a part of the width band or a plurality of width bands, Two-stage cylinder 16 with two-stage regenerator thick part
There is 21.

According to the present embodiment, it is not necessary to make the straightness of the two-stage cylinder 16 and the two-stage displacer 17 tight so that the two-stage cylinder 16 and the two-stage displacer 17 do not move due to meshing. The displacer 17 serves as a guide for reciprocating movement and also as a seal for preventing leaks, and cost can be reduced.

The present embodiment also contributes to the prevention of convection in the gap, and therefore, it is possible to operate the refrigerator in any posture where the refrigerating capacity is deteriorated by this convection. That is, convection, which is the main cause of performance deterioration, can be suppressed even when the angle is set to 0 ° with the low temperature side facing downward in the direction of gravity and the angle is tilted to 180 °. Since the fourth to sixth embodiments described below always have this effect, there is an advantage that the degree of freedom in installing the refrigerator is increased.

Next, a fourth embodiment of the regenerator type cryogenic refrigerator according to the present invention will be described with reference to FIG. FIG. 4 shows only the two-stage regenerator 6 and the one-stage expansion chamber 4 in an enlarged manner, and the refrigerator drive unit 1 and the one-stage regenerator 3 shown in FIGS. 1 to 3 are omitted. The same applies to FIGS. 5 and 6 described later.

In this embodiment, as shown in FIG. 4, the coating section 22 is provided on the two-stage cylinder 16 of the two-stage regenerator 6. The coating portion 22 can be partially provided by dividing the material having good slidability and wearability into the two-stage cylinder 16 at a plurality of locations.

Next, a fifth embodiment of the regenerator type cryogenic refrigerator according to the present invention will be described with reference to FIG. This embodiment is similar to the fourth embodiment, and the two-stage regenerator 6
The two-stage cylinder coating portion 23 is provided on the entire inner peripheral surface of the stage cylinder 16. This coating 23
Is a material with good slidability and wear resistance, and is the inner peripheral surface of the cylinder.
The outer peripheral surface of the step displacer 17 may be coated with the coating portion 23. In this case, the slidability and wearability may deteriorate, but for example, when it is desired to use a cartridge type regenerator of the pulse tube refrigerator in which the two-stage displacer 17 does not move, the gap is filled between the surfaces of the coating portion 23. The sealing property can be improved.

Next, a sixth embodiment of the regenerator type cryogenic refrigerator according to the present invention will be described with reference to FIG. In this embodiment, the two-stage displacer 17 of the two-stage regenerator 6 is filled with 2
The step cold storage material 18 is divided into upper and lower two cold storage materials 18a and 18b, and a partition plate 24 is provided between them. For each of the regenerator materials 18a and 18b, a material having a high specific heat in each operating temperature region is used.

According to the present embodiment, it is possible to cool at a lower temperature and improve the cold storage efficiency. The partition plate 24 is for preventing the two types of cold storage materials 18a and 18b from being mixed with each other. The partition plate 24 is made of the same material as the two-stage displacer 17, or is made of a material having the same heat shrinkage.

As a result, the partition plate 24 is loosened during cooling and the materials are mixed with each other, or the two-stage displacer 17 is pressed from the inner surface to increase the outer diameter of the two-stage cylinder 16 only at that portion. The problem of can be solved. In addition, in this Embodiment, it is applicable also to a Stirling refrigerator. In this case, it is only necessary to replace the two-stage displacer 17 with a piston.

Next, a seventh embodiment of a cold storage type cryogenic refrigerator according to the present invention will be described with reference to FIG. In this embodiment, the refrigerator in the first to sixth embodiments is applied to a two-stage pulse tube refrigerator. Reference numeral 25 denotes a first-stage cooling stage refrigerant flow passage provided in the first-stage cooling stage 5. The inlet side of the refrigerant flow passage 25 communicates with the lower end of the first-stage pulse tube 26, and the outlet side is connected to the first-stage expansion chamber 4. Are in contact. The first-stage pulse tube 26 is connected to the second-stage pulse tube refrigerator valve unit 27.

Reference numeral 28 is a two-stage stage refrigerant flow passage hole provided in the two-stage cooling stage 8. The inlet side of the refrigerant flow passage hole 28 is in contact with the second-stage expansion chamber 7, and the outlet side is a two-stage pulse tube 29. It is in communication. The two-stage pulse tube 29 is the valve unit 27.
Connected to.

The pulse tube refrigerator does not have a displacer and is composed of an immovable regenerator and a pulse tube which is a part of the expansion chamber. In this case, although there is no sliding surface, for example, when the two-stage regenerator 6 is made into a cartridge type so that it can be easily replaced, a seal is required. When the displacer 17 side is made of fiber reinforced resin, 2 when cooling
The gap gap between the stage cylinder 16 and the two-stage displacer 17 becomes small, and the leak gas can be reduced. This embodiment is also a separated type GM in which the regenerator itself does not move.
It can also be applied to a regenerator of a refrigerator. in this case,
The same application is possible on the displacer side.

[0045]

According to the present invention, gas convection is prevented in the gap between the displacer and the cylinder constituting the regenerator, and operation can be performed under any gravity without deteriorating the refrigeration performance. it can. In addition, cold maintenance can be performed as usual, stable operation can be performed for a long time, reliability is improved, and the inspection period can be extended.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing a first embodiment of a cold storage type cryogenic refrigerator according to the present invention in a side view.

FIG. 2 is a vertical cross-sectional view showing a second embodiment of a cold storage type cryogenic refrigerator according to the present invention in a side view.

FIG. 3 is a vertical cross-sectional view showing a third embodiment of a cold storage type cryogenic refrigerator according to the present invention in a side view.

FIG. 4 is a vertical cross-sectional view showing a fourth embodiment of a cold storage type cryogenic refrigerator according to the present invention in a side view.

FIG. 5 is a vertical cross-sectional view showing a fifth embodiment of a regenerator type cryogenic refrigerator according to the present invention in a side view.

FIG. 6 is a vertical cross-sectional view showing a sixth embodiment of a cold storage type cryogenic refrigerator according to the present invention in a side view.

FIG. 7 is a vertical cross-sectional view showing a seventh embodiment of a cold storage type cryogenic refrigerator according to the present invention in a side view.

FIG. 8 is a vertical cross-sectional view showing a part of a conventional regenerator type cryogenic refrigerator in a side view.

[Explanation of symbols]

1 ... Refrigerator drive part, 2 ... Flange part, 3 ... 1-stage regenerator,
4 ... 1 stage expansion chamber, 5 ... 1 stage cooling stage, 6 ... 2 stage regenerator, 7 ... 2 stage expansion chamber, 8 ... 2 stage cooling stage, 9 ... 1 stage cylinder, 10 ... 1 stage displacer, 11 ... 1 Cold storage material,
12 ... Upper end plate, 13 ... Lower end plate, 14 ... Refrigerant flow hole, 15 ... 1
Stage seal, 16 ... 2-stage cylinder, 17 ... 2-stage displacer, 18 ... 2-stage regenerator material, 19 ... 2-stage seal, 20 ... 2-stage regenerator bottom plate, 21 ... 2-stage regenerator thick part, 22 ... 2 Stage regenerator coating section, 23 ... Coating section for two-stage cylinder, 24 ...
Two-stage regenerator partition plate, 25 ... One-stage cooling stage refrigerant passage, 26 ... One-stage pulse tube, 27 ... Two-stage pulse tube refrigerator valve unit, 28 ... Two-stage cooling stage refrigerant passage hole, 29 ... Two-stage pulse tube.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Takashi Yazawa             2-4 Suehiro-cho, Tsurumi-ku, Yokohama-shi, Kanagawa               Toshiba Keihin Office (72) Inventor Toshiji Nakata             2-4 Suehiro-cho, Tsurumi-ku, Yokohama-shi, Kanagawa               Toshiba Keihin Office

Claims (6)

[Claims] 1. A compressor for compressing a refrigerant gas, a regenerator for inflowing a refrigerant compressed by the compressor, and an expansion chamber provided on a low temperature side of the regenerator, the regenerator comprising: In a regenerator type cryogenic refrigerator having a cylinder and a displacer that is reciprocally inserted in the cylinder and has a regenerator therein, the displacer has a heat contraction rate equal to or smaller than a heat shrinkage rate of a member forming the cylinder. A regenerator type cryogenic refrigerator comprising a member having a shrinkage ratio. 2. The regenerator has a plurality of stages, the displacer in the regenerator of the final stage is composed of a member having a negative heat shrinkage rate than the displacer in the regenerator of the first stage, and the machine of the cylinder and the displacer. The regenerator type cryogenic refrigerator according to claim 1, wherein the seal portion is provided with a portion having a small spring force and a short gap on the low temperature side. 3. The regenerator type cryogenic refrigerator according to claim 1, wherein the cylinder is provided with a plurality of thick portions for reducing a gap between the cylinder and the displacer. 4. The regenerator type cryogenic refrigerator according to claim 1, wherein a plurality of coating portions are provided on the inner surface of the cylinder. 5. A cool storage material of a plurality of different members is partitioned and filled through a partition plate in the displacer,
The partition plate is made of a member having the same heat shrinkage ratio as the displacer.
The regenerative cryogenic refrigerator described. 6. A compressor for compressing a refrigerant gas, a regenerator into which a refrigerant compressed by the compressor flows, and an expansion chamber provided on a low temperature side of the regenerator, the regenerator comprising: In a regenerator type cryogenic refrigerator having a cylinder and a displacer that is reciprocally inserted in the cylinder and has a regenerator therein, the regenerator has a plurality of stages, and an expansion chamber and a final stage of the first stage regenerator. Part of the cylinder is connected to a pulse tube, the final stage regenerator has a replaceable cartridge type seal part, the cylinder is made of stainless steel, and the displacer is made of fiber reinforced resin. Cold storage type cryogenic refrigerator.