JPH0544645A - Sealing device - Google Patents

Abstract

PURPOSE:To provide a nonlubrication type sealing device with which the sealing performance can be improved drastically without making the structure complicated. CONSTITUTION:As for a sealing device for sealing the gap between a cylinder 15 and a piston 19 without using lubricating oil, an edged shape spring ring 45 is fitted into the groove inside an inner peripheral seal ring 44, and the first and second outermost peripheral seal rings 42 and 43 are installed on the outer periphery of the inner peripheral seal ring 44. The first and second outermost peripheral seal rings 42 and 43 and the inner peripheral seal ring 44 are formed in each edged shape, and the gaps 46-48 are formed between the edged parts. These gaps 46-48 are arranged so as not to be superposed on the outer periphery of the piston 19. The sealing device having such structure is installed in the groove on the outer periphery of the piston 19, and the outer periphery is pushed to the inner peripheral surface of the cylinder 15 by the action of the spring ring 45.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sealing device,
In particular, the present invention relates to a seal device that seals a gap between a cylinder and a piston fitted in the cylinder without using lubricating oil.

[0002]

2. Description of the Related Art There are various types of sealing devices for sealing a gap between a cylinder and a piston fitted in the cylinder, but usually, most of these sealing devices lubricate a sliding contact portion. The method of lubricating with oil is adopted.
However, some devices incorporating a cylinder and a piston fitted into the cylinder are not suitable for a sealing device using lubricating oil. A typical example of such a device is a cryogenic refrigerator using helium gas as a refrigerant. In this refrigerator, if lubricating oil is used for the seal portion, the lubricating oil freezes at a low temperature, and there is a problem that the lubricating function is not fulfilled. Therefore, in a cryogenic refrigerator using helium gas as a refrigerant, the gap between the cylinder and the piston is usually sealed by a non-lubricating type seal device.

In FIG. 7, helium gas is used as a refrigerant,
Moreover, a conventional Gifford-McMahon type refrigerator incorporating a non-lubricated seal device is shown. This Gifford-McMahon type refrigerator is, for example, a refrigerant gas, that is, as disclosed in Japanese Patent Application No. 1-27678.
It comprises a cold head 1 for cooling the helium gas and a refrigerant gas guide / exhaust system 2 in which the refrigerant gas is circulated. In the cold head 1, a piston, that is, a displacer 12 for compressing a refrigerant gas formed of a heat insulating material is housed in a closed cylinder 11 so as to reciprocate. The displacer 12 is reciprocated by power from a motor 13. Be moved. The cylinder 11 is a large diameter first cylinder 14
And a small-diameter second cylinder 15 coaxially connected to the first cylinder 14. 1st cylinder 1
The fourth and second cylinders 15 are usually formed of a thin stainless steel plate or the like. The first and second cylinders 14,
First and second cooling stages 16 and 17 that are arranged in series are provided in the unit 15. That is, at the boundary between the first cylinder 14 and the second cylinder 15, a first stage cooling stage 16 for expanding the compressed refrigerant gas to cool the refrigerant gas is provided, and the second cylinder 15 is also provided. A second stage cooling stage 17 for expanding the compressed refrigerant gas to cool the refrigerant gas to a lower temperature than the cooling in the first stage cooling stage 16 is provided at the tip portion of the. There is.

The displacer 12 includes a first cylinder 14
It is composed of a first displacer 18 that reciprocates inside and a second displacer 19 that reciprocates inside the second cylinder 15. The first displacer 18 and the second displacer 19 are axially connected by a connecting mechanism 20. Inside the first displacer 18, a fluid passage 21 for forming a regenerator is formed in the axial direction. The fluid passage 21 accommodates a regenerator material 22 such as a mesh structure made of copper. Similarly, a fluid passage 23 extending in the axial direction is also formed in the second displacer 19, and a regenerator material 24 formed of a lead ball or the like is accommodated in the fluid passage 23. Sealing devices 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. Has been done.

The seal devices 25 and 26 have, for example, the structure shown in FIGS. 8 to 10 as a representative of the seal device 26. That is, in the sealing device 26, as shown in FIG. 9, the resin provided in the annular groove 27 formed in the outer peripheral surface of the second displacer 19 so that the outer peripheral surface contacts the inner peripheral surface of the second cylinder 15. The endless seal ring 28 made of metal is attached, and the endless spring ring 29 for pressing the seal ring 28 against the inner peripheral surface of the second cylinder 15 is attached to the inner surface of the seal ring 28. Has been done. At both ends of the seal ring 28, as shown in FIG. 10, overlapping portions 30 are formed in which both ends are superposed in the radial direction.

The upper end of the first displacer 18 is connected to the rotary shaft of the motor 13 via a connecting rod 31, a scotch yoke, or a crank shaft 32. Therefore,
When the motor 13 is actuated and its rotating shaft is rotated, the displacer 12 is synchronized with this rotation and the displacer 12 is indicated by a solid arrow 3 in the figure.
It is reciprocated as indicated by 3.

An inlet 34 and an outlet 35 for the refrigerant gas are provided in the upper portion of the side wall of the first cylinder 14, and the inlet 34 and the outlet 35 are connected to the refrigerant gas guide / exhaust system 2. The refrigerant gas introduction / exhaust system 2 constitutes a helium gas circulation system passing through the cylinder 11, and has an exhaust port 35.
Is connected to the inlet 34 via a low pressure valve 36, a compressor 37, and a high pressure valve 38. That is, the low-pressure (about 5 atm) helium gas is compressed to a high pressure (about 18 atm) by the compressor 37 by the refrigerant gas guide / discharge system 2, and the cylinder 11
Sent in. This low pressure valve 36 of the refrigerant gas discharge system 2
The high pressure valve 38 and the high pressure valve 38 are controlled to be opened / closed in the relationship described later in relation to the reciprocal movement of the displacer 12.

In the refrigerator thus constructed,
Cold is the first stage 16 and the second stage 17
It is generated in two stages. This first and second stage 1
6 and 17 are 30K in ideal condition without heat load
And, the first displacer 18 is cooled down to about 8K.
A temperature gradient from room temperature (300K) to 30K occurs between the upper and lower ends, and a temperature gradient from 30K to 8K occurs between the upper and lower ends of the second displacer 19. The temperatures of the first and second stages 16 and 17 change depending on the heat load of the cooling stage of each stage. Normally, the first stage cooling stage 16 has a temperature of 30 to 80K and a second stage. Cooling station
In Ji17, it becomes 8 to 20K.

When the motor 13 starts rotating, the displacer 12 is reciprocated between the bottom dead center and the top dead center. When the displacer 12 reaches the bottom dead center, the high pressure valve 38 is opened and the high pressure helium gas flows into the cold head 1. Next, the displacer 12 is moved to the top dead center. As described above, the sealing device 25 is provided 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 first cylinder 15, respectively. , 26 are mounted, 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 when the displacer 12 moves toward the top dead center. , A first stage expansion chamber 39 formed between the first displacer 18 and the second displacer 19 and a second stage expansion chamber 40 formed between the second displacer 19 and the tip wall of the second cylinder 15. To be done. With this inflow, the high-pressure helium gas is cooled by the regenerator material 2.
The high-pressure helium gas cooled by 2 and 24 and flowing into the first-stage expansion chamber 39 is cooled to about 30K, and the high-pressure helium gas flowing into the second-stage expansion chamber 40 is cooled to about 8K.

When the displacer 12 reaches the top dead center, the high pressure valve 38 is closed and the low pressure valve 36 is opened. When the low-pressure valve 36 is opened in this manner, the high-pressure helium gas in the first-stage expansion chamber 39 and the second-stage expansion chamber 40 is expanded to generate cold. Due to this cold, the first cooling stage 16 is further cooled, and the second cooling stage 1 is also cooled.
7 is also cooled to the 4K level. Then, when the displacer 12 moves to the bottom dead center again, the helium gas in the first-stage expansion chamber 39 and the second-stage expansion chamber 40 passes through the fluid passages 21 and 23 along with this, but this passage At this time, the regenerator materials 22, 24 are cooled, and the helium gas whose temperature has risen is passed from the cold head 1 through the low pressure valve 36 to the compressor 37.
Is discharged to. Such a cycle is repeated and the refrigerating operation is executed to cool the helium gas. This type of refrigerator is used for cooling a shield plate arranged in a heat insulating layer of a cryostat, for cooling an infrared sensor, or as a cooling source for a cryosorption pump.

It has been pointed out that the conventional refrigerator configured as described above has the following problems. That is, the sealing device 25 prevents the helium gas from flowing through the gap between the first cylinder 14 and the first displacer 18 between the room temperature portion and the first expansion chamber 39,
Further, the sealing device 26 prevents the helium gas from flowing through the gap between the second cylinder 15 and the second displacer 19 between the first expansion chamber 39 and the second expansion chamber 40. These sealing devices 25 and 26 do not use lubricating oil in order to maintain the purity (99.99%) of helium gas and prevent malfunction due to freezing.

Now, the temperature inside the first-stage expansion chamber 39 is 30
If the temperature inside the second expansion chamber 40 is 10 K, for example, if a leak occurs in the sealing device 26, it is 30
The K helium gas enters the second-stage expansion chamber 40 without contacting the regenerator material 24 in the second displacer 19, and conversely, the 10K helium gas enters the first-stage expansion chamber 39. As a result, the temperature of the first-stage cooling stage 16 drops and the temperature of the second-stage cooling stage 17 rises. FIG. 11 shows the relationship between the leakage amount ratio of helium gas in the sealing device 26 (the ratio of helium gas flowing through the sealing device 26 to the total amount of helium gas flowing into the two-stage expansion chamber 40) and the temperature of each stage cooling stage. The result obtained by calculating is shown. As can be seen from FIG. 11, the leakage at the sealing device 26 has a great influence on the temperature of each stage cooling stage. This is not limited to the sealing device 26, and the sealing device 25 has the same problem.

In the conventional refrigerator, as shown in FIGS. 8 to 10, the overlapping portion 30 is formed in the annular groove 27 formed on the outer peripheral surface of the second displacer 19 as shown in FIG. Attach only one end type seal ring 28,
Further, a sealing device 26 having a structure in which an end-shaped spring ring 29 for applying a pressing force is attached to the back side thereof is used. In the sealing device 26 having such a structure, when the seal ring 28 is thermally shrunk at an extremely low temperature, the overlapping portion 30
In particular, the adhesion in the circumferential direction is apt to deteriorate, and the leak amount of helium gas from the superposition section 30 increases, so that the second stage cooling stage
There is a problem that the temperature of the die 17 rises. Second stage cooling station
An increase in the temperature of the die 17 will result in a decrease in refrigerating capacity at a certain temperature.

[0014]

As described above, the conventional non-lubricating type sealing device cannot exhibit the desired sealing performance, and when this is incorporated into, for example, a cryogenic refrigerator. Has a problem of reducing the refrigerating capacity.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a non-lubricating type sealing device which can greatly improve the sealing performance without inviting a complicated structure.

[0016]

To achieve the above object, according to the present invention, a piston and a piston are fitted into an annular groove formed in the outer peripheral surface of the piston, and the outer surface of the piston is brought into contact with the cylinder. A sealing device is provided for sealing the gap between. According to the sealing device of the present invention,
The second outermost seal ring has an end shape, and first and second gaps are provided between the ends, and the second outermost seal ring is axially stacked and mounted in the annular groove,
In addition, a third seal ring, which is an end type and has a third gap between the ends, is mounted inside these first and second outermost peripheral seal rings, and A spring ring is mounted in the groove of the third seal ring, and presses the first and second seal rings against the inner peripheral surface of the cylinder via the third seal ring.

[0017]

By storing the spring ring in the third seal ring, the pressing force of the spring ring acts evenly on the first and second seal rings via the third seal, and the pressing force to the cylinder is increased. It is stable without one-sided contact, and gas leakage from the cylinder surface and seal can be reduced. Moreover, since the third seal ring can be inserted deep into the annular groove of the piston, gas leakage toward the center of the annular groove of the piston can be greatly reduced. Therefore, when incorporated in a cryogenic refrigerator, it can contribute to the improvement of refrigerating capacity.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the sealing device of the present invention will be described below with reference to the drawings.

FIG. 1 shows a Gifode-McMahon type refrigerator incorporating a sealing device according to an embodiment of the present invention. In FIG. 1, the same parts or the same parts as those shown in FIG. 7 are designated by the same reference numerals, and detailed description thereof will be omitted.

In this refrigerator, the second displacer 19
The gap between the outer peripheral surface of the second cylinder 15 and the second cylinder 15 is sealed by the sealing device 41 according to the embodiment of the present invention. The sealing device 41 is mounted in an annular groove 27 formed on the outer peripheral surface of the second displacer 19, as shown in FIGS. In this sealing device 41,
The outer sealings 42, 43 having a two-step structure are arranged along the axis of the second displacer 19 at the outermost periphery. The outer seal rings 42 and 43 have end shapes, and the outer peripheral surfaces thereof are in contact with the inner peripheral surface of the second cylinder 15. Inside the outer seal rings 42, 43, an end-shaped inner seal ring 44 is mounted, and further,
Inside the inner seal ring 44, for example, a spring ring 45 made of stainless steel and having an end shape is attached. The spring force from the spring ring 45 is applied to the outer seal rings 42, 43 via the inner seal ring 44.
Is added to the outer seal ring 42,
43 is pressed against the inner peripheral surface of the second cylinder 15.

The outer seal rings 42 and 43 and the inner seal ring 44 are each made of a resin-based material such as a composite material of ethylene tetrafluoride and a wear resistant material, a composite material of glass fiber and polyamid, or the like. The outer seal rings 42 and 43 are formed to have the same axial thickness and the same radial thickness. The inner seal ring 44 has an axial thickness equal to the sum of the axial thicknesses of the outer seal rings 42 and 43. Further, the inner seal ring 44 is provided with a groove inside thereof and is formed in a U-shaped cross section. The spring ring 45 is dimensioned to fit in the groove inside the inner seal ring 44.

The outer seal rings 42, 43 and the inner seal ring 44 formed in this manner have a small distance R between their ends as shown in FIGS. 2 and 4, respectively.
The gap 46 (47, 48) of the
6, 47, and 48 are approximately 120 in the circumferential direction as shown in FIG.
It is mounted in the annular groove 27 so as to form a degree.

When the sealing device has such a structure, a gap is generated in each of the three seal rings 42, 43 and 44, so that a total of three gaps 46, 47 and 48.
Will occur, but these gaps 46, 47, 48
Since they are arranged so as to be displaced in the circumferential direction, there is substantially no break in the sealing device, and the sealing device is a single continuous member pressed against the inner peripheral surface of the second cylinder 15. A sealing state equivalent to that with a seal ring attached is obtained. In addition, the inner seal ring 44 has
Since the spring ring 45 is installed and the spring ring 45 is installed in the inner groove, the pressing force of the spring ring is applied to the center of the sealing device, and a uniform pressing force without shoulder contact is obtained. As a result, according to the sealing device 41 of the present invention, gas leakage can be greatly reduced. Therefore, the second expansion chamber, that is, the second stage cooling station
It is possible to suppress an increase in the temperature of the die 17 and improve the refrigerating capacity.

FIG. 5 shows the measurement of the amount of gas leakage in a conventional refrigerator having the seal device shown in FIG. 9 and a refrigerator having the seal device 41 shown in FIG. 3 according to an embodiment of the present invention. Results are shown. This measurement result was obtained by making the axial width of the annular groove the same and the pressing force of the spring ring the same at room temperature and in a stationary state. Although it is different from the actual use condition, that is, the condition in which the displacer reciprocates at a low temperature, it is understood that the leakage material is greatly reduced. This tendency is considered to be reflected in the actual use condition. Further, FIG. 6 shows freezing curves of a conventional refrigerator incorporating the sealing device shown in FIG. 9 and a refrigerator incorporating the sealing device 41 shown in FIG. The horizontal axis represents the temperature (K) of the second stage cooling stage 17, and the vertical axis represents the heat load (W) applied to the second stage cooling stage 17. As can be seen from this figure, a refrigerator incorporating the seal device 41 of the present invention has a greater ability to be frozen at the same temperature. Therefore, it is understood that the refrigerating capacity can be improved by incorporating the sealing device 41 having the above structure.

In the embodiment described above, the present invention is applied to the seal device provided between the second displacer and the second cylinder, but the seal provided between the first displacer and the first cylinder is used. It can also be applied to devices. Further, it goes without saying that the sealing device according to the present invention can be incorporated not only in a cryogenic refrigerator but also in all similar devices requiring no lubrication. The present invention is not limited to the above-described embodiments, and it is needless to say that various modifications can be made without departing from the gist of the present invention.

[0026]

As described above, according to the present invention,
Provided is a sealing device which has a simple structure but can exert a good sealing function over a wide temperature range.

[Brief description of drawings]

FIG. 1 is a block diagram showing a Gifode-McMahon refrigerating machine in which a sealing device according to an embodiment of the present invention is incorporated by partially cutting away.

FIG. 2 is an axial view of a sealing device incorporated in the Gifode-McMahon type refrigerator shown in FIG.

FIG. 3 is a vertical sectional view showing a sealing device according to the present invention shown in FIG.

FIG. 4 is a view showing a form of both ends of a seal ring incorporated in the seal device according to the present invention shown in FIG.

FIG. 5 is a diagram showing the characteristics of a refrigerator incorporating the sealing device of the present invention in comparison with those of a refrigerator incorporating a conventional sealing device.

FIG. 6 is a diagram showing the characteristics of a refrigerator incorporating the sealing device of the present invention in comparison with those of a refrigerator incorporating a conventional sealing device.

FIG. 7 is a schematic configuration diagram of a Gifode-McMahon type refrigerator incorporating a conventional sealing device.

8 is a view of the sealing device incorporated in the conventional refrigerator, taken along the line AA in FIG. 7 and viewed from the arrow direction.

FIG. 9 is a vertical cross-sectional view showing a conventional sealing device partially taken out.

FIG. 10 is a view showing a form of both ends of a seal ring incorporated in a conventional sealing device.

FIG. 11 is a diagram for explaining a problem of a Gifode-McMahon type refrigerator incorporating a conventional sealing device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Cold head, 2 ... Refrigerant gas guide / exhaust system, 11 ... Cylinder, 12 ... Displacer, 13 ... Motor, 14 ... First cylinder, 15 ... Second cylinder, 16 ... First stage cooling stage, 17 ... 2nd stage cooling stage, 18 ... 1st displacer, 19 ... 2nd displacer, 21, 23 ... Fluid passage, 22, 24 ... Regenerator material, 27 ... Annular groove, 39 ... 1st expansion chamber, 40 ... 2 expansion chambers, 41, 41a ... Sealing device, 42, 43 ... Outer seal ring, 44 ... Inner seal ring, 45 ... Spring ring, 46, 47, 48 ... Breaks.

Claims (2)

[Claims] 1. A sealing device fitted in an annular groove formed on an outer peripheral surface of a piston, the outer surface of which is brought into contact with a cylinder to seal a gap between the cylinder and the piston, in an axial direction of the annular groove. First and second outermost seal rings, which are stacked along and attached to each other, are end-shaped, and are provided with first and second gaps respectively between the ends, and the first and second outermost seal rings. And a third seal ring, which is mounted inside the outermost peripheral seal ring 2 and has an end shape and a third gap is provided between the ends, and is installed in the groove of the third seal ring. And an endless spring ring that presses the first and second seal rings against the inner peripheral surface of the cylinder via the third seal ring.
And a third seal ring is arranged at different positions along the outer circumference of the piston. 2. The third seal ring has an axial thickness equal to the sum of the axial thicknesses of the first and second seal rings. Sealing device.