JPH0686964B2 - Expander for cryogenic refrigerator - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a structure of an expander for a cryogenic refrigerator, which expands a compressed refrigerant gas to generate a cryogenic level of refrigeration, In particular, it relates to measures for improving cooling capacity.

(Prior Art) Conventionally, as a structure of an expander for a cryogenic refrigerator arranged in a cryogenic refrigerator for generating cryogenic levels, for example, "Cryocoolers, Partl, p.204, (ISBN O-3
06-40715-9 (v.1), 1983 PlenumPress, New York) ", as shown in FIG. 5, a substantially hemispherical low temperature end (b) is provided at the tip of the cylinder (a). The displacer (d) having the built-in regenerator (c) is formed with a hemispherical tip to form an expansion space (f) between the tip and the inner wall surface of the low temperature end (b). The displacer (d) is provided with a pore (e) at the root of the cylindrical surface,
Refrigerant flows from the inside of the displacer (d) into the expansion space (f) through the pores (e) to expand the refrigerant in the expansion space (f), thereby improving the cooling effect of the low temperature end portion (b). What is about to be done is a known technique.

Further, as disclosed in the same document as the above, as shown in FIG. 6, the cylinder (a) has a double pipe structure, and the regenerator (c) is housed between the double pipes. , Low temperature end of cylinder (a) tip (b)
In the above, in the cylinder (a), an internal member (g) externally fitted to the inner pipe and having a predetermined gap between the outer pipe and the outer end face is provided between the double pipes of the cylinder (a), and the refrigerant flows through the gap. While forming the space (h), a pore (i) that connects the flow space (h) and the expansion space (f) at the inner tip of the cylinder (a) is formed in the center of the concave surface at the tip of the inner member (g). When the refrigerant is expanded, which causes cold, the refrigerant is re-generated (c).
It is a known technique to further improve the cooling effect at the low temperature end portion (b) by causing the gas to flow into the expansion space (f) through the circulation space (h).

(Problems to be Solved by the Invention) By the way, as a factor that impairs the cooling effect of the low temperature end portion (b), the cold of the expanded low temperature refrigerant in the expansion space (f) is effectively transmitted to the outer surface of the low temperature end. Sometimes there is no. Therefore, in comparison with the structure in which the refrigerant is circulated from the central hole on the tip surface of the displacer to the expansion space as in a normal device, in the one shown in FIG. , The refrigerant flows along the wall surface of the low temperature end portion (b), the heat transfer between the refrigerant and the low temperature end portion (b) is improved, and the cooling effect is improved. However, the cold end (b)
In the vicinity of the tip, the heat transfer between the refrigerant and the low temperature end (b) is still insufficient, and there is a problem that the overall cooling effect is not sufficiently improved.

On the other hand, in the case of FIG. 6 described above, the refrigerant sucked in and discharged from the low temperature end portion (b) exchanges heat with the entire surface, and a high cooling effect can be exhibited. However, on the other hand, since the cylinder (a) which requires high accuracy has a double pipe structure and the regenerator (c) is provided inside thereof, the manufacturing cost is high and the device is There is the problem of becoming large.

The present invention has been made in view of the above circumstances, and an object thereof is to prevent the mixing effect of refrigerants with a simple configuration, thereby improving the cooling capacity of an expander at low cost.

(Means for Solving the Problem) A first means for achieving the above object is, as shown in FIG. 1, a cylindrical cylinder member (1) having a closed end in an expander for a cryogenic refrigerator. ) And a cup shape that is fitted onto the tip end portion (1a) of the cylinder member (1) so as to have a predetermined gap over the entire outer shape of the tip end portion (1a) and is supported at the inlet in a confidential manner. A low temperature end (2) and a cylindrical displacer (3) which has a thin metal wire or spherical regenerator (4) inside and slides through a seal member (5) in the cylinder member (1). The displacer (3)
By the reciprocating motion of the high pressure refrigerant gas, the high pressure refrigerant gas is expanded to generate the cryogenic temperature at the low temperature end portion (2).

Further, an expansion space (6) in which the refrigerant expands is formed between the tip portion (1a) of the cylinder member (1) and the tip of the displacer (3), and the tip portion (1a) and the low temperature end portion (2) are formed. ), A circulation space (7) through which the refrigerant gas flows is formed, and on the cylindrical surface of the displacer (3) and the corresponding cylindrical surface of the tip portion (1a) of the cylinder member (1), the inside of the displacer (3) and the above A flow passage (10) communicating with the distribution space (7) so that the refrigerant gas can flow is provided, and the distribution space (7) and the expansion space (6) are provided at the center of the tip surface (1b) of the cylinder member (1). Through which the refrigerant gas can flow (1
1) is provided. .

A second solving means is the same as the first solving means, which is constituted by a circular metal wire net having a large number of regenerators (4) stacked, and the displacer (3) is impregnated and solidified in the vicinity of the outer circumference of the wire net. It has a cylindrical portion (3b) made of a resin.

(Operation) According to the invention of claim (1), the refrigerant is expanded from the inside of the displacer (3) to the low temperature end portion (2) and the tip end portion of the cylinder member (1) during the expansion of the refrigerant causing cold. It flows into the expansion space (6) through the distribution space (7) between (1a). Therefore, it flows through the circulation space (7) inside the low temperature end (2), and as a result, the low temperature end (2)
The cooling effect will be improved.

Moreover, in that case, since the regenerator (4) is housed in the displacer (3) and the cylinder member (1) has a single pipe structure, the entire apparatus can be made small and simple, and therefore, the manufacturing Cooling capacity is improved without incurring a significant increase in cost.

In the invention of claim (2), since the regenerator (4) is composed of a metal wire mesh, the coefficient of thermal expansion is about the same as that of the cylinder member (1), and the cylindrical surface of the displacer (3) is At the time of finishing, rigidity is maintained by the wire mesh inside, and good roundness can be obtained. Therefore, good fitting property between the outer circumference of the displacer (3) and the inner circumference of the cylinder member (1) is maintained.

Further, since the displacer (3) has a cylindrical portion (3b) formed by impregnating and solidifying a metal wire netting with resin, heat conduction between the wire netting as the internal cold storage material and the cylinder member (1) is effectively blocked. On the other hand, the heat exchange efficiency of the regenerator (4) is maintained high due to the high-density wire mesh.

Therefore, it is possible to cope with the downsizing of the device while maintaining the fitting property with the cylinder member (1) and the high heat exchange efficiency.

(Example) Hereinafter, an example of the present invention will be described with reference to Figs.

FIG. 1 shows a structure of a main part of an expander for a cryogenic refrigerator to which the inventions of claims (1) and (2) are applied. (1) is a cylindrical cylinder member (1) with a closed tip. Then, although not shown, the refrigerant gas compressed by the compressor flows into the cylinder member (1) through a supply passage such as a supply pipe (not shown).

Further, (2) is a cup-shaped low-temperature end portion (2) fitted outside the tip end portion (1a) of the cylinder member (1) so as to have a predetermined gap over the entire outer shape of the tip end portion (1a). ), And at the inlet, the tip (1
a) Confidentially supported by the cylindrical surface. (3) is a hollow cylindrical displacer that slides in the cylinder member (1) via a seal member (5), and a refrigerant gas such as helium gives cold heat to the inside of the displacer (3). A regenerator (4) that circulates while being stored is stored.

Then, the inner wall surface of the tip end portion (1a) of the cylinder member (1) and the tip end surface of the displacer (3) form an expansion space (6) in which the refrigerant expands, and the cylinder member (1).
The space between the outer wall surface of the tip portion (1a) and the inner wall surface of the low temperature end portion (2) forms a circulation space (7) through which the refrigerant flows.

On the other hand, as shown in FIG. 2, on the cylindrical surface of the displacer (3), circular holes (8), which are evenly arranged at four locations in the circumferential direction,
Is provided, and at the location corresponding to the circular hole (8) on the cylindrical surface of the tip end portion (1a) of the cylinder member (1), the cylinder member (1) extends over the up-and-down motion range of the displacer (3). ) Are provided with elongated holes (9) ,. That is, the circular holes (8), ... And the long holes (9), ... Form a flow passage (10) for communicating the inside of the displacer (3) with the flow space (7) so that the refrigerant gas can flow. Has been done.

Further, in the center of the tip surface (1b) of the cylinder member (1), there is provided a fine hole (11) for communicating the circulation space (7) with the expansion space (6) so that the refrigerant gas can flow therethrough. , The expansion space (6) from the distribution space (7) through the pores (11)
It is designed to allow the refrigerant to flow.

That is, when the displacer (3) moves rearward from the tip end side of the cylinder member (1), the refrigerant gas cooled through the regenerator (4) passes from the flow passage (10) through the distribution space (7) to the displacer. While flowing into the expansion space (6) whose volume is increasing due to the movement of (3), cold is generated in the low temperature end (2), while the displacer (3) moves from the rear of the cylinder member (1) to the front end side. When moving, the refrigerant gas cooled in the above process exchanges heat with the low temperature end portion (2) in a route opposite to the above, and then returns to the inside of the displacer (3) to transfer the cold heat to the regenerator (4). It stores heat and returns to the compressor side.

Further, as shown in FIGS. 3 and 4, inside the displacer (3), a tip member (3a) made of a cylindrical block made of copper is provided at the tip, and the regenerator (4) is provided with the tip. The displacer (3) consists of circular copper wire nets that are stacked on top of the member (3a).
An epoxy cylinder part (3a) and an epoxy cylindrical part that is machined to a size such that the outer peripheral surface is impregnated and solidified in the vicinity of the outer periphery of the wire mesh and then the outer peripheral surface fits into the inner cylinder surface of the cylinder member (1). 3b) and. That is, the displacer (3) and the regenerator (4) are integrally formed.

Therefore, in the invention of claim (1), when the refrigerant gas that causes cold is expanded, the refrigerant gas is formed as a gap between the low temperature end portion (2) and the tip end portion (1a) of the cylinder member (1). Since it flows into the expansion space (6) from the pores (11) provided in the center of the tip surface of the cylinder member (1) through the flow space (7) that is formed, the flow space () inside the low temperature end (2) ( 7), and as a result, the cooling effect of the low temperature end portion (2) is improved.

In that case, the cylinder member (1) has a single pipe structure, and the flow space (7) includes a tip portion (1a) of the cylinder member (1) and a cup-shaped low temperature end portion (2) covering the tip portion (1a). As a result of the construction of the device, a simple structure, in which the cup-shaped low temperature end (2) is added to the generally used cylinder structure, is sufficient. Therefore, the double structure shown in FIG. It is possible to improve the cooling capacity of the expander for a cryogenic refrigerator without incurring a large increase in manufacturing cost unlike the cylinder structure of a pipe.

In addition, since the regenerator (4) is housed inside the displacer (3) as compared with the double-tube cylinder structure, there is an advantage that the size of the entire apparatus can be reduced.

Next, regarding materials of the displacer (3) and the regenerator (4), conventionally, a cylindrical cloth is used as a resin having a thermal expansion coefficient close to that of stainless steel which is a material of the cylinder member and having a low thermal conductivity. The bakelite is used as a displacer, and copper wire mesh or spherical lead is used as a regenerator inside the displacer. In that case, the cloth-containing Bakelite will change its dimensions due to moisture absorption and the fitability with the cylinder member will deteriorate, and especially in the case of a small refrigerator, the thickness ratio of the cloth-containing Bakelite displacer to the internal regenerator material However, due to the weak rigidity of the cloth-filled bakelite cylinder, a high degree of roundness cannot be obtained during processing, and refrigerant leaks between the cylinder member and the inner wall. May occur.

On the other hand, in the invention of claim (2), since the regenerator (4) is composed of a copper wire mesh, the coefficient of thermal expansion is not so different from that of stainless steel normally used as the cylinder member (1). Further, when finishing the cylindrical surface of the displacer (3), the displacer (3) and the regenerator (4) are integrally formed, and the rigidity is maintained by the internal wire mesh, so that a good roundness can be obtained. You can Therefore, it is possible to maintain a good fit between the outer circumference of the displacer (3) and the inner surface of the cylinder member (1). Further, since the outer periphery is constituted by the cylindrical portion (3b) obtained by impregnating and solidifying the metal wire into the resin, the heat conduction between the metal wire mesh as the internal cold storage material and the cylinder member (1) is effectively prevented. sell. By appropriately pressing the copper wire mesh before impregnating it with the resin, the density of the wire mesh can be made sufficiently high, so that the heat exchange efficiency of the regenerator (4) can be kept high. That is, it is possible to cope with downsizing of the device while maintaining good fitting property with the cylinder member (1) and high heat exchange efficiency.

(Effect of the invention) As described above, according to the invention of claim (1), as the structure of the expander for a cryogenic refrigerator, the displacer is a regenerator built-in type, and a cylindrical cup-shaped member is provided at the tip of the cylinder member. The low temperature end of the cylinder is fitted with a predetermined gap to form a circulation space in which the refrigerant flows, and a refrigerant circulation passage is provided in the cylindrical surface of the displacer and the cylinder member, and the circulation space is formed in the center of the tip surface of the cylinder member. By providing pores that communicate with the expansion space at the inner tip of the cylinder member,
Since the refrigerant gas is made to flow from the inside of the displacer to the expansion space through the distribution space, the refrigerant gas flows in the distribution space inside the low temperature end without causing a mixing effect with the high temperature side refrigerant, and thus with a simple configuration. It is possible to improve the cooling capacity of the expander and downsize the device.

According to the invention of claim (2), since the regenerator is composed of a plurality of circular copper wire meshes and the cylindrical resin impregnated on the outer peripheral portion of the wire mesh is composed of the displacer,
The size of the device can be reduced while ensuring the fitting property with the cylinder member and the heat exchange rate.

[Brief description of drawings]

1 to 4 show an embodiment of the present invention, FIG. 1 is a longitudinal sectional view showing an essential part of an expander, and FIG. 2 is II-II of FIG.
A line sectional view, FIG. 3 is a partial vertical sectional view showing the structure of the displacer and the regenerator, and FIG. 4 is the IV of FIG.
FIG. 4 is a sectional view taken along line IV-IV 5 and 6 show an example of the structure of a conventional expander. FIG. 5 shows a structure in which a refrigerant is allowed to flow from an opening provided in a cylindrical surface of a displacer into an expansion space, and FIG. 6 shows a cylinder member. FIG. 3 is a vertical cross-sectional view showing the structure of a double tube structure. (1) …… Cylinder member, (1a) …… Tip, (1b)…
... Tip surface, (2) ... low temperature end, (3) ... displacer, (3a) ... cylindrical part, (4) ... regenerator,
(5) ... Seal member, (6) ... Expansion space, (7) ...
… Distribution space, (10) …… flow passage, (11) …… pores.

Claims (2)

[Claims] 1. A cylindrical cylinder member (1) having a closed tip, and a tip portion (1a) of the cylinder member (1) having a predetermined gap over the entire outer shape of the tip portion (1a). The cylinder-shaped low-temperature end portion (2) which is fitted on the outer periphery of the cylinder and is supported at the inlet in a confidential manner, and the regenerator (4) for a fine metal wire or a ball inside, and the inside of the cylinder member (1) is a sealing member. And a cylindrical displacer (3) that slides through (5), and the reciprocating motion of the displacer (3) expands the high-pressure refrigerant gas to bring the low temperature end (2) to a cryogenic level of cold. Is an expander for a cryogenic refrigerator, in which an expansion space (6) in which a refrigerant gas expands is provided between the tip portion (1a) of the cylinder member (1) and the tip of the displacer (3). ) Is formed, and the tip portion (1a) and the low temperature end portion (2) are formed.
A flow space (7) through which the refrigerant gas flows is formed by the gap between the displacer (3) and the cylindrical surface of the displacer (3) and the corresponding tip end portion (1a) of the cylinder member (1). A flow passage (10) is provided which communicates the inside of the cylinder with the circulation space (7) so that the refrigerant gas can flow therethrough, and the cylinder member (1) is expanded at the center of the tip surface (1b) with the circulation space (7). An expander for a cryogenic refrigerator, which is provided with pores (11) communicating with the space (6) so that a refrigerant gas can flow therethrough. 2. A regenerator (4) is composed of a plurality of circular metal wire nets stacked together, and a displacer (3) has a cylindrical portion (3b) made of a cylindrical resin impregnated and solidified near the outer circumference of the wire net. The expander for a low-temperature refrigerator according to claim 1, which has.