JPH0689954B2 - Cryogenic cooling unit structure - Google Patents

Description

The present invention relates to a cryogenic refrigerator such as a Stirling refrigerator,
Especially when the cooling target of the refrigerator is brought into direct contact with the object to be cooled,
The present invention relates to a cooling unit structure that prevents a reduction in effective cooling capacity due to contact thermal resistance or the like regardless of the size of a cooled object.

[Conventional technology]

Conventionally, regarding the structure of the cooling section of a cryogenic refrigerator such as a Stirling refrigerator, Infrastructured Fujis, Vol. 23, No. 2 (1983), pages 77 to 84 (Infra
An example is shown in red phys., Vol. 23, No. 2, (1983) pp77-84).

That is, a pressing plate for the cooled portion is attached to the cooled portion of the refrigerator via a spring, and the compression of the spring prevents the effective cooling capacity from decreasing due to contact thermal resistance.

[Problems to be solved by the invention]

In the above-mentioned related art, since heat is taken from the object to be cooled via the spring part and the cooling plate for increasing the contact pressure, the contact thermal resistance can be reduced, but the heat capacity and heat conduction of the spring part cause No consideration was given to the heat resistance that occurs. In addition, when cooling an object to be cooled having a size larger than the cylinder diameter, it is possible to make the cooling plate large, but since only the spring part serves as a heat flow path, a temperature distribution occurs on the cooling plate and uniform cooling is achieved. There was a problem when it was impossible.

In view of the above problems, the object of the present invention is not only to reduce the contact thermal resistance with the object to be cooled but also to provide uniform cooling with a small thermal resistance even when the size of the object to be cooled is larger than that of the displacer cylinder. An object is to provide a possible cryogenic refrigerator cooling unit.

[Means for solving problems]

In order to achieve the above-mentioned object, the structure of the cooling unit of the cryogenic refrigerator according to the present invention is such that in the cooling unit of the cryogenic refrigerator consisting of a reciprocating displacer and a cylinder surrounding the displacer, the end of the cylinder is Has a cross-sectional area that is larger than the cross-sectional area of the cylinder and that matches the size of the object to be cooled, and provides a space that is part of the expansion space, and at the same time, forms a bellows between the space and the displacer cylinder. It is provided with a pipe part. The former is provided to eliminate the temperature distribution in the cooling part and to uniformly cool the cooled object, and the latter is provided to increase the contact pressure with the cooled object and reduce the contact thermal resistance. .

[Action]

The cross-sectional area is larger than that of the cylinder for displacer,
In addition, the cooling medium, which has a size that fits the object to be cooled and has a space that forms part of the expansion space at the end of the cylinder, is filled with working medium. Repeats compression and expansion. That is, as in the conventional cooling unit, the working medium existing in the space of the expanded portion is a medium that removes heat from the object to be cooled, so that the portion of the tip of the space forming the additional space, which is in contact with the object to be cooled, has a temperature. A uniform temperature condition with almost no distribution. Further, if the portion that comes into contact with the object to be cooled is thinned to a place that can withstand the sealing pressure inside the refrigerator, the thermal resistance due to heat conduction can be suppressed to a small level.

On the other hand, the bellows structure has the following effects. That is, even if the additional cooling portion is positioned at a certain angle with the object to be cooled by the bellows, absorption is possible at a minute angle, and the cooling portion and the object to be cooled can be brought into uniform contact. Is. It is also possible to raise the contact pressure by bringing the cooling part into contact with the object to be cooled while the bellows is compressed, but it is possible to use the deformation of the bellows part due to the pressure difference between the filling pressure and the external atmospheric pressure. It is also possible to raise. This action can increase the contact pressure to reduce the contact thermal resistance.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. This drawing shows an enlarged cross-sectional view of the cooling unit by taking a Stirling refrigerator as an example. The cooling unit 1 for directly cooling the cooled body 6, the displacer 5, the cylinder 3 for the displacer 5, An expansion space 4 is formed by the bellows part 2 provided between the cooling part 1 and the cylinder 3. Although the displacer 5 vibrates vertically, the working medium in the expansion space 4 is compressed with the compression space, although not shown in the figure.
The expansion will provide the cooling capacity. Therefore, it can be considered that the working medium in the expansion space 4 has a uniform temperature in the steady state although it has a temperature distribution in the transient state. In particular, since the outside of the cooling unit 1 is usually covered with a vacuum heat insulating layer, there is a slight temperature gradient in the vicinity of the wall of the expansion space 4 due to the effect of radiation, but it is not so remarkable. Therefore, it is considered that the entire surface of the cooling part 1 in contact with the cooled body 6 has a constant temperature. Further, even if the cooling area of the cooling unit 1 is arbitrarily formed according to the area of the object to be cooled, there is no problem in the operation of the refrigerator, and the object to be cooled 6 can be cooled uniformly. .

On the other hand, since the bellows-shaped flexible portion is provided between the cooling unit 1 and the cylinder 3, the body 6 to be cooled is fixed to another member, and a slight inclination angle is formed between the cooling unit 1 and the cooling surface. Even if it has, it can be absorbed and a uniform surface contact can be realized. Moreover, since the bellows portion 2 has a spring effect,
The contact pressure to the cooled object 6 cannot be improved,
When the working medium pressure inside the refrigerator is higher than the outside atmospheric pressure, the higher contact pressure can be obtained due to the deformation of the bellows portion.

FIG. 2 shows an embodiment in which the bellows 2 is not provided. The expansion space 1 composed of the cooling unit 1 is a space that is not occupied by the displacer 5 even if the displacer 5 reciprocates,
That is, the dead volume. Considering the dead volume of the entire refrigerator as a reference, the rate of increase in the dead volume due to the provision of the new cooling unit 1 is not such a factor that causes a decrease in performance. In consideration of conventional experimental experience, if the dead volume of the cooling unit 1 is not more than ½ of the displacer scavenging volume, there is no particular problem in the performance of the refrigerator. If this is mathematically expressed using FIG. 2, it can be expressed by Equation (3) on the premise of Equations (1) and (2).

Ve = πd ² · / 4 (1) where Ve: displacer scavenging volume d: displacer outer diameter: displacer stroke Vd = πD ² t / 4 + πd ² t ′ / 4… (2) here Vd: Dead volume of cooling section D: Diameter of cooling section t: Height of cooling section t ′: Dead volume height of cylinder section Vd ≦ Ve / 2 (3) Design cooling section 1 under these conditions If this is done, it will hardly affect the performance of the refrigerator.

3 and 4 show the effect of the present invention as a diagram. FIG. 3 shows changes in thermal contact congruence with contact pressure. The thermal contact conductance is defined by the reciprocal of the thermal contact resistance, and the higher the thermal contact conductance, the more easily the heat is transferred. From this figure, it is possible to improve the effective cooling capacity because the heat loss can be reduced by increasing the contact pressure.

FIG. 4 shows changes in the amount of heat absorbed by the cooling part with respect to the contact area. When the contact heat resistance and the thickness of the cooling part are constant, the amount of heat absorption increases in proportion to the contact area with the object to be cooled. That is, the effective cooling capacity can be significantly improved by setting the cooling unit that matches the object to be cooled.

[Effects of the Invention] As described above, according to the present invention, the surface to be cooled of the object to be cooled can be cooled by the cooling surface that completely covers the surface of the object to be cooled. The cooling capacity can be improved. Further, since the bellows portion is provided, the contact pressure with respect to the cooled object can be increased,
By reducing the contact thermal resistance, it is possible to improve the effective cooling capacity. Further, even if there is a mounting error between the object to be cooled and the cooling portion, the bellows portion can absorb the error and uniform cooling can be performed.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of the present invention, FIG. 2 is a cross-sectional view showing another embodiment, and FIGS. 3 and 4 are characteristic diagram of a cooling unit demonstrating the effect of the present invention. Is. 1 ... Cooling part, 2 ... Bellows, 3 ... Cylinder, 4 ...
… Expansion space, 5 …… Displacer, 6 …… Cooled body.

Claims (2)

[Claims] 1. A cooling unit structure of a cryogenic refrigerator, wherein an expansion space is composed of a displacer and a cylinder surrounding the displacer, and the displacer reciprocates to obtain a cooling capacity at an end of the cylinder. A cross-sectional area larger than the cross-sectional area of the portion surrounding the displacer at the tip of the cylinder, and a space forming a part of the expansion space is provided, and a bellows-shaped portion is provided between the space and the displacer cylinder. A cooling unit structure of a cryogenic refrigerator characterized by the following. 2. The cooling unit structure of a cryogenic cooler according to claim 1, wherein the volume of the space is 1/2 of the scavenging volume determined by the product of the cross-sectional area of the displacer and the stroke.
A cooling section structure of a cryogenic refrigerator characterized by the following.