JPH09296964A - Pulse pipe refrigerator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to arrange a pulse tube by deforming the pulse tube according to a shape to be cooled and a vacant space of a device to be installed in. SOLUTION: First end portions of a pulse tube 3 and a cold storage device 1 having a shape corresponding to a circular curve are connected to each other through a cold stage 2 so that the pulse tube 3 and the cold storage device 1 are arranged along a circumference of a circle. When supply of operating gas from a compressor 10 into a cold storage device 1 and recovery of the gas from the cold storage device 1 to the compressor 10 are repeated, cold is generated at a portion of the cold stage 2 and heat is generated at another end portion of the pulse tube 3. The cold generated at the cold stage 2 is transmitted to a cold panel 8 via a cold plate 7 to cool the cold plate 8.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a pulse tube refrigerator.

[0002]

2. Description of the Related Art First, before explaining the operation principle of a pulse tube refrigerator, a Stirling refrigerator which produces cold by utilizing a phase difference between a pressure change and a volume change of a working gas like a pulse tube refrigerator. The principle of will be briefly described.

FIG. 5A is a schematic view showing a cross section of a general Stirling refrigerator. A displacer 53 is arranged in the cylinder 52. The displacer 53 is supported in the cylinder 52 by a spring or the like (not shown) so as to be capable of reciprocating in the left-right direction in the figure. A compression space 57 is formed on the left side of the displacer 53 in the figure, and an expansion space 58 is formed on the right side.

[0004] The compression space 57 is connected to the compressor 50 via gas passages 55 and 54. The expansion space 58 is connected to the regenerator 51 via the gas passage 56, and is connected to the regenerator 51.
Is connected to the compressor 50 via the gas passage 54.

[0005] A compressed gas is periodically supplied or recovered from a compressor 50 through a gas passage 54. At this time, the displacer 53 reciprocates with a certain time delay with respect to the change in the pressure in the cylinder 52. For this reason, the pressure and volume of the working gas in the compression space 57 and the expansion space 58 change with a certain phase difference. This phase difference causes heat generation or heat absorption.

In the case of FIG. 5 (A), heat is generated in the compression space 57 and cold is generated in the expansion space 58. The refrigerating capacity of the Stirling refrigerator is proportional to the area of the PV diagram representing the change in gas volume and pressure in the expansion space. P-
The area of the V-diagram is a function of the phase difference between the gas pressure change and the volume change, and the refrigeration capacity can be improved by appropriately controlling the phase difference.

FIG. 5B is a schematic view showing a cross section of a basic pulse tube refrigerator. One end (open end) of the pulse tube 60 is connected to the regenerator 51 via the gas passage 62. The regenerator 51 is connected to the compressor 50 via a gas passage 61. The other end of the pulse tube 60 is a completely closed end.

[0008] The compressed gas supplied from the compressor 50 passes through the gas passage 61, the regenerator 51, and the gas passage 62 and enters the pulse tube 60 isothermally. The low-pressure gas initially exists in the pulse tube 60, but the gas in the pulse tube 60 is also compressed by the gas introduced by being compressed. Due to the unidirectional compression effect of this gas, a temperature gradient is generated in the pulse tube 60. The heat of compression is transmitted to the wall of the pulse tube 60. Since this temperature gradient is positive with respect to the direction of the compressed flow, much of the heat of compression is generated at the closed end of the pulse tube 60.

When the gas is collected by the compressor 50, the gas in the pulse tube 60 expands. The direction of gas flow is
In contrast to the compression, a temperature gradient is generated in the pulse tube 60 that is negative with respect to the direction of the gas flow. But,
Since the heat is removed before the start of expansion, the average temperature of the entire working gas is lower than at the time of compression, so that the gas receives heat from the wall of the pulse tube 60. The open end of the pulse tube 60 becomes the lowest temperature portion due to this temperature gradient, and cold occurs in this portion.

In order to improve the cooling efficiency, it is necessary to bring the phase difference between the fluctuating pressure and the volumetric flow rate at the open end close to 90 degrees. The phase difference at the open end is smaller than the phase difference at the closed end due to the fact that the working gas is a compressed gas and a temperature gradient exists. Therefore, in order to make the phase difference at the open end 90 degrees, the phase difference at the closed end must be larger than 90 degrees.

However, in the pulse tube refrigerator, since there is no portion corresponding to the displacer in the Stirling refrigerator, it is difficult to control the phase difference between the fluctuation pressure of the working gas and the volume flow. Therefore, it is difficult to obtain a sufficient refrigeration capacity.

In order to solve the above problem, an improvement as shown in FIG. 5 (C) has been proposed. FIG. 5C is a schematic view showing a cross section of the orifice pulse tube refrigerator. The orifice pulse tube refrigerator has a flow path impedance 6 at the closed end of the pulse tube 60 of the basic type pulse tube refrigerator shown in FIG. 5 (B).
3, an intermediate pressure chamber 64 is provided. The flow path impedance 63 and the intermediate pressure chamber 64 perform the same function as the series circuit of the impedance of the electric circuit and the capacitor, respectively, and generate a phase difference between the fluctuating pressure of the working gas and the volume flow rate.

[0013]

The pulse tube refrigerator has a simple structure with no moving parts in the low temperature part. In the conventional Stirling refrigerator and Gifford McMahon refrigerator, the displacer reciprocates in the cylinder, so that the shape thereof is limited. That is, the cylinders of these refrigerators have a right cylindrical shape so that the displacer can easily reciprocate.

Since the conventional pulse tube refrigerator was intended to replace a Stirling refrigerator or the like, the shape of the pulse tube was a straight cylindrical shape similar to a cylinder. An object of the present invention is to provide a pulse tube refrigerator having a novel shape.

[0015]

According to one aspect of the present invention, a pulse tube having an internal cavity and having an axial direction arranged along a curved line or a polygonal line is connected to one end of the pulse tube. There is provided a pulse tube refrigerator having a regenerator, wherein the working gas is introduced into the pulse tube through the regenerator, the working gas is recovered from the pulse tube, and the regenerator performs heat exchange with the working gas. To be done.

Since the pulse tube refrigerator does not have a moving part such as a displacer, the pulse tube has a high degree of freedom regarding the shape of the pulse tube, and the pulse tube can be arranged along a curved line or a broken line. By modifying and disposing the pulse tube or the regenerator according to the shape of the object to be cooled and the shape of the empty space of the built-in device, it is possible to reduce the size and space of the device.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Referring to FIGS. 1 (A) and 1 (B),
The first embodiment of the present invention will be described by taking the case where the pulse tube refrigerator is applied to a cold trap of a vacuum pump as an example.

FIG. 1A is a plan sectional view of a cold trap using the pulse tube refrigerator according to the first embodiment, FIG.
FIG. 1B shows a cross-sectional view taken along alternate long and short dash line B1-B1 in FIG.

One end of each of the pulse tube 3 and the regenerator 1 having a shape along a semicircular curve is connected to the cold stage 2.
The pulse tube 3 and the regenerator 1 are connected to each other via
It is arranged along one circumference.

The pulse tube 3 is composed of, for example, a hollow stainless steel tube, and the regenerator 1 is composed of a hollow stainless steel tube filled with a regenerator material. As a cold storage material,
For example, a disc-shaped stainless mesh is used. The cold stage 2 is composed of, for example, a box made of oxygen-free copper,
A working gas is circulated between the regenerator 1 and the pulse tube 3.
The cold stage 2 has fins or a copper mesh inside and can effectively exchange heat with the working gas flowing inside.

A gas passage 6 is attached to the other end of the regenerator 1, and the tip of the gas passage 6 is connected to the compressor 10. The compressor 10 periodically repeats supply and recovery of compressed gas. The compressed working gas is supplied into the regenerator 1 via the gas flow path 6 in a half cycle in which the compressed gas is supplied from the compressor 10. In the other half cycle, the working gas in the regenerator 1 is recovered by the compressor 10.

An intermediate pressure chamber 4 is connected to the other end of the pulse tube 3 via a thin tube 5. The working gas is transported through the thin tube 5 between the pulse tube 3 and the intermediate pressure chamber 4. Thin tube 5
Acts as a flow path impedance for the flow of the working gas.

A cold plate 7 made of copper is arranged inside the circumference defined by the pulse tube 3 and the regenerator 1. The cold plate 7 is attached to the cold stage 2 and is thermally coupled thereto. Cold plate 7
3 cold panels 8 having the shape of a truncated cone
Is attached. The cold panel 8 is arranged concentrically with the circumference defined by the pulse tube 3 and the regenerator 1. A cylindrical heat insulating plate 9 is arranged between the cold panel 8 and the pulse tube 3 and the regenerator 1.

When the supply of the working gas from the compressor 10 into the regenerator 1 and the recovery of the working gas from the regenerator 1 to the compressor 10 are repeated, cold is generated in the cold stage 2 and the pulse tube 3 is used. Generates heat at the other end of. The cold generated in the cold stage 2 is transmitted to the cold panel 8 through the cold plate 7, and the cold plate 8 is cooled.

The thin tube 5 and the intermediate pressure chamber 4 serve to enhance the cooling efficiency of the pulse tube refrigerator. The reason why the cooling efficiency is improved by disposing the thin tube 5 and the intermediate pressure chamber 4 is considered as follows.

The working fluid fluid system is simulated by an electric circuit network,
When the fluctuating pressure is made to correspond to the alternating voltage, the thin tube connected between the pulse tube and the intermediate pressure chamber acts as an inductance. Also, the intermediate pressure chamber works as a capacitance. Therefore, by setting the magnitude of this inductance to an appropriate value, the phase difference between the fluctuating pressure and the volumetric flow rate at the high temperature end of the pulse tube can be made 90 degrees or more.

Since the working gas in the pulse tube is a compressible gas and there is a temperature difference in the tube, the phase difference at the low temperature end of the pulse tube is smaller than the phase difference at the high temperature end. Since the phase difference at the high temperature end can be set to 90 degrees or more, the phase difference at the low temperature end can be close to 90 degrees. As the phase difference approaches 90 degrees,
It is considered that the cooling efficiency is improved.

The heat insulating plate 9 blocks radiant heat from the high temperature end of the pulse tube 3 and enhances the cooling efficiency of the cold panel 8.
As shown in FIG. 1 (A), by arranging the pulse tube 3 and the regenerator 1 so as to surround the cold panel 8, it is possible to achieve a compact device configuration with few protruding portions. Further, since the pulse tube refrigerator does not generate vibration due to the reciprocating motion of the displacer, it is possible to suppress vibration of the cold panel and prevent falling of adsorbed substances due to vibration of the cold panel.

In FIGS. 1A and 1B, the case where the circumference of the cold panel 8 is surrounded by the pulse tube 3 and the regenerator 1 in a circumferential shape has been described. However, the pulse tube or the regenerator is an object to be cooled. It may be deformed into various shapes depending on the shape. For example, the pulse tube or the regenerator may be arranged along a part of the outer circumference of the ellipse or polygon, or may be arranged along the polygonal line. When the object to be cooled is used by incorporating it into the device, the pulse tube or the regenerator may be deformed according to the shape of the empty space of the device and placed in the empty space.

FIG. 1C shows a sectional view of a cold trap according to a modification of the first embodiment. A cold trap 20A is configured to include the regenerator 1A, the pulse tube 3A, the cold plate 7A, and the cold panel 8A. The cold trap 20A is shown in FIGS. 1 (A) and 1 (B).
It has the same configuration as the cold trap of. Cold traps 20B to 2 having the same configuration as the cold trap 20A
OEs are arranged so as to share the central axis of the circumference defined by the pulse tube and the regenerator of each pulse tube refrigerator.

By thus arranging a plurality of cold traps along the gas flow of the gas to be exhausted, the trap efficiency can be increased. FIG. 2 shows a perspective view of a cold trap according to another modification of the first embodiment. The pulse tube and the regenerator of the pulse tube refrigerator shown in FIGS. 1A to 1C have a circular cross section orthogonal to the direction of the working gas flow, and are arranged along an arc. On the other hand, in the pulse tube refrigerator shown in FIG. 2, the regenerator 1, the cold stage 2, the pulse tube 3, and the intermediate pressure chamber 4 of FIG. 1A are defined by the pulse tube 3 and the regenerator 1. The shape is extended in the central axis direction of the circumference. That is, the regenerator 1, the cold stage 2, and the pulse tube 3 are arranged along the side surface of the cylinder. Other configurations are shown in FIG.
This is the same as the cold trap shown in (A) and (B). The components of the cold trap shown in FIG.
The same reference numerals as those of the corresponding components of the cold trap shown in FIG.

By arranging the regenerator 1, the cold stage 2, and the pulse tube 3 along the side surface of the cylinder, it is possible to arrange the cold trap in a relatively long range along the gas flow to be exhausted.

Next, the case where the pulse tube refrigerator is applied to a magnetic resonance imaging apparatus (MRI) will be described as a second example.
An example will be described. FIG. 3 is a partially cutaway perspective view of an MRI using the pulse tube refrigerator according to the second embodiment. The cylindrical superconducting coil 21 is arranged in a liquid helium tank 22 coaxial with the cylindrical superconducting coil 21, and the periphery of the superconducting coil 21 is filled with liquid helium 29.

The outer periphery of the liquid helium tank 22 is connected to the regenerator 2
3, surrounded by a cold stage 24 and a pulse tube 25. The cold stage 24 is arranged above the liquid helium tank 22 in parallel with the central axis thereof. Regenerator 2
3, the cold stage 24 and the pulse tube 25 have the same configuration as the pulse tube refrigerator shown in FIG. A gas passage 27 for supplying a working gas is attached to the high temperature end of the regenerator 23, and an intermediate pressure chamber 26 is attached to the high temperature end of the pulse tube 25.

Below the cold stage 24, the cooling plate 2
8 is attached, and the cooling plate 28 is inserted in the liquid helium tank 22. The cooling plate 28 cools the evaporated helium gas to liquefy it again and returns it to the tank. In this way, effective utilization of liquid helium is achieved.

By arranging the regenerator 23 and the pulse tube 25 so as to surround the outer periphery of the liquid helium tank 22, the projecting portion around the liquid helium tank 22 can be reduced, and a compact device structure can be obtained. Further, since the pulse tube refrigerator does not have a movable part in the cooling part, it has an advantage that there is little vibration and maintenance and the like are easy.

FIG. 4 shows an MR according to a modification of the second embodiment.
The partially broken perspective view of I is shown. The MRI shown in FIG. 4 does not have a liquid helium bath, and the superconducting coil 21 has a heat conducting member 28.
It is connected to the cold stage 24 via A. The superconducting coil 21 is directly cooled by the cold generated in the cold stage 24.

Also in this case, as in the case of FIG. 3, it is possible to reduce the number of protrusions and to make the apparatus compact.
If the pulse tube refrigerator does not have sufficient refrigerating capacity,
The working gas may be precooled by a Gifford McMahon refrigerator or the like.

Although FIGS. 2 to 4 show the case where the pulse tube and the regenerator are arranged along the side surface of the cylinder, other shapes may be used depending on the shape of the object to be cooled. For example,
You may arrange | position along the side surface of an elliptic cylinder, and the side surface of a polygonal cylinder.

The present invention has been described in connection with the preferred embodiments.
The present invention is not limited to these. For example, it will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.

[0041]

As described above, according to the present invention,
By changing the shape of the pulse tube of the pulse tube refrigerator, the regenerator, or the like according to the shape of the object to be cooled or the empty space of the apparatus, a compact apparatus configuration can be achieved.

[Brief description of drawings]

FIG. 1 is a sectional view of a cold trap using a pulse tube refrigerator according to a first embodiment of the present invention and a modification thereof.

FIG. 2 is a perspective view of a cold trap using a pulse tube refrigerator according to another modification of the first embodiment of the present invention.

FIG. 3 is a partially cutaway perspective view of an MRI using a pulse tube refrigerator according to a second embodiment of the present invention.

FIG. 4 is a partially cutaway perspective view of an MRI using a pulse tube refrigerator according to a modification of the second embodiment of the present invention.

FIG. 5 is a schematic sectional view of a Stirling refrigerator and a pulse tube refrigerator according to a conventional example.

[Explanation of symbols]

 1, 1A Regenerator 2 Cold stage 3, 3A Pulse tube 4 Intermediate pressure chamber 5 Capillary tube 6 Gas flow path 7, 7A Cold plate 8, 8A Cold panel 9 Insulation plate 10 Compressor 20A-20E Cold trap 21 Superconducting coil 22 Liquid Helium tank 23 Regenerator 24 Cold stage 25 Pulse tube 26 Intermediate pressure chamber 27 Gas flow path 28 Cooling plate 28A Heat conduction member

Claims (5)

[Claims] 1. A pulse tube having an internal cavity and having an axial direction arranged along a curve or a polygonal line, and a regenerator connected to one end of the pulse tube, wherein the pulse is passed through the regenerator. A pulse tube refrigerator having the regenerator in which a working gas is introduced into the tube and the working gas is recovered from the pulse tube and exchanges heat with the working gas. 2. The pressure chamber according to claim 1, further comprising an intermediate pressure chamber connected to the other end of the pulse tube and defining another internal cavity communicating with the internal cavity of the pulse tube via a flow path impedance. Pulse tube refrigerator. 3. A cooling target member thermally coupled to an interconnection portion between the pulse tube and the regenerator, wherein the pulse tube and the regenerator surround the periphery of the cooling target member. 3. The pulse tube refrigerator according to claim 1, wherein the pulse tube refrigerator is arranged as described above. 4. The pulse tube defines an internal cavity along a portion of the circumference of a circle, ellipse, or polygon.
4. The pulse tube refrigerator according to any one of 3 to 3. 5. The pulse tube refrigerator according to claim 1, wherein the pulse tube defines an internal cavity along a part of a side surface of a cylinder, an elliptic cylinder, or a polygonal cylinder.