JPS62280553A - Expansion cylinder device for refrigerator - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention [Technical Field to Which the Invention Pertains] The present invention relates to a refrigerant seal structure ζ in an expansion cylinder device of a refrigerator that uses gas as a refrigerant.

[Prior art and its problems]

Refrigerators using a reverse Stirling cycle are known as refrigerators that use gases that are difficult to liquefy at low temperatures, such as helium, hydrogen, and nitrogen, as refrigerants, and an example of the configuration is shown in FIG. This refrigerator has an expansion cylinder 2 which has an expansion piston 1 built in. ! : A compression cylinder 4 with a built-in compression piston 3 is provided, and the end of the expansion cylinder 2 is connected to a cooled body 5.
It is hermetically sealed by a cooling section 6 that cools the air. Furthermore, a regenerator 7 made of, for example, a stainless steel wire mesh is provided inside the expansion piston 1, and one end of the expansion piston 1 is placed in a space inside the expansion cylinder 2, and the other end is placed in an expansion cylinder holder 8. Each opens into an internal space. The expansion piston 1 is connected to the bottom of the space within the expansion cylinder holder 8 by a spring 9. The expansion cylinder 2 and the compression cylinder 4 are communicated with each other via a communication pipe 10 and a space within the expansion cylinder holder 8. compression piston 3
is driven to reciprocate via a connecting rod 1 by an electric motor (not shown), and the resulting pressure fluctuation within the system further drives the expansion piston l. A vibration system is constituted by the mass of the expansion piston 1 including the regenerator 7, the fluid resistance of the regenerator 7, and the spring 9. By appropriately selecting the drive cycle of the compression piston 3, the expansion piston 1 and the compression piston 3 The phase difference between the reciprocating motion of M
Cooling can be carried out by setting the temperature to a certain level.

(1) Refrigerant gas is mainly compressed in the compression cylinder 4.

(2) Refrigerant gas is transferred from the compression cylinder 4 to the expansion cylinder 2. The refrigerant gas is cooled by radiating heat obtained through compression from the surface of the communication pipe 10 and cooling in the regenerator 7.

(3) Refrigerant gas mainly expands in the compression cylinder 2.

At this time, the refrigerant gas absorbs heat from the cooling part 6 and cools the cooling part 6.

(4) The refrigerant gas is returned from the expansion cylinder 2 to the compression cylinder 4 while cooling the regenerator 7, completing one cycle.

Near both ends of the expansion piston 1 are equipped seal members 12 and 13 made of a material with a low coefficient of friction, such as fluorocarbon resin. Seal members 12 and 1
3 is a seal between the outer field of the expansion piston 1 and the inner wall of the expansion cylinder 2, so that low-temperature refrigerant gas near the cooling part 6 leaks to the high-temperature expansion cylinder holder 8 through this space, or The refrigerant gas in the high-temperature part is provided so as not to enter the vicinity of the cooling part 6 through the opposite route and increase the temperature of the cooling part 6, thereby reducing the cooling capacity of the refrigerator. Since the part to be sealed is at an extremely low temperature, for example, the sealing members 12 and 13 are slid together with the inner wall of the expansion cylinder 2 as a clearance seal that creates a gap of only a few microns to several tens of microns. This significantly reduces seal drag without the use of lubricants. FIG. 7 (al is a cross-sectional view of an expansion cylinder device according to the prior art ζ, in which seal members 12 and 13 of the same diameter are installed near both ends of the expansion piston 1, and the seal members 12 and 13 are connected to the inner wall of the expansion cylinder 2. There are minute gaps 14 and 15 between them.

The tube walls of the expansion piston 1 and the expansion cylinder 2 are made of high heat to prevent heat from entering from the high-temperature expansion cylinder holder 8 fall into the low-temperature cooling section 6 through thermal conduction and reducing the cooling capacity. It is made thin to have heat resistance. Therefore, it is difficult to process with high precision, and since the rigidity is small and it is easily deformed, it is difficult for the expansion piston 1 to move coaxially with the expansion piston 2. However, since the expansion piston 1 is equipped with a seal member of the same diameter, Fig. 7 ib
When the expansion cylinder 2 is deformed and bent as shown in FIG. . In order to avoid this, if the diameters of the seal members 12 and 13 are decreased by 1 as shown by the dotted line to increase the gap between them and the inner wall of the expansion cylinder 2, the expansion piston 1 can move smoothly. This has the undesirable effect of increasing the leakage of refrigerant gas through the air and reducing the cooling capacity.

The same applies to the case where the expansion piston 1 is bent.

[Purpose of the invention]

This invention solves the above problems and is equipped with a seal that maintains low seal resistance even when the expansion piston or expansion cylinder has low processing accuracy or is bent, and also suppresses the amount of refrigerant gas leaking. The purpose is to provide an expansion cylinder device.

[Key points of the invention]

In this invention, by equipping seal members with different diameters near both ends of the expansion piston, the gap between the large-diameter rail member at one end and the inner wall of the expansion cylinder is made such that refrigerant gas does not easily leak. The gap between the small-diameter sealing member and the inner wall of the expansion cylinder is designed to have enough room to accommodate bending of the expansion cylinder or expansion piston.

[Embodiments of the invention]

FIG. 1 is a cross-sectional view of an embodiment of an expansion cylinder device according to the present invention, in which seal members 24 with different diameters are installed on the cooling section δ side of the expansion piston 21 and at the ends of 26 expansion cylinder holders, respectively. is equipped with. In the wooden embodiment, the diameter of the sealing member layer on the side of the cooling part δ is made smaller than the diameter of the sealing member U on the side of the expansion cylinder holder, but in -, the gap 27 with the expansion cylinder n becomes wider than the gap 28. ing.

FIG. 2 is a schematic diagram showing the effects of the embodiment of the present invention. i
al indicates a normal state, and if gaps n and 4 between the sealing member 23 and the inner wall of the expansion cylinder B are respectively δa and δb, δa>δb.

Further, if the value of the gap necessary for the seal to function as a clearance seal is δ0, then δh=δ0. WJz diagram (bl is the state where the expansion cylinder 22J is bent, and the amount of vertical displacement at the position i of the sealing member layer is taken as the amount of bending of the expansion cylinder n, and this is set as 61. In this state In order for the expansion piston 21 to move smoothly, a seal member n is required.

It is necessary to maintain a gap of δ0 between the cylinder and the inner wall of the expansion cylinder B, as shown in the figure (see below), where δ1>δ0.

On the other hand, when the diameters of the seal members 12 and 13 are the same as in the prior art, the seal members 12 and 13 each have a gap δ0 in the form shown in FIG. 2 fct for the same bending amount δ1 as above. must be maintained. Figure 2 Fdl is Ic
The state of l is returned to the state before the bending occurred,
Gap δa to be initially provided between seal members 12 and 13
' and δb' are +δ1(2) where δa/=δb'=+δ1+δ0. From (1) and (2) it is clear that J δb δa
' = δb', and when the same allowance is given for the same bending, the configuration according to the present invention can reduce the gap between the sealing member and the expansion cylinder 2 compared to the prior art l. .

In the present invention, the sealing member provided with the above-mentioned minute gap δ0 is only the sealing member layer, and since the sealing member is given a margin to escape from the bending of the expansion cylinder B, the sealing effect of the sealing member is low. It becomes. In contrast, the prior art seal members 12 and 13 have a wider gap with the expansion cylinder 2 than in the seal member layer, but on the other hand provide twice the seal length. However, even in such a state, the sealing characteristics of the structure according to the present invention are superior to those of the prior art, and this is shown below.

FIG. 3 is a schematic diagram showing the sealing portion, in which a layer of sealing material with a diameter of one width is arranged coaxially with the inner wall of the expansion cylinder 2 with a gap δ maintained therebetween. If we assume that the pressures on both sides of the seal are P and P2, and that the flow through the gap δ is laminar and that the gas is isothermal, then the leakage amount of refrigerant gas as a mass flow zG passing through the gap δ is as follows ( 3) is given in a form proportional to the third power of δ as in the equation (for example, Yasuki Nakayama: Introduction to Fluid Dynamics for Hydraulic and Pneumatic Engineers (7), Hydraulics and Pneumatics, Vol. 8, No. 1 (Sho. 21 of January 2052 issue)
(See formula (12/23) on page).

Here, μ, R, and T are the viscosity coefficients of the refrigerant gas, respectively.

Gas constant, absolute temperature. The leakage amount for the length 21 gap δ0 in the configuration of the present invention is Gl, and the configuration l of the prior art is
If the leakage amount for the length 2 stones 8 gaps + δ1 is 02, the seal length according to the prior art is twice as long, so G1t5 and G2 are respectively indicated. Here, it is assumed that D is sufficiently larger than δ0 and δl, and that the pressure on the seal image side ζ is the same for G1 and 02. (If we calculate the ratio of Gl and G2 from 41 and (5), we get G1 δ0. Since δo minus δ1 and G-2 is proportional to the cube of um, it is clear from equation 16) that Gl<02. As an example of numerically illustrating this effect, consider the case where δ0=15 microns=15 x 10 and δt=0.1 mm. Therefore, according to the present invention, in the above case, the amount of leakage of refrigerant gas can be suppressed to about 5% of that of the prior art.

Moreover, it is possible to cope with the bending of an equivalent expansion cylinder.

FIG. 4 is a sectional view showing the effect of the embodiment of the present invention,
The configuration according to the present invention is an expansion cylinder n and an expansion piston 2]
This shows that it is less susceptible to the effects of bending, etc. Fourth
Figure (al is when expansion cylinder n is bent, (b)
(C) is a case where the expansion piston 21 is bent, and (C) is a case where the outer wall and the inner wall of the expansion cylinder n are not finished coaxially due to insufficient machining accuracy. This shows that it can move smoothly.

FIG. 5 shows a different embodiment of the present invention,
Contrary to the embodiment shown in FIG. 1, the diameter between the seal members on the side of the cooling section δ is made larger than the diameter of the seal member 31 on the other side of the expansion cylinder holder. In this embodiment, measures against bending of the expansion piston 21 and the expansion cylinder A are completely the same as in the embodiment shown in FIG. Furthermore, since the seal member I on the side of the cooling unit 5 suppresses leakage of cooling gas,
The refrigerant gas in the expansion cylinder n is given a larger rate of change in volume than the embodiment shown in FIG. Seal members with different diameters are installed in the vicinity, and there is only a minute gap between the seal member with a larger diameter in the vicinity of one end and the inner wall of the expansion cylinder to the extent that it does not interfere with the smooth movement of the expansion piston. There should be enough space between the smaller diameter sealing member at the other end and the expansion cylinder I'E wall to prevent the movement of the expansion piston from being hindered even if the expansion cylinder or expansion piston is bent. This design allows for sufficient clearance between the refrigerant gas and the expansion piston, which would reduce the cooling capacity even if the expansion cylinder or piston is bent, or if the expansion cylinder and expansion piston are combined with poor machining accuracy. The expansion piston can be moved smoothly even under the above conditions without causing leakage.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of an embodiment of an expansion cylinder device according to the present invention, FIG. 2 is a schematic diagram for explaining the effects of the embodiment of the present invention, FIG. 3 is a schematic diagram of a seal portion, and FIG. Cross-sectional views showing the effects of the embodiments of the present invention in various cases 1. Fifth
The figures show different examples of the present invention, FIG. 6 is a block diagram of a refrigerator using a reverse Stirling cycle, and FIG. 7 is a sectional view of an expansion cylinder device according to the prior art. 1.2]: expansion piston, 2, 22: expansion cylinder, 5
: Cooled object, 6, 25: Cooling section, 12, 13, Z
3, 24, 29. Figure 1 Figure 4 Figure 5 Figure 6

Claims (1)

[Scope of Claims] 1) Between an expansion cylinder whose end is hermetically sealed by a cooling part for the object to be cooled and an inner surface of the expansion cylinder that is guided so as to be able to reciprocate in the longitudinal direction inside the expansion cylinder. and an expansion piston sealed by a sealing member against refrigerant gas, wherein the sealing members are composed of a pair having mutually different diameters and are always in a position to seal the vicinity of both ends of the expansion piston during reciprocating movement. An expansion cylinder device for a refrigerator, characterized in that: 2) An expansion cylinder device for a refrigerator according to claim 1, wherein the seal is a clearance seal.