JPH0215787B2 - - Google Patents

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to an ultra-low temperature refrigerator, and more specifically, an ultra-low temperature refrigerator that can generate refrigeration of 10K or less with small power consumption. Regarding.

(Conventional technology) As a conventional ultra-low temperature refrigerator,
There is something shown in the publication.

This device sequentially communicates a compression space defined in a compression cylinder by a compression piston, a cooler, a first regenerator, and a second regenerator, and also connects a stepped expansion piston to a stepped expansion cylinder. The defined first expansion space and second expansion space are communicated with a first regenerator and a second regenerator, respectively, and the expansion piston is advanced and reciprocated with a predetermined phase difference (90°) relative to the compression piston. forming the Stirling cycle,
The space that forms the refrigeration cycle (Stirling cycle) from the compression space to each expansion space becomes adiabatic by completing an adiabatic compression stroke - equal volume stroke - adiabatic expansion stroke - equal volume stroke due to the reciprocating sliding of each piston. During the expansion stroke, refrigeration of 80K and 30K is generated in the first and second expansion spaces, respectively.

That is, when the compression space is compressed by the compression piston sliding from the bottom dead center to the intermediate point, each expansion space is compressed by the expansion piston sliding from the midpoint to the top dead center, so the refrigeration cycle The working gas filled in the space forming the space is adiabatically compressed by both pistons, and when the compression space is compressed by the compression piston sliding from the midpoint to the top dead center, each expansion space is compressed by the expansion piston. is expanded by sliding from the top dead center to the intermediate point, so the space forming the refrigeration cycle undergoes a constant volume change, and the working gas passes through the cooler and the first regenerator to radiate heat and undergo the first expansion. While being moved into the space, the heat is further radiated through the cooler, the first regenerator, and the second regenerator, and then moved into the second expansion space. When the compression space is expanded by the compression piston sliding from the top dead center to the middle point, each expansion space is expanded by the expansion piston sliding from the middle point to the bottom dead center, so the working gas are adiabatically expanded in the first and second expansion spaces, respectively.
When refrigeration of 80K and 30K occurs, and then the compression space is expanded by the compression piston sliding from the middle point to the bottom dead center, each expansion space is expanded by the expansion piston sliding from the bottom dead center to the middle point. Due to the compression, the space forming the refrigeration cycle undergoes an equal volume change, and the working gas is moved into the compression space via the cooler while cooling each regenerator.

(Problems to be Solved by the Invention) In the conventional ultra-low temperature refrigerator described above, in order to generate even lower refrigeration, the third expansion space is communicated with the second regenerator via the third regenerator. Just set it up. However, the regenerator of the conventional ultra-low temperature refrigerator mentioned above is constructed by stacking and packing lead balls and plates, which are metals with large heat capacity, and these lead (lead balls) are as shown in Figure 4.
At low temperatures below 15K, the heat capacity per unit volume decreases, so the efficiency of the regenerator is low at low temperatures below 15K. Therefore, there was a problem in that even if the number of expansion stages was increased, refrigeration below 10K could not be efficiently generated. In other words, increasing the regenerator capacity (capacity of regenerator material) to compensate for the decrease in regenerator efficiency at low temperatures below 15K will lead to an increase in dead volume and pressure loss in the refrigeration cycle, and the power consumption of the cryogenic refrigerator will decrease. There was a problem in that the efficiency (refrigeration amount/power consumption) of the cryogenic refrigerator decreased.
These problems are solved between the second regenerator and the third expansion space, as shown in Japanese Utility Model Application Publication No. 56-88059.
This can be solved by installing a countercurrent heat exchanger that exchanges heat with the working gas of another refrigerator driven with a 180° phase difference, but this would require two refrigerators. , the configuration becomes complicated.

Therefore, the technical objective of the present invention is to reduce the power consumption for obtaining a predetermined amount of refrigeration with a simple configuration in an ultra-low temperature refrigerator.

[Structure of the invention]

(Means for solving the problem) The means for solving the above technical problem are:
The ultra-low temperature refrigerator is connected to the compression space, the cooler, the first regenerator, the second regenerator, the third regenerator, and the flow path of the regenerative heat exchanger, and the first regenerator and the first regenerator are connected to each other in order.
An expansion space, the second regenerator and the second expansion space, and a flow path of the regenerative heat exchanger and the third expansion space are connected to each other, and the third expansion space or the third regenerator is connected to the regenerator. One direction that allows working gas to flow from the third expansion space or the third regenerator to the space defined in the regenerative heat exchanger so as to surround the flow path of the heat exchanger. The space communicates with the other space through a valve, and the working gas flows from the space to the other space when the pressure in the space becomes higher than the pressure in the other space by a predetermined amount. The structure is such that they are communicated via a safety valve that allows for this.

(Operation and Effects of the Invention) According to the present invention, the one-way valve allows the working gas (helium gas) which has a large heat capacity at low temperatures (15K or less) to store heat without increasing the dead volume of the space forming the refrigeration cycle. It can be filled into the space of a type heat exchanger, and the filled working gas (helium gas) can exchange heat with the working gas in the spaces that form the refrigeration cycle (the spaces from the compression space to each expansion space). Therefore, refrigeration of 10K or less can be generated with small power consumption and in a short time with a simple configuration without increasing the capacity of the third regenerator. In addition, the working gas filled in the space of the regenerative heat exchanger is released from the space to another space by a safety valve when the pressure in the space becomes higher than the pressure in other spaces by a predetermined amount, so the temperature is extremely low. The pressure within the space of the regenerative heat exchanger is prevented from increasing abnormally after the refrigerator is stopped, and the durability of the regenerative heat exchanger can be improved.

(Example) Hereinafter, one example of the ultra-low temperature refrigerator according to the present invention will be described based on the drawings.

In FIG. 1, a compression space 3 formed by a compression cylinder 1 and a compression piston 2 sequentially passes through a cooler 4 and a first regenerator 5, and then passes through communication pipes 6, 7.
are in communication with one end side of the first expansion space 8 and the second regenerator 9, respectively. The other end of the second regenerator 9 communicates with the second expansion space 10 and one end of the third regenerator 13 through communication pipes 11 and 12, respectively. , and communicates with one end side of the flow path 15a of the regenerative heat exchanger 15 through the communication pipe 14. Further, the other end side of the flow path 15a of the regenerative heat exchanger 15 communicates with the third expansion space 17 through the communication pipe 16. The first regenerator 5, the second regenerator 9, and the third regenerator 13 are well-known regenerators in which balls, plates, and the like of metal (such as lead) having a large heat capacity are laminated and packed.

As shown in FIG. 2, the regenerative heat exchanger 15 has a space 15b surrounding an outer wall 15c of the flow path 15a and a fin 15d provided on the outer wall 15c. The space sequentially passes through the communication pipe 20, the one-way valve 19, and the communication pipe 18 to the third expansion space 17.
is communicated with. The one-way valve 19 allows helium gas to flow from the third expansion space 17 to the space 15b of the regenerative heat exchanger 15, and prevents the helium gas from flowing from the space 15b to the third expansion space 17. It's summery. In addition, the compression piston 2 has
A piston ring 23 is provided on a part of the outer circumference of the compression piston 2 for gas sealing, and a part of the outer wall of the rod 22 is also provided with a piston ring 23 for gas sealing. A seal 31 is provided.

Further, the space 15b of the regenerative heat exchanger 15 is communicated with other spaces via a communication pipe 32, a safety valve 33, and a communication pipe 34, and in this embodiment, the third regenerator 13 is connected via the communication pipe 34. is communicated with. Note that the other spaces may be any space other than the space 15b, and in addition to the third regenerator 13, for example, the compression space 3, the first regenerator 5, the first expansion space 8,
It may be the second regenerator 9, the second expansion space 10, the third expansion space 17, the buffer spaces 41, 45, etc. In addition, as shown in FIG. 1 and FIG.
When the pressure within the space 15b becomes higher than the predetermined amount,
Helium gas (working gas) from to the third regenerator 13
It has become possible to allow the flow of

The first expansion space 8, the second expansion space 10, and the third expansion space 17 are each formed by an expansion cylinder 24 and an expansion piston 25, each having a two-stage convex shape. On the outer periphery of each stage of the expansion piston 25,
Piston rings 26, 27, 3 for gas sealing in the first, second and third expansion spaces 8, 10, 17
8 is installed. Further, a rod 29 is connected to the expansion piston 25, and a seal 30 for gas sealing is installed on a part of the outer circumference of the rod 29. In FIG. 1, 41 and 45 are buffer spaces, respectively.

The rods 22 and 29 are connected to a reciprocating mechanism (for example, a crank mechanism, etc.), not shown, so that the expansion piston 25 advances approximately 90 degrees from the compression piston 2.

The operation of the present invention having the above configuration will be explained.

When the compression space 3 is compressed by the compression piston 2 sliding from the bottom dead center to the intermediate point, the expansion piston 25 is sliding 90 degrees in phase with respect to the compression piston 2, so the expansion piston 25 moves from the intermediate point to the intermediate point. It slides to the top dead center, and each expansion space 8, 10, 17 is also compressed.
Therefore, from the compression space 3 to each expansion space 8, 10,
The helium gas filled in the space forming the refrigeration cycle up to 17 is adiabatically compressed by both pistons 2 and 25. Next, as the compression piston 2 slides from the intermediate point to the top dead center, the compression space 3
is compressed, the expansion piston 25 slides from the top dead center to the intermediate point, thereby opening each expansion space 8, 1.
0,17 are expanded. Therefore, the space forming the refrigeration cycle undergoes an equal volume change, and the helium gas radiates heat through the cooler 4 and the first regenerator 5 and moves into the first expansion space 8. The heat is further radiated through the regenerator 5 and the second regenerator 9 and moved into the second expansion space 10 . Further, the helium gas passes through the cooler 4, the first regenerator 5, and the second regenerator 9, radiates heat, flows into the flow path 15a of the regenerative heat exchanger 15, and flows into the outer wall 15c.
The helium gas in the space 15b is cooled by the fins 15d and moved into the third expansion space 17 through the communication pipe 16.

When the compression space 3 is expanded by sliding the compression piston 2 from the top dead center to the intermediate point, each expansion space 8, 10, 17 is expanded. Therefore, the helium gas is adiabatically expanded and frozen in the first expansion space 8, and
Refrigeration is generated in the second expansion space 10 at a temperature lower than that in the first expansion space 8. In addition, the third expansion space 1
The helium gas that has flowed into the second expansion space 7 is similarly adiabatically expanded to generate refrigeration at a lower temperature than the second expansion space 10. Next, when the compression space 3 is expanded by sliding the compression piston 2 from the middle point to the bottom dead center, each expansion space 8, 10, 17 is expanded by the expansion piston 25 sliding from the bottom dead center to the middle point. As a result, the space forming the refrigeration cycle undergoes an equal volume change, and the helium gas cools the helium gas in the space 15b of the regenerative heat exchanger 15 and the regenerators 13, 9, and 5. One cycle is completed by being moved into the compression space 3 via the container 4.

By repeating this refrigeration cycle many times, the first expansion space 8, the second expansion space 10, and the third
The temperature of the helium gas in each expansion space 17 gradually decreases to approximately 100K in the first expansion space 8, approximately 30K in the second expansion space 10, and approximately 30K in the third expansion space 17.
15K refrigeration is generated, and a regenerative heat exchanger 15
It will also be about 15K.

By the way, when the temperature of the regenerative heat exchanger 15 decreases, the temperature of the helium gas in the space 15b of the regenerative heat exchanger 15 decreases, and the pressure in the space 15b becomes lower than the pressure in the third expansion space 17. Nari, 3rd
The helium gas in the expansion space 17 is sequentially transferred to the communication pipe 1.
8. Space 1 through one-way valve 19 and communication pipe 20
5b, and as shown in FIG. In this way, the one-way valve 19 operates (opens) unless the pressure in the space 15b of the regenerative heat exchanger 15 becomes lower than the pressure in the third expansion space 17.
Therefore, the space 15b does not become a dead volume of the space forming the refrigeration cycle.

When the temperature of the regenerative heat exchanger 15 reaches approximately 15K,
The further cooled helium gas that enters the third regenerator 13 from the second regenerator 9 through the communication pipe 12 is further cooled by the helium gas in the space 15b of the regenerative heat exchanger 15, and then passes through the communication pipe 16. , flows into the third expansion space 17. Here, as shown in FIG. 4, 10at helium gas has a larger heat capacity than a lead bulb at a low temperature of 15K or less, so the helium gas that has flowed into the flow path 15a of the regenerative heat exchanger 15 is absorbed into the space 15b. It is efficiently cooled by the helium gas, and freezing at an even lower temperature is generated in the third expansion space 17. The helium gas that has finished expanding in the third expansion space 17 is compressed by the expansion piston 25 and passes through the communication pipe 16 to the regenerative heat exchanger 1.
Helium gas flows into the flow path 15a of No. 5 and passes through the communication pipe 14 while cooling the helium gas in the space 15b.
It flows into the regenerator 13. The helium gas that has flowed into the third regenerator 13 is transferred to the cooler 4 while sequentially cooling the third regenerator 13, the second regenerator 9, and the first regenerator 5.
It flows into the compression space 3 via. Note that the helium gas that has finished expanding in the second expansion space 10 and the first expansion space 8 similarly cools the second regenerator 9 and the first regenerator 5, and the first regenerator 5, respectively.
It flows into the compression space 3 through the.

In this way, the temperature of the regenerative heat exchanger 15 is 15K.
By repeating this refrigeration cycle many times, the helium gas flowing into the flow path 15a of the regenerative heat exchanger 15 is is efficiently cooled, the first expansion space 8 generates refrigeration of approximately 70K, the second expansion space 10 generates refrigeration of approximately 25K (cooling the working gas in the communication pipe 14 to approximately 15K), and The third expansion space 17 can generate approximately 4K refrigeration by increasing the regenerator capacity of the third regenerator 13, without increasing the dead volume and pressure loss in the refrigeration cycle, with small power consumption, and in a short time. can.

When the operation of the refrigerator is stopped, the temperature of the space 15b of the regenerative heat exchanger 15 rises, and the pressure of helium gas within the space 15b rises. When the pressure of helium gas in the space 15b becomes a predetermined pressure or more than the pressure in the third regenerator 13 (pressure in other spaces),
The safety valve 33 opens, and the helium gas in the space 15b of the regenerative heat exchanger 15 flows out into the space forming the refrigeration cycle, and the pressure in the space 15b changes to the pressure in the third regenerator 13 (forming the refrigeration cycle). space)
is approximately equal to Therefore, the pressure in the space 15b of the regenerative heat exchanger 15 is prevented from increasing abnormally, and the durability of the regenerative heat exchanger 15 can be improved.

FIG. 5 shows another embodiment of the invention. In this embodiment, the outlet side of the safety valve 33 is connected to a buffer space 41, which is another space, through the communication pipes 34, 35, 36, 37, 38, 39, and 40, and the buffer space 41 is sequentially connected to the communication pipe. 42, aperture 4
3. It communicates with the compression space 3 through a communication pipe 44, so that the average pressure of the space forming the refrigeration cycle acts on the buffer space 41. The communication pipes 35, 37, and 39 are configured to be able to exchange heat with the third regenerator 13, the second regenerator 9, and the first regenerator 5, respectively. Further, the one-way valve 19 is configured to allow the flow of helium gas from the third regenerator 13 to the space 15b of the regenerative heat exchanger 15, and to prevent the flow of helium gas from the space 15b to the third regenerator 13. is connected to the third regenerator 1 via communication pipes 18 and 19.
3 and the space 15b of the regenerative heat exchanger 15. Note that the other configurations in FIG. 5 are the same as those in the embodiment shown in FIG. 1, and the same configurations are given the same numbers and symbols as those used in FIG. 1.

In this embodiment, as in the embodiment described above, the space 15b of the regenerative heat exchanger 15 is cooled, so that helium gas flows into the space 15b.
The regenerator 13 is filled with helium gas, and the helium gas in the space forming the refrigeration cycle is cooled. Therefore, after the temperature of the regenerative heat exchanger 15 reaches 15K, by repeating the refrigeration cycle many times, the helium gas with a large heat capacity in the space 15b of the regenerative heat exchanger 15 causes the regenerative heat exchanger 15 to Since the helium gas flowing into the flow path 15a of No. 15 is efficiently cooled,
The expansion space 8 cools at approximately 70K, and the second expansion space 10
generates refrigeration of about 25K (cools the working gas in the communication pipe 14 to about 15K), and the third expansion space 17
By increasing the regenerator capacity of the third regenerator 13, refrigeration of approximately 4K can be generated with small power consumption and in a short time without increasing the dead volume and pressure loss in the refrigeration cycle.

When the operation of the refrigerator is stopped, the helium gas in the space 15b of the regenerative heat exchanger 15 warms up, and when the pressure in the space 15b becomes higher than the pressure in the buffer space 41 by a predetermined amount, the safety valve 33 opens. , the helium gas in the space 15b is sequentially transferred to the communication pipes 35, 3.
6, 37, 38, 39, and 40, and flows into Batschaar space 41. As a result, space 15
The pressure inside b is made almost equal to the pressure inside the Batsha space 41, and the pressure is prevented from increasing abnormally, thereby improving the durability of the regenerative heat exchanger 15.
The helium gas passing through the communication pipes 35, 37, and 39 is heated by receiving heat from the wall of the third regenerator 13, the wall of the second regenerator 9, and the wall of the first regenerator 5, respectively. , to prevent heat leaks when the refrigerator is operating. Other functions are likely to be easily understood by those skilled in the art from the description of the embodiment shown in FIG. 1 above, so their description will be omitted.

In each of the embodiments described above, an example was shown in which the present invention was applied to a Stirling cycle ultra-low temperature refrigerator, but the present invention can also be adopted to an ultra-low temperature refrigerator of other cycles such as the Gifford-McMahon cycle.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view showing an embodiment of an ultra-low temperature refrigerator according to the present invention, FIG. 2 is a schematic cross-sectional view of a one-way valve and a regenerative heat exchanger in the embodiment shown in FIG. Figure 3 shows the helium gas pressure in the space 15b in the regenerative heat exchanger in the embodiment shown in Figure 1.
A graph showing the pressure change status of P ₂ and the helium gas pressure P ₁ in the third expansion space 17, Fig. 4 is a graph showing a comparison of the heat capacity per unit volume of 10at helium gas and a lead bulb, Fig. 5 FIG. 3 is a schematic cross-sectional view showing another embodiment of the invention. 1... Compression cylinder, 2... Compression piston, 3
...Compression space, 4...Cooler, 5...First regenerator, 8...First expansion space, 9...Second regenerator, 1
0...Second expansion space, 13...Third regenerator, 15
...Regenerative heat exchanger, 15a...Flow path, 15b...
...space, 15d...fin, 17...third expansion space, 19...one-way valve, 33...safety valve, 41...
...Batsuhua space.

Claims (1)

[Claims] 1 Compression space 3, cooler 4, first regenerator 5, second
Regenerator 9, third regenerator 13, and regenerator type heat exchanger 1
5, and the first regenerator 5 and the first expansion space 8, and the second regenerator 9 and the second
Expansion space 10, flow path 1 of the regenerative heat exchanger 15
5a and a third expansion space 17, respectively, and the third expansion space 17 or the third regenerator 13 surrounds the flow path 15a of the regenerative heat exchanger 15. The space 15b defined in the space 15 is connected to the space 15b via a one-way valve 19 that allows working gas to flow from the third expansion space 17 or the third regenerator 13 to the space 15b. is communicated with another space via a safety valve 33 that allows working gas to flow from the space 15b to the other space when the pressure in the space 15b becomes higher than the pressure in the other space by a predetermined amount. This ultra-low temperature refrigerator is characterized by: