JP2766335B2 - Cryogenic refrigerator - Google Patents

Description

The present invention relates to a cryogenic refrigerator, and more particularly, to a regenerative refrigerator.

(Prior Art) There are various types of cryogenic refrigerators. Among these are Gihod McMahon type refrigerators. This refrigerator is generally configured as shown in FIG.

That is, this refrigerator is largely divided into a cold head 1 and a refrigerant gas guide / discharge system 2. The cold head 1 includes a closed cylinder 11, a displacer 12 reciprocally housed in the cylinder 11,
The displacer 12 is composed of a motor 13 which supplies power required for reciprocation.

The cylinder 11 includes a large-diameter first cylinder 14 and a small-diameter second cylinder 15 coaxially connected to the first cylinder 14. A first stage 16 as a cooling surface is formed at a boundary wall between the first cylinder 14 and the second cylinder 15.
And a one-stage stage at the tip wall of the cylinder 15.
A two-stage stage 17 having a lower temperature than 16 is constituted. The displacer 12 includes a first displacer 18 that reciprocates in the first cylinder 14 and a second displacer 19 that reciprocates in the second cylinder 15. 1st displacer
The 18 and the second displacer 19 are connected in the axial direction by a connecting member 20. A fluid passage 21 extending in the axial direction is formed inside the first displacer 18, and the fluid passage 21 accommodates a cold storage material 22 formed of a copper mesh or the like. Similarly, a fluid passage 23 extending in the axial direction is formed inside the second displacer 19, and the fluid passage 23 accommodates a cold storage material 24 formed of a lead ball or the like. Seal mechanisms 25 and 26 are mounted between the outer peripheral surface of the first displacer 18 and the inner peripheral surface of the first cylinder 14, and between the outer peripheral surface of the second displacer 19 and the inner peripheral surface of the second cylinder 15, respectively. Have been.

The seal mechanisms 25 and 26 are configured as shown in FIGS. 13 to 14 as representatives of the seal mechanism 26, for example. That is, an end-shaped seal ring 28 is mounted in an annular groove 27 formed on the outer peripheral surface of the second displacer 19 so that the outer peripheral surface is in contact with the inner peripheral surface of the second cylinder 15. And an end-shaped spring ring 29 for pressing the seal ring 28 against the inner surface of the cylinder.

The upper end of the first displacer 18 in the figure is a connecting rod 31,
Motor 13 via scotch yoke or crankshaft 32
Is connected to the rotating shaft. Therefore, when the rotating shaft of the motor 13 rotates, the displacer is synchronized with this rotation.
12 reciprocates as shown by the solid arrow 33 in the figure.

An inlet 34 and an outlet 35 for the refrigerant gas are provided in the upper part of the side wall of the first cylinder 14, and the inlet 34 and the outlet 35 are connected to the refrigerant gas guide / discharge system 2. The refrigerant gas guide / discharge system 2 constitutes a helium gas circulation system via the cylinder 11, and the discharge port 35 is connected to a low pressure valve 36, a compressor 37,
It is connected to the inlet 34 via 38. That is, the refrigerant gas guide / discharge system 2 compresses helium gas of low pressure (about 5 atm) to high pressure (about 18 atm) by the compressor 37 and sends it into the cylinder 11. And the low pressure valve 36,
The opening and closing of the high-pressure valve 38 is controlled in a relationship described later in relation to the reciprocation of the displacer 12.

The operation of the refrigerator configured as described above will be briefly described as follows. In this refrigerator, a portion where cold occurs, that is, a portion provided for a cooling surface is a first stage 16 and a second stage 17. These cool to about 30K and 10K, respectively, when there is no heat load. Therefore, a temperature gradient from room temperature (300K) to 30K is applied between the upper and lower ends of the first displacer 18 in the drawing, and a temperature gradient from 30K to 10K is set between the upper and lower ends of the second displacer 19 in the drawing. However, this temperature varies depending on the heat load of each stage, and is usually 1
30-80K for stage 16 and 10-20K for stage 17
Between.

When the motor 13 starts rotating, the displacer 12 reciprocates between the bottom dead center. When the displacer 12 is at the bottom dead center, the high pressure valve 38 opens and high pressure helium gas flows into the cold head 1. Next, the displacer 12 moves to the top dead center. As described above, the first displacer
Between the outer peripheral surface of the first cylinder 14 and the inner peripheral surface of the first cylinder 14 and the second
Seal mechanisms 25 and 26 are mounted between the outer peripheral surface of the displacer 19 and the inner peripheral surface of the second cylinder 15, respectively.
For this reason, when the displacer 12 moves to the top dead center, the high-pressure helium gas passes through the fluid passage 21 formed in the first displacer 18 and the fluid passage 23 formed in the second displacer 19 and passes through the first displacer 18. One-stage expansion chamber 39 formed between the first and second displacers 19 and
It flows into a two-stage expansion chamber 40 formed between the displacer 19 and the tip wall of the second cylinder 15. With this trend,
High-pressure helium gas is cooled by cold storage materials 22, 24,
After all, the high pressure helium gas flowing into the one-stage expansion chamber 39 is 30
The high-pressure helium gas flowing into the two-stage expansion chamber 40 is cooled to about 8K. Here, the high pressure valve 38 closes,
The low pressure valve 36 opens. When the low-pressure valve 36 is thus opened, the high-pressure helium gas in the one-stage expansion chamber 39 and the two-stage expansion chamber 40 expands to generate cold. The first stage by this cold
16 and the second stage 17 are cooled. Then, the displacer 12 moves to the bottom dead center again, and accordingly, the helium gas in the first-stage expansion chamber 39 and the second-stage expansion chamber 40 is removed. The expanded helium gas is warmed by the cold storage materials 22 and 24 while passing through the fluid passages 21 and 23, and is discharged at normal temperature. Hereinafter, the above-described cycle is repeated to perform the refrigeration operation. This type of refrigerator is used for cooling a superconducting magnet, cooling an infrared sensor, or as a cooling source for a cryopump.

However, the conventional refrigerator configured as described above has the following problems. That is, the sealing mechanism 25 prevents helium gas from flowing through the gap between the first cylinder 14 and the first displacer 18 between the room temperature part and the first-stage expansion chamber 39.
26 prevents helium gas from flowing through the gap between the second cylinder 15 and the second displacer 19 between the first-stage expansion chamber 39 and the second-stage expansion chamber 40. These seal mechanisms 25 and 26 are used in high-purity (99.99%) helium gas, and cannot use a lubricant such as grease in order to prevent helium gas contamination.

Therefore, as described above, as shown in FIGS. 13 to 15, an end-shaped seal ring 28 is mounted in an annular groove 27 formed on the outer peripheral surface of the second displacer 19, and furthermore, Ended spring ring for applying pressing force to the back side
A seal mechanism 26 having a structure 29 is used. However, as shown in FIG. 15, the spring ring 29 having the end portion 30 applies the maximum pressing force to the seal ring at a position A which is 90 degrees in the circumferential direction from the end portion. The pressing force decreases as the distance increases, and the pressing force at the position B in the figure becomes zero. Therefore, a sufficient pressing force cannot be applied to the entire circumference of the seal ring 28. Therefore, the leakage amount of the helium gas in the sealing mechanism 26 having such a configuration is large, and as a result, there is a problem that the temperature of the second stage 17 is increased. An increase in the temperature of the second stage will result in a decrease in the refrigerating capacity at a certain temperature. This will be described in more detail.

Now, assuming that the temperature of the first-stage expansion chamber 39 is 30K and the temperature of the second-stage expansion chamber 40 is 10K, if leakage occurs at the seal mechanism 26, helium gas of 30K is supplied to the second displacer 1.
The helium gas of 10K enters the first-stage expansion chamber 39 without contacting the cold storage material 24 in the 9 and enters the two-stage expansion chamber 40. As a result, the temperature of the first stage 16 decreases, and the temperature of the second stage 17 increases. FIG. 16 shows the helium gas leak rate in the seal mechanism 26 (the ratio of the helium gas flowing through the seal mechanism 26 to the total amount of helium gas flowing into the two-stage expansion chamber 40) and each stage (the first stage 16, the second stage 16). The results obtained by calculating the relationship with the temperature in stage 17) are shown. As can be seen from this figure, leakage at the seal mechanism 26 has a large effect on the temperature of each stage. This is a seal mechanism
The same applies to the seal mechanism 25 as well as the seal mechanism 25.

(Problems to be Solved by the Invention) As described above, in the conventional Gihod-Maxhon type refrigerator, a complete seal can be performed by a seal mechanism for sealing a gap between the displacer and the cylinder. There was a problem that the refrigeration capacity was low due to this.

Therefore, an object of the present invention is to provide a refrigerator capable of greatly improving the sealing performance of a sealing mechanism and thereby improving the refrigerating capacity.

[Configuration of the invention]

(Means for Solving the Problems) The present invention provides a closed cylinder, a displacer slidably disposed in the cylinder and having a passage containing a cold storage material inside, and reciprocating the displacer. Means for introducing a refrigerant gas inlet and outlet provided at one end of the cylinder, and introducing the high-pressure refrigerant gas into the cylinder from the inlet in relation to the reciprocation of the displacer. In a cryogenic refrigerator equipped with a refrigerant gas guiding / discharging means for repeating a step of discharging from a discharge port, an annular groove formed on an outer peripheral surface of the displacer, and an outer peripheral surface formed in the annular groove inside the cylinder. At least one end-shaped seal ring mounted in contact with the peripheral surface, and mounted concentrically with the end shifted with respect to the inside of the seal ring. And a plurality of end-shaped spring rings.

Further, a plurality of end-shaped spring rings may be installed concentrically inside the seal ring.

Further, a plurality of end-shaped spring rings may be laminated in the axial direction inside the seal ring.

Further, the end portions of the plurality (N) of the end type spring rings may be mounted so as to be shifted by 360 ° / N in the circumferential direction.

(Operation) As described above, by arranging a plurality of end-shaped spring rings concentrically with shifted end portions, the amount of helium gas leakage through the seal mechanism can be significantly reduced.
Therefore, improvement of the refrigerating capacity can be realized.

(Example) Hereinafter, an example is described, referring to drawings.

FIG. 1 shows a cryogenic refrigerator according to one embodiment of the present invention. In this figure, the same parts as those in FIG. 12 are denoted by the same reference numerals. Therefore, the description of the overlapping part will be omitted.

The point that the cryogenic refrigerator according to this embodiment differs from the conventional cryogenic refrigerator is that the cryogenic refrigerator is mounted in an annular groove 27 formed on the outer peripheral surface of the second displacer 19 and the second displacer and the second displacer.
This is a configuration of a seal mechanism 41 for sealing a gap between the cylinder 15.

As shown in FIGS. 2 to 4, the seal mechanism 41 has an end-shaped seal ring 42 in the annular groove 27, and is mounted concentrically inside the seal ring 42 and has an inner periphery of the second cylinder 15. Ended spring rings 43 and 44 for applying a pressing force to the surface side are mounted. And the spring rings 43,44
As shown in FIG. 4, is mounted in the annular groove 27 so that a cut at a small distance R between both ends is substantially 90 degrees apart in the circumferential direction as shown in FIG.

With such a configuration, a portion where the pressing force of the spring ring 44 is the strongest is disposed in a portion where the pressing force of the spring ring 43 is the weakest, so that the pressing force on the seal ring 42 is made uniform in the circumferential direction. You. Therefore, helium gas leakage from the seal mechanism 41 can be significantly reduced, and the temperature rise in the second expansion chamber, that is, the second stage 17, can be suppressed, and the refrigerating capacity can be improved.

In the next embodiment, as shown in FIGS. 5 to 7, an end-shaped seal ring 42 is
End-shaped spring rings 43a and 44a that apply a pressing force to the inner peripheral surface side of the second cylinder 15 in a two-stage configuration in the axial direction are mounted inside 42. And the spring rings 43a, 44
As shown in FIG. 7, a is mounted in the annular groove 27 so that a cut at a small distance R between both ends is separated from the circumferential direction by approximately 90 degrees as shown in FIG.

With such a configuration, a portion where the pressing force of the spring ring 43a is the strongest is disposed in a portion where the pressing force of the spring ring 43a is originally low, so that the pressing force on the seal ring 42 is made uniform in the circumferential direction. Is done. Therefore, helium gas leakage from the seal mechanism 41 can be significantly reduced, and the temperature rise in the second expansion chamber, that is, the second stage 17, can be suppressed, and the refrigerating capacity can be improved.

Next, a reference example to the present invention will be described. This reference example uses a conventional sealing mechanism 26 as shown in FIGS.
(FIG. 13 to FIG. 14).
Instead, a spring ring 45 formed by bending a coil spring into a ring shape is used. With this configuration, a sufficient pressing force can be uniformly applied to the entire circumference of the seal ring.

FIG. 10 shows the measurement results of the gas leakage amount between the conventional refrigerator incorporating the seal mechanism shown in FIG. 13 and the refrigerator of the present invention incorporating the seal mechanism 41 shown in FIG. . This is a result of measurement at normal temperature and in a stationary state with equal width of the annular groove and equal pressing force of the spring ring. Although it is different from the actual use condition (low temperature, reciprocation), it can be seen that the leakage amount is greatly reduced. This tendency is considered to be reflected in the use conditions. Fig. 11 shows the
13 shows refrigeration curves of the conventional refrigerator incorporating the seal mechanism shown in FIG. 13 and the refrigerator according to the present invention incorporating the seal mechanism 41 shown in FIG. The horizontal axis indicates the temperature (k) of the second stage 17, and the vertical axis indicates the heat load (W) applied to the second stage 17. As can be seen from this figure, the refrigerator of the present invention has a greater ability to freeze at the same temperature. Therefore, it is understood that the refrigeration capacity can be improved by providing the seal mechanism 41a having the above configuration. This is the same for the seal mechanisms 41b and 41c of the embodiment and the reference example shown in FIGS.

In the above-described embodiment, only the seal mechanism provided between the second displacer and the second cylinder is used in the second embodiment.
5, 5 and 8, the seal mechanism provided between the first displacer and the first cylinder is also provided as a seal mechanism in FIGS. It may be constituted by the seal mechanisms 41a, 41b, 41c shown in FIG.

〔The invention's effect〕

As described above, according to the present invention, gas leakage at the seal mechanism can be significantly reduced, so that a further lowering of the temperature can be realized and the refrigeration capacity can be improved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a refrigerator according to an embodiment of the present invention, which is partially cut away, and FIG. 2 is a first embodiment of a sealing mechanism incorporated in the refrigerator viewed from an axial direction. Schematic diagram, third
The figure is a longitudinal sectional view showing the sealing mechanism taken out locally,
FIG. 4 is a schematic view showing the configuration of both ends of a seal ring incorporated in the seal mechanism, and FIG. 5 is a schematic view showing a second embodiment of the seal mechanism incorporated in the refrigerator viewed from the axial direction. ,
FIG. 6 is a longitudinal sectional view showing the sealing mechanism locally taken out, FIG. 7 is a schematic view showing both ends of a seal ring incorporated in the sealing mechanism, and FIG. 8 is incorporated in the refrigerator. FIG. 9 is a schematic view showing a third embodiment of the sealing mechanism viewed from the axial direction, FIG. 9 is a longitudinal sectional view showing the sealing mechanism in a locally extracted state, FIG. 10 and FIG. FIG. 12 is a diagram showing the characteristics of the refrigerator of the first embodiment in comparison with that of the conventional refrigerator, FIG. 12 is a schematic configuration diagram of the conventional refrigerator, and FIG. 13 is a diagram showing a sealing mechanism incorporated in the refrigerator. Figure viewed from the axial direction, No.
FIG. 14 is a longitudinal sectional view showing the sealing mechanism taken out locally,
FIG. 15 is a view showing a form of both ends of a seal ring incorporated in the seal mechanism, and FIG. 16 is a view for explaining a problem of the conventional refrigerator. 1 ... Cold head, 2 ... Refrigerant gas guide / discharge system, 11 ...
... cylinder, 12 ... displacer, 13 ... motor, 14
... 1st cylinder, 15 ... 2nd cylinder, 16 ... 1st stage, 17 ... 2nd stage, 18 ... 1st displacer, 19 ... 2nd displacer, 21, 23 ...
2,24 cold storage material, 27 annular groove, 28,42 seal ring, 39 first expansion chamber, 40 second expansion chamber, 41a, 41b, 41
c: Seal mechanism, 43, 43a, 44, 44a, 45 ... Spring ring.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) F25B 9/14 510

Claims (4)

(57) [Claims] 1. A closed cylinder, a displacer slidably disposed within the cylinder and having a passage containing a cold storage material therein, means for reciprocating the displacer, and A step of introducing a high-pressure refrigerant gas into the cylinder from the introduction port in association with the reciprocating motion of the displacer and discharging the high-pressure refrigerant gas from the discharge port provided at one end side is repeated. A cryogenic refrigerator provided with a refrigerant gas guiding / discharging means for mounting an annular groove formed on an outer peripheral surface of the displacer, and an outer peripheral surface in the annular groove being mounted in contact with an inner peripheral surface of the cylinder. At least one end-type seal ring; and a plurality of end-type spring rings mounted concentrically and with end portions shifted inside the seal ring. Cryogenic refrigerator, characterized by comprising; and a grayed. 2. The cryogenic refrigerator according to claim 1, wherein said plurality of end-type spring rings are installed concentrically inside said seal ring. 3. The cryogenic refrigerator according to claim 1, wherein the plurality of end-type spring rings are laminated in an axial direction inside the seal ring. 4. The cryogenic refrigeration according to claim 1, wherein the end portions of the plurality of (N) end-shaped spring rings are displaced 360 ° / N in a circumferential direction. Machine.