JP2880154B1 - Pulse tube refrigerator - Google Patents

Abstract

An object of the present invention is to provide a small, lightweight, and simple pulse tube refrigerator excellent in refrigeration capacity by reducing unnecessary heat flow into a low-temperature portion due to heat transfer in a regenerator. SOLUTION: Circulating means 14c, which circulates a fluid in a buffer tank 16 to a low pressure side 14c of a compression working chamber and generates a small steady flow of a working fluid in a regenerator 12 and a pulse tube 13.
A pre-cooling and refrigeration unit 30 is provided, which is provided with 21 and 22 and is connected to the regenerator 12 at a predetermined position in the flow direction of the steady flow, and releases the heat given to the regenerator 12 by the steady flow from the regenerator 12 at the predetermined position. Provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a pulse tube refrigerator,
In particular, the present invention relates to a pulse tube refrigerator used as a cooling device for low-temperature devices such as infrared sensors and high-temperature superconducting devices.

[0002]

2. Description of the Related Art Hitherto, for example, a Stirling refrigerator has been used as a cooling device for a device operating at a low temperature such as a high-temperature superconducting device. However, there has been an inconvenience that the structure is complicated and long-term operation is difficult. A pulse tube refrigerator has been attracting attention as a simple refrigerator having an alternative structure.

[0003] The pulse tube refrigerator includes a regenerator and a pulse tube provided in a vacuum insulated container, and a compressor for applying a periodic pressure change to a working fluid in the regenerator from outside the vacuum insulated container. This is a regenerative type cycle refrigerator in which an object to be cooled (such as an infrared sensor or a high-temperature superconducting device) is cooled by a low-temperature head installed at a low-temperature end of a pulse tube in a vacuum insulated container. In particular,
For example, a buffer tank is connected to the high-temperature end of the pulse tube via an orifice, and the displacement of the gas that does not contribute to the compression and expansion of the working fluid (gas) in the pulse tube (called a traveling wave component in thermoacoustic theory, etc.) An orifice-type pulse tube refrigerator is also known which promotes heat transfer by imparting heat. This orifice type can control the phase difference of the displacement of the gas against the pressure vibration (compression / expansion) of the high-pressure gas inside the pulse tube by the orifice.
By increasing the displacement of the traveling wave component that does not contribute to the pressure fluctuation, a greater refrigeration capacity than that of the so-called basic type can be expected.

Further, as shown in FIG. 5, a passage 6 for bypassing the regenerator 2 and the pulse tube 3 is provided between the discharge port of the compressor 1 and the high-temperature end 3a of the pulse tube 3.
There is also a so-called double inlet type pulse tube refrigerator in which the degree of restriction of the passage 6 is adjusted by a valve 7 provided in the passage 6. In this double inlet type pulse tube refrigerator, the regenerator 2 and the pulse tube 3
The gas filled inside is compressed, expanded and displaced from both sides. Further, by adjusting the opening of the valve 7, the amplitude of the gas displacement can be optimized, and the refrigeration capacity can be increased.

[0005]

The above-described pulse tube refrigerator is cooled by substantially the same principle as the Stirling refrigerator.
Specifically, it is understood that the gas at the cold end of the pulse tube behaves like the cold piston of a Stirling refrigerator. However, the power of the low-temperature side piston is regenerable because it is fixed to the same shaft as the compression piston in a Stirling engine, but it is fundamental in a pulse tube refrigerator because it is discarded as heat from an orifice or the like. However, there is a problem that refrigeration capacity and efficiency are inferior.

The present invention has been made to solve such a problem that the refrigerating capacity and efficiency are inferior.

[0007]

According to a first aspect of the present invention, there is provided a regenerator filled with a working fluid (gas), a pulse tube communicating with the regenerator, and a regenerator communicating with the regenerator. Fluid driving means for compressing, expanding and displacing the working fluid in the regenerator by a change in volume of the compression working chamber, and a buffer tank communicating with the pulse tube via a narrow tube having a throttle passage. Circulating means for circulating the fluid in the buffer tank to the low-pressure side of the compression working chamber and generating a minute steady flow of the working fluid in the regenerator and the pulse tube. And a pre-cooling refrigeration unit connected to the regenerator at a predetermined position in the flow direction of the steady flow and configured to release heat given to the regenerator by the steady flow from the regenerator at the predetermined position. And wherein the door.

According to the present invention, the working fluid (hereinafter, referred to as gas) in the pulse tube is compressed, expanded and displaced to carry the heat at the low-temperature end of the pulse tube to the high-temperature end, and to dissipate the heat at the high-temperature end. The removal provides a continuous cooling effect at the cold end. At this time, the circulation means generates a very slow steady flow from the regenerator to the pulse tube side in the regenerator and the pulse tube inside the regenerator and the pulse tube. A heat flow toward the low-temperature end occurs, but most of the heat released from the gas to the regenerator by the pre-cooling refrigeration means in a state where the average temperature of the gas substantially matches the tube wall of the regenerator and the pulse tube. It is removed at the pre-cooling position of the regenerator, which has the same effect as producing a steady flow at the cold end of the regenerator by the removed heat. in this way,
Unnecessary heat inflow to the low-temperature end of the regenerator is sufficiently suppressed by pre-cooling at a predetermined position higher than the low-temperature end by another refrigeration means called pre-cooling refrigeration means, and the apparent refrigeration capacity at the low-temperature end is reduced. Since it can be produced, it greatly contributes to the improvement of the cooling efficiency of the refrigerator determined only by the exhaust heat temperature and the heat absorption temperature.

The circulating means includes a communication passage formed in the piston for communicating the high pressure side and the low pressure side of the compression working chamber, and a reflux for returning the fluid in the buffer tank to the low pressure side of the compression working chamber. It is preferable to have a passage, and a check valve provided in the communication passage to allow a flow from the low pressure side to the high pressure side and prevent a flow in the opposite direction. By doing so, a durable circulating means having a simple configuration can be realized at low cost.

Further, the pre-cooling / refrigeration means has a heat bridge member connected to the regenerator at the predetermined position, and heat given to the regenerator upstream from the predetermined position by the steady flow, When the regenerator is discharged from the regenerator through the heat bridge member, it is possible to cope with a multi-specification refrigerator by using the same pre-cooling and freezing means by simply setting the connection position of the heat bridge member in the flow direction of the steady flow as appropriate. be able to.

Further, a second invention provides a regenerator filled with a working fluid, a pulse tube communicating with the regenerator, and a piston in a compression working chamber communicating with the regenerator. A pulse tube refrigerator comprising: fluid driving means for compressing, expanding and displacing a working fluid in a regenerator on a high pressure side of the regenerator; and a buffer tank communicating with the pulse tube through a narrow tube having a throttle passage. Refluxing the fluid in the buffer tank to the low pressure side of the compression working chamber,
Circulating means for generating a small steady flow of the working fluid in the regenerator and the pulse tube through the piston is provided, and the regenerator is connected to a first regenerator and a second regenerator adjacent in the flow direction of the steady flow. Wherein the cross-sectional area of the first regenerator is larger than the cross-sectional area of the second regenerator in a direction perpendicular to the flow direction of the steady flow.

With this configuration, the first regenerator has a higher regenerative storage capacity than the second regenerator, so that the first heat regenerator has a balance between the heat inflow due to the steady flow and the refrigerating capacity difference due to the difference in the regenerative power. The same effect can be obtained as in the case where the precooling is performed by the precooling / freezing means at a predetermined position where the regenerator and the second regenerator are adjacent to each other.

[0013]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a diagram showing one embodiment of a pulse tube refrigerator according to the first invention, and shows an example in which the present invention is applied to a superconducting filter system.
In the figure, reference numeral 11 denotes a vacuum heat insulating container. The vacuum heat insulating container 11 has a regenerator 12 having a plurality of fluid passages (details not shown) therein and a regenerator via a low-temperature part (not shown). And a pulse tube 13 connected to the pulse tube 12. The regenerator 12 has a plurality of plate-shaped regenerators made of, for example, stainless steel, copper, or a copper alloy stacked in a cylindrical casing, and a plurality (a plurality) of regenerators are formed by holes formed in the regenerators. Although the fluid passage is formed, the fluid passage may contain a large number of granular cold storage materials.

The fluid passage of the regenerator 12 and the internal space of the pulse tube 13 communicate with each other so as to form one working space, and a predetermined working fluid (for example, an inert gas, specifically, Is filled with helium, argon or nitrogen). The fluid passage of the regenerator 12 is provided with a high-pressure side working chamber 14b (high-pressure side of the compression working chamber) of a piston-type compressor 14 (fluid driving means) provided outside the vacuum heat insulating container 11.
The piston 14 a of the compressor 14 periodically compresses, expands and displaces the working fluid via the regenerator 12. The term “compressing / expanding the working fluid” as used herein means that the volume of the working fluid is changed periodically by applying a periodic pressure change (in the case of a small space, the same phase as the pressure change applied periodically is applied). Displacement of the working fluid means that the working fluid is simply moved in the axial direction of the pulse tube 13 (fluid having a phase different from the pressure change, which does not participate in the compression / expansion of the working fluid). Displacement occurs).

The regenerator 12 functions to absorb the heat of the working fluid when the working fluid is compressed and to compress the working fluid isothermally, while providing the accumulated heat to the working fluid when the working fluid is expanded, It functions to expand the fluid isothermally. The low-temperature portion between the regenerator 12 and the pulse tube 13 constitutes a so-called cold head, and a predetermined object to be cooled attached to the low-temperature portion, for example, the pulse tube 13
A plurality of superconducting filters provided at predetermined intervals in the circumferential direction are cooled. The superconducting filter is used as a bandpass filter for receiving a weak radio wave received by an antenna in a base station of a mobile communication system, for example. Of course, a filter module or the like including a low noise amplifier may be used.

The pulse tube 13 is formed by a thin metal pipe made of, for example, stainless steel, titanium or the like, and has an open end at the regenerator 12 side. It works like a piston at the end. The pulse tube 13 is connected to a buffer tank 16 via a thin tube 15 having an orifice 15a (throttle passage), and the thin tube 15 radiates heat on the high-temperature end side of the pulse tube 13.

The buffer tank 16 is connected to a low-pressure side working chamber 14 of the compressor 14 through a return passage 21 serving as a throttle passage.
c (the low pressure side of the compression working chamber), so that the working fluid can be recirculated from the buffer tank 16 to the low pressure side working chamber 14 c of the compressor 14. Further, a communication passage 14d is formed in the piston 14a of the compressor 14, and a check valve 22 that allows a flow from the low-pressure side working chamber 14c to the high-pressure side working chamber 14b and prevents a flow in the opposite direction. Is installed. These communication paths 14
d, the return passage 21 and the check valve 22 constitute a circulating means for generating a minute steady flow of the working fluid in the regenerator 12 and the pulse tube 13.

Reference numeral 31 denotes a heat bridge member made of, for example, copper and connected to the regenerator 12 at a predetermined position in the flow direction of the steady flow. The heat bridge member 31 is a member having a high thermal conductivity for releasing the heat given to the regenerator 12 upstream from the predetermined position by the steady flow of the working fluid from the regenerator 12, and The regenerator 12 is connected to the low-temperature section 30a of the pre-cooling refrigerator 30 so that heat given to the regenerator 12 is released from the regenerator 12 upstream of the predetermined position. The pre-cooling refrigerator 30 includes, for example, a compressor 34 having a piston 34a that reciprocates at a predetermined frequency, a regenerator 32 connected to the compressor 34 at one end, and a tip block connected to the other end of the regenerator 32. A pulse tube 33 having a shape, a thin tube 35 connected to a high-temperature end of the pulse tube 33, and a thin tube 3
5 and a buffer tank 37 which communicates with the pulse tube 33 through the throttle passage in the orifice 5.

Next, the operation of the pulse tube refrigerator will be described. First, the compressor 14 is driven, and the high-pressure working fluid (gas) in the regenerator 12 and the pulse tube 13 is compressed / expanded and displaced by a predetermined number of cycles. The heat of the part side is transferred to the high-temperature end side, and a constant temperature gradient is formed inside the pulse tube 13.

In this state, the average temperature of the working fluid (gas) inside the regenerator 12 and the pulse tube 13 substantially matches the respective inner wall temperatures of the regenerator 12 and the pulse tube 13. The gas flowing into the regenerator 12 transfers heat until it reaches the low-temperature part.
When the gas exits from the low-temperature end of the regenerator 12 and moves toward the high-temperature end of the pulse tube 13, the gas takes heat from the tube wall of the pulse tube 13.

Therefore, as shown in the upper part of FIG. 2, the temperature of the gas gradually decreases in the regenerator 12 from the inlet temperature Ta of the regenerator 12 (room temperature in the vacuum insulated container), and the temperature of the low-temperature part is reduced. The temperature drops to the temperature Tc, and then gradually rises to the high temperature end of the pulse tube 13. In this state, as shown in the lower part of FIG.
And gradually decreases in the low-temperature portion, and gradually increases from there to the high-temperature end of the pulse tube 13. Assuming that the system is completely reversible, the internal energy of the gas will be the same at the hot end of the regenerator 12 and the hot end of the pulse tube 13 even if a steady flow passes through the inside of the pulse tube 13. . In the figure, Tb is a pre-cooling position temperature (temperature at a predetermined position) lower than the room temperature Ta and higher than the low-temperature portion temperature Tc in the vacuum insulated container 11.

Considering that heat flows from a high temperature to a low temperature in the regenerator 12, the amount of heat discarded by the gas to the regenerator 12 is reduced to the predetermined position on the downstream side (low-temperature end side). ) Becomes larger. In this state, in the predetermined position where the gas temperature becomes Tb, that is, in the middle of the regenerator 12, heat of the heat amount Q1 is released by the pre-cooling of the pre-cooling refrigerator 30 via the heat bridge member 31. Therefore, the steady flow apparently has the heat quantity Q1 at the low temperature end of the regenerator 12.
Refrigeration capacity, and the refrigeration capacity will increase accordingly. In other words, due to the steady flow in the regenerator 12, the gas is stored in the regenerator 1 from the gas upstream of the predetermined position.
2 can be efficiently extracted to the outside at the predetermined position where the gas reaches the temperature Tb. Therefore, while performing only heat transfer from the low-temperature end side to the high-temperature end side of the pulse tube 13, the heat inflow to the low-temperature portion can be suppressed to the heat amount Q2 sufficiently smaller than the heat amount Q1,
The refrigeration capacity can be greatly improved.

As described above, according to the present invention, the regenerator 12 and the pulse tube 13 are provided inside the regenerator 12 and the pulse tube 13 by the circulating means.
A steady flow with a very slow flow from the side toward the pulse tube 13 is generated, and the gas flows into the regenerator 12 from the compressor 14 side in a state where the average temperature of the gas substantially matches the tube wall of the regenerator 12 and the pulse tube 13. Heat is supplied to the regenerator 12 until the gas reaches the low-temperature part, and the gas emitted from the low-temperature part is supplied to the pulse tube 1.
Heat is taken from the tube wall of the pulse tube 13 until the high temperature end of 3 is reached. Further, most of the heat Q1 of the heat released from the gas to the regenerator 12 is transferred to the precooling position by the precooling refrigerator 30. Release and remove reliably. As described above, since the steady flow has the same effect as generating the refrigeration capacity only for the amount of heat removed above, the refrigeration capacity of the pulse tube refrigerator is increased by pre-cooling at a predetermined position higher in temperature than the low temperature part. The cooling efficiency can be easily increased, and the cooling efficiency of the refrigerator determined only by the exhaust heat temperature and the heat absorption temperature can be easily and significantly improved.

In addition to this, a communication passage is formed in the piston so as to communicate the high pressure side and the low pressure side of the compression working chamber, and a recirculation passage for returning the fluid in the buffer tank to the low pressure side of the compression working chamber; By providing a check valve that allows the flow from the low pressure side to the high pressure side in the communication passage and blocks the flow in the opposite direction, a durable circulating means with a simple structure can be realized at low cost. can do.

In this embodiment, the pre-cooling refrigerator 30 has a heat bridge member 31 connected to the regenerator 12 at the predetermined position, and the regenerator 12 is located upstream from the predetermined position by the steady flow. Is released from the regenerator 12 via the heat bridge member 31. Therefore, the same precooling can be performed simply by appropriately setting the connection position of the heat bridge member 31 in the flow direction of the steady flow. The refrigerating means 30 can support a multi-specification refrigerator.

In the above-described embodiment, two compressors are provided, but it goes without saying that the compressor can be driven by one compressor. FIG. 3 is a diagram showing one embodiment of a pulse tube refrigerator according to the second invention. In this embodiment, the regenerator 50 includes a first regenerator 51 and a second regenerator 52 that are adjacent to each other in the flow direction of the steady flow. The cross-sectional area of one regenerator 51 is larger than the cross-sectional area of second regenerator 52 by a predetermined magnification.

Therefore, assuming an ideal regenerator and phases of pressure and gas displacement, the regenerators 51 and 52 can obtain a heat transport amount substantially proportional to the cross-sectional area. If there is no steady flow, the regenerator 52 has a larger temperature gradient.
If the design can be such that the difference between the heat inflow by the steady flow and the refrigerating capacity between the regenerators 51 and 52 is balanced, the same effect as the above-described example using two refrigerators can be obtained. However, in practice, the phases of the pressure and the gas displacement are not ideal, so that the efficiency is somewhat reduced.

In the above embodiment, the piston 14
4A, a check valve 22 (check valve) is mounted on the piston 14a. Alternatively, as shown in FIG. 4A, the communication passage of the piston 14a is ), Or as shown in FIG. 4 (b), the piston 14a of the compressor 14 is formed so as to completely separate the high-pressure side and the low-pressure side compression working chambers 14b and 14c having no communication passage, and both compression working chambers are formed. A pipe 61 (circulation means) with an orifice 62 communicating with 14b and 14c may be attached to the case of the compressor 14.

In these cases, a circulating flow (steady flow) often performed by a double-inlet type or the like performs a function replacing the check valve. The steady flow is caused by an acoustic mass flow or the like, and the acoustic mass flow is known as a typical nonlinear acoustic phenomenon. If a certain phenomenon is completed, a unidirectional flow as shown in FIGS. 4 (a) and 4 (b) occurs without the check valve, and the mass thereof is determined by a communication 14e having a throttle function disposed on the piston and a pipe. 61 and orifice 62 will control.

[0030]

As described above, according to the first aspect of the present invention, the regenerator and the pulse tube are provided with a circulating means for generating a small steady flow of the working fluid, and the circulating means is provided at a predetermined position in the flow direction of the steady flow. Precooling refrigeration means for releasing the heat given to the regenerator by the steady flow from the regenerator is provided, so most of the heat released from the gas to the regenerator can be easily precooled at a predetermined position higher than the low temperature part. The same effect as generating the refrigeration capacity by the amount of heat removed at the low temperature end of the regenerator by the steady flow while removing the refrigerant can be obtained, and the cooling efficiency of the refrigerator determined only by the exhaust heat temperature and the endothermic temperature Can greatly contribute to the improvement of

Also, a communication passage is formed in the piston so as to communicate the high pressure side and the low pressure side of the compression working chamber, and a recirculation passage for returning the fluid in the buffer tank to the low pressure side of the compression working chamber; And a check valve that allows the flow from the low pressure side to the high pressure side and prevents the flow in the opposite direction, to realize a durable circulating means with a simple configuration at low cost. Can be.

Further, the pre-cooling / refrigerating means has a heat bridge member connected to the regenerator at the predetermined position, and transfers heat given to the regenerator upstream of the predetermined position by the steady flow. If the regenerator is discharged from the regenerator through the heat bridge member, the same precooling and refrigeration means can be used for a multi-specific refrigerator by simply setting the connection position of the heat bridge member in the flow direction of the steady flow. can do.

Further, according to the second invention, the regenerator comprises a first regenerator and a second regenerator which are adjacent to each other in the flow direction of the steady flow, and are arranged in a direction orthogonal to the flow direction of the steady flow. Since the cross-sectional area of the first regenerator is made larger than the cross-sectional area of the second regenerator, the pre-cooled refrigeration is performed in a state where the heat inflow due to the steady flow and the refrigerating capacity difference due to the difference in the regenerative capacity are balanced. The same effect as the effect of pre-cooling by means can be obtained, and as a result, a pulse tube refrigerator with high refrigerating capacity and compactness can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing one embodiment of a pulse tube refrigerator according to a first invention.

FIG. 2 is a graph showing a change in internal energy of a steady flow and an influence on a pulse tube in one embodiment.

FIG. 3 is a schematic configuration diagram showing one embodiment of a pulse tube refrigerator according to a second invention.

FIG. 4 (a) is a main part configuration diagram showing another embodiment of the pulse tube refrigerator according to the second invention, and FIG. 4 (b) is a second embodiment.
It is a principal part block diagram which shows further another embodiment of the pulse tube refrigerator which concerns on 1st invention.

FIG. 5 is a schematic configuration diagram of a conventional double inlet type pulse tube refrigerator.

[Explanation of symbols]

 Reference Signs List 11 Vacuum insulated container 12 Regenerator 13 Pulse tube 14 Compressor (fluid driving means) 14b High-pressure side working chamber (high-pressure side of compression working chamber) 14c Low-pressure side working chamber (low-pressure side of compression working chamber) 14d, 14e Communication passage ( Circulation means) 15 Thin tube 15a Orifice (throttle passage) 16 Buffer tank 21 Reflux passage (Circulation means) 22 Check valve (Circulation means) 30 Pre-cooling refrigerator (Pre-cooling water stage) 30a Low-temperature section 31 Heat bridge member 50 Regenerator 51 First regenerator 52 Second regenerator 61 Piping (circulation means) 62 Orifice (circulation means)

Claims (4)

(57) [Claims] 1. A regenerator filled with a working fluid, a pulse tube communicating with the regenerator, a piston in a compression working chamber communicating with the regenerator, and a regenerator on the high pressure side of the compression working chamber by the piston. A pulse tube refrigerator comprising: a fluid driving means for compressing, expanding and displacing a working fluid in the buffer tube; and a buffer tank communicating with the pulse tube through a thin tube having a throttle passage. Circulating means for returning the fluid to the low pressure side of the compression working chamber and generating a small steady flow of the working fluid in the regenerator and the pulse tube through the piston is provided, and at a predetermined position in the flow direction of the steady flow. A pallet connected to the regenerator and provided with a pre-cooling refrigeration means for releasing the heat given to the regenerator by the steady flow from the regenerator at the predetermined position. Tube refrigerator. 2. A communication passage formed in said piston so as to communicate between a high pressure side and a low pressure side of said compression working chamber, and a fluid in said buffer tank is returned to a low pressure side of said compression working chamber. The recirculation passage for allowing a flow from the low-pressure side to the high-pressure side provided in the communication passage, and a check valve for preventing a flow in the opposite direction to the non-return side, and having a check valve. Pulse tube refrigerator. 3. The pre-cooling refrigeration means has a heat bridge member connected to the regenerator at the predetermined position, and heat supplied to the regenerator upstream from the predetermined position by the steady flow. The pulse tube refrigerator according to claim 1, wherein the regenerator is discharged from the regenerator through the heat bridge member. 4. A regenerator filled with a working fluid, a pulse tube communicating with the regenerator, and a piston in a compression working chamber communicating with the regenerator, the regenerator on the high pressure side of the compression working chamber by the piston. A pulse tube refrigerator comprising: a fluid driving means for compressing, expanding and displacing a working fluid in the buffer tube; and a buffer tank communicating with the pulse tube through a thin tube having a throttle passage. Circulating means for returning a fluid to the low-pressure side of the compression working chamber and generating a small steady flow of the working fluid in the regenerator and the pulse tube through the piston is provided. A first regenerator and a second regenerator adjacent to each other in a direction, wherein the cross-sectional area of the first regenerator is larger than the cross-sectional area of the second regenerator in a direction orthogonal to the flow direction of the steady flow. Pulse tube refrigerator, characterized in that had Unishi.