JPH0356860Y2 - - Google Patents

Description

[Detailed description of the invention] [Technical field to which the invention pertains] This invention relates to an expansion cylinder device for a refrigerator that uses gas as a refrigerant.

[Prior art and its problems]

For example, a reverse Stirling cycle is known as a refrigeration cycle that uses a gas that is difficult to liquefy at low temperatures, such as helium, hydrogen, or nitrogen, as a refrigerant gas. A refrigerator using this refrigeration cycle is equipped with an expansion cylinder 1 and a compression cylinder 2, as shown in the schematic configuration example in FIG. 4). Further, the cooling section 6 to which the object to be cooled 5 is attached is formed so as to hermetically seal the end 7 of the expansion cylinder 1. The expansion cylinder 1 and the compression cylinder 2 are connected by a pipe 8, and the refrigerant gas is transferred to the space 15 of the expansion cylinder 1 and the compression cylinder via a regenerator 9 as a refrigerant gas passage built in the expansion piston 3. 2 space 16
and are alternately transferred according to the reverse Stirling cycle described later. In the pipe 8, heat is radiated from the compressed refrigerant gas from its outer periphery or from a specially provided radiator. Note that reference numeral 19 is a seal provided on the outer periphery of each piston to prevent leakage of refrigerant gas.

The reverse Stirling cycle basically consists of two isothermal steps and two isovolumic steps as shown below. In order to realize each of these strokes, the expansion piston 3 and the compression piston 4 are adjusted to move synchronously with a predetermined phase difference.

(1) Isothermal compression stroke Refrigerant gas in the space 16 is compressed in the compression cylinder 1. The heat generated by compression is radiated to the outside through piping 8, resulting in an isothermal process. (Expansion piston: center → top dead center, compression piston: bottom dead center → center) (2) Isochoric heat radiation stroke A regenerator in which the compressed refrigerant gas has already been cooled in the previous cycle without changing its volume. The heat is radiated to the space 15 of the expansion cylinder 1, and the temperature becomes low. (Expansion piston: top dead center → center, compression piston: center → top dead center) (3) Isothermal expansion stroke The refrigerant gas in the space 15 of the expansion cylinder 1 removes heat from the surroundings as the expansion piston 3 moves. It expands isothermally at low temperatures. (Expansion piston: center → bottom dead center, compression piston: top dead center → center) (4) Equal volume endothermic stroke The refrigerant gas expanded at low temperature passes through the regenerator 9 again to the compression cylinder 2 without changing its volume. is returned to the space 16. At this time, the refrigerant gas absorbs heat from the regenerator 9, so the regenerator 9 is cooled, the temperature of the refrigerant gas rises, and one cycle is completed. (Expansion piston: bottom dead center → center, compression piston: center → bottom dead center) The above is an outline of the basic reverse Stirling cycle, and the cooled body 5 mainly performs the isovolumic heat radiation stroke in (2) above. cooled down. That is, in this process, the refrigerant gas that has become low temperature is transferred to the space 15 through the regenerator 9, flows along the inner wall of the end 7 of the expansion cylinder 1, and passes through the cooling section 6 and the end 7 to the object to be cooled 5. It absorbs more heat and cools it down. Also
The state change of the refrigerant gas during the isothermal expansion process in (3) is actually a polytropic change, which is between isothermal change and adiabatic change. The cooling effect is lower than that in the isovolume heat radiation stroke (2), but since there is almost no flow of refrigerant gas, the cooling effect is smaller than in the isovolume heat radiation stroke.

In such a refrigerator, it is important to efficiently remove heat from the object to be cooled 5 and to reduce the time required to lower the temperature to a predetermined cooling temperature as much as possible.

An example of the prior art for this purpose is an expansion cylinder device having the configuration shown in FIG. In this expansion cylinder device, a communication passage 14 is provided in the top portion 10 of the expansion piston 3 as a pore opening in the reciprocating direction of the expansion piston 3 from the regenerator 9 serving as a refrigerant gas passage to the space 15. As already mentioned, as the expansion piston 3 descends from the top dead center during the isovolumic heat dissipation stroke, low-temperature refrigerant gas flows into the space 15 through the communication path 14. At this time, since the communication passage 14 is a small hole, the cross-sectional area of the flow is narrowed, and therefore, a high-flow rate and low-temperature refrigerant gas is ejected from the communication passage. As this jet stream flows along the inner wall of the end 7 of the expansion cylinder 1, the refrigerant gas is transferred from the object 5 to the end 7 connected to the cooling section 6.
It absorbs heat and cools it through its inner wall. Furthermore, the end portion 7 is formed thickly so as to be continuous with the cooling portion 6.
The cross-sectional area of the heat transfer path from the cooling part 6 to the refrigerant gas is set large. As a result, even when a material with relatively low thermal conductivity, such as stainless steel, is used, the thermal resistance of the heat transfer path can be kept low, and good heat conduction can be obtained. Furthermore, the cooling section 6 is provided with mechanical rigidity so that it can sufficiently withstand the mechanical and thermal forces applied when fitting, tightening, or soldering the object 5 to be cooled.

However, in this configuration, only a part of the end face 17 of the cooling part first comes into contact with the low-temperature, high-speed refrigerant gas, and the flow along the inner wall surface of the end 7 of the expansion cylinder 1 has a flow rate that is higher than that circulating from the end face 17 of the cooling part. It has become a declining trend. Therefore, the inner wall surface of the end portion 7 does not function effectively for heat transfer to the refrigerant gas, and the disadvantage is that the requirements of improving cooling efficiency and shortening the falling time to a predetermined cooling temperature are not fully met. has.

In order to eliminate this drawback, a cylindrical guide 11 is provided at the top 10 of the expansion piston 3, as shown in FIG. There is something that has been formed.
With this configuration, a low-temperature flow is provided along the inner wall of the end portion 7, and the communication path 18 for refrigerant gas from the regenerator 9 to the space 15 is in the reciprocating direction of the expansion piston 3. It is formed by a pore 13 provided perpendicularly to the flow path 12 and the flow path 12 described above.
This configuration improves heat transfer to the refrigerant gas, but on the other hand, increases the heat capacity corresponding to the mass of the guide 11 and the mass of the thick portion of the end portion 7, which is longer by the length of the guide 11. This is the object to be cooled 5
In addition to this, an additional object to be cooled is added, and as a result, the problem of obtaining efficient cooling and rapid cooling down to a predetermined cooling temperature remains unsolved.

[Purpose of invention]

The object of this invention is to eliminate the above-mentioned drawbacks and provide an expansion cylinder device with high cooling efficiency and a short falling time to a predetermined cooling temperature.

[Key points of the idea]

This idea allows the refrigerant gas communication passage provided at the top of the expansion piston to be opened obliquely close to the inner wall at the end of the expansion cylinder. This method focuses on the fact that multiple velocity components are given in the direction, and in short, the refrigerant gas is guided along the inner wall surface of the end portion of the expansion cylinder by the velocity component in the direction along the inner wall surface of the end portion of the expansion cylinder without providing a guide. At the same time, the refrigerant gas is forced to collide with the inner wall of the end portion using a velocity component in the radial direction, creating a turbulent flow with a good heat transfer coefficient, thereby achieving good cooling. Furthermore, the refrigerant gas flows along the inner wall of the end and absorbs heat from the object to be cooled through the end, while the refrigerant gas is transferred to the expansion cylinder, that is, near the center position of the expansion piston from top dead center to top dead center. By focusing on the fact that the end of the expansion cylinder is thick from the inner end surface to the vicinity of the center position between the top and bottom dead center of the expansion piston, the heat capacity is increased more than necessary. It is designed to reduce thermal resistance.

[Example of idea]

FIG. 1 shows an embodiment of this invention, in which the refrigerant gas communication passage 24 is connected to the top 30 of the expansion piston 23.
A plurality of pores are provided on the slope forming the periphery of the expansion cylinder 21 , and open immediately adjacent to the inner wall surface of the end 27 of the expansion cylinder 21 . Moreover, the direction of the opening is set to be oblique to the reciprocating direction of the expansion piston 23. In this configuration, as in the prior art, in the process of the expansion piston 23 descending from the top dead center in the isovolumic heat dissipation stroke, the refrigerant gas, which has become low temperature through the regenerator 29, is transferred to the communication path 2.
4 and ejects into the end inner space 35 at high speed. However, in the configuration of this embodiment, since the communication passage 24 opens obliquely to the reciprocating direction of the expansion piston 23, the ejected refrigerant gas has two velocities, one in the reciprocating direction of the expansion piston 23 and the other in the radial direction. ingredients are given. The communication path 24 also connects the expansion cylinder 2
1, the refrigerant gas flows through the end 27 even without a guide as shown by the arrow in the figure, due to the velocity component in the reciprocating direction of the expansion piston 23. It flows at high speed along the inner wall and can circulate even to the inner end surface 36. Furthermore, due to the radial velocity component, the end 27
Since the refrigerant gas collides with the inner wall surface of the refrigerant, it becomes a turbulent flow with a large heat transfer effect. The effect of producing this turbulent flow is more pronounced when there is no guide, as in this embodiment, because the rectifying effect is not applied. Therefore, the turbulent refrigerant gas moves at high speed along the inner wall of the end portion 27, and as a result, heat transfer from the end portion 27 to the refrigerant gas is better than when a guide is provided. Furthermore, since the opening of the communication passage 24 is provided on the slope that contacts the inner wall surface of the expansion cylinder 21, the slope and the inner wall surface of the end portion 27 form a groove near the opening of the communication passage 24. The refrigerant gas ejected into the groove accelerates the gas flow, further increasing the cooling effect.

The refrigerant gas is ejected from the communication passage 24 in the above manner until the expansion piston 23 passes the center between the top and bottom dead centers, but after that, the expansion stroke continues while the expansion piston 23 moves to the bottom dead center. The amount of refrigerant gas passing through decreases, and therefore the flow velocity of the refrigerant gas along the inner wall surface of the end portion 27 also decreases. As mentioned above, the state change of the refrigerant gas in this stroke is a polytropic change, and due to the adiabatic expansion effect, which is a part of this change, the temperature of the refrigerant gas becomes even lower than in the case of the isovolume stroke. However, because the flow rate of the refrigerant gas is reduced, the amount of heat transferred from the end 27 to the refrigerant gas is significantly reduced, even though the temperature of the refrigerant gas is reduced. From this, end 2
It can be seen that the area in which it is necessary to reduce the thermal resistance of the heat transfer path in 7 is from the inner end surface 36 to the vicinity of the center of the vertical dead center of the expansion piston 23, and no further area is necessary. Inner end surface 3 shown in the embodiment of FIG.
The length l of the thick portion 23 from 6 is determined based on the above-mentioned reason and is given by l≈a+1/2L. Here, a is from the inner end surface 36 to the expansion piston 2.
3, and L is the distance between the top and bottom dead centers of the expansion piston 23, that is, the stroke. In this way, unnecessary increases in heat capacity can be suppressed.

As described above, in this embodiment, even without providing a guide, it is possible to create a flow of refrigerant gas with better heat transfer than in the case with a guide. Moreover, since there are no guides or unnecessary thick parts, it has only the minimum necessary heat capacity. These factors combine to improve cooling efficiency and shorten the time required for cooling to a predetermined cooling temperature.

FIG. 2 shows another embodiment of the present invention, in which a communicating passage 34 is provided with an opening direction different from that in FIG. 1. In other words, the communication passage 34 opens in a diagonal direction with respect to the radial direction of the expansion piston 23, so that the refrigerant gas contains not only the two components in the reciprocating direction of the expansion piston 23 and the radial direction. , three velocity components are given to which a circumferential component is added. As a result, the refrigerant gas is
(in the reciprocating direction and the circumferential direction), the flow turns along the inner wall surface of the end portion 27 of the expansion cylinder 21 in the circumferential direction as indicated by the arrow in FIG. 2, and is blown to the inner end surface 36. Since the turbulent flow effect due to the third velocity component (radial direction) described above is added to this, there is an advantage that the heat transfer from the inner wall of the end portion 27 to the refrigerant gas is even better, and the cooling characteristics are further improved.

Further, in the embodiments described above, the communication passages 24 or 34 are shown as a plurality of pores with circular cross sections, but the same effect can be obtained even if these are formed in the shape of slits (not shown).

A third embodiment shown in FIG. 3a is a further modification of the plurality of slit-shaped communication passages described above. In this embodiment, the communication path is a continuous narrow diameter 54 that goes around the vicinity of the inner wall of the end portion 27 of the expansion cylinder 21. As shown in the exploded view of the expansion piston 53 in FIG. 3b, this narrow diameter 54 is a circular plate with a cone-shaped surface 41 provided at the top 50 of the expansion piston 53 and a conical surface 42 at the edge. 43 is formed by arranging the conical surface 42 and the surface 41 to face each other with a minute interval therebetween. In order to maintain a uniform minute interval between the expansion pistons 53 and 54,
The disk 43 is fitted onto the shaft 44 provided at 0, supported by a pedestal 45 finished to a predetermined height, and the shaft 44 and the disk 43 are welded together by electron beam welding or the like. The communication hole 46 provided in the top portion 50 is for guiding the refrigerant gas from inside the expansion cylinder to the narrow hole 54 .
In the configuration of this embodiment, the refrigerant gas having two velocity components, one in the reciprocating direction of the expansion piston 53 and the other in the radial direction, is blown onto the inner wall of the end portion 27 without any spatial break. Even better heat transfer effects can be obtained than in the case where the communication passages are provided as holes or slits.

Further, a fourth embodiment is shown in FIG. In this embodiment, the inclined surface of the peripheral edge of the top portion 30 of the expansion piston 23 provided for opening the communication passage 24 obliquely is extended to form a conical flow guide surface 51. In this configuration, the refrigerant gas circulating up to the inner end surface 36 does not stay in the center of the end inner space 35, but descends along the flow guide surface 51 as indicated by the arrow in FIG. 4, improving heat transfer. This has the effect of creating a circulating flow. The flow guiding surface 51 is the expansion piston 23
Since it is inclined with respect to the reciprocating direction of the top part 30, the increase in the height of the top part 30 due to the provision of this part is small, and the increase in the length of the thick part 28 due to this part is also small, and it has no large thermal effect. It will not cause any damage. Although the flow guide surface 51 is formed as a conical surface in this embodiment, it may be formed as a curved surface such as a spherical surface as long as it performs the same function. Furthermore, the communication path 24 may also be a slit-like one or a continuous narrow one as described above.

[Effect of idea]

According to this invention, the refrigerant gas communication path from the refrigerant gas passage inside the expansion piston to the space inside the end of the expansion cylinder is provided very close to the inner wall of the end of the expansion cylinder, and opens obliquely. Therefore, the low-temperature refrigerant gas ejected from the communication passage into the space inside the end of the expansion cylinder has multiple velocity components, one along the inner wall surface of the end of the expansion cylinder and the other in the radial direction perpendicular to the inner wall. Given. Therefore, due to the former velocity component, the refrigerant gas flows along the inner wall surface of the end portion without providing any particular guide, and circulates to the inner end surface. Further, due to the latter velocity component, the refrigerant gas collides with the inner wall of the end portion with force, making the flow a turbulent flow that further improves heat transfer from the inner wall of the end portion. Moreover, this effect is particularly remarkable since there is no guide. As described above, the effect of the plurality of velocity components makes it possible to cool the cooling section more efficiently than when a guide is provided, and is also effective in reducing the heat capacity corresponding to the mass of the guide.

Furthermore, the thick wall part provided at the end of the expansion cylinder to reduce thermal resistance is necessary only in the area where the refrigerant gas is ejected. Since the length is set to the minimum necessary length to the vicinity of the central portion of the tube, it is also possible to avoid retaining excess heat capacity.

With the above-mentioned simple configuration, the heat transfer from the cooling part to the refrigerant gas is good, and unnecessary heat capacity is not retained, thereby increasing cooling efficiency and shortening the time to reach a predetermined cooling temperature. becomes possible.

[Brief explanation of drawings]

FIG. 1 is a perspective sectional view of an embodiment of an expansion cylinder device for a refrigerator according to the present invention, and FIGS. 2, 3, and 4 are perspective sectional views of different embodiments of the expansion cylinder device for a refrigerator according to the present invention. Figure, 5th
The figure is a schematic configuration diagram of a refrigerator for explaining a reverse Stirling cycle as an application example of the present invention, and FIGS. 6 and 7 are different sectional views of expansion cylinder devices of a refrigerator according to the prior art. 1, 21... Expansion cylinder, 2... Compression cylinder, 3, 23, 53... Expansion piston, 4... Compression piston, 5... Body to be cooled, 6, 26... Cooling section, 7, 27... End, 9, 29...Regenerator, 1
0, 30, 50...Top, 11...Guide, 12
... Channel, 13 ... Pore, 14, 18, 24, 3
4... Communication path, 15, 16... Space, 17... Cooling part end surface, 28... Thick wall part, 35... End inner space, 36... Inner end surface, 41... Surface, 42... Conical surface , 43... Disc, 44... Shaft, 45... Pedestal,
46...Flow hole, 51...Driving surface, 54...Slim.

Claims (1)

[Claims for Utility Model Registration] 1. An expansion cylinder whose end is hermetically sealed by a cooling section for the object to be cooled, and a reciprocating reciprocating cylinder with a top dead center near the cooling section inside the expansion cylinder, and a refrigerant gas passage. and an expansion piston provided inside, wherein a communication path from the refrigerant gas passage to the inner space at the end of the expansion cylinder is arranged so as to open obliquely in the vicinity of the top of the expansion piston and immediately adjacent to the inner wall of the expansion cylinder. An expansion cylinder device for a refrigerator, characterized in that the end of the expansion cylinder is formed thick from the inner end surface to the vicinity of the center position between the top and bottom dead centers of the expansion piston. 2. The expansion cylinder device for a refrigerator according to claim 1, wherein the communication passage is arranged to open obliquely with respect to the radial direction of the expansion piston. 3. The expansion cylinder device for a refrigerator as described in claim 1 of the utility model registration, characterized in that the communication passage is narrow. 4 Utility Model Registration The expansion cylinder device for a refrigerator according to claim 1, wherein the top of the expansion piston is formed with a curved surface that is convex with respect to the inner end surface of the expansion cylinder.