JP2771721B2 - Cryogenic refrigerator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cryogenic refrigerator.

[0002]

2. Description of the Related Art FIG. 6 shows, for example, Japanese Patent Publication No. 46-30433.
FIG. 1 is a configuration diagram showing a conventional cryogenic refrigerator shown in Japanese Patent Application Publication (US Pat. No. 629271). This cryogenic refrigerator is a Gifford McMahon cycle refrigerator. In the figure, reference numeral 1 denotes a working gas (for example, helium);
Is an intake valve for taking in the working gas 1, and 3 is an exhaust valve for taking out the working gas 1. Reference numeral 4 denotes a first-stage expansion chamber, 5 denotes a first-stage displacer for reciprocating and moving the working gas 1, and 6 denotes a first-stage regenerator for storing cold gas. For example, a stack of disk-shaped wire meshes of phosphor bronze is stored. Reference numeral 7 denotes a first-stage seal for preventing the working gas 1 in the first-stage expansion chamber 4 from flowing around the outer periphery of the first-stage displacer 5, and reference numeral 8 denotes a first-stage refrigeration for transmitting the cold of the first-stage expansion chamber 4 to the outside. The stage 9 is a first stage cylinder. 10 is a second-stage expansion chamber, 11 is a second-stage displacer for reciprocating and moving the working gas 1, 12
Is a second-stage regenerator for storing cold gas, and contains therein a second-stage regenerative material, for example, lead balls. 13
Is a second-stage seal that prevents the working gas 1 in the second-stage expansion chamber 10 from flowing around the outer periphery of the second-stage displacer 11;
Reference numeral 14 denotes a second-stage refrigeration stage for transmitting the cold of the second-stage expansion chamber 10 to the outside, and reference numeral 15 denotes a second-stage cylinder. 16 is a motor for driving each displacer 5, 11;
Is a drive shaft for transmitting the driving force of the motor 16, and 18 is a crank for converting rotary motion into linear motion. 19 is a compressor that compresses the working gas 1, 20 is a high-pressure buffer tank that reduces pressure fluctuations on the high pressure side, 21 is a low pressure buffer tank that reduces pressure fluctuations on the low pressure side, and 22 is a constant pressure difference between high pressure and low pressure. It is a differential pressure holding device that keeps. 23 is a refrigeration quantity Q ₁ is absorbed by the first stage cooling stage 24 is a refrigeration amount Q ₂ to which is absorbed by the second stage.

Next, the operation will be described. FIG. 7 is a PV diagram of the refrigerator. The vertical axis indicates the pressure in the second-stage expansion chamber 10, and the horizontal axis indicates the same volume. First, in the state D in FIG. 7, the second stage displacer 11 is at the lowermost end, and the intake valve 2 is closed and the exhaust valve 3 is open, so that the pressure in the second stage expansion chamber 10 becomes low. I have. D
In -A, the exhaust valve 3 is closed, the intake valve 2 is opened, and the pressure changes from a low pressure state to a high pressure state. At this time, the low-pressure helium gas 1 in the invalid volume space is adiabatically compressed to a high-pressure state, so that the temperature of the low-temperature portion of the second-stage regenerator 12 rises. Next, in AB, each displacer 5,
11 moves upward, and the high-pressure working gas 1 is introduced from the compressor 19 into the expansion chambers 4 and 10 while being cooled by the regenerators 6 and 12. Each of the regenerators 6 and 12 has a temperature gradient, and the upper end of the first-stage regenerator 6 is, for example, 300K.
The lower end is 50K, and the upper end of the second stage regenerator 12 is, for example, 50K and the lower end is about 10K. Therefore, the first
The working fluid 1 introduced into the stage expansion chamber 4 is cooled to about 50K, and the working fluid 1 introduced into the second stage expansion chamber 10 is cooled to about 10K. At this time, when the high-temperature working fluid 1 flows into the second-stage expansion chamber 10 from the second-stage seal 13, a thermal load is applied. ing. B is a state where the volume is maximized. At this time, since each regenerator is heated by the working fluid 1, the temperature distribution is higher than the initial temperature distribution. B-
In C, the intake valve 2 is closed and the exhaust valve 3 is opened. At this time, the working gas 1 expands from a high pressure state to a low pressure state, and cold occurs in each of the expansion chambers 4 and 10.

The expanded working gas 1 receives a part of the refrigeration amount Q ₁ 23 in the first stage refrigeration stage 8 and a part of the refrigeration amount Q ₂ 24 in the second stage refrigeration stage 14.
The working gas 1 then cools the regenerators 6 and 12 before returning to the compressor 19. The state of C is a state in which the pressure of each of the expansion chambers 4 and 10 has become low. In CD, the displacers 5, 11 move downward to discharge the low-pressure working gas 1. Working gas 1 inflated is discharged at this time also received the remaining heat of the refrigeration quantity Q ₁ 23 in the first stage cooling stage 8, the second stage cooling stage 14 also receives the remaining heat of the refrigeration quantity Q ₂ 24. The working gas 1 then cools the regenerators 6 and 12 before returning to the compressor 19. At this time, if the low-temperature working gas 1 leaks from the second-stage seal 13 part, a part of the low-temperature working gas 1 flows out without cooling the regenerator 12, causing a loss. For this reason, the second-stage seal 13 requires precise processing. In the process of BD, the regenerators 6 and 12 are cooled and thus return to the temperature distribution at the beginning of the cycle.

[0005]

Since the conventional cryogenic refrigerator is constructed as described above, high-temperature helium gas leaking from the seal portion flows into the low-temperature expansion space without being cooled by the regenerator. There is a problem that the thermal load is applied to the expansion space and the efficiency is reduced.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a cryogenic refrigerator that can prevent a decrease in refrigeration capacity and is efficient.

[0007]

In a cryogenic refrigerator according to the present invention, a seal portion of a working fluid of an expander is displaced by a displacer.
And a flow path resistance portion and a buffer volume portion are provided on the high temperature side of the seal portion. Ma
In addition, the flow path resistance portion is configured by a seal.

[0008] Further, an auxiliary regenerator is provided in a flow path at a portion where the seal of the expander seals.

[0009]

[Action] In the arrangement cryogenic refrigerator as described above, the high temperature of the seal portion provided on the hot side of the displacer
On the side , a flow path resistance section, for example, a clearance flow path and a buffer volume section are provided. In the cycle DA, fluid flows from the high temperature section to the low temperature section. At this time, since the pressure in the expansion chamber is low, a high pressure difference occurs before and after the seal in the conventional seal structure, and the fluid leaks. However, in the structure of the present invention, the pressure in the buffer volume above the seal (high temperature side) is increased. By appropriately adjusting the passage resistance, that is, the clearance, the pressure in the expansion chamber can be made substantially the same. Therefore, the pressure difference between before and after the seal is reduced, so that leakage from the seal is reduced, and heat loss is reduced. Also, since the flow path resistance part is configured by a seal,
The flow path resistance portion can be easily formed without requiring high precision processing.

Further, since the auxiliary regenerator is provided in the seal portion, high-temperature helium gas leaking from the seal portion is cooled by the auxiliary regenerator and introduced into the expansion space, thereby reducing heat loss.

[0011]

[Embodiment 1] FIG. 1 is a configuration diagram showing a main part of a cryogenic refrigerator according to a first embodiment of the present invention, wherein 1 to 24 are exactly the same as the above-described conventional apparatus. Reference numeral 25 denotes a flow path resistance part, in this case, a clearance flow path, and reference numeral 26 denotes a buffer volume part, both of which are displays.
On the hot side of the seal provided on the hot side of the heat sink
I have.

In the cryogenic refrigerator configured as described above, a clearance channel 25 and a buffer volume 26 are provided in the seal portion. In the cycle DA, fluid flows from the high temperature section to the low temperature section. At this time, the second stage expansion chamber 10
Is a low pressure, so that the second-stage seal 1
A high pressure difference occurred before and after No. 3 and a fluid leakage loss occurred. However, in the structure of the present embodiment, the pressure in the buffer volume 26 above the seal can be made substantially the same as the pressure in the second-stage expansion chamber 10 by appropriately adjusting the clearance of the clearance flow passage 26. And the leakage from the seal is reduced. In the cycle BC, fluid flows from the low-temperature section to the high-temperature section. However, in the same manner as described above, the pressure difference is reduced, and the leakage is reduced.
Since heat exchange with the step cool storage unit 12 is promoted, there is an effect of reducing loss.

Embodiment 2 FIG. Further, in the first embodiment, the clearance passage 26 is formed as the passage resistance portion. However, as shown in the main configuration diagram of FIG.
A separate seal, a flow resistance seal 25a, may be provided to make the pressure in the buffer volume 26 substantially equal to the pressure in the second-stage expansion chamber 10.

Embodiment 3 FIG. FIG. 3 is a block diagram showing a third embodiment of the present invention, and 27 is an auxiliary regenerator. In the cryogenic refrigerator configured as described above, the second-stage seal 13
Since the auxiliary regenerator 27 is provided in the section, the second-stage seal 13
Helium gas 1 leaked from the helium gas is cooled by the auxiliary regenerator 27 and introduced into the second-stage expansion chamber 10, so that heat loss is reduced. Further, since the auxiliary regenerator 27 is cooled by low-temperature helium gas when the expansion space is at a high pressure, the loss can be reduced continuously as in the case of the original regenerator.

Further, in the third embodiment, the auxiliary regenerator 27 is installed on the display side, but it may be installed on the cylinder side as shown in FIG. Further, as shown in the configuration diagram of FIG. 5, it may be installed on both the displacer side and the cylinder side.

In the above embodiment, the second-stage regenerator,
Although the description has been made with respect to the stage seal, it is apparent that the present invention can be applied to the first stage regenerator, the third stage regenerator, and further regenerators and seals.

In the above-described embodiment, the description is made for the Gifford McMahon refrigerator.
For example, it can be used for a Stirling refrigerator, a Billmeyer refrigerator, a chloride refrigerator, and a Solvay refrigerator. In the above embodiment, a two-stage refrigerator is described, but it is apparent that the present invention can be used for a single-stage refrigerator or a three-stage refrigerator or more.

[0018]

The cryogenic refrigerator according to the present invention is configured as described above and has the following effects. Display the seal of the working fluid of the expander
Since it is provided on the high temperature side of the sealer and the flow path resistance part and the buffer volume part are provided on the high temperature side of the seal part, the pressure difference before and after the seal part becomes small, leakage from the seal is reduced, and refrigeration efficiency is improved. . Also seals the flow path resistance
, So it can be formed easily without high precision processing.
Wear.

Further, since the auxiliary regenerator is provided in the flow path portion for sealing the working fluid at the seal portion of the expander, the high-temperature working fluid leaked from the seal portion is cooled by the auxiliary regenerator and introduced into the expansion space. Therefore, heat loss is reduced and refrigeration efficiency is improved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating a main part of a cryogenic refrigerator according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram illustrating a main part of a cryogenic refrigerator according to a second embodiment of the present invention.

FIG. 3 is a configuration diagram illustrating a cryogenic refrigerator according to a third embodiment of the present invention.

FIG. 4 is a configuration diagram showing another embodiment of the cryogenic refrigerator of Embodiment 3 of the present invention.

FIG. 5 is a configuration diagram illustrating another embodiment of the cryogenic refrigerator according to the third embodiment of the present invention.

FIG. 6 is a configuration diagram showing a conventional cryogenic refrigerator.

FIG. 7 is a PV diagram of the cryogenic refrigerator.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Working gas 10 2nd stage expansion chamber 11 2nd stage displacer 12 2nd stage regenerator 13 2nd stage seal 14 2nd stage refrigeration stage 15 2nd stage cylinder 19 Compressor 25 Clearance channel 26 Buffer capacity part 27 Auxiliary Regenerator

Claims (3)

(57) [Claims] 1. A compressor, as well as a cylinder, includes a expander consisting displacer and regenerator, in inflating the working fluid cryogenic refrigerator which generates cold, display the seal portion of the working fluid of the expander Sir hot side
Cryogenic refrigerator is characterized by providing a flow path resistance portion and the buffer volume on the high temperature side of the seal portion is provided on. 2. The flow path resistance part is constituted by a seal.
The cryogenic refrigerator according to claim 1, wherein: 3. A compressor, a cylinder and a display.
Equipped with expander consisting of heat sink and regenerator to expand working fluid
In a cryogenic refrigerator that generates cold by causing
At the seal part of the stretcher, in the flow path part that seals the above working fluid
A cryogenic refrigerator having an auxiliary regenerator.