JP3584762B2 - Method of manufacturing cold head vacuum vessel for refrigerator - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a cold head for use in cold accumulation refrigerator system, such as a Stirling refrigerator, a method for manufacturing a vacuum container provided in particular for sealing the cylinder at the cold head.
[0002]
[Prior art]
A Stirling refrigerator already filed by the present applicant (Japanese Patent Application No. 10-236111) will be described with reference to FIG. This Stirling refrigerator includes a gas compressor 20, a cold head 50, and a capillary tube 45 connecting the two.
[0003]
The gas compressor 20 has a plane-symmetric structure with the partition wall 22 interposed therebetween. Cylinders 23 are arranged on both sides of the partition 22. The cylinder 23 has a columnar inner peripheral surface, and is arranged such that the central axis thereof is perpendicular to the partition wall 22. A piston 24 is arranged in the internal cavity of the cylinder 23. The piston 24 has an outer peripheral surface that matches the inner peripheral surface of the cylinder 23. The compression chamber 25 is defined by the piston 24, the cylinder 23, and the partition wall 22. The compression chamber 25 communicates with a capillary tube 45 via a gas passage 26 formed in the partition 22.
[0004]
A piston rod 28 is connected to an end of the piston 24 opposite to the compression chamber 25. The piston rod 28 extends along an extension of the central axis of the cylinder 23. The piston rod 28 is supported by the thrust bearings 27 and 29 so as to be movable in the axial direction and prohibited from moving in the direction perpendicular to the axis. The thrust bearings 27 and 29 are fixed to the cylinder 23 via bearing support members 33 and 34, respectively.
[0005]
The piston 24 is held by the thrust bearings 27 and 29 so that a minute gap is formed between the inner peripheral surface of the cylinder 23 and the outer peripheral surface of the piston 24. If this gap is about 10 μm or less, it acts as a clearance seal.
[0006]
An annular gap 36 is formed in the cylinder 23 from the end face opposite to the partition 22 to the partition 22 so as to surround the internal space. An annular permanent magnet 37 is attached to the inner wall forming the outer peripheral surface of the gap 36. The cylinder 23 also serves as a yoke, and a magnetic circuit is formed by the permanent magnet 37, the cylinder 23, and the gap 36.
[0007]
An electromagnetic coil 40 is inserted into the gap 36 so as to link with the magnetic circuit. The electromagnetic coil 40 is fixed to the piston rod 28 via a coil support member 41.
[0008]
A current is supplied to the electromagnetic coil 40 via current leads 43 and 44. The current leads 43 and 44 include a coil spring for connecting between the bearing support member 34 fixed to the cylinder 23 and the coil support member 41 fixed to the piston rod 28. The coil spring is elastically deformed in the axial direction of the piston rod 28. As the coil spring constituting the current leads 43 and 44, a coil spring whose reciprocating motion of a movable part such as the piston 24 resonates with the operating frequency is employed.
[0009]
The space in which the piston 24, the thrust bearings 27, 29, the current leads 43, 44 and the like are arranged is sealed by the outer case 30.
[0010]
The cold head 50 includes a cylinder 51, a displacer (piston) 52, a coil spring 53, and an outer frame 57. The cylinder 51 has a columnar surface, for example, a cylindrical inner peripheral surface. One end of the cylinder 51 is closed, and the other end is closed by an outer frame 57. A displacer 52 is inserted into the internal cavity of the cylinder 51. A seal member 54 is disposed between the outer peripheral surface of the displacer 52 and the inner peripheral surface of the cylinder 51.
[0011]
An expansion space 55 is defined between the one end of the cylinder 51 and the displacer 52 through the low-temperature orifice 61, and an invalid space 56 is defined between the displacer 52 and the outer frame 57 through a room temperature (normal temperature) orifice 62. . In the displacer 52, a gas flow path 58 that connects the expansion space 55 and the invalid space 56 is provided. The gas flow path 58 is filled with a cold storage material 59 such as a copper wire net or a lead ball.
[0012]
The displacer 52 is elastically supported in the axial direction by a coil spring 53 disposed in the dead space 56. The ineffective space 56 communicates with the compression chamber 25 of the gas compressor 20 via the capillary tube 45 and the gas passage 26.
[0013]
The operating principle of such a Stirling refrigerator is described in detail in the above-mentioned application specification, and will be briefly described below.
[0014]
When an alternating current having a predetermined frequency is applied to the electromagnetic coil 40, the piston 24 reciprocates against the elastic force of the current leads 43 and 44. The phase of the alternating current is controlled so that the two pistons 24 on both sides of the partition wall 22 move in opposite directions. When the two pistons 24 move toward each other, the pressure inside the compression chamber 25 becomes high, and when they move away from each other, the pressure inside the compression chamber 25 becomes low. By repeating the reciprocating movement of the piston 24, the gas pressure can be changed periodically.
[0015]
By repeatedly supplying and exhausting the refrigerant gas to and from the cold head 50, a reverse Stirling cycle can be executed, and cold can be generated in the expansion space 55.
[0016]
The thrust bearings 27 and 29 support the piston 24 in the cylinder 23 with a predetermined clearance. For this reason, it is possible to prevent the abrasion of the piston 24 against the inner peripheral surface of the cylinder 23 due to one-sided contact, thereby improving reliability. In addition, a larger stroke can be secured as compared with the case where the piston 24 is supported by a leaf spring. Further, the thrust bearings 27 and 29 do not cause fatigue failure unlike the leaf spring. By increasing the stroke of the piston 24, the performance of the Stirling refrigerator can be improved.
[0017]
It is preferable to use vacuum grease for the thrust bearings 27 and 29. The use of vacuum grease can prevent contamination of the refrigerant gas. Further, as the thrust bearings 27 and 29, for example, a linear bearing such as a linear ball bearing LB type manufactured by NSK Corporation can be used. Further, a slide bearing may be used instead of the linear bearing. In the above example, the case where the radial position of the displacer 52 is fixed by the seal member 54 is shown. However, the displacer 52 may be supported by a thrust bearing similarly to the piston 24 of the gas compressor 20.
[0018]
Meanwhile, a refrigerator in which the cylinder 51 shown in FIG. 4 is further housed in a vacuum container is also known (for example, Japanese Patent Application Laid-Open No. 9-119728). This refrigerator has a flange for attaching a vacuum vessel to a portion corresponding to the outer frame 57 in FIG. 4, and the vacuum vessel is attached to this flange.
[0019]
An opening is provided at the tip of the vacuum container, and an optical window is attached so as to close this opening. Hereinafter, the mounting structure of the optical window will be described with reference to FIGS.
[0020]
In FIG. 5, a cold stage 72 is attached to the tip of a cylinder 71, and an infrared sensor 73 is mounted on the cold stage 72 via an insulating material. The cold head is used to cool the infrared sensor 73. The structure inside the cylinder 71 is the same as that described in FIG. 4, and the relationship between the cylinder 71 and the outer frame 74 is the same as that in FIG. A vacuum vessel 75 is attached to the flange of the outer frame 74 by bolting or the like. The vacuum vessel 75 is for keeping the periphery of the cylinder 71 airtight, and has an opening 75a at its tip. An optical window 76 is attached so as to close the opening 75a. The optical window 76 is for transmitting an electromagnetic wave of a specific wavelength, and is made of, for example, Ge (germanium), and is adhered to the periphery of the opening 75a with a polymer-based adhesive.
[0021]
6, similarly to FIG. 5, a cold stage 72 is attached to the tip of a cylinder 71, and an infrared sensor 73 is mounted on the cold stage 72 via an insulating material. A vacuum container 80 for keeping the periphery of the cylinder 71 airtight is attached to the flange portion of the outer frame 74 by bolting or the like. A circular plate 81 is integrated with the tip of the vacuum vessel 80, and an opening 81a is provided at the center of the plate. A concave portion 81b for receiving the optical window 76 is formed on the front side of the plate 81. The recess 81b is further provided with an annular groove 81c, and an O-ring 82 is accommodated in the groove 81c. The optical window 76 is fixedly held in the concave portion 81b by a holding plate 83 abutting on the front side of the plate 81. The holding plate 83 has an opening 83a in a region corresponding to the optical window 76, and is attached to the plate 81 with bolts or the like.
[0022]
[Problems to be solved by the invention]
However, the above-described optical window mounting structure has the following problems.
[0023]
In the example of FIG. 5, there is a problem that impurities are generated from the polymer-based adhesive at the time of vacuum sealing and the inside of the vacuum container 75 is contaminated.
[0024]
On the other hand, in the example of FIG. 6, there is a problem that the gas permeates through the O-ring 82 and the degree of vacuum is deteriorated.
[0025]
Therefore, an object of the present invention is to provide a method of manufacturing a vacuum container of a cold head for a refrigerator, which can improve the mounting structure of an optical window mounted on the vacuum container and improve airtightness.
[0027]
[Means for Solving the Problems]
According to the present invention, a cylinder of which one end is closed, is attached to the other end of the cylinder, the cylinder holder to define a closed space together with the cylinder, a display sub disposed within said cylinder, said displacer , the cylinder holder so as to include the support means the outer peripheral surface of the displacer is disposed oppositely across the inner circumferential surface with a small gap between the cylinder and is movable in the axial direction of the cylinder, the pre-Symbol cylinder Manufacturing a vacuum vessel in a cold head for a refrigerator having an attached vacuum vessel, the vacuum vessel having an opening at an end thereof, and having an optical window attached so as to close the opening. Forming a welding material layer of indium on the periphery of the opening of the vacuum vessel by ion bonding, and forming the opening in the optical window. In the region corresponding to the peripheral portion of the welding material layer is formed by ion bonding the same indium as the welding material layer, and these are put in a vacuum chamber, and the welding material layer on the vacuum vessel side and the welding material on the optical window are placed. A method for manufacturing a vacuum vessel is provided, wherein the optical window is welded to the vacuum vessel by heating the inside of the vacuum vessel in a state in which the layers are combined, and the inside of the vacuum vessel is evacuated .
[0029]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described with reference to FIG. FIG. 1 shows only the outside of the cylinder 11 and the cylinder holder 12 (corresponding to the outer frame 57 of FIG. 4), and the internal structure of the cold head is the same as that shown in FIG. A cold stage 18 is attached to the tip of the cylinder 11, and an infrared sensor 14 is mounted on the cold stage 18 via an insulating material 17.
[0030]
The vacuum vessel 13 is connected to the flange of the cylinder holder 12 by welding. The cylinder holder 12 is made of a Ni alloy, an Fe—Ni—Co alloy, or the like, and the vacuum vessel 13 is made of a material that can be EBW, TIG welded, or laser welded to the cylinder holder 12, for example, SUS. Reference numeral 13-2 denotes a welding lip for preventing thermal distortion during welding from spreading to the periphery.
[0031]
The vacuum vessel 13 is for maintaining a vacuum around the cylinder 11 and is described in the aforementioned Japanese Patent Application Laid-Open No. Hei 9-119728. An opening 13a is provided at the tip of the cylinder holder 13, and an optical window 19 made of Ge is attached by welding to be described later so as to close the opening 13a. Through the optical window 19, infrared rays are detected by the infrared sensor 14. The signal detected by the infrared sensor 14 is guided to the hermetic terminal 16 by the lead wire 15 and led out of the vacuum vessel 13.
[0032]
The method of welding the optical window 19 will be described with reference to FIGS. In FIG. 2A, an annular welding material layer 10-1 is formed by ion bonding on the periphery of the opening 13a of the vacuum vessel 13. Indium or the like is used as the material of the welding material layer 10-1. On the other hand, in FIG. 2B, the welding material layer 10-2 made of the same material as the welding material layer 10-1 is also ionized in the peripheral portion of the optical window 19, that is, in the region corresponding to the peripheral portion of the opening 13a in the vacuum vessel 13. It is formed by bonding. For example, a sputtering method is employed for the ion bonding.
[0033]
Then, as shown in FIG. 3, the optical window 19 is welded to the vacuum vessel 13 by heating while the welding material layer 10-1 on the vacuum vessel 13 side and the welding material layer 10-2 of the optical window 19 are combined. I do. The heating is performed in a vacuum atmosphere, and the heating temperature may be, for example, about 160 ° C. In this way, as shown in FIG. 1, a structure is obtained in which the optical window 19 is welded to the concave portion of the vacuum vessel 13 at the periphery. And according to such an airtight welding structure, the airtightness in the vacuum vessel 13 can be improved.
[0034]
Note that the present invention is not limited to the Stirling refrigerator described with reference to FIG. 4, but can be applied to other gas compressors, for example, a pulse tube refrigerator (for example, disclosed in Japanese Patent No. 2780934) and a GM refrigerator.
[0035]
【The invention's effect】
As described above, according to the present invention, the airtightness in the vacuum vessel can be improved by improving the mounting structure of the optical window provided in the vacuum vessel containing the cylinder in the cold head. Further, since the O-ring is not used, there is an advantage that the outer diameter of the vacuum vessel can be reduced and the size can be reduced.
[Brief description of the drawings]
FIG. 1 is a sectional view showing a structure of a vacuum vessel in a cold head for a refrigerator according to an embodiment of the present invention.
FIG. 2 is a view (FIG. 2A) of the vacuum container viewed from the direction of arrow A in FIG. 1 and FIG. It is the figure (FIG.2 (b)) seen from the direction opposite to the direction.
FIG. 3 is a cross-sectional view of a part of the vacuum vessel and the optical window as viewed from a side, for describing a mounting structure of an optical window in the vacuum vessel shown in FIG. 1;
FIG. 4 is a sectional view showing an example of a Stirling refrigerator to which the present invention is applied.
FIG. 5 is a partial cross-sectional view illustrating an example of a mounting structure of an optical window in a conventional vacuum vessel.
FIG. 6 is a partial cross-sectional view for explaining another example of the mounting structure of the optical window in the conventional vacuum vessel.
[Explanation of symbols]
10-1 10-2 Welding material layer 11, 51 Cylinder 12 Cylinder holder 13 Vacuum container 14, 73 Infrared sensor 15 Lead wire 16 Airtight terminal 17 Insulation material 18, 72 Cold stage 19, 76 Optical window 24 Piston 25 Compression chamber 26 Gas Flow paths 27, 29 Thrust bearing 28 Piston rod 30 Outer case 33, 34 Bearing support member 36 Gap 37 Permanent magnet 40 Electromagnetic coil 41 Coil support member 43, 44 Current lead 45 Capillary tube 50 Cold head 52 Displacer 53 Coil spring 54 Seal member 55 Expansion space 56 Invalid space 57 Outer frame 58 Gas flow path 59 Cold storage material

Claims (1)

A cylinder with one end closed,
A cylinder holder attached to the other end of the cylinder and defining a closed space with the cylinder;
A display support disposed within said cylinder,
A support means for supporting the displacer such that the outer peripheral surface of the displacer faces the inner peripheral surface of the cylinder with a small gap therebetween, and movably supports the cylinder in the axial direction ;
Before SL and a vacuum container mounted on said cylinder holder so as to include a cylinder,
The vacuum container has an opening at its tip, and a method for manufacturing a vacuum container in a cold head for a refrigerator having an optical window attached so as to close the opening,
Forming a welding material layer of indium on the periphery of the opening of the vacuum vessel by ion bonding,
A region corresponding to the periphery of the opening in the optical window is also formed by ion bonding with a welding material layer of indium, which is the same as the welding material layer,
Taking these into the vacuum chamber, and welding the optical window to the vacuum vessel by heating in vacuum chamber in a state in which a combination of the welding material layer of the vacuum container side said optical window and a welding material layer A method for manufacturing a vacuum container, wherein the inside of the vacuum container is evacuated .

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