JP6911649B2 - Multi-stage cold storage refrigerator - Google Patents

Description

The present invention relates to a multi-stage cold storage refrigerator.

A multi-stage cold storage refrigerator is often used to cool the object to be cooled to an extremely low temperature of 30 K or less. The multi-stage cold storage refrigerator is a multi-stage cylinder composed of a plurality of cylinders having different diameters concentrically arranged along the axial direction so that the diameter gradually decreases toward the tip. Be prepared. A cold storage means (for example, a cold storage material) is arranged in the multi-stage cylinder. A cooling stage is provided at the tip of each cylinder. Cryogenic temperature is generated at the cooling stage provided in the most advanced cylinder part. Therefore, by thermally connecting the cooled body to the most advanced cooling stage, the cooled body can be cooled to an extremely low temperature.

The multi-stage cold storage refrigerator is used, for example, in a cryostat. In this case, each cooling stage included in the multi-stage cold storage refrigerator is thermally connected to a heat shield arranged in the adiabatic vacuum chamber of the cryostat or a cooled body in the heat shield.

Patent Document 1 discloses a connection structure of a two-stage cold storage refrigerator in a cryostat. The two-stage cold storage refrigerator described in Patent Document 1 includes a multi-stage cylinder configured in two stages, a first-stage cooling stage arranged on the tip side of the first-stage cylinder portion of the multi-stage cylinder, and a multi-stage cylinder. It is provided with a second-stage cooling stage arranged on the tip side of the second-stage cylinder portion. Further, the cryostat has an adiabatic vacuum chamber, a first heat shield provided in the adiabatic vacuum chamber, and a second heat shield constituting a deep cooling portion arranged in the first heat shield. The first stage cooling stage of the two-stage cold storage refrigerator is thermally connected to the first heat shield, and the second stage cooling stage of the two-stage cold storage refrigerator heats the second heat shield that constitutes the deep cooling part. Is connected. Then, the second heat shield is cooled to an extremely low temperature by the second stage cooling stage.

Japanese Unexamined Patent Publication No. 9-287838

(Problems to be solved by the invention)
The target cooling temperature of each cooling stage provided at the tip of each cylinder portion of the multi-stage cylinder of the multi-stage cold storage refrigerator is lowered as the cooling stage is provided at the tip. For example, the target cooling temperature of the first-stage cooling stage provided in the first-stage cylinder (first-stage cylinder portion) of the two-stage cold storage refrigerator is 30K to 80K, which is the second stage at the tip of the first-stage cylinder. The target cooling temperature of the second stage cooling stage provided in the cylinder (second stage cylinder portion) is about 10K. Therefore, in this case, the cooled body to be cooled to an extremely low temperature of about 10 K is thermally connected to the second stage cooling stage.

Since the target cooling temperature of the cooling stage (that is, the high-stage cooling stage) provided on the tip side (that is, the high-stage side) of the multi-stage cylinder is extremely low, the temperature of the high-stage side cooling stage can be set to the target cooling temperature (for example, 10K). A large refrigerating capacity is required for cooling. However, the diameter of the cylinder portion on the high stage side is smaller than the diameter of the cylinder portion on the lower stage side, and the amount of the cooling medium such as the cold storage material filled therein is also small, so that the cooling stage on the higher stage side is cooled. Refrigeration capacity is small. Therefore, the cooling time for cooling the high-stage cooling stage to the target cooling temperature is very long, and therefore the cooling time of the object to be cooled cooled by the high-stage cooling stage to an extremely low temperature is very long. ..

An object of the present invention is to provide a multi-stage cold storage refrigerator having a structure capable of shortening the cooling time of a body to be cooled to be cooled to an extremely low temperature.

(Means to solve problems)
The multi-stage cooling storage type refrigerator (1) according to the present invention is composed of a plurality of cylinder portions (21, 22) having different diameters, and is formed in a stepped cylindrical shape so that the diameter gradually decreases toward the tip. The multi-stage cylinder (2), the cold storage means (33, 34) provided in the multi-stage cylinder, and the multi-stage cooling stages (60, 70) provided on the tips (21,221) sides of the plurality of cylinders, respectively. It is composed of a pressure fluctuation mechanism (5) that fluctuates the pressure in the multi-stage cylinder and a material that has a larger heat shrinkage rate than the material that constitutes the multi-stage cylinder, and one end (80a) of the material is a multi-stage cooling stage. It is fixed to the lower stage cooling stage (60), which is a cooling stage other than the highest stage cooling stage, extends from the lower stage cooling stage along the axial direction of the multi-stage cylinder, and is at the other end (80b). ) Is higher than the height position (B) along the axial direction of the multi-stage cylinder of the high-stage side cooling stage (70), which is the higher-stage side cooling stage than the lower-stage side cooling stage, at room temperature. The heat transfer member (80) located at the position (A) is arranged at a height higher than the height position of the higher stage cooling stage along the axial direction of the multi-stage cylinder, and the heat transfer member is at room temperature. The auxiliary cooling member (90), which sometimes comes into contact with the other end of the heat transfer member and is arranged facing the higher stage cooling stage with a gap (G) along the axial direction of the multi-stage cylinder, and the auxiliary cooling member are transmitted. It includes an urging member (95) that urges the thermal member toward the other end side.

In this case, when the temperature of the heat transfer member reaches the target cooling temperature of the lower stage cooling stage, the height position of the other end of the heat transfer member becomes lower than the height position of the higher stage cooling stage. It is preferable that the length of the heat transfer member along the axial direction of the multi-stage cylinder is set.

In the above invention, the "height position along the axial direction of the multi-stage cylinder" is a position represented by the distance from the lower-stage cooling stage along the axial direction of the multi-stage cylinder. Further, with respect to this height position, "high" means that the distance from the low-stage cylinder along the axial direction of the multi-stage cylinder is long. On the contrary, with respect to the height position, "low" means that the distance from the low-stage cylinder along the axial direction of the multi-stage cylinder is short.

According to the multi-stage cold storage refrigerator according to the present invention, one end of the heat transfer member is fixed to the lower stage cooling stage, and this heat transfer member assists at the other end when the temperature is normal. It is in contact with the cooling member. When the multi-stage cold storage refrigerator according to the present invention is operated in this state, the cold heat of the lower stage cooling stage is supplied to the cooled body (the cooled body assists) that is in thermal contact with the auxiliary cooling member via the heat transfer member. When it is a cooling member, it is transmitted to the auxiliary cooling member). That is, the object to be cooled is cooled by the cooling heat of the lower stage cooling stage. Since the cooling capacity of the lower cooling stage is high, the object to be cooled is cooled quickly.

Further, as the cooling of the lower stage cooling stage progresses, the heat transfer member heat-shrinks, so that the height position of the other end of the heat transfer member is lowered. Here, when the height position of the other end of the heat transfer member is higher than the height position of the higher stage cooling stage during cooling of the lower stage cooling stage, the urging member directs the heat transfer member toward the other end side. The urged auxiliary cooling member follows the decrease in the height position of the other end of the heat transfer member and moves toward the lower stage cooling stage side while maintaining contact with the heat transfer member. At this time, since a gap is provided between the auxiliary cooling member and the high-stage side cooling stage, the auxiliary cooling member and the high-stage side cooling stage are thermally insulated by such a gap. Since the high-stage cooling stage is not sufficiently cooled during cooling of the low-stage cooling stage, the presence of the above-mentioned gap prevents heat from flowing from the insufficiently cooled high-stage cooling stage to the auxiliary cooling member. can do.

Further cooling of the lower cooling stage progresses, and the temperature of the lower cooling stage is close to the target cooling temperature of the lower cooling stage (for example, a predetermined temperature αK within the temperature range of 30K to 80K) (for example, ( When α + 10) K) is reached, the heat transfer member further heat-shrinks, and the height position of the other end of the heat transfer member coincides with the height position of the high-stage cooling stage. Then, the gap provided between the auxiliary cooling member and the higher stage cooling stage disappears, and the auxiliary cooling member comes into contact with the higher stage cooling stage. At this time, the high-stage cooling stage is likely to be sufficiently cooled, in which case the auxiliary cooling member is cooled by the low-stage cooling stage and the high-stage cooling stage.

Then, when the temperature of the lower stage cooling stage reaches the target cooling temperature (for example, αK), the heat transfer member further heat-shrinks, and the height position on the other end side is higher than the height position on the higher stage side cooling stage. Will be located in a low position. Further, the auxiliary cooling member is in contact with the upper cooling stage and cannot move in the direction toward the lower cooling stage any more. That is, the high-stage cooling stage functions as a stopper for the movement of the auxiliary cooling member. Therefore, the auxiliary cooling member is separated from the heat transfer member. Therefore, the auxiliary cooling member and the body to be cooled that are in thermal contact with the auxiliary cooling member are cooled by the high-stage cooling stage. Then, the object to be cooled is cooled to an extremely low temperature (for example, 10K) by the cooling heat of the high-stage cooling stage. When the auxiliary cooling member and the body to be cooled in thermal contact with the auxiliary cooling member are cooled by the high-stage cooling stage, the auxiliary cooling member is separated from the heat transfer member as described above, so that the heat transfer member It is possible to prevent heat inflow from the first-stage cooling stage to the auxiliary cooling member via the above.

As described above, according to the present invention, the object to be cooled to be cooled to an extremely low temperature is cooled by the cooling heat of the lower stage cooling stage when the higher stage cooling stage is not sufficiently cooled. Then, when the high-stage cooling stage has been sufficiently cooled, the cooled body is cooled to an extremely low temperature by the cooling heat of the high-stage cooling stage. Since the refrigerating capacity of the lower-stage cooling stage is higher than the refrigerating capacity of the higher-stage cooling stage, the cooling time of the cooled object to be cooled to an extremely low temperature by the amount of cooling of the object to be cooled by the lower-stage cooling stage. Can be shortened.

In the present invention, the heat transfer member may be formed in a cylindrical shape so as to cover the outer periphery of the cylinder portion (high-stage side cylinder portion) provided with the high-stage side cooling stage. According to this, since the radiant heat from the outside is shielded by the heat transfer member, it is possible to effectively prevent the heat inflow to the upper cylinder portion due to the heat radiant.

Further, the heat transfer member may be made of aluminum. In this case, the multi-stage cylinder may be made of stainless steel. Aluminum has a high thermal conductivity and a higher thermal shrinkage than stainless steel. Therefore, according to this configuration, the difference in heat shrinkage between the heat transfer member (aluminum) and the multi-stage cylinder (stainless steel) is used to thermally connect and disconnect the heat transfer member and the auxiliary cooling member as described above. Can be realized.

Further, the multi-stage cylinder includes a first-stage cylinder portion and a second-stage cylinder portion having a diameter smaller than that of the first-stage cylinder portion, and a lower-stage cooling stage is provided on the tip side of the first-stage cylinder portion. It is preferable that the high-stage cooling stage is the second-stage cooling stage provided on the tip end side of the second-stage cylinder portion, and the multi-stage cold storage refrigerator is the two-stage cold storage refrigerator. According to this, in the two-stage cold storage type refrigerator, it is possible to shorten the cooling time of the object to be cooled that is cooled in the second-stage cooling stage.

It is a partial cross-sectional schematic diagram of the two-stage type GM refrigerator which concerns on embodiment. It is an enlarged view of the cross section near the auxiliary cooling plate. It is a partial cross-sectional schematic diagram of the two-stage type GM refrigerator which shows the state which the auxiliary cooling plate is in contact with the 2nd stage cooling stage. It is a partial cross-sectional schematic diagram of the two-stage GM refrigerator which shows the state which the auxiliary cooling plate is separated from a heat transfer sleeve. It is a graph which shows the temperature transition of the object to be cooled when the conventional two-stage GM refrigerator is operated. It is a graph which shows the temperature transition of the to be cooled body at the time of operating the two-stage GM refrigerator which concerns on embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic partial cross-sectional view showing a two-stage GM refrigerator, which is a cold storage type refrigerator according to the present embodiment. Note that FIG. 1 shows a cross section of the two-stage GM refrigerator in a non-operating state, that is, a cross section of the two-stage GM refrigerator in a normal temperature environment. As shown in FIG. 1, the two-stage GM refrigerator 1 according to the present embodiment includes a multi-stage cylinder 2, a displacer 3, a drive device 4, a pressure fluctuation mechanism 5, a first-stage cooling stage 60, and two stages. A cooling stage 70, a heat transfer sleeve 80, an auxiliary cooling plate 90, and a compression coil spring 95 are provided.

The multi-stage cylinder 2 has a first-stage cylinder portion 21 as a low-stage side cylinder portion and a second-stage cylinder portion 22 as a high-stage side cylinder portion. The first-stage cylinder portion 21 is formed in a cylindrical shape having one end portion 211 forming the tip end side and the other end portion 212 on the opposite side. The second-stage cylinder portion 22 is formed in a cylindrical shape having one end portion 221 constituting the tip end side and the other end portion 222 on the opposite side. In addition, in FIG. 1, one end portion (211, 221) of a cylinder portion (21, 22) is represented as an upper end portion, and the other end portion (212, 222) is represented as a lower end portion. However, "upper" and "lower" here are used only for convenience of explanation with reference to the drawings, and do not mean "upper" and "lower" in absolute space. Further, also in the following description, terms indicating directions such as "upper" and "lower" are used only for convenience of explanation with reference to the drawings, and "upper" and "lower" in absolute space are not necessarily used. It doesn't mean anything.

The inner diameter of the first-stage cylinder portion 21 is larger than the inner diameter of the second-stage cylinder portion 22, and the outer diameter of the first-stage cylinder portion 21 is larger than the outer diameter of the second-stage cylinder portion 22. The first-stage cylinder portion 21 and the second-stage cylinder portion 22 are coaxially arranged, and the other end portion 222 of the second-stage cylinder portion 22 is connected to one end portion 211 of the first-stage cylinder portion 21. Therefore, the multi-stage cylinder 2 has a stepped cylindrical shape in which the diameter gradually decreases toward the tip side (upper side in FIG. 1) (that is, from the lower stage side toward the higher stage side). That is, the multi-stage cylinder 2 is composed of a plurality of cylinder portions (21, 22) having different diameters, and is formed in a stepped cylindrical shape so that the diameter gradually decreases toward the tip. Further, the internal space of the first-stage cylinder portion 21 communicates with the internal space of the second-stage cylinder portion 22. Therefore, the shape of the internal space of the multi-stage cylinder 2 is a stepped cylindrical shape in which the diameter decreases toward the tip side (upper side in FIG. 1) (from the lower stage side toward the higher stage side).

The displacer 3 is arranged in the internal space of the multi-stage cylinder 2. The displacer 3 has a first-stage cold storage device 31 and a second-stage cold storage device 32. The first-stage cold storage 31 is formed in a cylindrical shape having a low-temperature end 311 and a high-temperature end 312 on the opposite side thereof, and the low-temperature end 311 side is located on one end 211 side of the first-stage cylinder 21, and the high-temperature end is located. It is arranged in the first-stage cylinder portion 21 so that the 312 side is located on the other end 212 side of the first-stage cylinder portion 21.

The second-stage cold storage 32 is formed in a cylindrical shape having a low temperature end portion 321 and a high temperature end portion 322 on the opposite side thereof. The inner diameter of the first-stage cold storage device 31 is larger than the inner diameter of the second-stage cold storage device 32, and the outer diameter of the first-stage cold storage device 31 is larger than the outer diameter of the second-stage cold storage device 32. The high temperature end 322 of the second stage cold storage 32 is connected to the low temperature end 311 of the first stage cold storage 31. Similar to the multi-stage cylinder 2, the displacer 3 also has a stepped cylindrical shape in which the diameter decreases toward the tip side (upper side in FIG. 1). As shown in FIG. 1, the second-stage cold storage device 32 extends upward from the upper end surface in FIG. 1 of the first-stage cold storage device 31 and enters the internal space of the second-stage cylinder portion 22.

The axial length (height) of the first-stage regenerator 31 is shorter than the axial length (height) of the internal space of the first-stage cylinder portion 21. Therefore, in the first-stage cylinder portion 21, spaces are formed above the upper end surface of the first-stage cold storage device 31 and below the lower end surface of the first-stage cold storage device 31, respectively. The first-stage expansion chamber 21a is formed by the space above the upper end surface of the first-stage cold storage device 31, and the back chamber 21b is formed by the space below the lower end surface of the first-stage cold storage device 31. As can be seen from FIG. 1, the first-stage expansion chamber 21a is composed of the space inside one end 211 of the first-stage cylinder portion 21, and the back chamber 21b is composed of the space inside the other end 212 of the first-stage cylinder 21. NS. Further, in the second-stage cylinder portion 22, a space is formed above the upper end surface of the second-stage regenerator 32. The second-stage expansion chamber 22a is formed by the space above the upper end surface of the second-stage cold storage device 32. The second-stage expansion chamber 22a is composed of a space inside one end portion 221 of the second-stage cylinder portion 22.

The displacer 3 is connected to the drive device 4 via a rod 36 connected to the lower end in FIG. 1 of the first-stage cold storage device 31. The drive device 4 is composed of, for example, a motor, a scotch yoke, or the like, and by driving the rod 36, the rod 36 is reciprocated in the axial direction thereof. By the reciprocating drive of the rod 36, the displacer 3 connected to the rod 36 reciprocates in the multi-stage cylinder 2.

In FIG. 1 of the multi-stage cylinder 2, the main passage 23 is formed at the lower end. One end of the main passage 23 opens into the back chamber 21b in the multi-stage cylinder 2. The other end of the main passage 23 is connected to the pressure fluctuation mechanism 5. The pressure fluctuation mechanism 5 has a function of fluctuating the pressure in the multi-stage cylinder 2. In the present embodiment, the pressure fluctuation mechanism 5 includes a compressor 51, a high-pressure on-off valve 52, a low-pressure on-off valve 53, an on-off control mechanism 54, and a common passage 55.

The compressor 51 sucks helium gas as a working gas from the suction port 51a, compresses the helium gas inside, and discharges the compressed high-pressure helium gas from the discharge port 51b. Therefore, a low pressure is generated on the suction port 51a side of the compressor 51, and a high pressure is generated on the discharge port 51b side of the compressor 51.

The high-pressure on-off valve 52 has two ports, and is configured to allow communication between the two ports when in the open state and to block communication between the two ports when in the closed state. One of the two ports of the high-pressure on-off valve 52 is connected to the discharge port 51b of the compressor 51, and the other port is connected to one end of the common passage 55. The low-pressure on-off valve also has two ports, and is configured to allow communication between the two ports when in the open state and to block communication between the two ports when in the closed state. One of the two ports of the low pressure on-off valve 53 is connected to the suction port 51a of the compressor 51, and the other port is connected to one end of the common passage 55. The other end of the common passage 55 is connected to the main passage 23 formed in the multi-stage cylinder 2.

The on-off control mechanism 54 controls the opening / closing operation of the on-off valve so that when one of the high-pressure on-off valve 52 and the low-pressure on-off valve 53 is open, the other is closed. By operating the opening / closing control mechanism 54, the pressure in the common passage 55 is switched from high pressure to low pressure or from low pressure to high pressure. The opening / closing of the high-pressure on-off valve 52 and the low-pressure on-off valve 53 by the opening / closing control mechanism 54, that is, switching between high and low pressure is periodically performed in conjunction with the reciprocating movement of the displacer 3 in the multi-stage cylinder 2. The high-pressure on-off valve 52, the low-pressure on-off valve 53, and the on-off control mechanism 54 may be composed of a valve unit in which these are integrated. In this case, a motor or the like built in the drive device 4 may be used as a drive source to interlock the reciprocating movement of the displacer 3 and the high / low voltage switching operation by the pressure fluctuation mechanism 5.

The internal space of the first-stage cold storage device 31 is filled with a first-stage cold storage material 33 made of a material having a large specific heat at a low temperature of about 30 K to 100 K as a cold storage means. The first-stage cold storage material 33 can be composed of a laminated body such as a wire mesh formed of phosphor bronze, for example. The internal space of the first-stage cold storage device 31 filled with the first-stage cold storage material 33 is hereinafter referred to as the first-stage filling space 31a. Further, the internal space of the second-stage cold storage device 32 is filled with a second-stage cold storage material 34 made of a material having a large specific heat at an extremely low temperature of about 4 to 20 K as a cold storage means. As the second-stage cold storage material 34, for example, a lead ball or the like can be used. The internal space of the second-stage cold storage device 32 filled with the second-stage cold storage material 34 is hereinafter referred to as the second-stage filling space 32a.

The first-stage cold storage device 31 is formed with the first-stage high-temperature side communication passage 313 and the first-stage low-temperature side communication passage 314. The first-stage high-temperature side communication passage 313 is formed on the lower end wall of the first-stage cold storage 31, which is a portion of the first-stage cold storage 31 on the high-temperature end 312 side, and is a lower portion in FIG. 1 of the first-stage filling space 31a. And the back chamber 21b communicate with each other. The first-stage low-temperature side communication passage 314 is formed at the upper end of the side peripheral wall of the first-stage cold storage 31, which is a portion of the first-stage cold storage 31 on the low-temperature end 311 side, and is formed in FIG. 1 of the first-stage filling space 31a. The upper portion and the first stage expansion chamber 21a are communicated with each other. In the present embodiment, a plurality of first-stage low-temperature side communication passages 314 are provided at equal intervals along the circumferential direction of the first-stage regenerator 31. The working gas flows into the inside of the first-stage cold storage device 31 or flows out from the inside of the first-stage cold storage device 31 via the first-stage low-temperature side communication passage 314 and the first-stage high-temperature side communication passage 313.

The second-stage cold storage device 32 is formed with a second-stage high-temperature side communication passage 323 and a second-stage low-temperature side communication passage 324. The second-stage high-temperature side communication passage 323 is formed in a lower portion of the side peripheral wall of the second-stage cold storage 32, which is a portion of the second-stage cold storage 32 on the high-temperature end 322 side, and is formed with the first-stage expansion chamber 21a. It communicates with the second stage filling space 32a. The second-stage low-temperature side communication passage 324 is formed at the upper end of the side peripheral wall of the second-stage cold storage 32, which is a portion of the second-stage cold storage 32 on the low-temperature end 321 side, and is formed in the second-stage filling space 32a. In FIG. 1, the upper portion and the second stage expansion chamber 22a communicate with each other. The working gas flows into the inside of the second-stage cold storage device 32 via the second-stage low-temperature side communication passage 324 and the second-stage high-temperature side communication passage 323, or the working gas flows from the inside of the second-stage cold storage device 32. leak.

In FIG. 1 on the outer peripheral side surface of the first-stage cold storage device 31, the first-stage seal ring 315 is attached to the lower portion in the circumferential direction. The first-stage seal ring 315 cuts off communication between the back chamber 21b and the first-stage expansion chamber 21a. Further, the second-stage seal ring 325 is attached to a portion below the outer peripheral side surface of the second-stage cold storage device 32 and facing the inner peripheral side surface of the second-stage cylinder portion 22. The second-stage seal ring 325 cuts off communication between the first-stage expansion chamber 21a and the second-stage expansion chamber 22a.

Wire meshes 35, 35 having a mesh diameter smaller than the diameter of the second-stage cold storage material 34 (for example, lead ball) filled in the second-stage filling space 32a are provided at the upper and lower ends of the second-stage filling space 32a. Arranged. The wire mesh 35, 35 prevents the second-stage cold storage material 34 in the second-stage filling space 32a from leaking to the outside. A sintered plate may be used instead of the wire mesh.

A first-stage cooling stage 60 as a lower-stage cooling stage is provided on one end 211 of the first-stage cylinder portion 21, that is, on the tip end side of the first-stage cylinder portion 21 (lower-stage cylinder portion). The first-stage cooling stage 60 has a cylindrical portion 61 and a disc portion 62. The cylindrical portion 61 is attached to the first-stage cylinder portion 21 so as to cover the side peripheral wall constituting the one-end portion 211 side of the first-stage cylinder portion 21. The disk portion 62 extends radially outward from the upper end portion in FIG. 1 of the cylindrical portion 61. Further, a plurality of through holes 63 penetrating in the axial direction (vertical direction in FIG. 1) are formed in the disk portion 62 along the circumferential direction. A bolt BT, which will be described later, is inserted into the through hole 63.

The second-stage cooling stage 70 as the higher-stage cooling stage is attached to one end 221 of the second-stage cylinder portion 22, that is, to the tip end side of the second-stage cylinder portion 22 (high-stage side cylinder portion). The second-stage cooling stage 70 has a cylindrical portion 71 and a disc portion 72. The cylindrical portion 71 is attached to the second-stage cylinder portion 22 so as to cover the side peripheral wall constituting the one-end portion 221 side of the second-stage cylinder portion 22. The disk portion 72 extends radially outward from the upper end portion in FIG. 1 of the cylindrical portion 71. Further, the disk portion 72 is formed with a screw hole 73 penetrating in the axial direction (vertical direction in FIG. 1). A bolt 94, which will be described later, is screwed into the screw hole 73.

A heat transfer sleeve 80 as a heat transfer member is arranged so as to cover the second stage cylinder portion 22 provided with the second stage cooling stage 70 (higher stage cooling stage). The heat transfer sleeve 80 has a cylindrical shape having one end 80a and the other end 80b, and is arranged on the disk portion 62 of the first-stage cooling stage 60. A plurality of screw holes 82 extending in the axial direction are formed in one end 80a of the heat transfer sleeve 80 along the circumferential direction. The screw hole 82 faces the through hole 63 formed in the disc portion 62 when one end 80a of the heat transfer sleeve 80 is coaxially placed on the disc portion 62 of the first-stage cooling stage 60. Formed at the position.

One end 80a of the heat transfer sleeve 80 is fixed to the first stage cooling stage 60. In this case, the heat transfer sleeve 80 is inserted into the disk portion so that the screw hole 82 formed in one end 80a of the heat transfer sleeve 80 and the through hole 63 formed in the disk portion 62 of the first-stage cooling stage 60 face each other. It is placed on 62, and in that state, the bolt BT is inserted into the through hole 63 and the screw hole 82 from the lower side of the disk portion 62. Then, the inserted bolt BT is screwed into the screw hole 82. As a result, one end 80a of the heat transfer sleeve 80 is fixed to the first-stage cooling stage 60. The heat transfer sleeve 80 extends upward in FIG. 1 from the first-stage cooling stage 60 with one end 80a fixed to the first-stage cooling stage 60. Here, the vertical direction of FIG. 1 coincides with the axial direction of the multi-stage cylinder 2. Therefore, the heat transfer sleeve 80 extends from the first-stage cooling stage 60 in the axial direction of the multi-stage cylinder 2 toward the second-stage cooling stage 70. The heat transfer sleeve 80 is formed with a through hole 81 penetrating from the inner peripheral wall surface to the outer peripheral wall surface. Due to the presence of the through hole 81, the pressure between the space inside the heat transfer sleeve 80 and the space outside the heat transfer sleeve 80 is made uniform.

Further, FIG. 1 is a cross-sectional view of the two-stage GM refrigerator 1 in the non-operating state as described above. That is, it is a cross-sectional view of the two-stage GM refrigerator 1 in a room temperature state. In this case, the heat transfer sleeve 80 is also at room temperature. As shown in FIG. 1, when the heat transfer sleeve 80 is at room temperature, the other end 80b of the heat transfer sleeve 80 is located above the second-stage cooling stage 70.

Here, in FIG. 1, it is assumed that the height position is represented by the distance from the first stage cooling stage 60 (lower stage cooling stage) along the axial direction of the multi-stage cylinder 2 (vertical direction in FIG. 1). In this case, when the heat transfer sleeve 80 is at room temperature, the height position A of the other end 80b of the heat transfer sleeve 80 is the height position B of the second stage cooling stage 70 (to be exact, the second stage cooling stage 70. It is higher than the height position B) of the upper surface of the disk portion 72. That is, the length from the first-stage cooling stage 60 to the other end 80b of the heat transfer sleeve 80 along the axial direction of the multi-stage cylinder 2 is longer than the length from the first-stage cooling stage 60 to the second-stage cooling stage 70. ..

An auxiliary cooling plate 90 as an auxiliary cooling member is arranged so as to face the tip end surface (upper end surface) of the second stage cooling stage 70 and the second stage cylinder portion 22. The auxiliary cooling plate 90 has a disk shape, and its outer diameter is substantially equal to the outer diameter of the heat transfer sleeve 80. The outer diameter of the auxiliary cooling plate 90 may be larger than the inner diameter of the heat transfer sleeve 80. The auxiliary cooling plate 90 is made of a material having high thermal conductivity. In this embodiment, the auxiliary cooling plate 90 is made of copper.

As shown in FIG. 1, the auxiliary cooling plate 90 is arranged above the second-stage cooling stage 70. That is, the auxiliary cooling plate 90 is arranged at a height position higher than the height position of the second stage cooling stage 70. Further, in the state shown in FIG. 1, the lower surface of the auxiliary cooling plate 90 is placed on the heat transfer sleeve 80 in a state of being in contact with the other end 80b of the heat transfer sleeve 80. At this time, a gap G along the axial direction of the multi-stage cylinder 2 is formed between the auxiliary cooling plate 90 and the second-stage cooling stage 70. Therefore, the auxiliary cooling plate 90 is arranged at a height position higher than the height position of the second stage cooling stage 70 along the axial direction of the multi-stage cylinder 2, and heat is transferred when the heat transfer sleeve 80 is at room temperature. It comes into contact with the other end 80b of the sleeve 80 and is arranged facing the second-stage cooling stage 70 with a gap G along the axial direction of the multi-stage cylinder 2.

The auxiliary cooling plate 90 is formed with a plurality of through holes 91 penetrating in the axial direction (vertical direction in FIG. 1) of the multi-stage cylinder 2 along the circumferential direction. A bolt 94 is inserted through the through hole 91. The bolt 94 is screwed and fixed to the second stage cooling stage 70.

FIG. 2 is an enlarged view of a cross section of the vicinity of the auxiliary cooling plate 90. As shown in FIG. 2, the through hole 91 formed in the auxiliary cooling plate 90 has a large diameter portion 91a and a small diameter portion 91b having a diameter smaller than that of the large diameter portion 91a, and the large diameter portion 91a and the small diameter portion 91b. Is formed coaxially along the axial direction of the multi-stage cylinder 2 (vertical direction in FIG. 2). The small diameter portion 91b of the through hole 91 faces the disk portion 72 of the second stage cooling stage 70. Further, a ring-shaped stepped surface 91c is formed at the boundary between the large diameter portion 91a and the small diameter portion 91b. The large diameter portion 91a and the stepped surface 91c may be omitted. That is, the through hole 91 may be composed of only the small diameter portion 91b.

The bolt 94 inserted into the through hole 91 has a bolt head 94a, a shaft portion 94b, and a screw portion 94c. The shaft portion 94b extends from the bolt head 94a, and the screw portion 94c extends coaxially with the shaft portion 94b from the tip of the shaft portion 94b. The outer diameters of the shaft portion 94b and the screw portion 94c are slightly larger than the diameter of the small diameter portion 91b of the through hole 91 of the auxiliary cooling plate 90. Further, the outer diameter of the bolt head 94a is larger than the outer diameter of the shaft portion 94b.

Further, the auxiliary cooling plate 90 is arranged upward in FIG. 2 of the second stage cooling stage 70 so that the small diameter portion 91b of the through hole 91 is coaxially arranged in the screw hole 73 formed in the second stage cooling stage 70. Will be done. Then, the shaft portion 94b of the bolt 94 is inserted into the through hole 91, and the screw portion 94c of the bolt 94 is screwed into the screw hole 73 of the second stage cooling stage 70. As a result, the bolt 94 is screwed and fixed to the second stage cooling stage 70.

Further, as can be clearly seen from FIG. 2, a compression coil spring 95 as an urging member is attached around the outer circumference of the shaft portion 94b of the bolt 94. In a state where the bolt 94 is screwed and fixed to the second stage cooling stage 70, the compression coil spring 95 is locked to the lower surface of the bolt head 94a of the bolt 94 at one end thereof and at the other end. It is locked to the stepped surface 91c of the through hole 91 of the auxiliary cooling plate 90. Since the bolt 94 is screwed and fixed to the second stage cooling stage 70, the urging force of the compression coil spring 95 acts on the auxiliary cooling plate 90. Due to such urging force, the auxiliary cooling plate 90 is urged downward in FIGS. 1 and 2. When the through hole 91 is composed of only the small diameter portion 91b, the compression coil spring 95 is locked to the bolt head 94a at one end thereof and to the upper surface of the auxiliary cooling plate 90 at the other end. NS.

Here, as can be seen from FIG. 1, the heat transfer sleeve 80 is arranged below the auxiliary cooling plate 90, and in the state shown in FIG. 1, the auxiliary cooling plate 90 contacts the other end 80b of the heat transfer sleeve 80. Has been done. Therefore, the urging force acting on the auxiliary cooling plate 90 acts on the heat transfer sleeve 80. Therefore, the auxiliary cooling plate 90 is urged to the other end side of the heat transfer sleeve 80 by the compression coil spring 95. In other words, the compression coil spring 95 urges the auxiliary cooling plate 90 toward the other end 80b side of the heat transfer sleeve 80.

The multi-stage cylinder 2 is made of a material having a low thermal conductivity among metals. Typically, the multi-stage cylinder 2 is made of stainless steel. Further, the bolt 94 and the compression coil spring are also made of a material having low thermal conductivity, for example, stainless steel. On the other hand, the heat transfer sleeve 80 is made of a material having high thermal conductivity among metals.

Further, the heat transfer sleeve 80 is made of a material having a higher heat shrinkage rate than the material constituting the multi-stage cylinder 2. Therefore, when the multi-stage cylinder 2 is made of stainless steel, the heat transfer sleeve 80 is made of a material having high thermal conductivity and a higher thermal shrinkage rate than stainless steel. If the multi-stage cylinder 2 is made of stainless steel, the heat transfer sleeve 80 may typically be made of aluminum.

Further, regarding the length (axial length) of the heat transfer sleeve 80 along the axial direction of the multi-stage cylinder 2, the temperature of the heat transfer sleeve 80 is the target cooling temperature of the first stage cooling stage 60 (for example, the temperature of 30K to 80K). When the temperature αK) reached in advance within the range, the height position A of the other end 80b of the heat transfer sleeve 80 is set to be lower than the height position B of the second stage cooling stage 70. NS.

The first-stage cooling stage 60 and the second-stage cooling stage 70 are made of a material having high thermal conductivity. Typically, the first-stage cooling stage 60 and the second-stage cooling stage 70 are made of copper.

The operation of the two-stage GM refrigerator 1 having the above configuration will be briefly described below. When the displacer 3 is located at the uppermost position (top dead center) in FIG. 1 in the multi-stage cylinder 2, the high-pressure on-off valve 52 of the pressure fluctuation mechanism 5 is open and the low-pressure on-off valve 53 is closed. Therefore, the high-pressure working gas flows into the multi-stage cylinder 2 via the common passage 55 and the main passage 23.

<High-voltage transfer process>
The displacer 3 is then displaced downward with respect to the multistage cylinder 2. Then, the high-pressure working gas in the back chamber 21b flows into the first-stage filling space 31a in the first-stage regenerator 31 through the first-stage high-temperature side communication passage 313. The working gas that has flowed into the first-stage filling space 31a is cooled by removing cold heat (low temperature) from the first-stage cold storage material 33. Then, the working gas cooled by the first-stage cold storage material 33 flows out from the first-stage cold storage 31 through the first-stage low-temperature side communication passage 314 and flows into the first-stage expansion chamber 21a.

Further, the working gas in the first-stage expansion chamber 21a flows into the second-stage filling space 32a in the second-stage regenerator 32 through the second-stage high-temperature side communication passage 323. The working gas that has flowed into the second-stage filling space 32a is cooled by removing cold heat from the second-stage cold storage material 34. Then, the working gas cooled by the second-stage cold storage material 34 flows out from the second-stage cold storage device 32 through the second-stage low-temperature side communication passage 324 and flows into the second-stage expansion chamber 22a.

<Expansion process>
Then, after the high-pressure on-off valve 52 of the pressure fluctuation mechanism 5 is closed, the low-pressure on-off valve 53 is opened. As a result, the working gas in the first-stage expansion chamber 21a located on the one-end 211 side of the first-stage cylinder portion 21 and the inside of the second-stage expansion chamber 22a located on the one-end 221 side of the second-stage cylinder portion 22. Each of the working gases of the above performs an expansion work. Due to such expansion work, cold heat is generated in each of the expansion chambers 21a and 22a.

<Low voltage transfer process>
Next, the displacer 3 is displaced upward with respect to the multi-stage cylinder 2. Then, the working gas in the second-stage expansion chamber 22a flows into the second-stage regenerator 32 via the second-stage low-temperature side passage 324, and the second-stage filling space in the second-stage regenerator 32. It passes through 32a. At this time, the working gas is heated by being deprived of cold heat by the second-stage cold storage material 34 in the second-stage filling space 32a. The working gas in the second-stage filling space 32a further flows out from the second-stage regenerator 32 and flows into the first-stage expansion chamber 21a via the second-stage high-temperature side communication passage 323.

Further, the working gas in the first-stage expansion chamber 21a flows into the first-stage regenerator 31 via the first-stage low-temperature side communication passage 314, and passes through the first-stage filling space 31a in the first-stage regenerator 31. At this time, the working gas is heated by being deprived of cold heat by the first-stage cold storage material 33 in the first-stage filling space 31a. The working gas in the first-stage filling space 31a further flows out from the first-stage regenerator 31 via the first-stage high-temperature side communication passage 313, passes through the main passage 23, the common passage 55, and the low-pressure on-off valve 53, and reaches the compressor 51. Inflow.

<Compression process>
Next, the low-pressure on-off valve 53 of the pressure fluctuation mechanism 5 closes, and the high-pressure on-off valve 52 opens. As a result, the high-pressure working gas flows into the multi-stage cylinder 2 via the common passage 55 and the main passage 23. The heat generated by the compression work of the compressor 51 is dissipated to the outside by a radiator (not shown) provided on the discharge side of the compressor 51.

By repeating the above-mentioned thermal cycle (GM cycle), the inside of the first-stage expansion chamber 21a is cooled to, for example, about αK, and the inside of the second-stage expansion chamber 22a is cooled to, for example, about 10K. The cold heat generated in the first-stage expansion chamber 21a is transferred to the first-stage cooling stage 60, and the cold heat generated in the second-stage expansion chamber 22a is transferred to the second-stage cooling stage 70. Therefore, the target cooling temperature of the first-stage cooling stage 60 is about αK, and the target cooling temperature of the second-stage cooling stage 70 is about 10K. Cold heat is taken out from each cooling stage.

By the way, in general, when a two-stage GM refrigerator is operated in a room temperature environment, the first-stage cooling stage is first cooled. During the cooling of the first stage cooling stage, the cooling rate of the second stage cooling stage is very slow. When the temperature of the first-stage cooling stage is cooled to a temperature close to the target cooling temperature (for example, αK), the cooling rate of the second-stage cooling stage becomes faster. As described above, the cooling rate of the second-stage cooling stage is much slower than the cooling rate of the first-stage cooling stage. Further, the refrigerating capacity of the first-stage cooling stage is larger than the refrigerating capacity of the second-stage cooling stage. In other words, the refrigerating capacity of the second stage cooling stage is smaller than the refrigerating capacity of the first stage cooling stage. As described above, due to the extremely slow cooling rate of the second-stage cooling stage and the small refrigerating capacity of the second-stage cooling stage, the second-stage cooling stage is used to cool the object to be cooled from room temperature to extremely low temperature. When trying to cool to (for example, 10K), it takes a very long time to complete the cooling.

In this regard, the two-stage GM refrigerator 1 according to the present embodiment is configured so that the cooling time of the object to be cooled to be cooled to an extremely low temperature can be shortened. This will be described below.

When the two-stage GM refrigerator 1 according to the present embodiment is in a non-operating state, that is, in a normal temperature environment, the heat transfer sleeve 80 is in thermal contact with the auxiliary cooling plate 90 as shown in FIG. is doing. Further, a non-cooling body (for example, a heat shield plate) to be cooled by the second-stage cooling stage 70 is thermally connected to the auxiliary cooling plate 90.

When the two-stage GM refrigerator 1 in the state shown in FIG. 1 operates, the first-stage cooling stage 60 is first cooled. Here, according to the two-stage GM refrigerator 1 according to the present embodiment, the heat transfer sleeve 80 is fixed to the first-stage cooling stage 60, and the heat transfer sleeve 80 is attached to the auxiliary cooling plate 90 at room temperature. There is thermal contact. Therefore, the cold heat generated in the first stage cooling stage 60 is transferred to the auxiliary cooling plate 90 via the heat transfer sleeve 80. As a result, the auxiliary cooling plate 90 is cooled during the cooling of the first stage cooling stage 60. Therefore, the cooled body thermally connected to the auxiliary cooling plate 90 is cooled by the cooling heat of the first stage cooling stage 60 via the auxiliary cooling plate 90 and the heat transfer sleeve 80.

Further, when the heat transfer sleeve 80 is cooled as the first stage cooling stage 60 is cooled, the heat transfer sleeve 80 is thermally shrunk. Here, since the heat transfer sleeve 80 is fixed to the first-stage cooling stage 60 at one end 80a (lower end), the height position of the other end 80b (upper end) of the heat transfer sleeve 80 due to heat shrinkage. Decreases.

As the cooling of the first-stage cooling stage 60 progresses, the heat transfer sleeve 80 heat-shrinks, so that the height position of the other end 80b of the heat transfer sleeve 80 is lowered. Here, while the height position A of the other end 80b of the heat transfer sleeve 80 is higher than the height position B of the second stage cooling stage 70, the compression coil spring 95 causes the heat transfer sleeve 80 to move to the other end 80b side. The auxiliary cooling plate 90, which is urged toward the heat transfer sleeve 80, follows the decrease in the height position of the other end 80b of the heat transfer sleeve 80, and keeps contact with the heat transfer sleeve 80 at the lower part of FIG. 1, that is, one step. It moves toward the eye cooling stage 60 side. At this time, since the gap G between the auxiliary cooling plate 90 and the second-stage cooling stage 70 is secured, the auxiliary cooling plate 90 and the second-stage cooling stage 70 are thermally insulated. Since the second-stage cooling stage 70 is not sufficiently cooled during the cooling of the first-stage cooling stage 60, the gap G is secured so that the second-stage cooling stage 70 that is not sufficiently cooled can be moved to the auxiliary cooling plate 90. It is possible to prevent the inflow of heat.

Since the multi-stage cylinder 2 is also cooled during the cooling of the first-stage cooling stage 60, the multi-stage cylinder 2 also heat-shrinks. However, since the multi-stage cylinder 2 is made of stainless steel having a small heat shrinkage rate, the amount of heat shrinkage is also small. Therefore, the height of the second-stage cooling stage 70 provided in the second-stage cylinder portion 22 of the multi-stage cylinder 2 is high. The position does not change so much even when the multi-stage cylinder 2 is cooled.

Further cooling of the first-stage cooling stage 60 progresses, and the temperature of the first-stage cooling stage 60 reaches a temperature (for example, (α + 10) K) close to the target cooling temperature (for example, a predetermined temperature αK within the temperature range of 30K to 80K). Then, the heat transfer sleeve 80 further heat-shrinks, and the height position A of the other end 80b of the heat transfer sleeve 80 coincides with the height position B of the second-stage cooling stage 70. Then, the gap G provided between the auxiliary cooling plate 90 and the second-stage cooling stage 70 disappears, and the auxiliary cooling plate 90 comes into contact with the second-stage cooling stage 70. FIG. 3 is a schematic partial cross-sectional view of the two-stage GM refrigerator 1 showing a state in which the auxiliary cooling plate 90 is in contact with the second-stage cooling stage 70.

When the two-stage GM refrigerator 1 is in the state shown in FIG. 3, the auxiliary cooling plate 90 is in thermal contact with the first-stage cooling stage 60 via the heat transfer sleeve 80, and the second-stage cooling stage is in contact with the first-stage cooling stage 60. It is also in thermal contact with 70. Further, when the temperature of the first-stage cooling stage 60 is cooled to a temperature close to the target cooling temperature, the cooling of the second-stage cooling stage 70 becomes faster, and the temperature of the second-stage cooling stage 70 is relatively low. Probability is high. Therefore, in the state shown in FIG. 3, the cooled body to be thermally connected to the auxiliary cooling plate 90 and the auxiliary cooling plate 90 is cooled by the first-stage cooling stage 60 and the second-stage cooling stage 70.

Then, when the cooling of the first-stage cooling stage 60 further progresses and the temperature of the first-stage cooling stage 60 reaches the target cooling temperature (for example, αK), the heat transfer sleeve 80 further heat-shrinks and the height of the other end 80b. The position A is located lower than the height position B of the second stage cooling stage 70. Further, as shown in FIG. 3, when the height position A of the other end 80b of the heat transfer sleeve 80 coincides with the height position B of the second stage cooling stage 70, the auxiliary cooling plate 90 is the second stage cooling stage 70. It is in contact with and cannot move further downward (in the direction toward the first-stage cooling stage 60). That is, the second-stage cooling stage 70 functions as a stopper for the downward movement of the auxiliary cooling plate 90. Therefore, when the height position A of the other end 80b of the heat transfer sleeve 80 is located lower than the height position B of the second stage cooling stage 70, the auxiliary cooling plate 90 is located at the other end 80b of the heat transfer sleeve 80. The auxiliary cooling plate 90 is separated from the heat transfer sleeve 80 because it cannot move following the decrease in the height position of the.

FIG. 4 is a schematic partial cross-sectional view of the two-stage GM refrigerator 1 showing a state in which the auxiliary cooling plate 90 is separated from the heat transfer sleeve 80. In the state shown in FIG. 4, the auxiliary cooling plate 90 is separated from the first-stage cooling stage 60 and thermally contacts the second-stage cooling stage 70. Therefore, the body to be cooled that is thermally connected to the auxiliary cooling plate 90 and the auxiliary cooling plate 90 is cooled only by the second stage cooling stage 70. Here, at the time when the auxiliary cooling plate 90 and the object to be cooled are cooled only by the second stage cooling stage 70, the auxiliary cooling plate 90 and the object to be cooled are reduced to, for example, about αK by the cooling heat of the first stage cooling stage 60. It is cooled. Therefore, even if the refrigerating capacity of the second-stage cooling stage 70 is small, the auxiliary cooling plate 90 and the object to be cooled can be cooled to an extremely low temperature (for example, 10K) in a relatively short time.

FIG. 5 is a graph showing the transition of the temperature of the cooled body when the cooled body is cooled to an extremely low temperature (for example, 10 K) by using a conventional two-stage GM refrigerator. The horizontal axis of FIG. 5 is time, the vertical axis is temperature [K], and the graph A in FIG. 5 shows the temperature transition of the object to be cooled. The body to be cooled is thermally connected to the second-stage cooling stage. Further, the temperature transition of the first-stage cooling stage is shown in Graph B in FIG.

As shown in FIG. 5, when the two-stage GM refrigerator is operated, the temperature of the first-stage cooling stage drops immediately, but the temperature of the second-stage cooling stage does not drop immediately, so that the second-stage cooling The temperature of the object to be cooled, which is thermally connected to the stage, does not decrease for a while and remains at room temperature (about 300K). From the time when the temperature of the first-stage cooling stage approaches the target cooling temperature (αK), the temperature of the second-stage cooling stage decreases rapidly, so that the temperature of the object to be cooled also decreases accordingly. Then, the temperature of the object to be cooled reaches the target cooling temperature (10K) at the time T2 after the temperature of the first stage cooling stage reaches the target cooling temperature at the time T1.

As described above, in the conventional two-stage GM refrigerator, the temperature of the second-stage cooling stage does not decrease unless the temperature of the first-stage cooling stage decreases to a temperature close to the target cooling temperature. Therefore, it takes a long time for the temperature of the object to be cooled to be cooled by the second-stage cooling stage to reach an extremely low temperature.

FIG. 6 is a graph showing the temperature transition of the cooled body when the cooled body is cooled to an extremely low temperature (for example, 10 K) by using the two-stage GM refrigerator 1 according to the present embodiment. The horizontal axis of FIG. 6 is time, the vertical axis is temperature [K], and the graph A in FIG. 6 shows the temperature transition of the object to be cooled. The temperature transition of the first-stage cooling stage 60 is shown in Graph B of FIG.

As shown in FIG. 6, when the two-stage GM refrigerator 1 is operated, the temperature of the first-stage cooling stage 60 immediately drops. Further, since the object to be cooled is cooled by the cooling heat of the first-stage cooling stage 60 at the initial stage of cooling, the temperature of the object to be cooled also decreases following the temperature decrease of the first-stage cooling stage 60. The cold heat of the first-stage cooling stage 60 is taken away by the object to be cooled via the heat transfer sleeve 80 and the auxiliary cooling plate 90, but since the cooling capacity of the first-stage cooling stage 60 is high, the cooling capacity of the first-stage cooling stage 60 is increased accordingly. The cooling rate does not decrease significantly. Therefore, the time T1'for the temperature of the first-stage cooling stage 60 to reach the target cooling temperature is the time until the temperature of the first-stage cooling stage of the conventional two-stage GM refrigerator shown in FIG. 5 reaches the target cooling temperature. It is almost the same as T1.

Since the object to be cooled is cooled during the cooling of the first-stage cooling stage 60 as described above, the temperature of the object to be cooled at T1'when the temperature of the first-stage cooling stage 60 reaches the target cooling temperature (αK). Is low enough. Then, after the time T1', the object to be cooled is cooled by the second stage cooling stage 70. Since the temperature of the object to be cooled is sufficiently lowered at the time point T1', even if the object to be cooled is subsequently cooled by the second-stage cooling stage 70 having a low refrigerating capacity, the temperature reaches an extremely low temperature (for example, 10K). The time until T2'is shorter than the time T2 until the cooled body reaches an extremely low temperature when the conventional two-stage GM refrigerator shown in FIG. 5 is used. In this way, the cooling time of the object to be cooled to be cooled to an extremely low temperature (for example, 10 K) can be shortened.

As described above, according to the two-stage GM refrigerator 1 according to the present embodiment, when the object to be cooled to be cooled to an extremely low temperature is not sufficiently cooled by the second-stage cooling stage 70, the first-stage cooling stage 60 is used. It is cooled by cold heat. Then, when the second-stage cooling stage 70 has been sufficiently cooled, the object to be cooled is cooled to an extremely low temperature by the cooling heat of the second-stage cooling stage 70. Since the refrigerating capacity of the first-stage cooling stage 60 is higher than the refrigerating capacity of the second-stage cooling stage 70, it is cooled to an extremely low temperature by the amount that the object to be cooled is cooled by the first-stage cooling stage 60 at the initial stage of cooling start. The cooling time of the object to be cooled can be shortened.

Further, the heat transfer sleeve 80 is formed in a cylindrical shape so as to cover the outer periphery of the second stage cylinder portion 22. Therefore, the radiant heat from the outside is shielded by the heat transfer sleeve 80. Therefore, it is possible to effectively prevent heat inflow to the second stage cylinder portion 22 due to heat radiation.

Further, the heat transfer sleeve 80 is made of aluminum, and the multi-stage cylinder 2 is made of stainless steel. Therefore, by utilizing the difference in heat shrinkage between the heat transfer sleeve 80 (aluminum) and the multi-stage cylinder 2 (stainless steel), the heat transfer sleeve 80 and the auxiliary cooling plate 90 can be thermally connected and disconnected as described above. It can be realized.

Although the embodiments of the present invention have been described above, the present invention should not be limited to the above embodiments. For example, in the above embodiment, the two-stage type cold storage refrigerator has been described, but the present invention can also be applied to a multi-stage type cold storage refrigerator other than the two-stage type. Further, in the above embodiment, the GM refrigerator is shown as the cold storage refrigerator, but other cold storage refrigerators such as the pulse tube refrigerator and the Sterling type pulse tube refrigerator are also described. The invention can be applied. As described above, the present invention can be modified as long as it does not deviate from the gist thereof.

1 ... Two-stage GM refrigerator (multi-stage cold storage refrigerator), 2 ... Multi-stage cylinder, 21 ... First-stage cylinder, 21a ... First-stage expansion chamber, 211 ... One end, 212 ... Other end, 22 ... Second-stage cylinder, 22a ... Second-stage expansion chamber, 221 ... One end, 222 ... The other end, 3 ... Displacer, 4 ... Drive, 5 ... Pressure fluctuation mechanism, 31 ... First-stage refrigerator, 32 ... 2nd stage refrigerator, 33 ... 1st stage cold storage material, 34 ... 2nd stage cold storage material, 60 ... 1st stage cooling stage (low stage cooling stage), 70 ... 2nd stage cooling stage (high stage side cooling stage), 80 ... Heat transfer sleeve (heat transfer member), 80a ... One end, 80b ... Other end, 81 ... Through hole, 90 ... Auxiliary cooling plate (auxiliary cooling member), 91 ... Through hole, 91a ... Large diameter part, 91b ... Small diameter part, 91c ... stepped surface, 94 ... bolt, 94a ... bolt head, 94b ... shaft part, 94c ... screw part, 95 ... compression coil spring (urging member), G ... gap

Claims (5)

A multi-stage cylinder composed of a plurality of cylinders having different diameters and formed in a stepped cylindrical shape so that the diameter gradually decreases toward the tip.
The cold storage means provided in the multi-stage cylinder and
A plurality of cooling stages provided on the tip side of each of the plurality of cylinders, and a plurality of cooling stages.
A pressure fluctuation mechanism that fluctuates the pressure in the multi-stage cylinder,
It is made of a material having a higher heat shrinkage rate than the material constituting the multi-stage cylinder, and one end thereof is a lower-stage cooling stage which is a cooling stage other than the highest-stage cooling stage among the plurality of stages of the cooling stages. It is fixed and extends from the low-stage cooling stage along the axial direction of the multi-stage cylinder, and the other end is a cooling stage on the higher stage side than the low-stage cooling stage at room temperature. A heat transfer member located at a height position higher than the height position along the axial direction of the multi-stage cylinder of the high-stage side cooling stage, and
It is arranged at a height position higher than the height position of the high-stage side cooling stage along the axial direction of the multi-stage cylinder, and comes into contact with the other end of the heat transfer member when the heat transfer member is at room temperature. Auxiliary cooling members arranged face-to-face with the high-stage cooling stage with a gap along the axial direction of the multi-stage cylinder.
An urging member that urges the auxiliary cooling member toward the other end side of the heat transfer member, and
To prepare
Multi-stage cold storage refrigerator. In the multi-stage cold storage refrigerator according to claim 1,
When the temperature of the heat transfer member reaches the target cooling temperature of the lower stage cooling stage, the height position of the other end of the heat transfer member becomes lower than the height position of the higher stage cooling stage. A multi-stage cold storage refrigerator in which the length of the heat transfer member is set along the axial direction of the multi-stage cylinder. In the multi-stage cold storage refrigerator according to claim 1 or 2.
The heat transfer member is a multi-stage cold storage type refrigerator formed in a cylindrical shape so as to cover the outer periphery of a cylinder portion provided with the high-stage cooling stage. In the multi-stage cold storage refrigerator according to any one of claims 1 to 3,
A multi-stage cold storage refrigerator in which the heat transfer member is made of aluminum and the multi-stage cylinder is made of stainless steel. In the multi-stage cold storage refrigerator according to any one of claims 1 to 4.
The multi-stage cylinder includes a first-stage cylinder portion and a second-stage cylinder portion having a diameter smaller than that of the first-stage cylinder portion.
The low-stage cooling stage is a first-stage cooling stage provided on the tip end side of the first-stage cylinder portion.
The high-stage cooling stage is a second-stage cooling stage provided on the tip end side of the second-stage cylinder portion.
A multi-stage cold storage refrigerator in which the multi-stage cold storage refrigerator is a two-stage cold storage refrigerator.

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