JP2600714B2 - Double tube refrigerator - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a pulse tube type double-tube refrigerator that realizes extremely low temperature of 100 K or less by using a pulse tube.

[Prior Art] The basic principle of a cryogenic refrigerator currently used at present is to generate a cooling gas by expanding a gas compressed at a high temperature (normal temperature) at a low temperature. And as a common means at that time, the volume of the expansion chamber is increased or decreased with a movable element,
Inflating the gas is performed.

However, a mechanism that exercises mechanical movement under cryogenic temperature for the purpose of increasing or decreasing the volume inevitably has drawbacks that are difficult to solve in the following points. Specifically, vibrations are generated, the mechanism is complicated and the cost is increased, it is not possible to eliminate factors such as abrasion and the like that hinder the device life, and it is difficult to seal at low temperatures.

Therefore, a device having no movable part at cryogenic temperature is intended. A pulse tube is known as a gas expansion element meeting such a requirement. The pulse tube itself has a simple structure made of thin stainless steel thin tubes, etc., but when a gas is introduced inside and reciprocated, a temperature gradient is formed and the low-temperature end is opposed to the gas introduction side. Create a hot end on the side. Such a heat exchange function is considered to be because the pressure pulse introduced into the pulse tube forms a gas piston to perform adiabatic compression and expansion functions.

In recent years, a small cryogenic refrigerator having a combination of the pulse tube and the regenerator has been proposed.
FIG. 4 shows the structure of this refrigerator. The low-temperature end 1a of the pulse tube 1 and the low-temperature end 2a of the regenerator 2 communicate with each other through the heat absorbing portion 3, and the compressor (piston) 4 passes through the gas passage 5 to the high-temperature end 2b of the regenerator 2. The supplied gas is configured to be introduced from the low-temperature end 1a of the pulse tube 1 to the high-temperature end 1b through the regenerator 2 and the heat absorbing section 3. In addition, in the figure, 6 is a heat radiating portion (after cooler) provided in the gas passage 5 connected to the regenerator high temperature end 2b, and 7 is a pulse tube high temperature end.
A heat radiator (heat exchanger) provided in 1b, and 8 denotes a cooling water pipe constituting these heat radiators 6 and 7.

The operation of this refrigerator is as follows. Now, when the piston 4 is pushed in, the gas enters the heat absorbing section 3 and the low temperature end 1a of the pulse tube while being precooled through the inside of the regenerator 2. Then, the high-pressure gas introduced into the low temperature end 1a of the pulse tube 1 compresses the gas remaining therein toward the high temperature end 1b. At this time, the gas in the pulse tube 1 moves through the tube 1 having a temperature gradient while undergoing adiabatic compression and rising in temperature. Then, the compressed gas enters the heat radiating portion 7 at the high temperature end 1b of the pulse tube, where it is radiated and cooled. Next, when the piston 4 is pulled up, the radiator 7
The gas that has released the heat in step (1) adiabatically expands in the pulse tube 1 and drops to a low temperature, and then is returned while cooling the heat absorbing section 3 and the regenerator 2. Then, by repeating such a cycle, an extremely low temperature of 100 K or less can be obtained in the heat absorbing portion 3.

As described above, the pulse tube refrigerator has a great feature that a small cryogenic refrigerator can be realized without having a movable part at a cryogenic temperature.

[Problems to be Solved by the Invention] However, according to the pulse tube refrigerator having the structure proposed in the prior art, on the other hand, there are problems such as a large amount of heat entering the low temperature side. The pulse tube 1 and the regenerator 2 are of course shielded on the low-temperature side by a vacuum (not shown). In this case, the pulse tube 1 and the regenerator 2 forming a pair are separately disposed, and both are kept at a low temperature. Since it has a large temperature gradient from the ends 1a and 2a to the high-temperature ends 1b and 2b, it is inevitable that a large amount of heat enters from each tube.

[Means for Solving the Problems] The present invention improves the problem of heat invasion and, from the viewpoint of consolidating the devices, combines the essential components of the pulse tube and the regenerator with one another. An object of the present invention is to provide a pulse tube type double tube refrigerator arranged inside the other side to constitute a double tube.

[Operation] If the pulse tube and the regenerator are configured as an inner / outer double tube as described above, both can be supported as an integral body, so that heat intrusion on the low temperature side due to heat conduction from the support member on the high temperature side is reduced. can do. At the same time, the occupied space can be reduced as compared with the case where the components are separately arranged.

[Embodiment] FIGS. 1 and 2 show an embodiment of the present invention, which has a double tube structure in which a pulse tube 1 is arranged on the outside and a regenerator 2 is arranged on the inside. . That is,
An annular hollow portion of the pulse tube 1 is formed between the outer tube A and the inner tube B, and a perforated structure constituting the regenerator 2 is inserted and fixed to the inner periphery of the inner tube B. B are integrated. Then, the low temperature end 1 a of the outer pulse tube 1 and the low temperature end 2 a of the inner regenerator 2 are communicated via the heat absorbing section 3. Also, inside regenerator 2
Is communicated with the compressor 4 via the gas passage 5. Further, heat radiating portions 7 and 6 provided at the high temperature ends 1b and 2b, respectively.
Is configured with a common water cooling tube 8 in this case. The outer cylinder A is surrounded by a vacuum shield (not shown).

With the double-tube refrigerator configured as described above, the same cycle as that of the pulse tube refrigerator described above is performed, so that the cryogenic temperature is realized in the heat absorbing unit 3 without the movable unit, and the following improvement is made. The effect is obtained. One is that external heat intrusion can be reduced, thereby increasing the refrigeration efficiency and obtaining a further extremely low temperature. On the other hand, the pulse tube 1, the regenerator 2, and the heat radiating parts 7, 6 can be compactly integrated to achieve a compact and simple apparatus.

In the above embodiment, as in the case of the conventional example shown in FIG.
Although the case where the Stirling cycle is used for the pulse tube refrigerator has been described as an example, the Stirling cycle may operate a GM cycle. However, in the case of using the GM cycle, it is necessary to add a timing valve that alternately switches between high and low pressures at a predetermined timing on the inlet side of the regenerator 2.

Further, in the above embodiment, the internal and external heat radiating portions 7 on the high temperature side,
6 can also be integrated.

As described above, the pulse tube 1 is placed outside and the regenerator 2
Although the example in which is disposed inside has been described, the positional relationship between the two may be reversed. FIG. 3 shows an embodiment of the present invention, in which a regenerator 2 is provided in an annular gap between the outer cylinder A and the inner cylinder B.
The inner tube B having a hollow portion is used as the pulse tube 1.

[Effects of the Invention] As described above, in the present invention, since the pulse tube and the regenerator are configured as inner and outer double tubes, the characteristics of the pulse tube type refrigerator having no movable part in the low temperature part are secured. However, an increase in heat intrusion can be suppressed, and the size and structure of the refrigerator can be simplified.

[Brief description of the drawings]

1 and 2 show an embodiment of the present invention. FIG. 1 is a schematic vertical sectional view of a double pipe constituting a refrigerator main body, and FIG. 2 is a sectional view taken along line II of FIG. FIG. FIG. 3 is a cross-sectional view (corresponding to the II position in FIG. 1) of a double pipe showing another embodiment of the present invention. FIG. 4 is a system diagram showing a conventional example of a pulse tube type refrigerator. A: Outer cylinder, B: Inner cylinder 1: Pulse tube 2, Regenerator 1a, 2a: Low temperature end, 1b, 2d: High temperature end 3: Heat absorbing section 4, Compressor 6, 7 ... heat dissipation part

Claims (1)

(57) [Claims] 1. A double-tube refrigerator in which a pulse tube and a regenerator are arranged in a double tube with one disposed inside the other.