EP0399813A2 - Cryogenic refrigerator - Google Patents
Cryogenic refrigerator Download PDFInfo
- Publication number
- EP0399813A2 EP0399813A2 EP90305632A EP90305632A EP0399813A2 EP 0399813 A2 EP0399813 A2 EP 0399813A2 EP 90305632 A EP90305632 A EP 90305632A EP 90305632 A EP90305632 A EP 90305632A EP 0399813 A2 EP0399813 A2 EP 0399813A2
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- EP
- European Patent Office
- Prior art keywords
- cylinder
- displacer
- cooling member
- passage
- cryogenic refrigerator
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02G—HOT GAS OR COMBUSTION-PRODUCT POSITIVE-DISPLACEMENT ENGINE PLANTS; USE OF WASTE HEAT OF COMBUSTION ENGINES; NOT OTHERWISE PROVIDED FOR
- F02G1/00—Hot gas positive-displacement engine plants
- F02G1/04—Hot gas positive-displacement engine plants of closed-cycle type
- F02G1/043—Hot gas positive-displacement engine plants of closed-cycle type the engine being operated by expansion and contraction of a mass of working gas which is heated and cooled in one of a plurality of constantly communicating expansible chambers, e.g. Stirling cycle type engines
- F02G1/053—Component parts or details
- F02G1/0535—Seals or sealing arrangements
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B9/00—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point
- F25B9/14—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point characterised by the cycle used, e.g. Stirling cycle
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02G—HOT GAS OR COMBUSTION-PRODUCT POSITIVE-DISPLACEMENT ENGINE PLANTS; USE OF WASTE HEAT OF COMBUSTION ENGINES; NOT OTHERWISE PROVIDED FOR
- F02G2253/00—Seals
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02G—HOT GAS OR COMBUSTION-PRODUCT POSITIVE-DISPLACEMENT ENGINE PLANTS; USE OF WASTE HEAT OF COMBUSTION ENGINES; NOT OTHERWISE PROVIDED FOR
- F02G2258/00—Materials used
- F02G2258/10—Materials used ceramic
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2309/00—Gas cycle refrigeration machines
- F25B2309/003—Gas cycle refrigeration machines characterised by construction or composition of the regenerator
Definitions
- the present invention relates to a cryogenic refrigerator and, more particularly, a refrigerator of the refrigerant-accumulating type.
- cryogenic refrigerators are now on the market.
- One of them is of the Gifford-McMahon type. This refrigerator is usually arranged as shown in Fig. 1.
- the refrigerator comprises generally a cold head 1 and a coolant gas introducing and discharging system 2.
- the cold head 1 includes a closed cylinder 11, a displacer 12 freely reciprocating in the cylinder 11, and a motor 13 for driving the displacer 11.
- the cylinder 11 includes a first large-diameter cylinder 14 and a second small-diameter cylinder 15 coaxially connected to the first cylinder 14.
- the border wall between the first 14 and the second cylinder 15 forms a first stage 16 as a cooling face and the front wall of the cylinder 15 forms a second stage 17 which is lower in temperature than the first stage 16.
- the displacer 12 includes a first displacer 18 reciprocating in the first cylinder 14 and a second displacer 19 reciprocating in the second cylinder 15.
- the first and second displacers 18 and 19 are connected to each other in the axial direction of the cylinder 11 by a connector 20.
- a fluid passage 21 is formed in the first displacer 18, extending in the axial direction of the displacer 18, and a cooling member 22 formed of copper meshes or the like is housed in the fluid passage 21.
- a fluid passage 23 is formed in the second displacer 19, extending in the axial direction of the displacer 19, and a cooling member 24 formed of lead balls or the like is formed in the fluid passage 23.
- Seal systems 25 and 26 are located between the outer circumference of the first displacer 18 and the inner circumference of the first cylinder 14 and between the outer circumference of the second displacer 19 and the inner circumference of the second cylinder 15, respectively.
- the top of the first displacer 18 is connected to the rotating shaft of the motor 13 through a connector rod 31 and a Scotch yoke or crankshaft 32.
- the displacer 12 reciprocates, as shown by an arrow in Fig. 1, synchronizing with the rotating shaft of the motor 13.
- An inlet 34 and an outlet 35 for introducing and discharging coolant gas extend from the upper portion of one side of the first cylinder 14 and they are connected to the coolant gas introducing and discharging system 2.
- the coolant gas introducing and discharging system 2 serves as a helium gas circulating system, comprising connecting the outlet 35 to the inlet 34 through a low-pressure valve 36, a compressor 37 and a high-pressure valve 38. Namely, this system 2 is intended to compress low-pressure (about 5 atm) helium to high-pressure (about 18 atm) one by the compressor 37 and send it into the cylinder 11.
- the low- and high-pressure valves 36 and 38 are opened and closed, as will be described later, in a relation to the reciprocation of the displacer 12.
- That portions in the refrigerator where cooling is effected or which act as cooling faces are the first and second stages 16 and 17, which are cooled or refrigerated to about 30 K and 10 K, respectively, when no thermal load is present. Therefore, a temperature gradient ranging from a normal temperature (300 K) to 30 K exists between the top and bottom of the first displacer 18 and a temperature gradient ranging from 30 K to 10 K exists between the top and bottom of the second displacer 19. These temperature gradients, however, are changed by thermal loads at the step stages and it usually ranges from 30 K to 80 K at the first stage 16 while it ranges from 10 K to 20 K at the second stage 17.
- the displacer 12 When the motor 13 starts its rotation, the displacer 12 reciprocates between top and bottom dead centers. When the displacer 12 is at the bottom dead center, the high-pressure valve 38 is opened, allowing high-pressure helium gas to flow into the cold head 1. The displacer 12 then moves to the top dead center. As described above, the seal systems 25 and 26 are arranged between the outer circumference of the first displacer 18 and the inner circumference of the first cylinder 14 and between the outer circumference of the second displacer 19 and the inner circumference of the second cylinder 15, respectively.
- high-pressure helium gas flows into a first stage expansion chamber 39 formed between the first 18 and the second displacer 19 and then into a second stage expansion chamber 40 formed between the second displacer 19 and the front wall of the second cylinder, passing through the fluid passage 21 in the first displacer 18 and the fluid passage 23 in the second displacer 19. While flowing in this manner, high-pressure helium gas is cooled or refrigerated by the cooling members 22 and 24, so that high-pressure helium gas flowing into the first stage expansion chamber 39 can be cooled to about 30 K and high-pressure helium gas flowing into the second stage expansion chamber 40 can be cooled to about 8 K.
- the high-pressure valve 38 is closed and the low-pressure valve 36 is opened.
- the low-pressure valve 36 is opened, high-pressure helium gas in the first stage expansion chamber 39 and the second stage expansion chamber 40 is expanded and cooling is effected.
- the first stage 16 and the second stage 17 are cooled by this cooling phenomenon.
- the displacer 12 moves to the bottom dead center again and helium gas in the first stage expansion chamber 39 and the second stage expansion chamber 40 is removed as the movement of the displacer 12.
- the expanded helium gas is warmed by the cooling members 22 and 24 while passing through the fluid passages 21 and 22, and is an ordinary temperature and discharged. Thereafter, the above-mentioned cycle is repeated and the refrigerating operation is performed.
- This type of the refrigerator is used for cooling a superconducting magnet or an infrared sensor, or as a cooling source of a cryopump.
- the cylindrical fluid passage 23 is formed in the second displacer 19 and the inside of the passage is filled with the ball or grain-like cooling member 24.
- Speed distribution in helium gas flowing through the passages which were filled with balls or grains was measured and it was found that velocity of flow was the lowest in the center of the flow of helium gas and that it became higher and higher as coming remoter from the center of the flow of helium gas outward in the radial direction thereof.
- the conventional refrigerators arranged as shown in Fig. 1 had a problem as described below.
- the seal system 25 prevents helium gas from flowing from the normal temperature section to the first expansion chamber 39 and vice versa, passing through a clearance between the first cylinder 14 and the first displacer 18, while the seal system 26 prevents helium gas from flowing from the first stage expansion chamber 39 to the second stage expansion chamber 40 and vice versa, passing through a clearance between the second cylinder 15 and the second displacer 19.
- These seal systems 25 and 26 are used in helium gas of high purity (99.99%) and no lubricating material such as grease cannot be used to them because it contaminates helium gas.
- the seal system 26 is located at the low temperature section (30 to 80 K) and it is asked to have a shape like the piston seal. Providing that the first stage expansion chamber 39 has a temperature of 30 K while the second stage expansion chamber 40 has a temperature of 10 K and that helium gas leaks at some portion of the seal system 26, helium gas of 30 K will enter into the second stage expansion chamber 40 without contacting the cooling member 24 in the second displacer 19 and helium gas of 10 K will enter into the first stage expansion chamber 39. As the result, the temperature of the first stage 16 falls and that of the second stage 17 rises. Fig.
- the seal system 26 used comprises fitting a turn of sealing 28 provided with overlapped ends 30 as shown in Fig. 6 into a ring-shaped groove 27 on the outer circumference of the second displacer 19 and arranging a spring ring 29 on the backside of the sealing 28 to urge the sealing 28 against the second cylinder 15, as shown in Figs. 4 through 6.
- a considerable amount of helium gas is allowed to leak through the overlapped ends 30 of the sealing 28, thereby causing the temperature of the second stage 17 to rise. This results in reducing refrigerating capacity at a certain temperature.
- the conventional refrigerators arranged as shown in Fig. 1 had another problem as described below.
- magnetic material is used as a part or whole of the cooling member 24 in the second displacer 19, it is quite difficult to process the magnetic material into balls or meshes such as the cooling member 22 in the first displacer 18.
- the magnetic material is therefore melted to a bulky mass, which is ground and screened to grains each having a size of about 100 to 500 ⁇ m. These grains substantially same in size are used as the cooling member.
- each of these grains has sharp edges and tips which are several ⁇ m in size, and these sharp edges and tips are broken off the grains while the refrigerator is under operation.
- the cooling member 24 is covered by sheets of net at the top and bottom thereof not to drop from the second displacer 19, but these sheets of net have meshes each having a size of several tens ⁇ m and fine edges and tips broken off the grains of magnetic material pass through these meshes of the nets together with helium gas.
- the meshes of the nets which cover the top and bottom of the cooling member 24 are made smaller in size, however, the pressure loss of helium gas is increased. This is not a merit.
- the fine edges and tips of magnetic material dropped from the second displacer 19 adhere to the seal 25 to thereby increase the amount of helium gas leaded through the seal 25. This lowers the refrigerating capacity of the refrigerator to a great extent.
- the conventional refrigerators arranged as shown in Fig. 1 had a further problem as described below.
- the first and second displacers 18 and 19 are filled with the cooling members 22 and 24, clearances are caused between the cooling members and the displacers.
- effective heat exchange cannot be carried out between the gas and the cooling member.
- An object of the present invention is to provide a cryogenic refrigerator capable of causing coolant gas to uniformly flow through a cooling member to increase the refrigerating capacity of the refrigerator.
- Another object of the present invention is to provide a cryogenic refrigerator capable of enhancing sealing performance between a cylinder and a displacer to increase the refrigerating capacity of the refrigerator.
- a further object of the present invention is to provide a cryogenic refrigerator capable of preventing the cooling member from creating fine powder to increase the refrigerating capacity of the refrigerator.
- a cryogenic refrigerator comprising a closed cylinder provided with an inlet and an outlet for introducing and discharging a coolant gas into and out of the cylinder; a displacer slidably housed in the closed cylinder and housing a cooling member therein and having a passage through which the coolant gas flows; a means coaxially arranged in and along the passage of the displacer in which the cooling member is housed to divide the passage into outer and inner ones; a means for reciprocating the displacer in the cylinder; and a means for repeating the process of introducing the high pressure coolant gas into the cylinder through the inlet and discharging it out of the cylinder, synchronizing with the reciprocating displacer.
- a cryogenic refrigerator comprising a closed cylinder provided with an inlet and an outlet for introducing and discharging a coolant gas into and out of the cylinder; a displacer slidable arranged in the closed cylinder and housing a cooling member therein and having a passage through which the coolant gas flows; plural gas penetrating diaphragms arranged in the passage in which the cooling member is housed and separated from one another by a certain interval in a direction perpendicular to the direction in which the passage is directed; a means for reciprocating the displacer in the cylinder; a means for repeating the process of introducing the coolant gas into the cylinder through the inlet and discharging it out of the cylinder through the outlet in a relation to the reciprocating displacer.
- a cryogenic refrigerator comprising a closed cylinder provided with an inlet and an outlet for introducing and discharging a coolant gas into and out of the cylinder; a displacer slidable arranged in the closed cylinder and housing a cooling member therein and having a passage through which the coolant gas flows; plural gas penetrating diaphragms arranged in the passage in which the cooling member is housed and separated from one another by a certain interval in a direction perpendicular to the direction in which the passage is directed; a means for reciprocating the displacer in the cylinder; a means for repeating the process of introducing the high pressure coolant gas into the cylinder through the inlet and discharging it out of the cylinder through the outlet in a relation to the reciprocating displacer and first and second sealing members arranged along the axis of the displacer to seal the clearance between the closed cylinder and the displacer; wherein said displacer has two ring-shaped grooves on the outer circum
- a cryogenic refrigerator comprising a closed cylinder provided with an inlet and an outlet for introducing and discharging a coolant gas into and out of the cylinder; a displacer slidably arranged in the closed cylinder and housing a cooling member therein and having a passage through which the coolant gas flows; a means for reciprocating the displacer; and a means for repeating the process of introducing the coolant gas into the cylinder through the inlet and discharging it out of the cylinder through the outlet in a relation to the reciprocating displacer; wherein said cooling member is those grains of a magnetic matter which are coated by a metal film.
- a cryogenic refrigerator comprising a closed cylinder provided with an inlet and an outlet for introducing and discharging a coolant gas into and out of the cylinder; a displacer slidably arranged in the closed cylinder and housing a cooling member therein and having a passage through which the coolant gas flows: a fibrous member arranged between the displacer and the cooling member; a means for reciprocating the displacer; and a means for repeating the process of introducing the high pressure coolant gas into the cylinder through the inlet and discharging it out of the cylinder through the outlet in a relation to the reciprocating displacer.
- Fig. 8 is a sectional view showing an example of the Gifford-McMahon type refrigerator, which is same in arrangement as the one shown in Fig. 1 except a fluid path or passage 123.
- the refrigerator includes generally a cold head 101 and a coolant gas introducing and discharging system 102.
- the cold head 101 comprises a closed cylinder 111, a displacer 112 housed in the cylinder 111 and freely reciprocating therein, and a motor 113 for driving the displacer 112 to reciprocate in the cylinder 111.
- the cylinder 111 includes a first large-diameter cylinder 114 and a second small-diameter cylinder 115 coaxially connected to the cylinder 114.
- the border wall between the first cylinder 114 and the second cylinder 115 forms a first stage 116 which serves as a cooling face, and the front wall of the cylinder 115 forms a second stage 117 which is lower in temperature than the first stage 116.
- the displacer 112 includes a first displacer 118 reciprocating in the first cylinder 114 and a second displacer 119 reciprocating in the second cylinder 115.
- the first and second displacers 118 and 119 are connected to each other by a connector member 120 in the axial direction of the cylinder 112.
- a fluid passage 121 is formed in the first displacer 118, extending in the axial direction of the displacer 118, and a cooling member 122 made by copper meshes or the like is contained in the fluid passage 121.
- a fluid passage 123 is also formed in the second displacer 119, extending in the axial direction of the displacer 119, and a cooling member 124 made by copper balls or the like is contained in the fluid passage 123.
- Seal systems 125 and 126 are located between the outer circumference of the first displacer 118 and the inner circumference of the first cylinder 114 and between the outer circumference of the second displacer 119 and the inner circumference of the second cylinder 115, respectively.
- the top of the first displacer 118 is connected to the rotating shaft of the motor 113 through a connector rod 131 and a Scotch yoke or crankshaft 132.
- the displacer 112 is reciprocated as shown by an arrow in Fig. 8, synchronizing with the rotating shaft of the motor 113.
- An inlet 134 and an outlet 135 for coolant gas extend outwards from the upper portion of one side of the first cylinder 114 and they are connected to the coolant gas introducing and discharging system 102.
- This system 102 serves to circulate helium gas flowing through the cylinder 111 and comprises connecting the outlet 135 to the inlet 134 through a low-pressure valve 136, a compressor 137 and a high-pressure valve 138.
- the system 102 also serves to compress low pressure helium gas (about 5 atm) to high pressure one (about 18 atm) through the compressor 137 and send it into the cylinder 111.
- the low- and high-pressure valves 136 and 138 are opened and closed in a relation to the reciprocating displacer 112.
- a pipe 142 is coaxially housed in the fluid passage 123 and allows helium gas to flow inside and outside the pipe 142.
- a fluid passage 143 inside the pipe 142 is filled with a cooling member 145 shaped like balls each having a diameter of 0.4 mm and another fluid passage 144 outside the pipe 142 is filled with a cooling member 146 shaped like balls each having a diameter of 0.2 mm.
- the passage of helium gas is divided into two in the same direction as helium gas flows, and the large-diameter cooling balls 145 are housed in the inner fluid passage 143. This reduces the pressure loss of helium gas flowing through the inner fluid passage 143 and the amount of helium gas flowing through the passage 143 is increased accordingly. The partial flow of helium gas can be thus reduced to a greater extent. This enables the cooling efficiencies of the cooling balls 145 and 146 to be increased so as to enhance the refrigerating capacity of the refrigerator.
- Fig. 10 shows results obtained by measuring the flow speed distributions of helium gas flowing through the cooling members in the fluid passages shown in Figs. 2 and 9. These results were obtained under normal temperature and with the refrigerators kept static, providing that the outer diameters of the fluid passages, the amounts of the cooling members contained in the fluid passages and the materials by which the cooling members are made are same. These conditions are different from those (cryogenic temperature and reciprocating motion) under which the refrigerators are practically operated, but it is understood that the flow speed distribution of helium gas flowing through the cooling member in the fluid passage shown in Fig. 9 is more uniform. It is supposed that this trend can be kept under the practical conditions. Fig.
- FIG. 11 shows refrigerating curves achieved by the conventional cryogenic refrigerator in which the fluid passage 23 shown in Fig. 2 is incorporated and by the cryogenic refrigerator of the present invention in which the fluid passage 123 shown in Fig. 9 is incorporated.
- the horizontal axis of the coordinate shown in Fig. 11 represents temperatures (K) of the second stage 117 and the vertical axis thereof heat loads (W) added to the second stage 117.
- refrigerating capacity under same temperature is higher in the case of the cryogenic refrigerator according to the present invention. It is therefore understood that refrigerating capacity can be increased when the fluid passage 123 which has the above-described arrangement is employed.
- the fluid passage in this example is divided into two concentric ones, it may be divided into three or more ones.
- the diameter of the ball is not limited to 0.4 mm or 0.2 mm.
- Figs. 12 and 13 show a second example of the cryogenic refrigerator according to the present invention, in which the pipe 142 is coaxially housed in the fluid passage 141, the passage of helium gas is divided to flow inside and outside the pipe 142, and a cooling member 124 contained in the inner and outer passages 143 and 144 is shaped like balls each having same size.
- the passage of helium gas is divided into two in same direction as helium gas flows, so that the partial flow of helium gas can be reduced to a greater extent, as compared with that in the conventional case. Therefore, cooling efficiency achieved by the cooling member 124 can be increased to thereby enhance the refrigerating capacity of the refrigerator.
- Fig. 14 shows results obtained by measuring the flow speed distributions of helium gas flowing through the cooling members contained in the fluid passages shown in Figs. 2 and 13. These results were obtained under normal temperature and with the refrigerators kept static, providing that the outer diameters of the fluid passages, the amounts, shapes and sizes of the cooling members contained in the fluid passages, and the materials by which the cooling members are made are same. These conditions are different from those (cryogenic temperature and reciprocating motion) under which the refrigerators are practically operated but it is understood that the flow speed distribution of helium gas flowing through the cooling member in the fluid passage shown in Fig. 13 is more uniform. It is supposed that this trend can be kept under the practical conditions.
- the fluid passage in this example is divided into two concentric ones, it may be divided into three or more ones. They may be neither concentric nor cylindrical.
- Fig. 15 shows a third example of the cryogenic refrigerator according to the present invention.
- This third example is different from the first example in the arrangement of a fluid passage 141 which is formed in the second displacer 119 and in which the cooling member 124 is contained.
- the cooling member 124 shaped like balls, and sheets of meshes 147 are contained in the fluid passage 141 in such a way that they are alternately piled in the fluid passage 141 in direction perpendicular to the flow of helium gas.
- helium gas flowing through the passage 141 can be made uniform by the sheets of meshes.
- the partial flow of helium gas can be thus reduced to a greater extent, as compared with that in the conventional case. Therefore, cooling efficiency achieved by the cooling member 124 can be increased so as to enhance the refrigerating capacity of the refrigerator.
- Fig. 17 shows results obtained by measuring the flow speed distributions of helium gas flowing through the cooling members in the fluid passages shown in Figs. 2 and 16. These results were measured under normal temperature and with the refrigerators kept static, providing that the outer diameters of the fluid passages, the amounts, shapes and sizes of the cooling members and the materials by which the cooling members are made are same. These conditions are different from those (cryogenic temperature and reciprocating motion) under which the refrigerators are practically operated, but it is understood that the flow speed distribution of helium gas flowing through the fluid passage shown in Fig. 16 is more uniform. It is supposed that this trend can be kept under the practical conditions. Glass wool or the like may be used as spacers instead of the sheets of meshes.
- the fluid passage in the second displacer has been arranged as shown in Figs. 9, 13 and 16 in the case of the above-described three examples
- the fluid passage in the first displacer may be arranged as shown in Figs. 9, 13 and 16.
- These arrangements of the fluid passage can be applied to the cryogenic refrigerator which includes third and fourth displaces.
- the fluid passage in which the cooling member is housed may be arranged as shown in Figs. 9, 13 and 16 even in the case of those cryogenic refrigerators in which the displacers and the cooling accumulator are not combined as a unit.
- Fig. 18 shows a fourth example of the cryogenic refrigerator according to the present invention. Same components as those in the first example shown in Fig. 8 will be represented by same reference numerals and description on these components will be omitted.
- This example is different from the conventional cryogenic refrigerators by seal systems 151 and 155 which are fitted into ring-shaped grooves 127 and 128 on the outer circumference of the second displacer 119 to seal the clearance between the second displacer 119 and the second cylinder 115.
- the seal system 151 includes an outer ring 152 having both ends, an inner ring 153 located on the backside of the outer ring 152, and a spring ring 154 coaxially located on the backside of the inner ring 153 to urge the ring 153 against the inner circumference of the second cylinder 115, these rings being fitted in the ring-shaped groove 127.
- the outer and inner rings 152 and 153 are made of resin.
- the section of the inner ring 153 is shaped like a fallen L and the section of the outer ring 152 is a rectangle seated on the L-shaped section of the inner ring 153.
- the clearance between both ends of the outer ring 152 is shifted from that between both ends of the inner ring 153 by 180°.
- both of the outer and inner rings 152 and 153 are combined with each other in this manner, the outer circumferences of the outer and inner rings 152 and 153 are contacted with the inner circumference of the second cylinder 115 while keeping two inner sides of the inner ring 153 contacted with two outer sides of the outer ring 152.
- the sections of the outer and inner rings 152 and 153 in the seal system 151 are symmetrical with respect to the axis of the second cylinder 115 relative to those of the outer and inner rings 156 and 157 in the seal system 155.
- Fig. 22 shows results obtained by measuring the amounts of helium gas leaking through the conventional cryogenic refrigerator into which the seal system shown in Fig. 5 is incorporated and through the cryogenic GM refrigerator into which the seal systems 151 and 155 are incorporated. These results were measured under normal temperature and with the refrigerators kept static, providing that the widths of the ring-shaped grooves are made equal, that the shapes of the seal rings are same and that the materials by which the seal rings are made are same. These conditions are different from those (cryogenic temperature and reciprocating motion) under which the refrigerators are practically operated, but it is understood that the amount of helium gas leaked can be reduced to a considerable extent. It is supposed that this trend will be kept under practical conditions. Fig.
- FIG. 23 shows refrigerating curves achieved by the conventional cryogenic refrigerator into which the seal system shown in Fig. 5 is incorporated and by the cryogenic refrigerator of the present invention into which the seal systems 151 and 155 shown in Fig. 21 are incorporated.
- the horizontal axis of the coordinate shown in Fig. 23 represents temperatures (K) of the second stage 117 and the vertical axis thereof denotes heat loads (W) added to the second stage 117.
- refrigerating capacity under same temperature is higher in the case of the cryogenic refrigerator according to the present invention. This teaches us that the refrigerating capacity can be increased when the seal systems 151 and 155 are employed.
- seal systems 151 and 155 have been arranged only between the second displacer and the second cylinder in the case of the above-described example, they may be arranged between the first displacer and the first cylinder.
- Fig. 24 shows a fifth example of the cryogenic refrigerator according to the present invention. Same components as those in the example shown in Fig. 8 will be represented by same reference numerals and description on these components will be omitted.
- a filler 167 is previously arranged along the inner walls of the first and second displacers 118 and 119 and the cooling members 122 and 124 are then housed inside the fillers 167 in the displacers 118 and 119.
- the filler 167 is cotton wool made of glass, metal, ceramic and other artificial inorganic fibers.
- a sixth example of the cryogenic refrigerator according to the present invention will be described. This example is different from the conventional refrigerator by a magnetic material M whose grains are used as the cooling member 124 contained in the second displacer 119.
- the magnetic material M is melted and then ground and screened to grains each having an appropriate size of 100 to 500 ⁇ m.
- Each of the screened and selected grains of the magnetic material M has many sharp edges and tips each having a size of several ⁇ m to several tens ⁇ m and an angle smaller than 30°.
- Fig. 25 shows a grain of the magnetic material M which is obtained after the magnetic material M is ground and screened. Edges or tips 171 of the grain are broken off and lost in the refrigerator while the refrigerator is under operation. In order to prevent this, the grain is plated by metal to coat the edges or tips of the grain with a film S of metal.
- this metal is more excellent in toughness than the magnetic material M, that its thermal conductivity is substantially same as that of the magnetic material M and that it can be more easily processed to coat the grain of the magnetic material M.
- Gold, silver, copper, nickel, chrome, aluminum, lead and molybdenum, for example, can be used as the metal film S. An alloy of these metals may be used, too.
- the metal film S is formed according to the plating or depositing manner. It is preferable that the metal film S has a thickness of several ⁇ m to several tens ⁇ m.
- Fig. 26A shows a grain of the magnetic material M which is obtained after the plating process.
- the sharp edge or tip 171 of the grain is coated by the plating metal S and when these grains of the magnetic material M are used as the cooling member, fine powder of the magnetic material M can be prevented from dropping from the second displacer 119 and adhering to the seal systems and the like to lower the refrigerating capacity of the refrigerator.
- the sharp edges or tips 171 of the grain are fixed and rounded by the metal film S and because the metal film S serves as a lubricating layer or cushion to prevent stress from being added to the edges or tips 171 of the grain.
- the sharp edges or tips 171 can be thus prevented from breaking off from the grain of the magnetic material M.
- Fig. 27 shows refrigerating curves achieved by the cryogenic refrigerator in which grains obtained by grinding the magnetic material M were used as the cooling member, and by the one in which grains obtained by grinding the magnetic material M were plated and then used as the cooling member. These refrigerating curves were obtained after the lapse of 100 hours since the refrigerators were under operation.
- the horizontal axis of a graph shown in Fig. 27 denotes temperatures (K) of the second stage 117 and the vertical axis thereof represents heat loads (W) added to the second stage 117.
- the refrigerating curves were overlapped with each other just after the refrigerators were started, but they showed a difference in the refrigerating capacities of the two refrigerators after the lapse of 100 hours.
- the refrigerator in which plated grains of the magnetic material M were used as the cooling member showed same refrigerating capacity as that just after the start of its operation. After the refrigerating curves were obtained, both of the refrigerators were dismantled and examined. Fine powder of the magnetic material M adhered to the seal 126 in the case of the refrigerator in which grains of the magnetic material M obtained by grinding the material M were used as the cooling member, but no such thing could be found in the case of the refrigerator in which grains of the magnetic material M were plated and then used as the cooling member. It is therefore supposed that fine powder of the magnetic material M which adhered to the seal causes the amount of gas leaked through the seal 126 to be increased to thereby lower the refrigerating capacity of the refrigerator, as seen in Fig. 27. This makes it apparent that the use of plated grains of the magnetic material M as the cooling member is more effective.
- the grains of the magnetic material M each having the sharp edges or tips 171 shown in Fig. 25 are used as they are, these edges or tips 171 are broken off from the grains and lost in the refrigerator while the refrigerator is being operated. According to tests conducted, all of the edges or tips 171 each having an angle smaller than 30° were broken off from the grains of the magnetic material M after the operation of the refrigerator.
- the grains of the magnetic material M having those edges or tips whose angles are smaller than 30° are used as the cooling member, therefore, fine powder of these edges or tips can be prevented from dropping from the cooling accumulator into the refrigerator.
- the grains of the magnetic material M having no edges or tips whose angles are smaller than 30° can be obtained by grinding the magnetic material M, screening grains thus obtained and then mixing the grains thus selected in an organic solvent such as alcohol or inactive gas such as argon by means of the mixer.
- Fig. 28 shows a grain of the magnetic material M obtained after the mixing process. As seen in Fig. 28, sharp edges or tips are removed from the grain by the mixing process. When these grains of the magnetic material M are used as the cooling member, it can be prevented that the sharp edges or tips are broken off from the grains of the magnetic material M and dropped, as fine powder, from the second displacer 119 into the refrigerator, while the refrigerator is being operated, to adhere to the seal and the like and lower the refrigerating capacity of the refrigerator.
- the magnetic material may be shaped like grains, powder and fabrics (such as the sheet of meshes). It may also be made porous.
- the magnetic material may include Er3Ni, ErNi2, GdRh or the like.
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Abstract
Description
- The present invention relates to a cryogenic refrigerator and, more particularly, a refrigerator of the refrigerant-accumulating type.
- Various kinds of cryogenic refrigerators are now on the market. One of them is of the Gifford-McMahon type. This refrigerator is usually arranged as shown in Fig. 1.
- The refrigerator comprises generally a
cold head 1 and a coolant gas introducing anddischarging system 2. Thecold head 1 includes a closedcylinder 11, a displacer 12 freely reciprocating in thecylinder 11, and amotor 13 for driving thedisplacer 11. - The
cylinder 11 includes a first large-diameter cylinder 14 and a second small-diameter cylinder 15 coaxially connected to thefirst cylinder 14. The border wall between the first 14 and thesecond cylinder 15 forms afirst stage 16 as a cooling face and the front wall of thecylinder 15 forms asecond stage 17 which is lower in temperature than thefirst stage 16. Thedisplacer 12 includes afirst displacer 18 reciprocating in thefirst cylinder 14 and asecond displacer 19 reciprocating in thesecond cylinder 15. The first andsecond displacers cylinder 11 by aconnector 20. Afluid passage 21 is formed in thefirst displacer 18, extending in the axial direction of thedisplacer 18, and acooling member 22 formed of copper meshes or the like is housed in thefluid passage 21. Similarly, afluid passage 23 is formed in thesecond displacer 19, extending in the axial direction of thedisplacer 19, and acooling member 24 formed of lead balls or the like is formed in thefluid passage 23.Seal systems first displacer 18 and the inner circumference of thefirst cylinder 14 and between the outer circumference of thesecond displacer 19 and the inner circumference of thesecond cylinder 15, respectively. - The top of the
first displacer 18 is connected to the rotating shaft of themotor 13 through aconnector rod 31 and a Scotch yoke orcrankshaft 32. When the shaft of themotor 13 is rotated, therefore, the displacer 12 reciprocates, as shown by an arrow in Fig. 1, synchronizing with the rotating shaft of themotor 13. - An
inlet 34 and anoutlet 35 for introducing and discharging coolant gas extend from the upper portion of one side of thefirst cylinder 14 and they are connected to the coolant gas introducing and dischargingsystem 2. The coolant gas introducing and dischargingsystem 2 serves as a helium gas circulating system, comprising connecting theoutlet 35 to theinlet 34 through a low-pressure valve 36, acompressor 37 and a high-pressure valve 38. Namely, thissystem 2 is intended to compress low-pressure (about 5 atm) helium to high-pressure (about 18 atm) one by thecompressor 37 and send it into thecylinder 11. The low- and high-pressure valves displacer 12. - That portions in the refrigerator where cooling is effected or which act as cooling faces are the first and
second stages first displacer 18 and a temperature gradient ranging from 30 K to 10 K exists between the top and bottom of thesecond displacer 19. These temperature gradients, however, are changed by thermal loads at the step stages and it usually ranges from 30 K to 80 K at thefirst stage 16 while it ranges from 10 K to 20 K at thesecond stage 17. - When the
motor 13 starts its rotation, the displacer 12 reciprocates between top and bottom dead centers. When thedisplacer 12 is at the bottom dead center, the high-pressure valve 38 is opened, allowing high-pressure helium gas to flow into thecold head 1. Thedisplacer 12 then moves to the top dead center. As described above, theseal systems first displacer 18 and the inner circumference of thefirst cylinder 14 and between the outer circumference of thesecond displacer 19 and the inner circumference of thesecond cylinder 15, respectively. When thedisplacer 12 moves to the top dead center, therefore, high-pressure helium gas flows into a firststage expansion chamber 39 formed between the first 18 and thesecond displacer 19 and then into a secondstage expansion chamber 40 formed between thesecond displacer 19 and the front wall of the second cylinder, passing through thefluid passage 21 in thefirst displacer 18 and thefluid passage 23 in thesecond displacer 19. While flowing in this manner, high-pressure helium gas is cooled or refrigerated by thecooling members stage expansion chamber 39 can be cooled to about 30 K and high-pressure helium gas flowing into the secondstage expansion chamber 40 can be cooled to about 8 K. Here, the high-pressure valve 38 is closed and the low-pressure valve 36 is opened. When the low-pressure valve 36 is opened, high-pressure helium gas in the firststage expansion chamber 39 and the secondstage expansion chamber 40 is expanded and cooling is effected. Thefirst stage 16 and thesecond stage 17 are cooled by this cooling phenomenon. Then, thedisplacer 12 moves to the bottom dead center again and helium gas in the firststage expansion chamber 39 and the secondstage expansion chamber 40 is removed as the movement of thedisplacer 12. The expanded helium gas is warmed by thecooling members fluid passages - However, the above-structured conventional cryogenic refrigerators had the following problems. Specifically, the
cylindrical fluid passage 23 is formed in thesecond displacer 19 and the inside of the passage is filled with the ball or grain-like cooling member 24. Speed distribution in helium gas flowing through the passages which were filled with balls or grains was measured and it was found that velocity of flow was the lowest in the center of the flow of helium gas and that it became higher and higher as coming remoter from the center of the flow of helium gas outward in the radial direction thereof. This means that a larger amount of helium gas flows only into some area of thecooling member 24 and that thecooling member 24 must exchange heat with excessive helium gas at this area thereof when heat exchange is to be done between helium gas and thecooling member 24. This teaches us that thecooling member 24 is not efficiently used. Therefore, cooling efficiency (or heat exchanging efficiency achieved by a cooling means) is reduced at the area of the cooling member, thereby resulting in reducing refrigerating capacity at a certain temperature. - The conventional refrigerators arranged as shown in Fig. 1 had a problem as described below. The
seal system 25 prevents helium gas from flowing from the normal temperature section to thefirst expansion chamber 39 and vice versa, passing through a clearance between thefirst cylinder 14 and thefirst displacer 18, while theseal system 26 prevents helium gas from flowing from the firststage expansion chamber 39 to the secondstage expansion chamber 40 and vice versa, passing through a clearance between thesecond cylinder 15 and thesecond displacer 19. Theseseal systems seal system 26 is located at the low temperature section (30 to 80 K) and it is asked to have a shape like the piston seal. Providing that the firststage expansion chamber 39 has a temperature of 30 K while the secondstage expansion chamber 40 has a temperature of 10 K and that helium gas leaks at some portion of theseal system 26, helium gas of 30 K will enter into the secondstage expansion chamber 40 without contacting thecooling member 24 in thesecond displacer 19 and helium gas of 10 K will enter into the firststage expansion chamber 39. As the result, the temperature of thefirst stage 16 falls and that of thesecond stage 17 rises. Fig. 3 shows, as results calculated, the relation between the ratio of the amount of helium gas leaked through the seal system 26 (or ratio of the amount of helium gas flowing into the secondstage expansion chamber 40 through theseal system 26 relative to the total amount of helium gas flowing into thechamber 40 through the passage) and the temperature of each of the first andsecond stages seal system 26 adds large influence to the temperature of each of thestages seal system 25. - In the conventional refrigerators, the
seal system 26 used comprises fitting a turn of sealing 28 provided withoverlapped ends 30 as shown in Fig. 6 into a ring-shaped groove 27 on the outer circumference of thesecond displacer 19 and arranging aspring ring 29 on the backside of the sealing 28 to urge the sealing 28 against thesecond cylinder 15, as shown in Figs. 4 through 6. In the case of theseal system 26 having the above-described arrangement, a considerable amount of helium gas is allowed to leak through theoverlapped ends 30 of the sealing 28, thereby causing the temperature of thesecond stage 17 to rise. This results in reducing refrigerating capacity at a certain temperature. - Providing that the temperature of the first
stage expansion chamber 39 is 30 K while that of the secondstage expansion chamber 40 is 10 K and that helium gas leaks through the sealing portion, helium gas of 30 K will enter into the secondstage expansion chamber 40 while helium gas of 10 K into the firststage expansion chamber 39, without fully contacting thecooling member 24 in thesecond displacer 19. As the result, the temperature of thefirst stage 16 lowers while that of thesecond stage 17 rises. Fig. 7 shows, as results calculated, what relation exists between the ratio of the amount of helium gas leaking through the clearances (or ratio of the amount of helium gas flowing into the secondstage expansion chamber 40 through the sealing portion relative to the total amount of helium gas flowing into thechamber 40 through the cooling member) and the temperature of each of the first andsecond stages - The conventional refrigerators arranged as shown in Fig. 1 had another problem as described below. When magnetic material is used as a part or whole of the
cooling member 24 in thesecond displacer 19, it is quite difficult to process the magnetic material into balls or meshes such as thecooling member 22 in thefirst displacer 18. The magnetic material is therefore melted to a bulky mass, which is ground and screened to grains each having a size of about 100 to 500 µm. These grains substantially same in size are used as the cooling member. However, each of these grains has sharp edges and tips which are several µm in size, and these sharp edges and tips are broken off the grains while the refrigerator is under operation. Thecooling member 24 is covered by sheets of net at the top and bottom thereof not to drop from thesecond displacer 19, but these sheets of net have meshes each having a size of several tens µm and fine edges and tips broken off the grains of magnetic material pass through these meshes of the nets together with helium gas. When the meshes of the nets which cover the top and bottom of thecooling member 24 are made smaller in size, however, the pressure loss of helium gas is increased. This is not a merit. The fine edges and tips of magnetic material dropped from thesecond displacer 19 adhere to theseal 25 to thereby increase the amount of helium gas leaded through theseal 25. This lowers the refrigerating capacity of the refrigerator to a great extent. In addition, the fine edges and tips of magnetic material dropped come to thecompressor 37, passing through thefirst displacer 18 and thevalve 36. As the result, thevalve 36 can be blocked and thecompressor 37 can be damaged by them. When ground grains of magnetic material are used as the cooling member as described above, the capacity of the refrigerator is lowered and the refrigerator itself is damaged. - The conventional refrigerators arranged as shown in Fig. 1 had a further problem as described below. When the first and second displacers 18 and 19 are filled with the cooling
members - An object of the present invention is to provide a cryogenic refrigerator capable of causing coolant gas to uniformly flow through a cooling member to increase the refrigerating capacity of the refrigerator.
- Another object of the present invention is to provide a cryogenic refrigerator capable of enhancing sealing performance between a cylinder and a displacer to increase the refrigerating capacity of the refrigerator.
- A further object of the present invention is to provide a cryogenic refrigerator capable of preventing the cooling member from creating fine powder to increase the refrigerating capacity of the refrigerator.
- According to the present invention, there is provided a cryogenic refrigerator comprising a closed cylinder provided with an inlet and an outlet for introducing and discharging a coolant gas into and out of the cylinder; a displacer slidably housed in the closed cylinder and housing a cooling member therein and having a passage through which the coolant gas flows; a means coaxially arranged in and along the passage of the displacer in which the cooling member is housed to divide the passage into outer and inner ones; a means for reciprocating the displacer in the cylinder; and a means for repeating the process of introducing the high pressure coolant gas into the cylinder through the inlet and discharging it out of the cylinder, synchronizing with the reciprocating displacer.
- According to the present invention, there is provided a cryogenic refrigerator comprising a closed cylinder provided with an inlet and an outlet for introducing and discharging a coolant gas into and out of the cylinder; a displacer slidable arranged in the closed cylinder and housing a cooling member therein and having a passage through which the coolant gas flows; plural gas penetrating diaphragms arranged in the passage in which the cooling member is housed and separated from one another by a certain interval in a direction perpendicular to the direction in which the passage is directed; a means for reciprocating the displacer in the cylinder; a means for repeating the process of introducing the coolant gas into the cylinder through the inlet and discharging it out of the cylinder through the outlet in a relation to the reciprocating displacer.
- According to the present invention, a cryogenic refrigerator can be provided comprising a closed cylinder provided with an inlet and an outlet for introducing and discharging a coolant gas into and out of the cylinder; a displacer slidable arranged in the closed cylinder and housing a cooling member therein and having a passage through which the coolant gas flows; plural gas penetrating diaphragms arranged in the passage in which the cooling member is housed and separated from one another by a certain interval in a direction perpendicular to the direction in which the passage is directed; a means for reciprocating the displacer in the cylinder; a means for repeating the process of introducing the high pressure coolant gas into the cylinder through the inlet and discharging it out of the cylinder through the outlet in a relation to the reciprocating displacer and first and second sealing members arranged along the axis of the displacer to seal the clearance between the closed cylinder and the displacer; wherein said displacer has two ring-shaped grooves on the outer circumference thereof and each of the sealing members includes two sealing rings each having both ends and piled one upon the other in the ring-shaped groove in the axial direction of the displacer and a spring ring having both ends and located on the back side of these sealing rings.
- According to the present invention, a cryogenic refrigerator can be provided comprising a closed cylinder provided with an inlet and an outlet for introducing and discharging a coolant gas into and out of the cylinder; a displacer slidably arranged in the closed cylinder and housing a cooling member therein and having a passage through which the coolant gas flows; a means for reciprocating the displacer; and a means for repeating the process of introducing the coolant gas into the cylinder through the inlet and discharging it out of the cylinder through the outlet in a relation to the reciprocating displacer; wherein said cooling member is those grains of a magnetic matter which are coated by a metal film.
- According to the present invention, a cryogenic refrigerator can be provided comprising a closed cylinder provided with an inlet and an outlet for introducing and discharging a coolant gas into and out of the cylinder; a displacer slidably arranged in the closed cylinder and housing a cooling member therein and having a passage through which the coolant gas flows: a fibrous member arranged between the displacer and the cooling member; a means for reciprocating the displacer; and a means for repeating the process of introducing the high pressure coolant gas into the cylinder through the inlet and discharging it out of the cylinder through the outlet in a relation to the reciprocating displacer.
- This invention can be more fully understood from the following detailed description when taken in conjunction with the accompanying drawings, in which:
- Fig. 1 is a cross sectional view showing a conventional Gifford-McMahon type cryogenic refrigerator;
- Fig. 2 is a cross sectional view showing a second displacer of the refrigerator of Fig. 1;
- Fig. 3 is a graph showing the relationship between a rate of leakage and temperature of stages in a sealing mechanism of the refrigerator of Fig. 1;
- Figs. 4 to 6 are cross sectional views showing the sealing mechanism of the refrigerator of Fig. 1;
- Fig. 7 is a graph showing the relationship of a rate of leakage and temperature of stages between a second displacer and a cooling member of the refrigerator of Fig. 1;
- Fig. 8 is a cross sectional view showing a Gifford-McMahon type cryogenic refrigerator relating to one embodiment of the present invention;
- Fig. 9 is a cross sectional view showing a second displacer of the refrigerator of Fig. 8;
- Fig. 10 is a graph showing the comparison between the speed distribution in helium gas in the cooling member of the second displacer of the refrigerator of Fig. 1 and that of the second displacer of the refrigerator of Fig. 8;
- Fig. 11 is a graph showing the comparison between the cooling curve of the refrigerator of Fig. 1 and that of the refrigerator of Fig. 8;
- Fig. 12 is a cross sectional view showing a Gifford-McMahon type cryogenic refrigerator relating to a second embodiment of the present invention;
- Fig. 13 is a cross sectional view showing a second displacer of the refrigerator of Fig. 12;
- Fig. 14 is a graph showing the comparison between the speed distribution in helium gas in the cooling member of the second displacer of the refrigerator of Fig. 1 and that of the second displacer of the refrigerator of Fig. 12;
- Fig. 15 is a cross sectional view showing a Gifford-McMahon type cryogenic refrigerator relating to a third embodiment of the present invention;
- Fig. 16 is a cross sectional view showing a second displacer of the refrigerator of Fig. 15;
- Fig. 17 is a graph showing the comparison between the speed distribution in helium gas in the cooling member of the second displacer of the refrigerator of Fig. 1 and that of the second displacer of the refrigerator of Fig. 15;
- Fig. 18 is a cross sectional view showing a Gifford-McMahon type cryogenic refrigerator relating to a fourth embodiment of the present invention;
- Figs. 19 to 21 are cross sectional views showing a sealing mechanism of the refrigerator of Fig. 18;
- Fig. 22 is a graph showing the relationship between leakage of helium and difference in pressure in the refrigerator, in which the sealing mechanism of Fig. 5 is incorporated, and the refrigerator, in which the sealing mechanism of Fig. 21 is incorporated;
- Fig. 23 is a graph showing the cooling curves of the refrigerator, in which the sealing mechanism of Fig. 5 is incorporated, and the refrigerator, in which the sealing mechanism of Fig. 20 is incorporated;
- Fig. 24 is a cross sectional view showing a Gifford-McMahon type cryogenic refrigerator relating to a fifth embodiment of the present invention;
- Fig. 25 is a view showing a magnetic member using as a cooling member of the cryogenic refrigerator;
- Figs. 26A and 26B are views showing the state that the magnetic member of Fig. 25 is plated with metal;
- Fig. 27 is a graph showing the cooling curves of the refrigerator in which the magnetic member of Fig. 25 is incorporated, and the refrigerator in which the magnetic member of Figs. 26A and 26B is incorporated; and
- Fig. 28 is a view showing the magnetic member after mixing.
- Some preferred embodiments of the present invention will be described in detail.
- Fig. 8 is a sectional view showing an example of the Gifford-McMahon type refrigerator, which is same in arrangement as the one shown in Fig. 1 except a fluid path or
passage 123. - The refrigerator includes generally a
cold head 101 and a coolant gas introducing and dischargingsystem 102. Thecold head 101 comprises aclosed cylinder 111, adisplacer 112 housed in thecylinder 111 and freely reciprocating therein, and amotor 113 for driving thedisplacer 112 to reciprocate in thecylinder 111. - The
cylinder 111 includes a first large-diameter cylinder 114 and a second small-diameter cylinder 115 coaxially connected to thecylinder 114. The border wall between thefirst cylinder 114 and thesecond cylinder 115 forms afirst stage 116 which serves as a cooling face, and the front wall of thecylinder 115 forms asecond stage 117 which is lower in temperature than thefirst stage 116. Thedisplacer 112 includes afirst displacer 118 reciprocating in thefirst cylinder 114 and asecond displacer 119 reciprocating in thesecond cylinder 115. The first andsecond displacers connector member 120 in the axial direction of thecylinder 112. Afluid passage 121 is formed in thefirst displacer 118, extending in the axial direction of thedisplacer 118, and a coolingmember 122 made by copper meshes or the like is contained in thefluid passage 121. Similarly, afluid passage 123 is also formed in thesecond displacer 119, extending in the axial direction of thedisplacer 119, and a coolingmember 124 made by copper balls or the like is contained in thefluid passage 123.Seal systems first displacer 118 and the inner circumference of thefirst cylinder 114 and between the outer circumference of thesecond displacer 119 and the inner circumference of thesecond cylinder 115, respectively. - The top of the
first displacer 118 is connected to the rotating shaft of themotor 113 through aconnector rod 131 and a Scotch yoke orcrankshaft 132. When the shaft of themotor 113 is rotated, therefore, thedisplacer 112 is reciprocated as shown by an arrow in Fig. 8, synchronizing with the rotating shaft of themotor 113. - An
inlet 134 and anoutlet 135 for coolant gas extend outwards from the upper portion of one side of thefirst cylinder 114 and they are connected to the coolant gas introducing and dischargingsystem 102. Thissystem 102 serves to circulate helium gas flowing through thecylinder 111 and comprises connecting theoutlet 135 to theinlet 134 through a low-pressure valve 136, acompressor 137 and a high-pressure valve 138. Thesystem 102 also serves to compress low pressure helium gas (about 5 atm) to high pressure one (about 18 atm) through thecompressor 137 and send it into thecylinder 111. The low- and high-pressure valves reciprocating displacer 112. - As shown in Fig. 9, a
pipe 142 is coaxially housed in thefluid passage 123 and allows helium gas to flow inside and outside thepipe 142. Afluid passage 143 inside thepipe 142 is filled with a coolingmember 145 shaped like balls each having a diameter of 0.4 mm and anotherfluid passage 144 outside thepipe 142 is filled with a coolingmember 146 shaped like balls each having a diameter of 0.2 mm. - The passage of helium gas is divided into two in the same direction as helium gas flows, and the large-
diameter cooling balls 145 are housed in theinner fluid passage 143. This reduces the pressure loss of helium gas flowing through theinner fluid passage 143 and the amount of helium gas flowing through thepassage 143 is increased accordingly. The partial flow of helium gas can be thus reduced to a greater extent. This enables the cooling efficiencies of thecooling balls - Fig. 10 shows results obtained by measuring the flow speed distributions of helium gas flowing through the cooling members in the fluid passages shown in Figs. 2 and 9. These results were obtained under normal temperature and with the refrigerators kept static, providing that the outer diameters of the fluid passages, the amounts of the cooling members contained in the fluid passages and the materials by which the cooling members are made are same. These conditions are different from those (cryogenic temperature and reciprocating motion) under which the refrigerators are practically operated, but it is understood that the flow speed distribution of helium gas flowing through the cooling member in the fluid passage shown in Fig. 9 is more uniform. It is supposed that this trend can be kept under the practical conditions. Fig. 11 shows refrigerating curves achieved by the conventional cryogenic refrigerator in which the
fluid passage 23 shown in Fig. 2 is incorporated and by the cryogenic refrigerator of the present invention in which thefluid passage 123 shown in Fig. 9 is incorporated. The horizontal axis of the coordinate shown in Fig. 11 represents temperatures (K) of thesecond stage 117 and the vertical axis thereof heat loads (W) added to thesecond stage 117. As apparent from Fig. 11, refrigerating capacity under same temperature is higher in the case of the cryogenic refrigerator according to the present invention. It is therefore understood that refrigerating capacity can be increased when thefluid passage 123 which has the above-described arrangement is employed. Although the fluid passage in this example is divided into two concentric ones, it may be divided into three or more ones. The diameter of the ball is not limited to 0.4 mm or 0.2 mm. - Figs. 12 and 13 show a second example of the cryogenic refrigerator according to the present invention, in which the
pipe 142 is coaxially housed in thefluid passage 141, the passage of helium gas is divided to flow inside and outside thepipe 142, and a coolingmember 124 contained in the inner andouter passages member 124 can be increased to thereby enhance the refrigerating capacity of the refrigerator. - Fig. 14 shows results obtained by measuring the flow speed distributions of helium gas flowing through the cooling members contained in the fluid passages shown in Figs. 2 and 13. These results were obtained under normal temperature and with the refrigerators kept static, providing that the outer diameters of the fluid passages, the amounts, shapes and sizes of the cooling members contained in the fluid passages, and the materials by which the cooling members are made are same. These conditions are different from those (cryogenic temperature and reciprocating motion) under which the refrigerators are practically operated but it is understood that the flow speed distribution of helium gas flowing through the cooling member in the fluid passage shown in Fig. 13 is more uniform. It is supposed that this trend can be kept under the practical conditions. Although the fluid passage in this example is divided into two concentric ones, it may be divided into three or more ones. They may be neither concentric nor cylindrical.
- Fig. 15 shows a third example of the cryogenic refrigerator according to the present invention.
- This third example is different from the first example in the arrangement of a
fluid passage 141 which is formed in thesecond displacer 119 and in which the coolingmember 124 is contained. - As shown in Fig. 16, the cooling
member 124 shaped like balls, and sheets ofmeshes 147 are contained in thefluid passage 141 in such a way that they are alternately piled in thefluid passage 141 in direction perpendicular to the flow of helium gas. - When the
fluid passage 141 is arranged in this manner, helium gas flowing through thepassage 141 can be made uniform by the sheets of meshes. The partial flow of helium gas can be thus reduced to a greater extent, as compared with that in the conventional case. Therefore, cooling efficiency achieved by the coolingmember 124 can be increased so as to enhance the refrigerating capacity of the refrigerator. - Fig. 17 shows results obtained by measuring the flow speed distributions of helium gas flowing through the cooling members in the fluid passages shown in Figs. 2 and 16. These results were measured under normal temperature and with the refrigerators kept static, providing that the outer diameters of the fluid passages, the amounts, shapes and sizes of the cooling members and the materials by which the cooling members are made are same. These conditions are different from those (cryogenic temperature and reciprocating motion) under which the refrigerators are practically operated, but it is understood that the flow speed distribution of helium gas flowing through the fluid passage shown in Fig. 16 is more uniform. It is supposed that this trend can be kept under the practical conditions. Glass wool or the like may be used as spacers instead of the sheets of meshes.
- Although the fluid passage in the second displacer has been arranged as shown in Figs. 9, 13 and 16 in the case of the above-described three examples, the fluid passage in the first displacer may be arranged as shown in Figs. 9, 13 and 16. These arrangements of the fluid passage can be applied to the cryogenic refrigerator which includes third and fourth displaces. The fluid passage in which the cooling member is housed may be arranged as shown in Figs. 9, 13 and 16 even in the case of those cryogenic refrigerators in which the displacers and the cooling accumulator are not combined as a unit.
- Fig. 18 shows a fourth example of the cryogenic refrigerator according to the present invention. Same components as those in the first example shown in Fig. 8 will be represented by same reference numerals and description on these components will be omitted.
- This example is different from the conventional cryogenic refrigerators by
seal systems grooves second displacer 119 to seal the clearance between thesecond displacer 119 and thesecond cylinder 115. - As shown in Figs. 19 and 20, the
seal system 151 includes anouter ring 152 having both ends, aninner ring 153 located on the backside of theouter ring 152, and aspring ring 154 coaxially located on the backside of theinner ring 153 to urge thering 153 against the inner circumference of thesecond cylinder 115, these rings being fitted in the ring-shapedgroove 127. The outer andinner rings inner ring 153 is shaped like a fallen L and the section of theouter ring 152 is a rectangle seated on the L-shaped section of theinner ring 153. The clearance between both ends of theouter ring 152 is shifted from that between both ends of theinner ring 153 by 180°. When both of the outer andinner rings inner rings second cylinder 115 while keeping two inner sides of theinner ring 153 contacted with two outer sides of theouter ring 152. As shown in Fig. 21, the sections of the outer andinner rings seal system 151 are symmetrical with respect to the axis of thesecond cylinder 115 relative to those of the outer andinner rings seal system 155. When the clearances in theseal system 151 are shifted from those in theseal system 155 in the circumferential direction of thesecond cylinder 115, therefore, helium gas can be prevented from leaking through these clearances. The leakage of helium gas can be thus reduced to a greater extent by theseseal systems second stage 117 can be prevented from rising to thereby enhance the refrigerating capacity of the refrigerator. - Fig. 22 shows results obtained by measuring the amounts of helium gas leaking through the conventional cryogenic refrigerator into which the seal system shown in Fig. 5 is incorporated and through the cryogenic GM refrigerator into which the
seal systems seal systems second stage 117 and the vertical axis thereof denotes heat loads (W) added to thesecond stage 117. As apparent from Fig. 23, refrigerating capacity under same temperature is higher in the case of the cryogenic refrigerator according to the present invention. This teaches us that the refrigerating capacity can be increased when theseal systems - Although the
seal systems - Fig. 24 shows a fifth example of the cryogenic refrigerator according to the present invention. Same components as those in the example shown in Fig. 8 will be represented by same reference numerals and description on these components will be omitted.
- When the first and
second displacers members filler 167 is previously arranged along the inner walls of the first andsecond displacers members fillers 167 in thedisplacers filler 167 is cotton wool made of glass, metal, ceramic and other artificial inorganic fibers. - When
clearances 148 between the inner wall of thefirst displacer 118 and the coolingmember 122 and between the inner wall of thesecond displacer 119 and the coolingmember 124 are filled with thefillers 167, the leakage of gas can be prevented to effectively carry out heat exchange between the coolingmembers - A sixth example of the cryogenic refrigerator according to the present invention will be described. This example is different from the conventional refrigerator by a magnetic material M whose grains are used as the cooling
member 124 contained in thesecond displacer 119. - The magnetic material M is melted and then ground and screened to grains each having an appropriate size of 100 to 500 µm. Each of the screened and selected grains of the magnetic material M has many sharp edges and tips each having a size of several µm to several tens µm and an angle smaller than 30°.
- Fig. 25 shows a grain of the magnetic material M which is obtained after the magnetic material M is ground and screened. Edges or
tips 171 of the grain are broken off and lost in the refrigerator while the refrigerator is under operation. In order to prevent this, the grain is plated by metal to coat the edges or tips of the grain with a film S of metal. - It is preferable that this metal is more excellent in toughness than the magnetic material M, that its thermal conductivity is substantially same as that of the magnetic material M and that it can be more easily processed to coat the grain of the magnetic material M. Gold, silver, copper, nickel, chrome, aluminum, lead and molybdenum, for example, can be used as the metal film S. An alloy of these metals may be used, too. The metal film S is formed according to the plating or depositing manner. It is preferable that the metal film S has a thickness of several µm to several tens µm.
- Fig. 26A shows a grain of the magnetic material M which is obtained after the plating process. As seen in Fig. 26B, the sharp edge or tip 171 of the grain is coated by the plating metal S and when these grains of the magnetic material M are used as the cooling member, fine powder of the magnetic material M can be prevented from dropping from the
second displacer 119 and adhering to the seal systems and the like to lower the refrigerating capacity of the refrigerator. This is because the sharp edges ortips 171 of the grain are fixed and rounded by the metal film S and because the metal film S serves as a lubricating layer or cushion to prevent stress from being added to the edges ortips 171 of the grain. The sharp edges ortips 171 can be thus prevented from breaking off from the grain of the magnetic material M. - Fig. 27 shows refrigerating curves achieved by the cryogenic refrigerator in which grains obtained by grinding the magnetic material M were used as the cooling member, and by the one in which grains obtained by grinding the magnetic material M were plated and then used as the cooling member. These refrigerating curves were obtained after the lapse of 100 hours since the refrigerators were under operation. The horizontal axis of a graph shown in Fig. 27 denotes temperatures (K) of the
second stage 117 and the vertical axis thereof represents heat loads (W) added to thesecond stage 117. The refrigerating curves were overlapped with each other just after the refrigerators were started, but they showed a difference in the refrigerating capacities of the two refrigerators after the lapse of 100 hours. The refrigerator in which plated grains of the magnetic material M were used as the cooling member showed same refrigerating capacity as that just after the start of its operation. After the refrigerating curves were obtained, both of the refrigerators were dismantled and examined. Fine powder of the magnetic material M adhered to theseal 126 in the case of the refrigerator in which grains of the magnetic material M obtained by grinding the material M were used as the cooling member, but no such thing could be found in the case of the refrigerator in which grains of the magnetic material M were plated and then used as the cooling member. It is therefore supposed that fine powder of the magnetic material M which adhered to the seal causes the amount of gas leaked through theseal 126 to be increased to thereby lower the refrigerating capacity of the refrigerator, as seen in Fig. 27. This makes it apparent that the use of plated grains of the magnetic material M as the cooling member is more effective. - A seventh example of the cryogenic refrigerator according to the present invention will be described.
- When the grains of the magnetic material M each having the sharp edges or
tips 171 shown in Fig. 25 are used as they are, these edges ortips 171 are broken off from the grains and lost in the refrigerator while the refrigerator is being operated. According to tests conducted, all of the edges ortips 171 each having an angle smaller than 30° were broken off from the grains of the magnetic material M after the operation of the refrigerator. When the grains of the magnetic material M having those edges or tips whose angles are smaller than 30° are used as the cooling member, therefore, fine powder of these edges or tips can be prevented from dropping from the cooling accumulator into the refrigerator. The grains of the magnetic material M having no edges or tips whose angles are smaller than 30° can be obtained by grinding the magnetic material M, screening grains thus obtained and then mixing the grains thus selected in an organic solvent such as alcohol or inactive gas such as argon by means of the mixer. - Fig. 28 shows a grain of the magnetic material M obtained after the mixing process. As seen in Fig. 28, sharp edges or tips are removed from the grain by the mixing process. When these grains of the magnetic material M are used as the cooling member, it can be prevented that the sharp edges or tips are broken off from the grains of the magnetic material M and dropped, as fine powder, from the
second displacer 119 into the refrigerator, while the refrigerator is being operated, to adhere to the seal and the like and lower the refrigerating capacity of the refrigerator. - Same refrigerating capacity test as that in the sixth example was conducted using the grains of the magnetic material M as the cooling member. Same results as those shown in Fig. 27 were obtained. Further, the refrigerators were dismantled and examined after the test and same thing as that in the sixth example could be found.
- Although description has been made about those refrigerators in which the displacer and the cooling accumulator are combined with each other as a unit, the present invention can be applied to the other refrigerators in which the displacer and the cooling accumulator are not combined as a unit.
- Further, description has been made about the refrigerator of the Gifford-McMahon type which is typical of the cryogenic refrigerators, but the present invention can be applied to the other cryogenic refrigerators of the improved Solvay, Stirling and cycle types.
- Still further, the magnetic material may be shaped like grains, powder and fabrics (such as the sheet of meshes). It may also be made porous.
- The magnetic material may include Er₃Ni, ErNi₂, GdRh or the like.
Claims (14)
a closed cylinder (111) provided with an inlet (134) and an outlet (135) for introducing and discharging a coolant gas into and out of the cylinder (111);
a displacer (119) slidably housed in the closed cylinder (111) and housing a cooling member (124) therein and having a passage (123) through which the coolant gas flows;
a means (142) coaxially arranged in the passage (123) of the displacer (119) in which the cooling member (124) is housed, for dividing the passage (123) into outer and inner ones;
a means for reciprocating the displacer (119) in the cylinder (111); and
a means for repeating the process of introducing the high pressure coolant gas into the cylinder (111) through the inlet and discharging it out of the cylinder (111), synchronizing with the reciprocating displacer (119).
a closed cylinder (111) provided with an inlet (134) and an outlet (135) for introducing and discharging a coolant gas into and out of the cylinder (111); a displacer (119) slidable arranged in the closed cylinder (111) and housing a cooling member (124) therein and having a passage (123) through which the coolant gas flows;
plural gas permeable diaphragms (147) arranged in the passage (141) in which the cooling member (124) is housed and separated from one another in a direction perpendicular to the direction in which the passage (141) is directed;
a means for reciprocating the displacer (119) in the cylinder (111); and
a means for repeating the process of introducing the coolant gas into the cylinder (111) through the inlet and discharging it out of the cylinder (111) through the outlet (135) in a relation to the reciprocating displacer.
a closed cylinder (111) provided with an inlet (134) and an outlet (135) for introducing and discharging a coolant gas into and out of the cylinder (111);
a displacer (119) slidably arranged in the closed cylinder (111) and housing a cooling member (124) therein and having a passage through which the coolant gas flows;
a means for reciprocating the displacer (119); and
a means for repeating the process of introducing the coolant gas into the cylinder (111) through the inlet (134) and discharging it out of the cylinder (111) through the outlet (135) in a relation to the reciprocating displacer (119);
wherein said cooling member (124) is those grains of a magnetic material which are coated by a metal film.
a closed cylinder (111) provided with an inlet (134) and an outlet (135) for introducing and discharging a coolant gas into and out of the cylinder (111);
a displacer (119) slidably arranged in the closed cylinder (111) and housing a cooling member (124) therein and having a passage (141) through which the coolant gas flows:
a fibrous member (167) arranged between the displacer (119) and the cooling member (124);
a means for reciprocating the displacer (119); and
a means for repeating the process of introducing the coolant gas into the cylinder (111) through the inlet (134) and discharging it out of the cylinder (111) through the outlet (135) in a relation to the reciprocating displacer (119).
a step of grinding a magnetic material;
a step of screening grains of the magnetic material obtained; and
a step of mixing the screened grains of the magnetic material to remove sharp edges and tips from the grains.
Applications Claiming Priority (10)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP1127772A JPH0668418B2 (en) | 1989-05-23 | 1989-05-23 | Cold storage material manufacturing method and cryogenic refrigerator |
JP127771/89 | 1989-05-23 | ||
JP127772/89 | 1989-05-23 | ||
JP1127771A JPH0668417B2 (en) | 1989-05-23 | 1989-05-23 | Cryogenic refrigerator |
JP26515989A JPH03129258A (en) | 1989-10-13 | 1989-10-13 | Extremely low-temperature freezer |
JP1265158A JP2766341B2 (en) | 1989-10-13 | 1989-10-13 | Cryogenic refrigerator |
JP265158/89 | 1989-10-13 | ||
JP265159/89 | 1989-10-13 | ||
JP297578/89 | 1989-11-17 | ||
JP29757889A JP2732686B2 (en) | 1989-11-17 | 1989-11-17 | refrigerator |
Publications (3)
Publication Number | Publication Date |
---|---|
EP0399813A2 true EP0399813A2 (en) | 1990-11-28 |
EP0399813A3 EP0399813A3 (en) | 1991-03-06 |
EP0399813B1 EP0399813B1 (en) | 1993-10-06 |
Family
ID=27527153
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP19900305632 Expired - Lifetime EP0399813B1 (en) | 1989-05-23 | 1990-05-23 | Cryogenic refrigerator |
Country Status (2)
Country | Link |
---|---|
EP (1) | EP0399813B1 (en) |
DE (1) | DE69003738T2 (en) |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0508830A2 (en) * | 1991-04-11 | 1992-10-14 | Kabushiki Kaisha Toshiba | Cryogenic refrigerator |
US5447034A (en) * | 1991-04-11 | 1995-09-05 | Kabushiki Kaisha Toshiba | Cryogenic refrigerator and regenerative heat exchange material |
EP1384961A2 (en) * | 1994-08-23 | 2004-01-28 | Kabushiki Kaisha Toshiba | Regenerator material for extremely low temperatures and regenerator for extremely low temperatures using the same |
Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR2000669A1 (en) * | 1968-01-24 | 1969-09-12 | Raytheon Co | |
GB1168814A (en) * | 1965-11-11 | 1969-10-29 | Philips Nv | Improvements in and relating to methods of manufacturing Heat-Exchangers and to Heat-Exchangers manufactured by said methods |
US4366676A (en) * | 1980-12-22 | 1983-01-04 | The Regents Of The University Of California | Cryogenic cooler apparatus |
US4825660A (en) * | 1986-06-11 | 1989-05-02 | Aisin Seiki Kabushiki Kaisha | Cryogenic refrigerator |
-
1990
- 1990-05-23 DE DE1990603738 patent/DE69003738T2/en not_active Expired - Lifetime
- 1990-05-23 EP EP19900305632 patent/EP0399813B1/en not_active Expired - Lifetime
Patent Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB1168814A (en) * | 1965-11-11 | 1969-10-29 | Philips Nv | Improvements in and relating to methods of manufacturing Heat-Exchangers and to Heat-Exchangers manufactured by said methods |
FR2000669A1 (en) * | 1968-01-24 | 1969-09-12 | Raytheon Co | |
US4366676A (en) * | 1980-12-22 | 1983-01-04 | The Regents Of The University Of California | Cryogenic cooler apparatus |
US4825660A (en) * | 1986-06-11 | 1989-05-02 | Aisin Seiki Kabushiki Kaisha | Cryogenic refrigerator |
Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0508830A2 (en) * | 1991-04-11 | 1992-10-14 | Kabushiki Kaisha Toshiba | Cryogenic refrigerator |
EP0508830A3 (en) * | 1991-04-11 | 1993-01-07 | Kabushiki Kaisha Toshiba | Cryogenic refrigerator |
US5447034A (en) * | 1991-04-11 | 1995-09-05 | Kabushiki Kaisha Toshiba | Cryogenic refrigerator and regenerative heat exchange material |
EP1384961A2 (en) * | 1994-08-23 | 2004-01-28 | Kabushiki Kaisha Toshiba | Regenerator material for extremely low temperatures and regenerator for extremely low temperatures using the same |
EP1384961A3 (en) * | 1994-08-23 | 2004-08-04 | Kabushiki Kaisha Toshiba | Regenerator material for extremely low temperatures and regenerator for extremely low temperatures using the same |
Also Published As
Publication number | Publication date |
---|---|
DE69003738T2 (en) | 1994-03-10 |
EP0399813A3 (en) | 1991-03-06 |
EP0399813B1 (en) | 1993-10-06 |
DE69003738D1 (en) | 1993-11-11 |
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