JP2011141074A - Cryogenic refrigerator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cryogenic refrigerator that improves precooling properties by shortening precooling time, simplifying handleability, and preventing the deterioration or the like due to thermal strain, to the utmost extent with a single refrigerator. <P>SOLUTION: The cryogenic refrigerator supplies a refrigerant the pressure of which is raised by a compressor 18 into a coldhead 11 and expands the refrigerant to generate frigidness, and again transfers the refrigerant that have been expanded in the coldhead 11 to the compressor 18 to raise the pressure of the refrigerant. The cryogenic refrigerator includes: a bypass pipe 27 that connects a high-pressure pipe 20, into which the refrigerant pressurized by the compressor 18 is supplied, with a low-pressure pipe 19, with which the refrigerant introduced from the outside of a compressor unit 17 is provided to the compressor 18; a pressure regulating valve 26 that regulates at least one inner pressure of pipes of the high-pressure pipe 20 and the low-pressure pipe 19, and is provided in the bypass pipe 27; an outlet 38 for taking out the refrigerant in the bypass pipe 27 to the outside of the compressor unit 17; an inlet 37 for introducing the refrigerant from the outside of the compressor unit 17 to the inside of the compressor unit 17. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a cryogenic refrigerator that cools an object to be cooled to a cryogenic temperature, and more particularly, to a cryogenic refrigerator that has improved precooling characteristics even with a single refrigerator.

  A cryogenic refrigerator that cools an object to be cooled to a cryogenic temperature, for example, can be applied to cooling of a superconducting coil, and handling is greatly simplified without using a refrigerant such as liquid helium or liquid nitrogen. Refrigerators used are composed of a compressor that compresses and circulates refrigerant and a cold head that generates cold, and a lineup of refrigerators that meet the cooling specifications of the object to be cooled is being lined up.

  As a cooling specification of the object to be cooled, there is a refrigerating capacity corresponding to a required cooling temperature and how much heat load and heat penetration amount need to be cooled at that temperature. Further, there may be a demand for shortening the time for cooling from room temperature to the predetermined temperature. In that case, the refrigerating capacity from room temperature to the specified temperature needs to be large, but generally the heat capacity of the object to be cooled increases near the room temperature, compared to the refrigerating capacity required at extremely low temperatures, so long-time precooling is necessary. Become. In particular, in the case of cooling a large-sized device, it may take several weeks to several months. For example, at the time of pre-cooling, cooling by another means, for example, a method of cooling by drawing liquid nitrogen may be used in combination.

  The technique regarding the cryogenic refrigerator as described above is described in, for example, the following Patent Documents 1, 2, and 3.

JP 2008-116171 A JP 2005-201604 A Japanese Patent No. 3673410

  As described above, in general, the heat capacity of the object to be cooled becomes large near room temperature and the long-time pre-cooling is necessary for the refrigerating capacity required at a very low temperature. It has been difficult to apply a design that satisfies the cooling specifications for maintaining a low temperature to a single refrigerator. Therefore, the precooling time is forced to be long, or other means are used together as a precooling means. In the latter case, however, the cost of the apparatus is increased, the inconvenience of handling, etc. There were disadvantages.

  FIG. 7 is an explanatory view showing a state of cooling the superconducting coil 124 using the cryogenic refrigerator 100 together with the cryogenic refrigerator 100 as an example of a conventional cryogenic refrigerator. The above problem will be further described with reference to FIG.

  In FIG. 7, reference numerals 101 to 117 are components constituting the cryogenic refrigerator 100. Specifically, 101 is a cold head, 102 is a cooling stage, 103 is a refrigerant discharge joint, and 104 is refrigerant introduction. Joint, 105 is a refrigerant low-pressure pipe, 106 is a refrigerant high-pressure pipe, 107 is a compressor unit, 108 is a compressor, 109 is a compressor unit low-pressure pipe, 110 is a compressor unit high-pressure pipe, 111 is a refrigerant introduction joint, 112 Is a refrigerant discharge joint, 113 is a buffer tank, 114 is an oil mist trap, 115 is an adsorber, 116 is a pressure regulating valve, and 117 is a bypass pipe. Further, 124 is a superconducting coil, and 125 is a heat transfer plate.

  A cryogenic refrigerator 100 shown in FIG. 7 is a GM (Gifford-McMahon) refrigerator in which an expander unit (cold head) 101 and a compressor unit 107 are separated from each other. The head 101 is connected by a refrigerant low-pressure pipe 105 and a refrigerant high-pressure pipe 106 so that the refrigerant can circulate.

  In the cryogenic refrigerator 100, the pressure of the refrigerant is increased by the compressor 108 in the compressor unit 107, and the increased pressure is sent to the high-pressure pipe 110 in the compressor unit, and is provided on the path of the high-pressure pipe 110 in the compressor unit. The oil mist trap 114, the adsorber 115 and the refrigerant discharge joint 112 are discharged to the outside of the compressor unit 107.

  Subsequently, the refrigerant discharged from the compressor unit 107 is introduced into the cold head 101 via the refrigerant high-pressure pipe 106 and the refrigerant introduction joint 104 provided in the cold head 101, and is expanded inside the cold head 101. . Inside the cold head 101, cold is generated as the high-pressure refrigerant expands. The low-pressure refrigerant after expansion is discharged from the refrigerant discharge joint 103 provided in the cold head 101 to the refrigerant low-pressure pipe 105 outside the cold head 101, and again from the refrigerant introduction joint 111 provided in the compressor unit 107. To be introduced.

  Subsequently, the refrigerant introduced into the compressor unit 107 is introduced into the compressor unit low-pressure pipe 109 in the compressor unit 107 connected to the refrigerant low-pressure pipe 105 via the refrigerant introduction joint 111, It is again introduced into the compressor 108 via a buffer tank 113 provided on the path of the low-pressure pipe 109.

  In the case of cooling by a refrigerator as shown in FIG. 7, the cooling interface with the object to be cooled (for example, the superconducting coil 124 shown in FIG. 7) is caused by heat conduction by bringing the cooling stage 102 into thermal contact with the object to be cooled. Due to the cooling mechanism, cooling of the object to be cooled becomes local, inefficiency due to temperature difference from the object to be cooled, and generation and deterioration of thermal strain due to temperature difference in the object to be cooled occur. .

  Since the cooling stage 102 of the conventional cryogenic refrigerator 100 shown in FIG. 7 is a single location, it can only be cooled from one side of the superconducting coil 124, and the other end is difficult to cool, so at both ends of the superconducting coil 124, A temperature difference corresponding to the effective thermal conductivity occurs. The thermal strain due to this temperature difference deteriorates the superconducting coil 124. In order to prevent this, the pre-cooling capability is intentionally suppressed, and cooling may be performed so as not to cause a temperature difference.

  In the conventional cryogenic refrigerator 100, a pressure regulating valve 116 and a bypass pipe 117 are installed in the compressor unit 107. The pressure regulating valve 116 has a small refrigerant flow amount during operation when the temperature of the cold head 101 is close to room temperature during initial cooling, and a large pressure difference is applied between the low-pressure pipe 109 and the high-pressure pipe 110. The pressure difference between the low-pressure pipe 109 and the high-pressure pipe 110 becomes a predetermined value or more, the high-pressure pipe 110 becomes a predetermined pressure or more, or the low-pressure pipe 109 does not cause deterioration or damage of the parts. Has a function of opening the pressure regulating valve 116 and lowering the differential pressure.

  When cooled to a predetermined temperature, the flow rate to the cold head 101 increases, so that the pressure regulating valve 116 is closed and no refrigerant flows through the bypass valve provided in the bypass pipe 117. As described above, during the initial cooling, the compressor 108 has excess refrigerant, and the input power is not effectively used.

  As described above, when the configuration of cooling with one refrigerator is adopted, it is difficult to satisfy the requirements up to the precooling characteristics (reduction of precooling time, ease of handling, prevention of deterioration due to thermal strain).

  The present invention has been made in consideration of the above-mentioned problems, and as far as possible with a single refrigerator, shortening the precooling time, ease of handling, and improving precooling characteristics such as prevention of deterioration due to thermal strain. It aims at providing the cryogenic refrigerator which aimed.

  In order to solve the above-described problems, a cryogenic refrigerator according to the present invention includes a compressor unit and a cold head separated from the compressor unit, and the refrigerant pressurized by the compressor of the compressor unit is A cryogenic refrigerator that supplies the cold head and expands the cold head to generate cold, and again introduces the refrigerant that has been expanded in the cold head into the compressor of the compressor unit to increase the pressure. A bypass pipe for connecting a high-pressure side pipe to which the refrigerant boosted by the compressor is supplied and a low-pressure side pipe for supplying the refrigerant introduced from the outside of the compressor unit to the compressor, and the bypass pipe A pressure regulating valve for regulating a pressure in at least one of the high-pressure side pipe and the low-pressure side pipe, and the bypass A takeout retrieve the refrigerant in the pipe to the outside of the compressor unit, characterized by comprising, an inlet port for introducing a refrigerant into the compressor unit from the outside of the compressor unit.

  ADVANTAGE OF THE INVENTION According to this invention, precooling characteristics, such as shortening of precooling time, simplicity of handling, and prevention of deterioration due to thermal strain, can be improved while adopting a configuration of cooling with one refrigerator.

The block diagram which showed schematically the structure of the cryogenic refrigerator which concerns on the 1st Embodiment of this invention. The block diagram which showed schematically the structure of the cryogenic refrigerator which concerns on the 2nd Embodiment of this invention. The block diagram which showed schematically the structure of the cryogenic refrigerator which concerns on the 3rd Embodiment of this invention. The block diagram which showed schematically the structure of the cryogenic refrigerator which concerns on the 4th Embodiment of this invention. The block diagram which showed schematically the structure of the cryogenic refrigerator which concerns on the 5th Embodiment of this invention. The block diagram which showed schematically the structure of the cryogenic refrigerator which concerns on the 6th Embodiment of this invention. It is a block diagram of the conventional cryogenic refrigerator, and is explanatory drawing which illustrates roughly the cooling method of the to-be-cooled body (superconducting coil) by this cryogenic refrigerator.

  Hereinafter, a cryogenic refrigerator according to the present invention will be described with reference to the accompanying drawings. The cryogenic refrigerator according to the present invention employs a GM (Gifford-McMahon) refrigerator in which a compressor unit and an expander unit (cold head) are separated as a part of the configuration, and other configurations are adopted. It is configured by adding.

[First Embodiment]
FIG. 1 is a configuration diagram schematically showing a configuration of a first cryogenic refrigerator 10A, which is an example of a cryogenic refrigerator according to the first embodiment of the present invention.

  The first cryogenic refrigerator 10A includes a cold head (expander unit) 11, a cooling stage 12, a refrigerant discharge joint 13, a refrigerant introduction joint 14, a refrigerant low-pressure pipe 15, a refrigerant high-pressure pipe 16, and compression. Compressor unit 17, compressor 18, compressor unit internal low-pressure pipe 19, compressor unit internal high-pressure pipe 20, refrigerant introduction joint 21, refrigerant discharge joint 22, buffer tank 23, and oil mist trap 24 In addition to the GM refrigerator (corresponding to the cryogenic refrigerator 100 shown in FIG. 7) having the adsorber 25, the pressure adjusting valve 26, and the bypass pipe 27, the pressure adjusting valve bypass flow introducing joint 37 is further provided. And a pressure regulating valve bypass flow discharge joint 38.

  In general, the GM refrigerator has a small mass flow rate of refrigerant because the refrigerant density is small in the initial cooling stage where the cooling stage 12 is near room temperature and cooling is not yet completed. Therefore, the pressure on the low pressure side decreases and the pressure on the high pressure side increases. In the compressor 18, a seal mechanism is necessary to prevent the refrigerant from leaking from the high pressure side to the low pressure side. However, if the differential pressure between the high pressure side and the low pressure side is large, the seal deteriorates and breaks, and the amount of leakage increases. Therefore, in order to prevent this, a bypass pipe 27 connecting the high pressure side and the low pressure side is provided, and further, the pressure on the low pressure side is not made lower than a predetermined value in the bypass pipe 27, and the pressure on the high pressure side is not made higher than a predetermined value. Alternatively, the pressure regulating valve 26 is provided so that the differential pressure between the high-pressure side and the low-pressure side does not exceed a certain level.

  Here, the cold head 11, the cooling stage 12, the refrigerant discharge joint 13, the refrigerant introduction joint 14, the refrigerant low-pressure pipe 15, the refrigerant high-pressure pipe 16, the compressor unit 17, and the compressor 18 included in the first cryogenic refrigerator 10 </ b> A. The compressor unit low-pressure pipe 19, compressor unit high-pressure pipe 20, refrigerant introduction joint 21, refrigerant discharge joint 22, buffer tank 23, oil mist trap 24, adsorber 25, and pressure regulating valve 26 are, for example, This is substantially the same as that of the conventional cryogenic refrigerator (GM refrigerator) as shown in FIG.

  That is, in the first cryogenic refrigerator 10A, the compressor unit 17 and the cold head 11 are connected by the refrigerant low-pressure pipe 15 and the refrigerant high-pressure pipe 16 so that the refrigerant can circulate. The refrigerant whose pressure has been increased by the compressor 18 in the compressor 17 is the high-pressure pipe 20 in the compressor unit, the oil mist trap 24, the adsorber 25, the refrigerant discharge joint 22, the refrigerant high-pressure pipe 16, the refrigerant introduction joint 14, the cold head 11, and the refrigerant discharge. The refrigerant can be circulated back to the compressor 18 again via the joint 13, the refrigerant low-pressure pipe 15, the refrigerant introduction joint 21, the low-pressure pipe 19 in the compressor unit, and the buffer tank 23.

  The pressure regulating valve 26 of the first cryogenic refrigerator 10A is provided in a bypass pipe 27 that bypasses the pressurized high-pressure refrigerant and the decompressed low-pressure refrigerant produced by the compressor 18, and the high-pressure pressure, the low-pressure side pressure, or Adjust both.

  The bypass pipe 27 of the first cryogenic refrigerator 10 </ b> A includes a low-pressure pipe 19 in the compressor unit and a high pressure in the compressor unit in order to bypass the pressurized high-pressure refrigerant created by the compressor 18 and the decompressed low-pressure refrigerant. The pipe 20 bypasses the pipe 20. The bypass pipe 27 of the first cryogenic refrigerator 10 </ b> A includes a pressure regulating valve bypass flow introduction joint 37 for discharging the refrigerant flowing through the bypass pipe 27 to the outside of the compressor unit 17 in the middle of the path, and the compressor. It differs from the basic configuration of a conventional GM refrigerator in that it is provided with a pressure regulating valve bypass flow discharge joint 38 for introducing (returning) the unit 17 from outside to inside.

  The pressure regulating valve bypass flow introduction joint 37 is provided in the middle of the path of the bypass pipe 27, and plays a role as an outlet (discharge port) when the refrigerant flowing through the bypass pipe 27 is taken out of the compressor unit 17. The pressure regulating valve bypass flow discharge joint 38 serves as an inlet when returning the refrigerant flowing through the bypass pipe 27 into the compressor unit 17.

  In the first cryogenic refrigerator 10A configured in this manner, the density of the refrigerant is small in the initial cooling stage where the cooling stage 12 is near room temperature (cooling is not completed), as in the conventional GM refrigerator. Therefore, since the mass flow rate of the refrigerant is small, the pressure on the low pressure side decreases and the pressure on the high pressure side increases. Therefore, during the initial precooling, the amount of refrigerant flowing through the bypass pipe 27 is large, and a large amount of refrigerant exists on the compressor unit 17 side.

  Thereafter, as the cooling progresses and the cooling temperature of the cooling stage 12 decreases, the flow rate flowing to the cold head 11 side increases, and the amount of refrigerant flowing to the bypass pipe 27 decreases. Then, when the cooling stage 12 finally reaches a predetermined temperature (cooling is completed), pressure adjustment becomes unnecessary, the pressure adjustment valve 26 is closed, and the flow rate of the bypass pipe 27 becomes zero.

  In view of this, the first cryogenic refrigerator 10A is configured so that the excess refrigerant flowing in the bypass pipe 27 is compressed from the viewpoint of effectively using the refrigerant that is present on the compressor unit 17 side in the initial cooling stage (initial precooling). A pressure regulating valve bypass flow introduction joint 37 and a pressure regulating valve bypass flow discharge joint 38 are provided so that the unit 17 can be taken in and out freely. By configuring the first cryogenic refrigerator 10A in this way, the refrigerant remaining on the compressor unit 17 side during the initial precooling can be used easily.

  As described above, according to the first cryogenic refrigerator 10 </ b> A, the pressure regulating valve bypass can be used so that excess refrigerant flowing in the bypass pipe 27 can be taken out of the compressor unit 17 during initial cooling (initial precooling). By providing the flow discharge joint 38, excess refrigerant can be taken out from the pressure regulating valve bypass flow discharge joint 38 and used simply for purposes other than the refrigerator. Further, by providing the bypass piping 27 with the pressure regulating valve bypass flow introduction joint 37 together with the pressure regulating valve bypass flow discharge joint 38, the refrigerant taken out and used for purposes other than the refrigerator can be easily returned.

[Second Embodiment]
FIG. 2 is a configuration diagram schematically showing the configuration of a second cryogenic refrigerator 10B, which is an example of a cryogenic refrigerator according to the second embodiment of the present invention.

  The second cryogenic refrigerator 10B shown in FIG. 2 is discharged from the pressure regulating valve bypass flow discharge joint 38 to the outside of the compressor unit 17 with respect to the first cryogenic refrigerator 10A shown in FIG. A refrigerant path that returns to the pressure regulating valve bypass flow introduction joint 37 through the pressure regulating valve bypass flow discharge pipe 39 and the pressure regulating valve bypass flow return pipe 40 provided in the pipe, and a heat exchanger 41 provided on the path. , 42, and 43, but the other points are not substantially different.

  Therefore, in the present embodiment, the second cryogenic refrigerator 10B is different from the first cryogenic refrigerator 10A in the pressure regulation valve bypass flow discharge pipe 39, the pressure regulation valve bypass flow return pipe 40, the counter flow. The heat exchanger 41, the cooling stage heat exchanger 42, and the coil part cooling heat exchanger 43 will be mainly described, and the other components will be denoted by the same reference numerals and description thereof will be omitted.

  As shown in FIG. 2, the second cryogenic refrigerator 10B is discharged from the pressure regulating valve bypass flow discharge joint 38 to the first cryogenic refrigerator 10A shown in FIG. 17 is further provided with a refrigerant path that returns to the pressure regulating valve bypass flow introduction joint 37 through the pressure regulating valve bypass flow discharge pipe 39 and the pressure regulating valve bypass flow return pipe 40 provided outside. Further, on the path constituted by the pressure adjustment valve bypass flow discharge joint 38, the pressure adjustment valve bypass flow discharge pipe 39, the pressure adjustment valve bypass flow return pipe 40, and the pressure adjustment valve bypass flow introduction joint 37, a counter flow A heat exchanger 41, a cooling stage heat exchanger 42 attached to the cooling stage 12, and a cooled object cooling heat exchanger 43 that cools the cooled object 46 are provided.

  In the second cryogenic refrigerator 10B, the refrigerant flowing through the bypass pipe 27 is discharged from the pressure adjustment valve bypass flow discharge joint 38 of the pressure machine unit 17, passes through the pressure adjustment valve bypass flow discharge pipe 39, and passes through the second cryogenic refrigerator 10B. After being cooled by the cooling stage heat exchanger 42 attached to the cooling stage 12 of the cryogenic refrigerator 10B, it is led to the cooling object cooling heat exchanger 43 and cooled by the cooling object cooling heat exchanger 43. After the heat exchange with the body 46, the pressure adjustment valve bypass flow return pipe 40 passes through the pressure adjustment valve bypass flow return pipe 40, and the pressure control valve bypass flow introduction joint 37 returns to the compressor unit 17.

  In addition, as shown in FIG. 2, the pressure regulating valve bypass flow discharge pipe 39 is further provided in part of the pressure regulating valve bypass flow discharge pipe 39 and the pressure regulating valve bypass flow return pipe 40 to thereby discharge the pressure regulating valve bypass flow. When the refrigerant circulating through the pipe 39 and the pressure regulating valve bypass flow return pipe 40 is cooled to a low temperature, it can be cooled more efficiently.

  According to the second cryogenic refrigerator 10B configured as described above, as a specific method of using the surplus refrigerant of the first cryogenic refrigerator 10A, the pressure regulating valve bypass flow discharge joint of the compressor unit 17 is used. By providing a circulation cooling pipe that discharges the refrigerant from 38 and returns to the pressure adjustment valve bypass flow introduction joint 37, that is, a pressure adjustment valve bypass flow discharge pipe 39 and a pressure adjustment valve bypass flow return pipe 40, surplus at the time of initial cooling is provided. The refrigerant can be used for cooling the object to be cooled 46 for precooling.

  Therefore, the surplus refrigerant at the time of the initial cooling can be easily used, and this refrigerant is used to heat not only the local range by the cooling part (cooling stage 12) of the cold head 11 but also the cooling object to be cooled. The exchanger 43 can also be cooled, and a refrigerator capable of cooling a wider range than before can be configured.

  In the second cryogenic refrigerator 10B shown in FIG. 2, the number of the heat exchanger 43 for cooling the object to be cooled is one, but may be plural. When there are a plurality of cooling object cooling heat exchangers 43, a plurality of places can be cooled.

  Further, in the second cryogenic refrigerator 10B shown in FIG. 2, there is one circulation path for discharging the refrigerant from the pressure regulating valve bypass flow discharge joint 38 of the compressor unit 17 and returning to the pressure regulating valve bypass flow introduction joint 37. However, a plurality of circulation paths can be formed in parallel.

[Third Embodiment]
FIG. 3 is a configuration diagram schematically showing the configuration of a third cryogenic refrigerator 10C, which is an example of a cryogenic refrigerator according to the third embodiment of the present invention.

  A third cryogenic refrigerator 10C shown in FIG. 3 is a superconducting magnet (superconducting coil 44 and heat transfer plate 45 shown in FIG. 3) as a body 46 to be cooled of the second cryogenic refrigerator 10B shown in FIG. ). The superconducting coil 44 and the heat transfer plate 45 shown in FIG. 3 are in contact with the cooling stage 12 of the third cryogenic refrigerator 10C to be cooled, and in addition to the heat for the object to be cooled by cooling the circulating refrigerant. It is also cooled by heat exchange in the exchanger 43.

  In the third cryogenic refrigerator 10C, when the flow rate to the cold head 11 at the time of pre-cooling is small, in order to cool the entire superconducting coil 44 with a reduced temperature gradient, After the cooling stage 12 is cooled to a predetermined temperature, the amount of thermal strain due to temperature change decreases at low temperatures, and the thermal conductivity of Cu, Al, and other thermal conductors increases. As a result, sufficient heat transfer characteristics can be obtained by local cooling of the cold head 11, so that cooling with a circulating refrigerant is unnecessary. Then, as the mass of refrigerant to the cold head 11 increases, the flow rate of the circulating refrigerant decreases and automatically becomes zero.

  According to the third cryogenic refrigerator 10C configured as described above, the temperature of the entire superconducting coil 44 can be reduced from the room temperature by reducing the temperature gradient of the entire superconducting coil 44, while preventing deterioration of the superconducting coil 44 due to thermal strain. It is possible to obtain an initial cooling characteristic that fully exhibits the refrigerating capacity of the machine, and after the initial precooling is completed, the flow rate of the refrigerant to the bypass pipe 27 becomes 0. The flow rate of the circulating refrigerant around the discharge pipe 39 and the pressure regulating valve bypass flow return pipe 40 can be automatically reduced to zero. Therefore, it is possible to configure a superconducting magnet and its cooling system that do not require switching operation from initial precooling to steady cooling, that is, easy operation.

  In the third cryogenic refrigerator 10C shown in FIG. 3, the number of the cooling object cooling heat exchanger 43 is one, but a plurality of the cooling bodies may be plural, as in the second cryogenic refrigerator 10B. It is.

[Fourth Embodiment]
FIG. 4 is a configuration diagram schematically showing a configuration of a fourth cryogenic refrigerator 10D which is an example of a cryogenic refrigerator according to the fourth embodiment of the present invention.

  The fourth cryogenic refrigerator 10D shown in FIG. 4 is not substantially different from the third cryogenic refrigerator 10C shown in FIG. The superconducting coil 44, which is the cooling body 46, is physically in contact and is different in that it is in thermal contact.

  That is, in the fourth cryogenic refrigerator 10D, the cooling stage 12 of the cold head 11 and the superconducting coil 44 that is the object to be cooled 46 are not in thermal contact with each other, and the pressure regulating valve bypass that is a circulation cooling pipe is used. Both sides of the superconducting coil 44 are cooled by handling only the flow discharge pipe 39 and the pressure regulating valve bypass flow return pipe 40. Further, the pressure regulating valve 26 was set so that the refrigerant flow rate of the circulating cooling was not zero even after the cooling stage 12 was cooled to a predetermined temperature.

  In the fourth cryogenic refrigerator 10D configured as described above, as shown in FIG. 4, the cooling stage 12 of the cold head 11 and the object to be cooled 46 are spatially separated from each other, Since the thermal contact with the cooled object 46 is cut off, the cooled object 46 does not exchange heat directly with the cold head 11.

  As a result, in the fourth cryogenic refrigerator 10D, when the fourth cryogenic refrigerator 10D stops, it is possible to avoid heat intrusion directly from the cold head 11 side into the superconducting coil 44 that is the object to be cooled. Since the amount of heat entering the superconducting coil 44 can be kept to a small amount of heat entering from the cooling pipe having a good heat insulating property, the low temperature holding property of the superconducting coil 44 can be improved.

  Further, if a material having a low thermal conductivity such as stainless steel is applied to the material of the pressure regulating valve bypass flow discharge pipe 39 and the pressure regulating valve bypass flow return pipe 40, the above-described effect can be further enhanced.

  As described above, according to the fourth cryogenic refrigerator 10D, for example, when the fourth cryogenic refrigerator 10D stops during a power failure, the temperature increase rate of the superconducting coil 44 is reduced, so The time required for coping is greatly increased. Further, at the time of maintenance such as replacement of the cold head 11, it is not necessary to raise the temperature of the superconducting magnet to near room temperature, and only the cold head 11 can be returned to room temperature almost independently and replacement work can be performed. In particular, in the superconducting coil 44 having a large heat capacity, it is not necessary to raise the temperature of the superconducting coil 44 to room temperature and to recool it. Therefore, it is possible to configure a superconducting magnet and its cooling system that can greatly reduce the maintenance time.

[Fifth Embodiment]
FIG. 5 is a configuration diagram schematically showing a configuration of a fifth cryogenic refrigerator 10E which is an example of a cryogenic refrigerator according to the fifth embodiment of the present invention.

  A fifth cryogenic refrigerator 10E shown in FIG. 5 is a first cryogenic refrigerator 10B in place of a cold head 11 (single-stage refrigerator) having a one-stage cooling stage 12 with respect to the second cryogenic refrigerator 10B. The difference is that the cold head 11 (two-stage refrigerator) including the stage stage 47 and the second stage stage 48 is used, but there is no substantial difference in other points. Therefore, in the present embodiment, the description will be focused on the different refrigerators, and the components that are not substantially different will be denoted by the same reference numerals and description thereof will be omitted.

  As shown in FIG. 5, the fifth cryogenic refrigerator 10E includes a first stage cooling stage 47 on the high temperature side and a second one on the low temperature side instead of the cooling stage 12 of the second cryogenic refrigerator 10B. A stage cooling stage 48 is provided.

  In the fifth cryogenic refrigerator 10E, the refrigerant passing through the bypass pipe 27 in the compressor unit 17 is taken out from the pressure regulating valve bypass flow discharge joint 38, and the pressure regulating valve bypass flow discharge pipe 39 from which the refrigerant is taken out is heated. The pressure regulating valve bypass flow return pipe 40 is provided which is connected to the refrigerant in the pipe and is cooled by the first stage cooling stage 47 and returns to the compressor unit 17 through the heat exchanger 43 with the cooled object 46. . Further, the cooled object 46 is thermally connected to a second cooling stage 48 that can obtain a lower temperature than the first stage 47.

  In the fifth cryogenic refrigerator 10E configured as described above, since the refrigerant flows through the bypass pipe 27 at the initial stage of cooling, the refrigerant cooled by the first stage cooling stage 47 and the second stage cooling stage 48 By both, the to-be-cooled body 46 is cooled. In addition, when the cooled object 46 is cooled to a sufficiently low temperature, the amount of refrigerant flowing through the bypass pipe 27 can be reduced to a small amount or 0, so that the first temperature that is higher than the second cooling stage 48 is obtained. Cooling by the stage cooling stage 47 is stopped, and cooling is performed only by the second stage cooling stage 48 that can reach a lower temperature than the first stage cooling stage 47.

  According to the fifth cryogenic refrigerator 10E, at the time of initial pre-cooling in the cooling of the cooled object 46 having a large heat capacity, it is possible to cool using both of the first-stage cooling stage 47 and the second-stage cooling stage 48. The initial cooling time can be greatly shortened. Further, since the cooling is switched to the cooling of only the second stage cooling stage 48 when cooled to a predetermined temperature, the cooled object 46 can be cooled to a temperature lower than the temperature reached by the first stage cooling stage 47.

  The pressure regulating valve bypass flow discharge pipe 39 and the pressure regulating valve bypass flow return pipe 40 are made of a metal having a low thermal conductivity, such as stainless steel, and are kept at a predetermined length at room temperature and the first stage cooling stage. 47, the first stage cooling stage 47 and the object to be cooled 46 are connected to the heat exchanger 43 for the object to be cooled, and so on, from the pressure adjustment valve bypass flow discharge pipe 39 and the pressure adjustment valve bypass flow return pipe 40. The amount of heat penetration can be reduced, and the temperature reached when the refrigerant is not flowing can be reduced.

  Further, in the fifth cryogenic refrigerator 10E shown in FIG. 5, the example of the two-stage refrigerator including the cooling stages 47 and 48 is shown, but the same applies to the refrigerator having two or more stages. Can be applied. That is, the same action can be achieved by configuring the high-temperature side cooling stage above the final stage in the same manner as the first cooling stage 47 shown in FIG. 5 and the final cooling stage as the second cooling stage 48. An effect is obtained.

[Sixth Embodiment]
FIG. 6 is a configuration diagram schematically showing a configuration of a sixth cryogenic refrigerator 10F, which is an example of a cryogenic refrigerator according to the sixth embodiment of the present invention.

  The sixth cryogenic refrigerator 10F shown in FIG. 6 is configured to cool the superconducting coil 44 and the heat transfer plate 45 in the cooled object 46 of the fifth cryogenic refrigerator 10E shown in FIG. is there. In other words, with respect to the third cryogenic refrigerator 10C shown in FIG. 3, instead of the cold head 11 (one-stage refrigerator) including the one-stage cooling stage 12, the first stage 47 and the first stage The difference is that a cold head 11 (two-stage refrigerator) including the two-stage stage 48 is used, but the other points are not substantially different.

  In the sixth cryogenic refrigerator 10F configured as described above, the temperature gradient of the entire superconducting coil 44 can be reduced and cooling can be performed from room temperature, and deterioration of the superconducting coil 44 due to thermal strain can be prevented, while It is possible to obtain an initial cooling characteristic that fully exhibits the refrigerating capacity. Moreover, the switching operation from the initial precooling to the steady cooling is unnecessary (the operation is simple).

  On the other hand, at the time of initial pre-cooling, the cooling capacity can be reduced by using the refrigeration capacities of both the first stage cooling stage 47 and the second stage cooling stage 48, so that the initial cooling time can be greatly shortened and the cooling is performed to a predetermined temperature. Then, since the cooling is switched to the cooling of only the second stage cooling stage 48, the cooled object 46 can be cooled to a temperature lower than the temperature reached by the first stage cooling stage 47.

  According to the sixth cryogenic refrigerator 10F, the temperature gradient of the entire superconducting coil 44 can be reduced and cooling can be performed from room temperature, and the refrigerating capacity of the refrigerator is fully achieved while preventing deterioration of the superconducting coil 44 due to thermal strain. The initial cooling characteristics exhibited in the above can be obtained. In particular, since the first stage cooling stage 47 and the second stage cooling stage 48 are provided, at the time of initial precooling, cooling can be performed using the cooling capacity of both the first stage cooling stage 47 and the second stage cooling stage 48, The initial cooling time can be greatly shortened.

  In addition, after cooling to a predetermined temperature, the cooling target 46 is set to a temperature higher than the temperature reached by the first stage cooling stage 47 because only the second stage cooling stage 48 is switched without performing any special switching operation. It can be cooled to a lower temperature. Therefore, the operation is very simple when switching from the initial precooling to the steady cooling. Furthermore, by applying such a sixth cryogenic refrigerator 10F, it is possible to shorten the initial precooling time, maintain the performance at the ultimate temperature, and configure a superconducting magnet that is easy to operate and its cooling system. .

  As described above, according to the cryogenic refrigerators 10A, 10B, 10C, 10D, 10E, and 10F, while adopting the configuration of cooling with one refrigerator, the precooling time is shortened, the handling is easy, and the deterioration due to thermal strain. It is possible to improve the pre-cooling characteristics such as prevention.

  That is, the cryogenic refrigerators 10 </ b> A, 10 </ b> B, 10 </ b> C, 10 </ b> D, 10 </ b> E, and 10 </ b> F are pressure-adjusted so that excess refrigerant flowing through the bypass pipe 27 can be taken out of the compressor unit 17 during initial cooling (initial precooling). By providing the valve bypass flow discharge joint 38, surplus refrigerant can be taken out from the pressure regulating valve bypass flow discharge joint 38 and used simply for purposes other than the refrigerator. Further, by providing the bypass piping 27 with the pressure regulating valve bypass flow introduction joint 37 together with the pressure regulating valve bypass flow discharge joint 38, the refrigerant taken out and used for purposes other than the refrigerator can be easily returned.

  Furthermore, the cryogenic refrigerators 10B, 10C, 10D, 10E, and 10F can easily use the excess refrigerant at the time of initial cooling, and the cooling unit (cooling stage 12) of the cold head 11 using this refrigerant. In addition to the local range according to the above, it is possible to cool the object to be cooled by the heat exchanger 43 for cooling the object to be cooled, and it is possible to configure a refrigerator capable of cooling a wider range than before.

  Furthermore, in the cryogenic refrigerators 10C and 10F in which the superconducting coil 44 is the object to be cooled 46, the temperature gradient of the entire superconducting coil 44 can be reduced and cooling can be performed from room temperature. It is possible to obtain an initial cooling characteristic that fully exhibits the refrigerating capacity of the refrigerator while preventing the flow rate, and after the initial precooling is completed, the flow rate of the refrigerant to the bypass pipe 27 becomes 0, so that the pressure is not switched. The flow rate of the circulating refrigerant around the regulating valve bypass flow discharge pipe 39 and the pressure regulating valve bypass flow return pipe 40 can be automatically reduced to zero. Therefore, it is possible to configure a superconducting magnet and its cooling system that do not require switching operation from initial precooling to steady cooling, that is, easy operation.

  Further, in the fourth cryogenic refrigerator 10D, the object to be cooled 46 is not directly cooled from the cold head 11, so that when the operation of the refrigerator is stopped, the heat intrusion from the refrigerator is directly cooled. Therefore, the amount of heat penetration from the cooling pipe having good heat insulation characteristics is reduced, and the low temperature holding characteristics of the superconducting coil 44 can be improved.

  Furthermore, since the cryogenic refrigerators 10E and 10F employ a multistage type (two stage type in the examples shown in FIGS. 5 and 6), the cooled object 46 (or the superconducting coil 44) having a large heat capacity. In the initial pre-cooling in the cooling of (), cooling can be performed using the refrigeration capacities of both the first stage cooling stage 47 and the second stage cooling stage 48, and the initial cooling time can be greatly shortened. Furthermore, since cooling to only the second stage cooling stage 48 is performed when it is cooled to a predetermined temperature, the cooled object 46 (superconducting coil 44) is cooled to a temperature lower than the temperature reached by the first stage cooling stage 47. can do.

  Note that the present invention is not limited to the above-described embodiments as they are, and may be embodied by modifying constituent elements without departing from the scope of the invention in the implementation stage.

  In addition, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the above embodiments. For example, you may delete some components from all the components shown by embodiment. Furthermore, you may combine the component covering different embodiment suitably.

10A, 10B, 10C, 10D, 10E, 10F Cryogenic refrigerator 11 Cold head (expander unit)
12 Cooling stage 13 Refrigerant discharge joint 14 Refrigerant introduction joint 15 Refrigerant low-pressure pipe 16 Refrigerant high-pressure pipe 17 Compressor unit 18 Compressor 19 Compressor unit internal low-pressure pipe 20 Compressor unit high-pressure pipe 21 Refrigerant introduction joint 22 Refrigerant discharge joint 23 Buffer Tank 24 Oil mist trap 25 Adsorber 26 Pressure adjustment valve 27 Bypass pipe 37 Pressure adjustment valve bypass flow introduction joint 38 Pressure adjustment valve bypass flow discharge joint 39 Pressure adjustment valve bypass flow discharge pipe 40 Pressure adjustment valve bypass flow return pipe 41 Counterflow heat Exchanger 42 Cooling stage heat exchanger 43 Heat exchanger 44 for cooling object to be cooled Superconducting coil 45 Heat transfer plate 46 Object to be cooled 47 First stage cooling stage 48 Second stage cooling stage 100 Conventional cryogenic refrigerator 101 Cold head (Expander unit)
102 Cooling stage 103 Refrigerant discharge joint 104 Refrigerant inlet joint 105 Refrigerant low-pressure pipe 106 Refrigerant high-pressure pipe 107 Compressor unit 108 Compressor 109 Compressor unit low-pressure pipe 110 Compressor unit high-pressure pipe 111 Refrigerant inlet joint 112 Refrigerant discharge joint 113 Buffer Tank 114 Oil mist trap 115 Adsorber 116 Pressure regulating valve 117 Bypass piping 124 Superconducting coil 125 Heat transfer plate

Claims (7)

A compressor unit and a cold head separated from the compressor unit are provided. The refrigerant is pressurized by the compressor of the compressor unit, supplied to the cold head, and expanded in the cold head to generate cold. In the cryogenic refrigerator that increases the pressure by introducing again the refrigerant after being expanded in the cold head to the compressor of the compressor unit,
A bypass pipe connecting a high-pressure side pipe to which a refrigerant boosted by the compressor is supplied and a low-pressure side pipe for supplying the refrigerant introduced from the outside of the compressor unit to the compressor;
A pressure adjusting valve that is provided in the bypass pipe and adjusts the internal pressure of at least one of the high-pressure side pipe and the low-pressure side pipe;
An outlet for taking out the refrigerant in the bypass pipe to the outside of the compressor unit;
An inlet for introducing refrigerant into the compressor unit from the outside of the compressor unit;
A cryogenic refrigerator having the above structure. A pipe that connects the take-out port and the introduction port, and that constitutes a circulation path for taking out the refrigerant in the bypass pipe from the take-out port to the outside of the compressor unit and returning the taken-out refrigerant to the inside of the compressor unit. Is installed,
The circulation path includes a cooling stage heat exchanger provided in the cooling stage of the cold head, and at least one or more cooled object heat exchangers that cool the cooled object downstream of the cooling stage heat exchanger. The cryogenic refrigerator according to claim 1, wherein the cryogenic refrigerator is configured to be connected in series. The cryogenic refrigerator according to claim 1 or 2, wherein the cold head has a plurality of cooling stages. The object to be cooled is thermally connected to the final cooling stage of the cold head, and the cooling stage heat exchanger is provided in any one of the first cooling stages than the final cooling stage. The cryogenic refrigerator according to claim 3. The cryogenic refrigerator according to any one of claims 2 to 4, wherein the object to be cooled is a superconducting coil. The to-be-cooled body is a superconducting coil, and is configured to be in thermal contact with the to-be-cooled body heat exchanger at least one place different from the place directly cooled from the cooling stage of the cold head. The cryogenic refrigerator according to any one of claims 2 to 5, characterized in that The cooled object heat exchanger includes at least a first cooled object heat exchanger and a second cooled object heat exchanger, and the first cooled object heat exchanger and the second cooled object heat exchanger. The cryogenic temperature according to claim 2, wherein the cooling body heat exchanger is in thermal contact with the body to be cooled, and the cooling stage and the body to be cooled are cut off from thermal contact. refrigerator.

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