JPH06300376A - Cryostat with precooling part of pulse-tube type refrigerator - Google Patents

Abstract

PURPOSE:To reduce a heat flowing into a cold head by thermal conduction and thermal radiation from a virtually ordinary temperature and thereby to attain a high efficiency in a cryostat of a pulse tube type refrigerating machine constructed of a pulse tube, the cold head, a cold accumulator, etc. CONSTITUTION:A pulse tube 107 is disposed at the axial center of a cold accumulator 105 joined to a cold head 106, while a directional part 119 giving directionality to a flow of a working fluid is provided in a part from a low- temperature part to an ordinary-temperature part in the pulse tube 107, and a precooling part 117 provided in an outer tube of the cold accumulator in the circumferential direction of the directional part 119 is cooled from inside by the working fluid.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The invention of the present application relates to a pulse tube, a cold head, a regenerator of a pulse tube type refrigerating machine of an orifice type with an expander, which has a pulse tube as one of its constituent elements, and has an expander at almost room temperature. It is related to a cryostat composed of etc.

[0002]

2. Description of the Related Art FIG. 8 shows a pulse tube refrigerator disclosed by the present inventors at the 7th International Cryocooler Conference (held in Santa Fe, New Mexico, USA, November 17-19, 1992). It shows an outline. This pulse tube refrigerator has a compression space 1 for fluid and an expansion space 2 at room temperature.
And a pipe 3, a radiator 4 that radiates and cools the compression heat of the fluid, a regenerator 5, and a cold head 6 that takes out cold heat.
The pulse tube 7 and the pipe 8 are connected to each other.

The expansion piston 10, which is reciprocated by a motor (not shown) through a crankshaft 11, has a compression piston 9 depending on a required freezing temperature, element characteristics, and operating conditions.
Crank pin 13 having a crank angle advanced from the crank pin 12 of several degrees to several tens of degrees (also referred to as a phase angle difference, the crank angle is zero when the compression piston 9 and the expansion piston 10 are respectively at the top dead center). It is connected to and reciprocated. 14 is a piston ring. Reference numeral 15 denotes a crank angle setting mechanism, which can set an arbitrary crank angle.

A compression space 1 and an expansion space 2 at room temperature
The volume change of not only the crankshaft but also the linear motor (not shown) can directly obtain the same result by directly reciprocating the compression piston 9 and the expansion piston 10 while maintaining a certain crank angle. Is.

As announced at the above-mentioned conference, the fluid sealed in the compression space 1 at about 10 to 20 atm is compressed when the compression piston 9 moves toward the top dead center, and the expansion piston 1
For example, when 0 is advanced by 25 degrees from the compression piston 9, it goes to the bottom dead center, so that the heat is radiated by the radiator 4 from the pipe 3 and the temperature becomes almost room temperature and enters the regenerator 5, which is successively cooled to 45K.
In a certain degree, it is accelerated by the pulse tube 7 through the cold head 6, enters the expansion space 2 from the pipe 8 and adiabatically expands to perform the work of rotating the crankshaft 11. At this time, the temperature of the fluid near the cold head 6 remaining in the regenerator 5 and the pulse tube 7 drops further than 45 K due to adiabatic expansion. For example, it becomes 36K. When the expansion piston 10 moves toward the top dead center, the working fluid in the expansion space 2 is pushed out, and the pipe 8, the pulse pipe 7, and the cold head 6 cool the object to be cooled (electric sensor, etc.) (not shown), and the regenerator 5 It is warmed up and heated to near room temperature in the radiator 4, and returns to the compression space 1 through the pipe 3 to complete one cycle. By continuing this, 80K in a few minutes,
Eventually, a freezing temperature of about 24K can be obtained depending on the performance of the regenerator 5.

[0006]

The problem of further lowering the temperature of the cold head 6 in the pulse tube type refrigerator of FIG. 8 is that heat conduction from approximately room temperature (the outer cylinder of the regenerator, the regenerator material, and When the object to be cooled is an electrical sensor, heat from multiple sensor leads (heat conduction) and heat from heat radiation directly flow into the cold head to raise the freezing temperature and reduce the performance of the refrigerator. To make the freezing temperature unstable.

According to the invention of this application, in a cryostat comprising a regenerator of a pulse tube refrigerator, a cold head, a pulse tube and the like, heat flowing into the cold head due to heat conduction and heat radiation from almost room temperature is reduced. The purpose is to increase the refrigeration efficiency.

[0008]

The cryostat of the pulse tube refrigerator according to the invention of this application has a pulse tube arranged at the center of the axis of a regenerator joined to a cold head, and the pulse tube is operated. A configuration in which a direction portion that gives directionality to the fluid flow is provided between the low temperature portion and the room temperature portion, and the precooling portion provided in the outer cylinder of the regenerator in the circumferential direction of this direction portion is cooled by the working fluid from the inside. Is the basis.

It is preferable to bond a shield plate covering the cold head and the low temperature portion of the pulse tube to the precooling portion.

Further, it is preferable that the cold head is provided with a conical portion for efficiently accelerating and decelerating the working fluid and at the same time increasing the heat transfer area.

Furthermore, it is preferable to provide internal fins for heat exchange with the working fluid in the precooling section.

Further, the pulse tube may be constructed by connecting from a low temperature portion to a substantially normal temperature portion by connecting ports provided with a plurality of pulse tubes having different diameters in a directional portion, so that the fluid resistance is small. preferable. Ideally, the pulse tube can be solved by making the low temperature part thin and the opening part conical tube type at the room temperature part, but it is difficult to manufacture.

[0013]

In the invention of this application, for example, the normal temperature is 3
If the temperature of the cold head is 00K and the temperature of the cold head is 20K, the temperature of the pre-cooling section is 80K to 130K.
Since the working fluid cools the pre-cooling section from the inside, the heat entering from the normal temperature is removed by the pre-cooling section.
The cold head temperature is lower and at the same time the refrigeration efficiency is increased.

If a heat shield plate covering a part of the cold head and the pulse tube is joined to the pre-cooling portion, heat penetration due to heat radiation from room temperature is reduced and the temperature of the cold head becomes lower.

The freezing temperature of the cold head is 60K to 10K.
Even in the 0K region, setting the precooling section to 150K to 200K is effective in stabilizing the freezing temperature.

[0016]

1 and 2 show details of a first embodiment of the invention of this application. 1 and 2, the regenerator 105 is composed of a lower first regenerator unit 105A and an upper second regenerator unit 105B, and a lower end of an outer cylinder 105A1 of the first regenerator unit 105A is provided with a substrate 116. And the upper end of the outer cylinder 105A1 of the first regenerator part 105A and the lower end of the outer cylinder 105B1 of the second regenerator part 105B are joined to the pre-cooling part 117, and the outer cylinder 10 of the second regenerator part 105B is joined.
The cold head 106 is joined to the upper end of 5B1.

The cold head 106 is provided with a conical portion 106A for efficiently accelerating and decelerating the working fluid and at the same time increasing the heat transfer area. In this conical portion 106A, the working fluid passes from the regenerator 105 through the cold head 106 and enters the pulse tube 107 to accelerate the working fluid and adiabatically expand it to lower the temperature.
From 07, the deceleration upon entering the regenerator 105 functions to reduce the friction loss of the working fluid, and has the effect of increasing the heat transfer area of the cold head 106 to efficiently cool the cooled object. It is a thing. This conical part 1
The cone angle of 06A is reduced from 90 degrees to 30 degrees as the working fluid velocity increases.

The pulse tube 107 arranged at the axial center of the regenerator 105 is also composed of a lower first pulse tube section 107A and an upper second pulse tube section 107B, and a first pulse tube section 107A.
The lower end portion of the first pulse tube portion 107A is fitted into the radiator 104 joined to the substrate 116, and the directional portion 1 is inserted into the upper end portion of the first pulse tube portion 107A.
The lower tubular portion 119A of 19 is fitted, the lower end of the second pulse tube portion 107B is fitted in the central connection port of the direction portion 119, and the direction portion 120 is provided at the upper end portion of the second pulse tube portion 107B.

A heat shield plate 121 for covering the second regenerator section 105B and the cold head 107 is joined to the pre-cooling section 117,
A vacuum cover 122 that covers the heat shield plate 121, the pre-cooling unit 117, and the first regenerator unit 105A is bonded to the substrate 116.

The radiator 104 has a pipe 10 extending from the compression space.
3 is connected, and a pipe 108 for connecting the pulse tube 107 and the expansion space is attached, and the pipe 103-radiator 104-first regenerator portion 105A-direction portion 119-second regenerator portion 10 is connected.
5B-Cold head 106-Second pulse tube section 107B
-First pulse tube portion 107A-To configure the flow path of the pipe 108.

An internal fin 117A for heat exchange with the working fluid is formed in the precooling section 117, and the flow of the working fluid is directed to the internal fin 117A by the direction section 119. The cold head 106 is also formed with internal fins 106B for exchanging heat with the working fluid, and the direction 120 directs the flow of the working fluid to the internal fins 106B.

A large number of bronze or stainless meshes are inserted as a regenerator material in the first regenerator portion 105A, and a myriad of rare earths having a large magnetic specific heat processed into a myriad of spheres in the second regenerator portion 105B. Insert lead etc. as a cold storage material.

As the working fluid, helium, hydrogen, argon, air, nitrogen and other gases, or a plurality of mixed gases having different molecular weights are used.

When a metal tube such as stainless steel is used as the pulse tube 107 to prevent heat interference with the regenerator material, the outer wall of the pulse tube 107 is covered or baked with a tube of a non-heat conductor such as Teflon. , A low heat conductivity ceramic tube or the like.

FIG. 3 is a schematic view of the first embodiment described above. 4 to 7 are schematic views of the second to fifth embodiments of the invention of this application.

In FIG. 3 schematically showing the first embodiment, the outer cylinder diameter of the regenerator 105 is the same from the cold head 106 to the room temperature portion (lower end), and the pulse tube 107 arranged at the axial center of the regenerator 105. Has the same diameter from the low temperature part (upper end) to the room temperature part (lower end).

The second embodiment shown in FIG. 4 is a cold head 20.
The outer cylinder diameter of the regenerator 205 joined to 6 at the upper end has a stepped shape with two steps, and the diameter of the pulse tube 207 arranged at the axial center of the regenerator 105 is from the low temperature portion (upper end) to the room temperature portion (lower end). The pulse tubes 207 are provided with the directional portions 220 and 219 at the upper end and the center of the pulse tube 207 for directing the flow of the working fluid, and the precooling portion 217 provided on the outer cylinder of the regenerator 205 is cooled by the working fluid from the inside. There is. At the center of the lower surface of the cold head 206, a conical portion 206A is provided as in the first embodiment.

The third embodiment shown in FIG. 5 is a cold head 30.
6, the outer cylinder diameter of the regenerator 305 joined at the upper end is the same from the cold head 306 to the room temperature portion, and the diameter of the pulse tube 307 disposed at the axial center of the regenerator 305 has a two-stepped shape (low temperature portion is Pulse tube 307 with small diameter and large diameter at room temperature
The directional portions 320 and 319 that direct the flow of the working fluid are provided at the upper end of the small diameter part and the upper end of the large diameter part of the precooling part 317 provided in the outer cylinder of the regenerator 305 and are cooled by the working fluid from the inside. is there. At the center of the lower surface of the cold head 306, a conical portion 306A is provided as in the first embodiment.

The fourth embodiment shown in FIG. 6 is a cold head 40.
6, the outer cylinder diameter of the regenerator 405 joined at the upper end has a stepped shape of two stages as in FIG. 4, and the diameter of the pulse tube 407 disposed at the axial center of the regenerator 405 is the same as that of FIG. Similarly 2
The pulse tube 407 has a stepped shape, and the directional portion 42 that gives directionality to the flow of the working fluid is provided at the upper end of the small diameter portion and the upper end of the large diameter portion of the pulse tube 407.
0 and 419 are provided, and the precooling unit 417 provided in the outer cylinder of the regenerator 405 is cooled from the inside by the working fluid.
At the center of the lower surface of the cold head 406, a conical portion 406A is provided as in the first embodiment.

The fifth embodiment shown in FIG. 7 is a cold head 50.
6, the outer cylinder diameter of the regenerator 505 joined at the upper end has a three-stepped shape, and the diameter of the pulse tube 507 disposed at the axial center of the regenerator 505 has a three-stepped shape. Providing directional portions 520, 519, 519A for directing the flow of the working fluid at the upper ends of the small diameter portion, the medium diameter portion, and the large diameter portion,
Two pre-cooling parts 517, 51 provided on the outer cylinder of the regenerator 505
7A is cooled from the inside by a working fluid. At the center of the lower surface of the cold head 506, a conical portion 506A is provided as in the case of the first example.

In the first to fifth embodiments, the pulse tube has the same diameter from the low temperature portion to the normal temperature portion or has a shape that gradually increases as the temperature approaches the normal temperature portion, but the viscosity of the working fluid increases as the temperature increases. Considering the increase in size, it is ideal to use a conical pulse tube having a small diameter (small cross-sectional area) at a low temperature portion and becoming thicker as it approaches a room temperature portion.

[0032]

As described above, according to the invention of this application, the heat entering the cold head from room temperature can be reduced and the refrigeration efficiency can be increased. In addition, since the cryostat can be made extremely compact, it is possible to obtain excellent effects such as easy handling of the cryostat.

[Brief description of drawings]

FIG. 1 is a diagram showing details of the configuration of a first embodiment of the invention of this application.

FIG. 2 is an enlarged view of a main part of FIG.

FIG. 3 is a diagram showing a schematic configuration of a first embodiment of the invention of this application.

FIG. 4 is a diagram showing an outline of a configuration of a second embodiment of the invention of this application.

FIG. 5 is a diagram showing an outline of a configuration of a third embodiment of the invention of this application.

FIG. 6 is a diagram showing a schematic configuration of a fourth embodiment of the invention of this application.

FIG. 7 is a diagram showing a schematic configuration of a fifth embodiment of the invention of this application.

FIG. 8 is a diagram showing a schematic configuration of a pulse tube refrigerator.

[Explanation of symbols]

1 ... Compression space 2 ... Expansion space 3,103 ... Piping 4,104 ... Radiator 5,105,205,305,405,505 ... Regenerator 6,106,206,306 , 406, 506 ... Cold head 7, 107, 207, 307, 407, 507 ... Pulse tube 8 ... Piping 9 ... Compression piston 10 ... Expansion piston 11 ... Crank shaft 12, 13 ... Crank pin 14 ... Piston ring 15 ... Crank angle setting mechanism 106A, 206A, 306A, 406A, 506A
..Cone shaped parts 117, 217, 317, 417, 517 ... Pre-cooling part 117A ... Internal fins 119, 219, 319, 419, 519 ... Direction part 121 ... Heat shield plate

Claims (5)

[Claims] 1. A cryostat comprising a regenerator, a cold head, a pulse tube and the like of a pulse tube refrigerator,
A pulse tube is arranged at the axial center of the regenerator joined to the cold head, and the pulse tube is provided with a directional section for directing the flow of the working fluid between the low temperature section and the room temperature section. A cryostat with a precooling unit for a pulse tube refrigerator, in which a precooling unit provided in an outer cylinder of a regenerator in a circumferential direction is cooled from inside by a working fluid. 2. The cryostat with a precooling section for a pulse tube refrigerator according to claim 1, wherein a heat shield plate covering the cold head and the low temperature section of the pulse tube is joined to the precooling section. 3. The pulse tube refrigerator with a precooling portion according to claim 1, wherein the cold head is provided with a conical portion for efficiently accelerating and decelerating the working fluid and at the same time increasing the heat transfer area. Cryostat. 4. The cryostat with a precooling section for a pulse tube refrigerator according to claim 1, wherein the precooling section is provided with internal fins for heat exchange with a working fluid. 5. The pulse tube is configured by connecting a low temperature portion to a substantially normal temperature portion in a regenerator by connecting ports provided with a plurality of pulse tubes having different diameters in a direction portion.
The cryostat with a precooling section of the pulse tube refrigerator according to any one of 4 to 4.