JPH05296587A - Multi-stage cold accumulation type refrigerator - Google Patents

Abstract

PURPOSE:To prevent the degradation of a sealing performance caused by fine particles of a cold storage material, prevent an increase in the sliding resistance of a sealing section and enhance refrigeration efficiency by installing a plurality of filters in a cold preserver in order to prevent the fine particles of the cold storage material from flowing outside the cold preserver. CONSTITUTION:A multi-stage refrigerator is housed inside a vessel 1 in such a fashion that its multi-stage cylinders 1a to 1c are connected to displacers 2 to 4 respectively. In addition, multi-stage cold preservers 5 to 7 are housed inside each of the displacers 2 to 4 filled with multi-stage cold storage materials 6a to 7a respectively. In this case, a plurality of multi-stage filters 25 to 27 are laid out inside the multi-stage cold preservers 5 to 7 respectively. When introducing a high pressure helium gas fluid into each of the cold preservers 5 to 7, the gas fluid is adapted to flow from suction and exhaust ports 2a to 4a on one side to suction and exhaust ports 2b to 4b on the other side, thereby passing the gas fluid through each of the filters 25 to 27. This construction makes it possible to shut down the flow of the fine particles generated from each of the cold preservers 5a to 7a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-stage regenerator having a plurality of stages of regenerators each filled with a regenerator material.

[0002]

2. Description of the Related Art In recent years, superconducting magnets have come to be used in medical MRI (Magnetic Resonance Imaging) and linear motors. The superconducting coils of electromagnets used in these devices are liquid helium. It is common to cool inside. Therefore, the problem of how to reduce the consumption of helium during operation is a particularly important issue in maintaining the above-mentioned equipment.

Also, a typical cold storage refrigerator is Gifford-McMahon.
A refrigerator (hereinafter, abbreviated as GM refrigerator) has been widely used as a refrigerator that operates at liquid nitrogen or liquid hydrogen temperature, but recently, it has become a liquid helium temperature (4.
It can also be applied as a refrigerator operating at 2K), and is gradually being put into practical use as a helium refrigerator.

The major reason for such practical application is as follows.
A cool storage material of a compound containing a rare earth element having a larger specific heat has been developed as compared with a cool storage material of lead or copper that has been conventionally used in an extremely low temperature range (for example, JP-A-1-31026).
It is considered that the first factor is that it has become possible to obtain an operating temperature equal to or lower than the temperature of liquid helium.

FIG. 4 shows, for example, "Low Temperature Engineering" (Vol. 24,
FIG. 4 is a schematic sectional view of a conventional multistage GM refrigerator shown on page 223 of No. 4, 1989 Low Temperature Engineering Association).

In the figure, reference numeral 1 designates first to third stage cylinders 1a, 1b, which have successively smaller diameters and are connected in series.
Containers 1c, 2, 3 and 4 are first to third stage displacers that are successively connected in series and have a smaller diameter and are housed in the container 1. These displacers 2, 3 and 4 are It is possible to reciprocate integrally in the vertical direction in the figure. In addition, each displacer 2, 3 and 4 has a first
Intake / exhaust holes 2a, 3a, 4a and second intake / exhaust holes 2b,
3b and 4b are provided.

Reference numerals 5, 6 and 7 are first to third stages in which first to third stage displacers 2, 3 and 4 are filled with first to third stage regenerator materials 5a, 6a and 7a, respectively.
A first-stage to third-stage stainless wire mesh which is a stage regenerator and prevents the regenerator materials 5a, 6a and 7a from closing the intake and exhaust holes 2a to 4b at both ends of the regenerators 5, 6 and 7, respectively. 5b, 6
b and 7b are arranged. Further, phosphor bronze wire mesh and lead balls are used for the first-stage and second-stage regenerator materials 5a and 6a, and a compound containing a rare earth element (hereinafter abbreviated as a rare earth substance) is used for the third-stage regenerator material 7a. Yes.) Is used.

Reference numerals 8, 9 and 10 are each displacer 2, 3,
The first to third stage seals are attached to the outer periphery of the cylinder 4 and are in close contact with the inner periphery of each of the cylinders 1a, 1b, 1c, and are made of, for example, a fluorine resin. 11, 12 and 13 are first to third expansion chambers formed in the cylinders 1a, 1b and 1c, respectively, and 14, 15 and 16 are expansion chambers 11, 12 and
In order to take out the cold generated from 13, each cylinder 1a,
The first to third thermal stages (heat stages) are fixed to the outer circumferences of 1b and 1c.

Reference numeral 17 is a motor housing attached to the container 1, 18 is a switching valve provided in the motor housing 17 and having an intake valve and an exhaust valve, and 19 is a switching valve.
Helium compressor connected to 18, 20 is helium compressor 19
Is a high-pressure side supply pipe connected between the switching valve 18 and the intake valve of the switching valve 18, and 21 is a low-pressure side return pipe connected between the helium compressor 19 and the exhaust valve of the switching valve 18.

Reference numeral 22 denotes a drive motor mounted on the outer periphery of the motor housing 17, and the drive motor 22 has a rotary shaft 22a penetrating the side wall of the motor housing 17. 23 is a slide shaft that is connected to the end of the first-stage displacer 2 and penetrates through the motor housing 17, and 24 is provided inside the motor housing 17, and drives the slide shaft 23 to reciprocate by the rotation of the rotary shaft 22a. It is a unit, and the slide shaft 23 and the switching valve 18 are mechanically synchronously controlled. In addition, 31 is a 1st stage freezing part, 32 is a 2nd stage freezing part, 33
Is the third stage freezer.

Next, the operation will be described. First, the first
In the state where the volume of the third-stage or third-stage expansion chambers 11, 12, 13 is minimum, the compressed high-pressure helium gas from the helium compressor 19 is passed through the supply pipe 20 and the intake valve to the first-stage freezing section. Introduce to 31. This high-pressure gas is supplied to the first intake / exhaust hole 2
After passing through a, it enters the first-stage regenerator 5, is cooled to a predetermined temperature by the first-stage regenerator material 5a, is discharged from the second intake / exhaust hole 2b, and is guided to the first-stage expansion chamber 11. After that, the high-pressure gas moves to the second-stage freezing unit 32 and the third-stage freezing unit 33 in the same manner as the operation in the first-stage freezing unit 31, and is performed by the second-stage and third-stage regenerator materials 6a and 7a. It is cooled sequentially.

Next, the displacers 2, 3, 4 are moved so that the volumes of the expansion chambers 11, 12, 13 are maximized with the intake valve open, and the expansion chambers 11, 12, 13 are moved. Fill with high pressure gas. From this state, by closing the intake valve and opening the exhaust valve at once, the helium gas has a low pressure, and cold is generated in each of the expansion chambers 11, 12, and 13.

After that, the helium gas is supplied to each regenerator 5,
The temperature rises while the cold heat is taken by 6 and 7 and returns to the original room temperature, and returns from the exhaust valve to the helium compressor 19 via the return pipe 21. Next, the displacers 2, 3 and 4 are moved to minimize the volumes of the expansion chambers 11, 12 and 13, and then the exhaust valve is closed and the intake valve is opened, whereby the freezing 1
The cycle is complete.

In each of the thermal stages 14, 15 and 16, heat is transferred to and from an object to be cooled (not shown). In the above example, approximately 70K in the first stage, 20K in the second stage, The freezing temperature is 4K level in 3 stages.

FIG. 5 is a work flow chart showing a conventional regenerator material filling method for a GM refrigerator. First, the regenerator 5,
The stainless wire nets 5b, 6b, and 7b are inserted and attached to the bottoms of the displacers 2, 3, and 4 which compose 6, 7 (step S
After 1), the regenerator material 5 that has been washed in advance (step S2)
A, 6a, and 7a are packed (step S3). After this,
The upper portions of the displacers 2, 3 and 4 are closed (steps S4 and S5) with other stainless wire nets 5b, 6b and 7b and caps (not shown). After this, the displacers 2, 3 and 4 are connected to the cylinders 1a, 1b and 1 of each stage.
will be incorporated into c.

[0016]

In the conventional multi-stage regenerator having the above-described structure, the inside of the regenerators 5, 6 and 7 in operation is filled with a high pressure gas fluid (10 to 20 kg /
cm ² G) reciprocates, so the regenerator material 5
A, 6a, 7a contact each other, causing mechanical wear and damage. As a result, fine powder is generated inside the regenerators 5, 6, 7 and the fine powder adheres to the seal portion between the cylinders 1a, 1b, 1c and the displacers 2, 3, 4. Particularly, since the rare earth material regenerator material 7a used in the third stage is a brittle material as compared with a normal metal, there is a problem that fine powder is remarkably generated and the sealing performance is significantly reduced. ..

After a certain amount of operating time, the fine powder itself bites into the seals 8, 9, 10 itself, increasing the sliding resistance with the cylinders 1a, 1b, 1c, and switching valve 18 There is also a problem in that the fine powder adheres to the seat surface of, and the sealing effect of the switching valve 18 itself is impaired.

The present invention has been made to solve the above problems, and it is possible to prevent deterioration of the sealing performance due to the fine powder of the regenerator material generated from the regenerator, and to seal the seal. The purpose of the present invention is to obtain a multi-stage regenerative refrigerator capable of preventing an increase in sliding resistance of a portion, thereby improving refrigeration efficiency and stabilizing refrigeration temperature, and improving reliability. And

[0019]

A multi-stage regenerator of the present invention is provided with a plurality of filters in a regenerator.

[0020]

In the present invention, the filter inside the regenerator prevents the fine powder of the regenerator material from flowing out of the regenerator.

[0021]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic cross-sectional view of a multi-stage GM refrigerator according to an embodiment of the present invention. The same or corresponding parts as in FIG.

In the figure, 25 is a first-stage filter provided in the first-stage regenerator 5 with a plurality of sheets, 26 is a second-stage filter provided in the second-stage regenerator 6 with a third-stage filter 27. Stage regenerator 7
A plurality of third-stage filters are provided inside, and as each of the filters 25, 26, 27, for example, polyester having a thickness of several mm is used.

In the multi-stage GM refrigerator as described above, cold is generated by the same operation as the conventional example. Therefore, when introducing the high-pressure helium gas fluid into the regenerators 5, 6, 7, the first intake / exhaust holes 2 of the displacers 2, 3, 4 are introduced.
The gas fluid flows from a, 3a, 4a toward the second intake / exhaust holes 2b, 3b, 4b. When the gas is expanded, the gas fluid flows in the opposite direction. In any case, the gas fluid is the filter 25. , 26, 27.

Therefore, even if fine powder of the regenerator material 5a, 6a, 7a is generated, the fine powder is filtered by the filters 25, 26,
It is blocked by 27, and the outflow of fine powder to the outside of the regenerators 5, 6, 7 is prevented. This prevents the sealing performance from deteriorating and prevents the sliding resistance of the sealing portion from increasing. In particular, the third-stage regenerator 7 using a rare earth material that is brittle in strength has a great effect.

Next, a method of filling the cold storage material 5a, 6a, 7a will be described. FIG. 2 is a work flow diagram showing an example of the filling method. First, the regenerator materials 5a, 6a, 7a are put into a temporary container or the like and shaken for a predetermined time (step S7). After that, the normal regenerator materials 5a, 6a, 7a are selected using a sieve or the like (step S7), and the regenerator materials 5a, 6a, 7a are selected.
Are washed (step S2). Other procedures are the same as those described with reference to FIG. However, displacer 2,
When the regenerator materials 5a, 6a, 7a are packed in the 3, 4, the filters 25, 26, 27 are inserted at appropriate intervals.

With this procedure, the cold storage materials 5a, 6a, 7a, which are easily destroyed, can be removed in advance, so that the amount of fine powder generated can be greatly reduced. Such a method is particularly effective when the cool storage material 7a made of a rare earth material is used. In addition, the spherical regenerator material 5a,
By using 6a and 7a, the amount of fine powder generated can be similarly reduced.

FIG. 3 is a work flow chart showing another example of the filling method. In the case of this example, first, the cold storage materials 5a, 6
a, 7a and the filters 25, 26, 27 to the displacer 2,
After packing in 3, 4, a temporary cap (not shown) is attached (step S8), and the displacers 2, 3, 4 are vibrated at a somewhat gentle constant frequency (step S9). As a result, the cold storage material 7a is packed in a denser state.

After this, the temporary cap is removed (step S10), and the inside of the displacer 4 is checked to see if it has reached a predetermined packing volume (step S11). If there is a margin in volume due to the above vibration, the regenerator materials 5a, 6a,
7a is further replenished and the above operation is repeated until a predetermined packing volume is reached. In this way, when it is confirmed that the predetermined packing volume has been reached, the stainless wire nets 5b, 6
Attach b, 7b and cap.

By filling in this manner, the regenerator materials 5a, 6a, 7a come into close contact with each other without a gap, so that mechanical wear or damage due to the pressure of the high pressure gas fluid during operation does not occur. In addition, the amount of fine powder generated can be significantly reduced.

The method as shown in FIGS. 2 and 3 is effective to some extent even when the filters 25, 26 and 27 are not used, but when combined with the filters 25, 26 and 27, the filters 25, 26 and 27 are obtained. , 27 functions can be maintained for a long time, so it is more effective. Alternatively, the methods shown in FIGS. 2 and 3 may be combined.

[0031]

As described above, the multistage regenerator of the present invention is provided with a plurality of filters in the regenerator.
Since the fine powder of the regenerator material is prevented from flowing out of the regenerator, it is possible to prevent the sealing performance from being deteriorated by the fine powder and to prevent the sliding resistance of the seal portion from increasing. As a result, the refrigerating efficiency can be improved, the freezing temperature can be stabilized, and the reliability can be improved.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a multi-stage GM refrigerator according to an embodiment of the present invention.

FIG. 2 is a work flow diagram showing an example of a method for filling the cold storage material of FIG.

FIG. 3 is a work flow diagram showing another example of the method for filling the cold storage material in FIG.

FIG. 4 is a schematic sectional view of an example of a conventional multi-stage GM refrigerator.

5 is a work flow diagram showing an example of a method for filling the cold storage material in FIG. 4. FIG.

[Explanation of symbols]

 5 1st stage regenerator 5a 1st stage regenerator 6 2nd stage regenerator 6a 2nd stage regenerator 7 3rd stage regenerator 7a 3rd stage regenerator 25 1st stage filter 26 2nd stage filter 27 3rd stage filter

Claims (1)

[Claims] 1. A multi-stage regenerator having a plurality of regenerators each filled with a regenerator material for preventing fine powder of the regenerator material from flowing out of the regenerator. A multi-stage regenerator with a plurality of filters provided in the regenerator.