JPH0689961B2 - Cryogenic refrigerator - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cryogenic refrigerator equipped with a free-display type expander, and more particularly to measures for increasing the capacity of the device.

(Prior Art) Conventionally, as a cryogenic refrigerator, for example, a displacer is reciprocated in a cylinder by a slack piston or the like that moves up and down in response to rectangular wave-shaped high and low pressure from a compressor connected by high-pressure and low-pressure piping. A GM cycle cryogenic refrigerator, which is operated to expand compressed refrigerant gas in a cylinder to generate cold in the cylinder, is well known.

On the other hand, as another type of cryogenic refrigerator, a Stirling cycle cryogenic refrigerator in which a compressor that supplies a sine-shaped pressure wave and an expander that has a displacer suspended by a spring are connected to each other by a high-low pressure common pipe Is also a known device.

(Problems to be Solved by the Invention) However, the conventional GM cycle cryogenic refrigerator has a problem that noise and vibration are large because a rectangular wave pressure wave is supplied to the cylinder. Therefore, it is possible to use a Stirling cycle cryogenic refrigerator, but it is usually difficult to increase the capacity of a free displacer type Stirling cycle refrigerator due to the capacity of the compressor and the cylinder structure.

The present invention has been made in view of the above problems, and an object thereof is to achieve low noise and low vibration by using a plurality of free displacer type Stirling cycle refrigerators and GM cycle refrigerators in combination. It is to provide a cryogenic refrigerator with a large capacity.

(Means for Solving the Problem) In order to achieve the above-mentioned object, a solution means of the present invention is to connect a plurality of free displacer type expanders used in a Stirling cycle refrigerator to a compressor for a GM cycle refrigerator. To do.

Specifically, as shown in FIG. 1, a compressor (5) for a GM cycle refrigerator, which compresses a refrigerant gas such as helium,
High-pressure side and low-pressure side piping (3), (4) in the compressor (5)
And a expander unit (2) that expands the refrigerant gas compressed by the compression device (5) and is connected to the cryogenic refrigerator.

And, a plurality of free displacer type expanders (9), ... Connected to the expander unit (2) so that refrigerant gas can flow through the high pressure side and low pressure side pipes (3), (4), The connection state between each expander (9) and the high-pressure side and low-pressure side pipes (3), (4) is set so that at least two sets of the plurality of expanders (9), ... A connection switching mechanism (31) for switching is provided.

(Operation) With the above configuration, in the present invention, the connection switching mechanism (31) sequentially switches the expanders (9), ... so that the expanders (9), ... are connected to the low pressure side pipe (4). The expander (9) connected to 4) enters an expansion cycle, causing cold at the low temperature end of the lower end of the cylinder (10).

In that case, switching between high pressure and low pressure is performed more times than in the GM refrigerator, so that the refrigerant flows more smoothly and the fluid noise is reduced. Further, since the displacer is a free displacer type, no noise is generated by hitting the upper or lower part of the cylinder like the displacer of the GM refrigerator. Further, at least two sets of the plurality of expanders (9), ... Are sequentially switched to the expansion cycle by the connection switching mechanism (31), so that the expanders (9) ,. The expansion and contraction of the expander unit (2) as a whole are offset, so that the vibration of the device is effectively reduced.

Further, since the plurality of expanders (9), ... Are provided, the capacity of the entire expander unit (2) can be increased by the number of expanders (9) ,.
Since it is for the GM cycle refrigerator, the expansion unit (2) can be increased in capacity without causing capacity shortage as in the Stirling cycle refrigerator.

(Example) Hereinafter, the Example of this invention is described based on drawing.

1 and 2 show the structure of the main part of a cryogenic refrigerator according to an embodiment of the present invention, (1) is a compressor unit,
(2) is an expander unit, both units (1),
Between (2), high-pressure side pipe (3) and low-pressure side pipe (4)
Is connected so that the refrigerant can flow. The compressor unit (1) is provided with suction of helium gas as a refrigerant,
A compressor (5) for performing compression and discharge and an oil separator (6) interposed on the discharge side of the compressor (5) are arranged as main devices, and the oil separator (6) is arranged via the low pressure pipe (4). After compressing the low-pressure helium gas returned from the expander unit (2) to a high pressure by the compressor (5), the oil separator (6) separates the lubricating oil mixed in the helium gas, and the high-pressure pipe ( It has a structure of a type used for GM cycle cryogenic temperature in which rectangular wave pressure gas is supplied to the expander unit (2) via 3).

On the other hand, the expander unit (2) has a cylindrical motor housing portion (8) and a lower end surface of the motor housing portion (8) on a circle concentric with the outer circumference of the motor housing portion (8). Six small cylindrical expanders (9), which are equally divided and extend vertically downward, ...
And are provided.

Each of the expanders (9) has the same structure and accommodates a bottomed cylindrical cylinder (10) with one end open and a regenerator (12), and reciprocates vertically in the cylinder (10). A moving cylindrical displacer (11), a spring (13) for suspending the displacer (11) in the motor housing (8), and the spring (13) provided at the lower end of the motor housing (8). ) For fixing the cylindrical support member (1
4) consists of Here, on the upper and lower wall surfaces of the displacer (11), the upper space (10a) and the lower space (10b) of the cylinder (10) partitioned by the displacer (11).
Communication holes (11a) and (11b) for communicating the refrigerant with the inside of the displacer (11) are respectively provided, and when the upper space (10a) of the cylinder (10) communicates with the low pressure side, the displacer ( 11) moves upward, the volume of the lower space (10b) of the cylinder (10) increases, and the refrigerant gas expands in the lower space (10b) through the regenerator (12), whereby the cylinder (10). It is designed to generate cold at the low temperature end of the lower part.

A helium gas supply port (16) is attached to the motor housing (8) slightly below the center of the side surface of the casing (8a) of the motor housing (8) and is connected to the high-pressure side pipe (3). ), A helium gas discharge port (17) attached near the lower end of the side surface of the casing (8a) and connected to the low pressure side pipe (4), and a lower end of the motor housing (8) to the casing (8a). A disk-shaped valve stem (18) fitted and fixedly supporting the expander (9), ..., Cylinder (10), and mounted on the upper surface of the valve stem (18) in a concentric circle position. (18) Disk-shaped rotary valve (19) that rotates on top, and motor housing (8)
And a motor (20) for rotating the rotary valve (19), which is attached to the upper part of the casing so as to occupy the upper half of the inner space of the casing (8a).

Here, inside the casing (8a) of the motor housing (8), there is a predetermined volume between the motor (20), the valve stem (18), and the rotary valve (19), and A surge volume chamber (8b) communicating with the supply port (16) is formed, and the valve stem (18) has
The central hole (14) of the support member (14) of each of the expanders (9), ...
Six communication holes (18a), ... Corresponding to a) are provided, and the rotary valve (19) has one communication hole on the same circumference as the communication hole (18a) of the valve stem (18). A hole (19a) is provided, and the communication hole (19a) is formed in the valve stem (1
When it matches the communication hole (18a) of 8), the communication hole (19a)
The expander (9) corresponding to a) is the surge volume chamber (8
The high pressure side pipe (3) is sequentially connected via b).

In addition, the valve stem (18) has a valve stem (1
A communication passage (18b) is provided which opens at a central position on the upper surface of 8), extends downward by a predetermined depth, and then extends in a radial direction and opens at a portion corresponding to the discharge port (17). The valve (19) is opened at the center position of its lower surface, extends a predetermined distance upward, and then is defined as the communication hole (19a).
After extending in the opposite radial direction by 80 °, the valve stem (1
A communication passageway (19b) opening at a portion corresponding to the communication passageway (18a) of 8) is provided, and as shown in FIG. 3, the communication passageway (19b) is a communication hole (19b) of the valve stem (18). Cylinder (10) of expander (9) corresponding when it matches with 18a)
The inside is communicated with the low pressure side pipe (4) sequentially through the communication passages (18b) and (19b). That is, when one expander (9) communicates with the low pressure side pipe (4), the expander (9) on the opposite side of 180 ° communicates with the high pressure side pipe (3) to rotate the rotary valve (19). Accordingly, the six expanders (9), ... Repeat the expansion cycle in sequence.

That is, by the valve stem (18), the rotary valve (19) and the motor (20), at least two sets of the plurality of expanders (9), ... ) And the high-pressure side and low-pressure side pipes (3) and (4), the connection switching mechanism (31) is switched.

Therefore, in the above-described embodiment, the connection switching mechanism (31) switches the expanders (9), ... In order to sequentially connect the low-pressure side pipe (4) to the low-pressure side pipe (4). The expanded expander (9) enters the expansion cycle. That is,
The refrigerant gas in the upper space (10a) of the cylinder (10) is discharged from the low pressure side pipe (4) to the compressor (5) side, and the lower pressure of the upper space (10a) causes the displacer (11) to move to the spring (13). ), The volume of the lower space (10b) of the cylinder (10) increases, and the refrigerant gas causes the communication holes (11a) and (11b) of the displacer (11).
And, by flowing into the lower space (10b) through the regenerator (12) and expanding, cold is produced at the low temperature end of the lower portion of the Linda (10).

When the expander (9) is connected to the high pressure side pipe (3) by switching the connection switching mechanism (31), the upper space (10a) becomes high pressure and the displacer (11) moves downward. The refrigerant gas in the lower space (10b) moves upward in the route opposite to the above, and at the same time stores cold heat in the regenerator (12).

In that case, the compressor (5) is that of a normal GM cycle refrigerator, and a rectangular wave pressure wave is supplied to the expander unit (2), but switching between high and low pressure is performed by the GM refrigerator. Since it is performed a number of times as compared with the above, the refrigerant flows more smoothly and the fluid noise is reduced. Further, since the displacer is a free displacer type, no noise is generated by hitting the upper or lower part of the cylinder like the displacer of the GM refrigerator. Therefore, the noise of the displacer (11) is reduced as compared with the conventional displacer driven by a slack piston or the like.

Further, since the plurality of expanders (9), ... Are sequentially switched to the expansion cycle by the connection switching mechanism (31), the expanders (9), ..
When one expander (9) contracts due to the occurrence of cold, the other expanders (9), ... Are put into an expanded state, and the expansion and contraction of the expander unit (2) as a whole are offset, thus vibrating the device. Will be effectively reduced.

Further, since a plurality of expanders (9), ... Are arranged, even the free displacer type Stirling cycle expander has the capacity of the expander unit (2) as a whole. The number can be increased. Further, since the compressor (5) is for the GM cycle refrigerator, the expander unit (2) does not cause a capacity shortage like a linear motor compressor generally used in a free displacer type Stirling cycle refrigerator. It is possible to cope with the increase in capacity.

In addition, in the above-mentioned embodiment, although the rectangular wave-shaped pressure wave is supplied to each expander (9), ..., The connection switching mechanism (3
By controlling the switching timing of 1), it is possible to convert to a pseudo-sine wave pressure wave, and in that case, the effect of reducing vibration and noise will be remarkably exhibited.

Further, in the above embodiment, the plurality of expanders (9), ... Are switched one by one to the expansion cycle one by one, but the configuration of the connection switching mechanism (31) of the present invention is limited to the above embodiment. Instead, for example, two expanders (9), ...
Even if the connection is switched such that the expansion cycle is alternately divided into three groups, the expansion and contraction of the entire expansion unit (2) are canceled out, and a vibration reducing effect is obtained.

(Effects of the Invention) As described above, according to the present invention, in a cryogenic refrigerator, a compressor for a G-M cycle refrigerator and a plurality of free displacers connected in a flowable manner to the refrigerant of the compressor. A type expander is arranged, and the connection state between the compressor and each expander is switched so that at least two sets of the plurality of expanders sequentially repeat the expansion cycle. It is possible to provide a large-capacity device while achieving reduction and reduction of vibration due to cancellation of expansion and contraction change due to internal pressure fluctuation of the expander.

[Brief description of drawings]

The drawings show an embodiment of the present invention, FIG. 1 is a vertical cross-sectional view taken along the line I-I of FIG. 2 showing the structure of the apparatus, FIG.
FIG. 3 is a partial vertical cross-sectional view of the device showing the connection state of the connection switching mechanism during the expansion cycle of the expander. (2) …… Expander unit, (3) …… High pressure side piping,
(4) …… Low-pressure side piping, (5) …… Compressor, (9) ……
Expander, (31) …… Connection switching mechanism.

Claims (1)

[Claims] 1. A compressor (5) for a GM cycle refrigerator, which compresses a refrigerant gas such as helium, and is connected to the compressor (5) by high-pressure side and low-pressure side pipes (3), (4). A cryogenic refrigerator comprising: an expander unit (2) for expanding the refrigerant gas compressed by the compressor (5), wherein the expander unit (2) includes the high-pressure side and low-pressure side pipes. (3), a plurality of free displacer type expanders (9), ...
The expanders (9) are connected to the high-pressure side and low-pressure side pipes (3), (4) so that at least two sets of the plurality of expanders (9), ... A cryogenic refrigerator characterized in that a connection switching mechanism (31) for switching is arranged.