JP6257394B2 - Regenerator type refrigerator - Google Patents

Description

  The present invention relates to a regenerator type refrigerator that accumulates cold generated by Simon expansion of high-pressure refrigerant gas supplied from a compressor.

  There exists a thing of patent document 1 as a regenerator type refrigerator, for example. This cool storage type refrigerator expands the helium gas in the expansion chamber to generate cold. The cold of the helium gas generated in the expansion chamber is transmitted to the cooling stage while being accumulated in the regenerator, reaches a desired cryogenic temperature, and cools the cooling target connected to the cooling stage.

JP 2006-242484 A

  As the refrigerant gas, for example, helium gas is used. The compressor compresses low-pressure (for example, 0.8 MPa) helium gas to generate high-pressure (for example, 2.2 MPa) helium gas. The density difference between the density of the high-pressure helium gas and the density of the low-pressure helium gas has a large temperature dependence in the vicinity of extremely low temperatures, and the density difference becomes maximum especially when the temperature is around 8K. For this reason, a large amount of helium gas is accumulated in a region where the temperature in the regenerator is about 8K, the pressure difference of the entire refrigerator is reduced, and the refrigeration performance is lowered.

  This invention is made | formed in view of the said subject, and aims at providing the technique which raises the refrigerating performance of a regenerator type refrigerator more effectively.

  In order to solve the above problems, a regenerator type refrigerator of an aspect of the present invention is a regenerator type refrigerator, a nonmagnetic regenerator material that accumulates cold generated by expansion of helium gas, and a nonmagnetic regenerator A regenerator including a container filled with the material. The part which accommodated the nonmagnetic cool storage material among the containers contains the 1st area | region where the temperature during operation | movement of a cool storage type refrigerator becomes 6K or more and 15K or less, and the 2nd area | region used as the temperature range other than that. The porosity in the first region is smaller than the porosity in the second region.

  According to the regenerator type refrigeration of the present invention, it is possible to provide a technique for more effectively enhancing the refrigeration performance of the regenerator type refrigerator.

It is a mimetic diagram shown about one embodiment of a regenerator type freezer and a regenerator concerning an embodiment. It is a figure which shows the temperature change of each density of helium gas of 2.2 MPa and helium gas of 0.8 MPa, and the temperature change of the density difference of both. It is a figure which shows typically the enlarged view of the high temperature side area | region of the 2nd regenerator which concerns on embodiment. FIGS. 4A to 4B are diagrams schematically showing four second nonmagnetic regenerator materials adjacent to each other in the case of closest packing. It is a figure which shows typically a mode that the 1st cool storage material is arrange | positioned so that the space | gap of the four 2nd nonmagnetic cool storage materials with the closest packing may be contact | connected. FIGS. 6A to 6B are diagrams schematically illustrating a sintered body of a nonmagnetic regenerator material that is filled in the first region by the second regenerator 34 according to the first modification of the embodiment. . It is the one part expanded schematic diagram of the 2nd cool storage device which concerns on the 2nd modification of embodiment.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the accompanying drawings.

  The regenerator type refrigerator 1 according to the embodiment is a Gifford-McMahon (GM) type regenerator type refrigerator using helium gas as a refrigerant gas, for example. As shown in FIG. 1, the regenerator refrigerator 1 includes a first displacer 2 and a second displacer 3 connected to the first displacer 2 in the longitudinal direction. The first displacer 2 and the second displacer 3 are connected via, for example, a pin 4, a connector 5, and a pin 6.

  The first cylinder 7 and the second cylinder 8 are integrally formed, and each has a high temperature end and a low temperature end. The low temperature end of the first cylinder 7 and the high temperature end of the second cylinder 8 are connected at the bottom of the first cylinder 7. The second cylinder 8 is formed in a form extending in the same axial direction as the first cylinder 7 and is a cylindrical member having a smaller diameter than the first cylinder 7. The 1st cylinder 7 is a container which accommodates the 1st displacer 2 so that reciprocation is possible in a longitudinal direction. The second cylinder 8 is a container for accommodating the second displacer 3 so as to be reciprocally movable in the longitudinal direction.

  For example, stainless steel is used for the first cylinder 7 and the second cylinder 8 in consideration of strength, thermal conductivity, helium blocking ability, and the like. The outer periphery of the second displacer 3 is a cylinder made of metal such as stainless steel. On the outer peripheral surface of the second displacer 3, a film of an abrasion resistant resin such as a fluororesin may be formed.

  A scotch yoke mechanism (not shown) that reciprocates the first displacer 2 and the second displacer 3 is provided at the high temperature end of the first cylinder 7. The first displacer 2 and the second displacer 3 reciprocate along the first cylinder 7 and the second cylinder 8, respectively. The first displacer 2 and the second displacer 3 each have a high temperature end and a low temperature end.

  The first displacer 2 has a cylindrical outer peripheral surface, and the first displacer 2 is filled with a first cold storage material. The internal volume of the first displacer 2 functions as the first regenerator 9. A rectifier 10 is installed in the upper part of the first regenerator 9, and a rectifier 11 is installed in the lower part. A first opening 13 through which refrigerant gas flows from the room temperature chamber 12 to the first displacer 2 is formed at the high temperature end of the first displacer 2.

  The room temperature chamber 12 is a space formed by the first cylinder 7 and the high temperature end of the first displacer 2, and the volume changes as the first displacer 2 reciprocates. The room temperature chamber 12 is connected to a common supply / exhaust pipe among the pipes connecting the intake and exhaust systems including the compressor 14, the supply valve 15, and the return valve 16. In addition, a seal 17 is attached between the portion of the first displacer 2 from the high temperature end and the first cylinder 7.

  A second opening 19 is formed at the low temperature end of the first displacer 2 for introducing the refrigerant gas into the first expansion space 18 via the first clearance C1. The first expansion space 18 is a space formed by the first cylinder 7 and the first displacer 2. The volume of the first expansion space 18 changes as the first displacer 2 reciprocates. A first cooling stage 20 that is thermally connected to an object to be cooled (not shown) is disposed at a position corresponding to the first expansion space 18 in the outer periphery of the first cylinder 7. The first cooling stage 20 is cooled by the refrigerant gas passing through the first clearance C1.

  The second displacer 3 has a cylindrical outer peripheral surface, and the inside of the second displacer 3 has two stages in the axial direction with the rectifier 21 at the upper end, the rectifier 22 at the lower end, and the partition material 23 positioned between the upper and lower sides. It is divided into. Of the internal volume of the second displacer 3, the high temperature side region 24 on the higher temperature side than the partition member 23 is filled with a second cold storage material made of a nonmagnetic material such as lead or bismuth. The low temperature side region 25 on the low temperature (lower stage) side of the partition material 23 is filled with a cold storage material different from the high temperature side region 24, for example, a second cold storage material of magnetic material such as HoCu2. Lead, bismuth, HoCu2 and the like are formed in a spherical shape, and a plurality of spherical shaped products are gathered to form a cold storage material. The partition member 23 prevents the cold storage material in the high temperature side region 24 and the cold storage material in the low temperature side region 25 from mixing. The high temperature side region 24 and the low temperature side region 25, which are internal volumes of the second displacer 3, function as the second regenerator 34. The first expansion space 18 and the high temperature end of the second displacer 3 are communicated with each other through a communication path around the connector 5. Refrigerant gas flows from the first expansion space 18 to the second regenerator 34 through this communication path.

  The high temperature side region 24 is further divided into a first region 24a and a second region 24b. Details of the first region 24a and the second region 24b will be described later.

  A third opening 27 is formed at the low temperature end of the second displacer 3 for allowing the refrigerant gas to flow through the second expansion space 26 via the second clearance C2. The second expansion space 26 is a space formed by the second cylinder 8 and the second displacer 3, and the volume changes as the second displacer 3 reciprocates. The second clearance C <b> 2 is formed by the low temperature end of the second cylinder 8 and the second displacer 3.

  A second cooling stage 28 that is thermally connected to the object to be cooled is disposed at a position corresponding to the second expansion space 26 on the outer periphery of the second cylinder 8. The second cooling stage 28 is cooled by the refrigerant gas passing through the second clearance C2.

  For the first displacer 2, for example, cloth-containing phenol is used from the viewpoint of specific gravity, strength, thermal conductivity, and the like. The first regenerator material is made of, for example, a wire mesh. Moreover, the 2nd displacer 3 is comprised by pinching | interposing the spherical 2nd cool storage materials, such as lead and bismuth, for example in the axial direction with a felt and a metal net. Note that, as described above, the internal volume of the second displacer 3 may be divided into a plurality of regions by a partition material.

  The first displacer 2 and the second displacer 3 may include a lid portion 29 and a lid portion 30 at the low temperature end, respectively. The lid portion 29 and the lid portion 30 have a two-stage cylindrical shape from the viewpoint of joining with the displacer body. The lid portion 29 is fixed to the first displacer 2 by a press-fit pin 31, and the lid portion 30 is fixed to the second displacer 3 by a press-fit pin 32.

  Next, the operation of the regenerator type refrigerator 1 according to the embodiment will be described. At a certain point in the refrigerant gas supply process, the first displacer 2 and the second displacer 3 are located at the bottom dead center of the first cylinder 7 and the second cylinder 8. When the supply valve 15 is opened at the same time or at a slightly shifted timing, high-pressure helium gas (for example, 2.2 MPa helium gas) is supplied into the first cylinder 7 from the supply / discharge common pipe via the supply valve 15. Then, the air flows into the first regenerator 9 inside the first displacer 2 from the first opening 13 located at the upper part of the first displacer 2. The high-pressure helium gas that has flowed into the first regenerator 9 is cooled by the first regenerator material and enters the first expansion space 18 via the second opening 19 and the first clearance C1 that are located below the first displacer 2. Supplied.

  The high-pressure helium gas supplied to the first expansion space 18 flows into the second regenerator 34 inside the second displacer 3 through the communication passage around the connector 5. The high-pressure helium gas that has flowed into the second regenerator 34 is supplied to the second expansion space 26 through the third opening 27 and the second clearance that are positioned below the second displacer 3 while being cooled by the second regenerator material. Is done.

  In this way, the first expansion space 18 and the second expansion space 26 are filled with the high-pressure helium gas, and the supply valve 15 is closed. At this time, the first displacer 2 and the second displacer 3 are located at the top dead center in the first cylinder 7 and the second cylinder 8. When the return valve 16 is opened at the same time or slightly shifted timing, the refrigerant gas in the first expansion space 18 and the second expansion space 26 is decompressed and expanded, and low-pressure helium gas (for example, 0.8 MPa helium). Gas). At this time, cold is generated by the expansion of the refrigerant gas. The helium gas in the first expansion space 18 that has become low temperature due to expansion absorbs the heat of the first cooling stage 20 through the first clearance C1. The helium gas in the second expansion space 26 absorbs the heat of the second cooling stage 28 through the second clearance C2.

  The first displacer 2 and the second displacer 3 move toward the bottom dead center, and the volumes of the first expansion space 18 and the second expansion space 26 decrease. The helium gas in the second expansion space 26 is returned to the first expansion space 18 via the second clearance C2, the third opening 27, the second regenerator 34, and the communication path. Further, the helium gas in the first expansion space 18 is returned to the suction side of the compressor 14 through the second opening 19, the first regenerator 9, and the first opening 13. In that case, the 1st cool storage material, the 2nd cool storage material, and the 3rd cool storage material are cooled with refrigerant gas. That is, the 1st cool storage material, the 2nd cool storage material, and the 3rd cool storage material accumulate cold produced by expansion of refrigerant gas. This process is defined as one cycle, and the regenerator type refrigerator 1 cools the first cooling stage 20 and the second cooling stage 28 by repeating this cooling cycle.

  As described above, the cooling cycle in the regenerator refrigerator 1 includes an operation in which helium gas, which is a refrigerant gas, repeatedly flows in and out of the second regenerator. During the operation of the regenerator refrigerator 1, the second regenerator 34 has a temperature gradient of about 40K to 4K from the high temperature end toward the low temperature end. Hereinafter, the density change of the helium gas existing in the second regenerator will be described.

  FIG. 2 is a diagram showing the temperature change of the density in the cryogenic temperature region and the temperature change of the density difference between the 2.2 MPa helium gas and the 0.8 MPa helium gas. The temperature range shown in FIG. 2 corresponds to the temperature range of the helium gas in the second regenerator 34 during operation of the regenerator refrigerator 1.

  As shown in FIG. 2, the density difference between the 2.2 MPa helium gas and the 0.8 MPa helium gas becomes maximum when the temperature is about 8K. When the temperature of the helium gas is lower than 8K, the density difference between the 2.2 MPa helium gas and the 0.8 MPa helium gas increases monotonically with respect to the temperature, and when the helium gas temperature is higher than 8K, The density difference decreases monotonically with temperature.

Here, let M be the mass of helium gas present in the second regenerator 34. Further, the high temperature end of the second regenerator 34, i.e. the mass per unit time of the helium gas flowing to the rectifier 21 of the upper end and m _in, the mass per unit of the helium gas flowing out time from the lower end of the rectifier 22 m _out And If helium gas flows into the second regenerator 34, the mass M of helium gas present in the second regenerator 34 increases. On the other hand, if helium gas flows out from the second regenerator 34, the mass M of helium gas present in the second regenerator 34 decreases. Therefore, the amount of change dM / dt per unit time of the mass M of the helium gas existing in the second regenerator 34 can be expressed by the difference between the inflow mass min and the outflow mass mout. From the above, the following relational expression (1) is obtained.
_{m in = m out + dM /} dt (1)
Here, dM / dt represents the differentiation of the mass M of helium gas existing in the second regenerator 34 with respect to time t.

As described above, the second regenerator 34 is inside the second displacer 3, and the second displacer 3 is configured by sandwiching a spherical second regenerator material such as lead or bismuth in the axial direction with a felt and a metal mesh. Composed. Accordingly, since the volume of the second regenerator 34 can be regarded as constant, the value is set to V. Further, if the average density of the helium gas in the second regenerator 34 is ρ, the mass M of the refrigerant gas existing in the second regenerator 34 can be expressed by the following equation (2).
M = Vρ (2)

Substituting equation (2) into equation (1) yields the following equation (3).
_{m in = m out + Vdρ /} dt (3)
Here, dρ / dt represents a time derivative of the density ρ of helium gas.

In the formula (3), the density of the helium gas flowing into the second regenerator 34 is assumed not to vary with time, m _{in =} m _out next, helium gas by the amount that flows into the second regenerator 34, the second It flows out of the regenerator 34. That is, it means that the mass M of the helium gas present in the second regenerator 34 does not change. In the actual cooling cycle, when the supply valve 15 is opened, high-pressure helium gas is supplied through the supply valve 15. As a result, the high-pressure helium gas also flows into the second regenerator 34, and the low-pressure helium gas charged in the second regenerator 34 is pressurized to become high-pressure helium gas.

As shown in FIG. 2, there is a difference in density between high-pressure helium gas and low-pressure helium gas. Therefore, when high-pressure helium gas flows into the second regenerator 34 and the low-pressure helium gas in the second regenerator 34 is boosted to become high-pressure helium gas, the density of the helium gas is the density indicated by the solid line in FIG. The difference increases. From the above, the following inequality (4) is obtained.
_{m in -m out = Vdρ / dt} > 0 (4)

  As described above, the high-pressure helium gas that has flowed into the second regenerator 34 is cooled by the second regenerator material through the third opening 27 located at the lower portion of the second displacer 3 and the second clearance. It is supplied to the expansion space 26. However, the inequality (4) indicates that the mass of helium gas flowing out from the second regenerator into the second expansion space 26 is smaller than the mass of helium gas flowing into the second regenerator. This means that the second regenerator 34 acts like a buffer of helium gas, and accumulates helium gas. As a result, the pressure increase in the second expansion space 26 is suppressed, and the pressure difference is also reduced.

When the return valve 16 is opened, the high-pressure helium gas in the second regenerator 34 becomes low-pressure helium gas. At this time, the right side in the equation (3) is a negative value with the density difference indicated by the straight line in FIG. 2 as an absolute value. Therefore, the following inequality (5) is obtained.
_{m in -m out = Vdρ / dt} <0 (5)

  This indicates that the mass of helium gas flowing out from the second regenerator 34 is larger than the mass of helium gas flowing into the second regenerator 34 from the second expansion space 26. The more the helium gas is expanded in the second expansion space 26, the more cold is generated. For that purpose, it is preferable that helium gas is quickly discharged from the second expansion space 26 and the second regenerator 34 and returned to the compressor 14. However, the equation (5) indicates that not only the helium gas expanded in the second expansion space 26 and flowing into the second regenerator 34, but also the helium gas remaining in the second regenerator 34 from the second regenerator 34. It shows that it leaks. Since the ability of the compressor 14 to collect the helium gas is constant, the recovery of the helium gas discharged from the second expansion space 26 is delayed by the amount of the helium gas remaining in the second regenerator 34.

  Therefore, in the regenerator type refrigerator 1 according to the embodiment, the temperature range in which the density difference between the high-pressure helium gas and the low-pressure helium gas is maximized in the portion of the second regenerator 34 containing the nonmagnetic regenerator material. The portion including is configured so that helium gas is less likely to accumulate than other portions. In addition, the part which accommodated the nonmagnetic regenerator material of the 2nd regenerator 34 is the high temperature side area | region 24 specifically mentioned above.

  Here, the temperature at which the density difference between the high-pressure helium gas and the low-pressure helium gas becomes maximum is about 9K, as shown in FIG. Therefore, the temperature range including the temperature at which the density difference between the high-pressure helium gas and the low-pressure helium gas is maximized is a temperature range having a predetermined spread including 9K. Specifically, the temperature range is 5K to 20K, and more preferably the temperature range is 6K to 15K. The temperature range may be from 7K to 11K.

  Hereinafter, during the operation of the regenerator type refrigerator 1 according to the embodiment, in the high temperature side region 24 of the second regenerator 34, a temperature range in which the density difference between the high pressure helium gas and the low pressure helium gas is maximized. This region is referred to as “first region 24a”. Moreover, in the part which accommodated the nonmagnetic cool storage material among the 2nd cool storage devices 34, area | regions other than 1st area | region 24a are called "2nd area | region 24b." The second regenerator 34 according to the embodiment makes it difficult for helium gas to accumulate by making the porosity in the first region 24a smaller than the porosity in the second region 24b.

  As described above, the regenerator material filled in the second regenerator 34 has a spherical shape. Generally, when a container is filled with many spheres having the same radius, the filling rate is constant regardless of the radius of the sphere. It is known that when the spheres having the same radius are closely packed, the filling rate is about 74%. In addition, in the processing of the regenerator material, the radius of the sphere varies strictly. However, when considering the filling rate, the variation due to the processing accuracy is considered to be negligible. Therefore, when the first region 24a is filled with a spherical nonmagnetic regenerator, the porosity is considered to be about 100% -74% = 26% at the minimum.

  Therefore, in the second regenerator 34 according to the embodiment, as shown in FIG. 1, the first region 24 a is filled with nonmagnetic regenerator materials having different particle diameters. Thereby, compared with the case where it fills with the cool storage material of the same radius, the porosity of the 1st area | region 24a can be made small.

  FIG. 3 is a diagram schematically showing an enlarged view of the high temperature side region 24 of the second regenerator 34 according to the embodiment. As shown in FIG. 3, in the high temperature side region 24 of the second regenerator 34, the first region 24 a has a particle size larger than the particle size of the first nonmagnetic regenerator material 35 and the first nonmagnetic regenerator material 35. The second nonmagnetic regenerator material 36 having Further, in the high temperature side region 24 of the second regenerator 34, particles in the second region 24 b are larger than the particle size of the first nonmagnetic regenerator material 35 and smaller than the particle size of the second nonmagnetic regenerator material 36. A third nonmagnetic regenerator material 37 having a diameter is filled. The first nonmagnetic regenerator material 35, the second nonmagnetic regenerator material 36, and the third nonmagnetic regenerator material 37 may have different particle diameters. Therefore, the first nonmagnetic regenerator material 35, the second nonmagnetic regenerator material 36, and the third nonmagnetic regenerator material 37 may be different materials or the same material.

  Hereinafter, the ratio of the radius of the first nonmagnetic regenerator material 35 to the radius of the second nonmagnetic regenerator material 36 will be considered.

  FIGS. 4A to 4B are diagrams schematically showing four second nonmagnetic regenerator materials 36 adjacent to each other in the case where the closest packing is performed. FIG. 4A is a diagram showing four positional relationships adjacent to each other at the time of closest packing. In FIG. 4A, it is assumed that the four second nonmagnetic regenerator materials 36 adjacent to each other have the same radius.

  When four spheres of the same radius are closely packed, the centers of the four spheres constitute four vertices of a regular tetrahedron. In the example shown in FIG. 4A, three second nonmagnetic regenerators 36a, second nonmagnetic regenerators 36b, and second nonmagnetic regenerators 36c are arranged in contact with each other on the same plane, on which A fourth second nonmagnetic regenerator material 36d is placed.

  FIG. 4B is a plane including the centers of the second nonmagnetic regenerator material 36a, the second nonmagnetic regenerator material 36b, and the second nonmagnetic regenerator material 36c, and the second nonmagnetic regenerator material 36a and the second nonmagnetic regenerator material 36c. It is a figure which shows a cut surface when cut | disconnecting the cool storage material 36b and the 2nd nonmagnetic cool storage material 36c. In FIG. 4B, points 38a, 38b, and 38c are respectively the second nonmagnetic regenerator material 36a, the second nonmagnetic regenerator material 36b, and the second nonmagnetic regenerator material 36c in FIG. 4A. Central. A triangle having the points 38a, 38b, and 38c as three vertices is an equilateral triangle constituting the bottom surface of the regular tetrahedron.

  Let R be the radius of the second nonmagnetic cold storage material 36a, the second nonmagnetic cold storage material 36b, the second nonmagnetic cold storage material 36c, and the second nonmagnetic cold storage material 36d. At this time, as is apparent from FIG. 4B, the centers of the second nonmagnetic cold storage material 36a, the second nonmagnetic cold storage material 36b, the second nonmagnetic cold storage material 36c, and the second nonmagnetic cold storage material 36d are apexes. The length of one side of the regular tetrahedron is 2R.

  FIG. 4A shows a state in which the second nonmagnetic regenerator material 36a, the second nonmagnetic regenerator material 36b, the second nonmagnetic regenerator material 36c, and the second nonmagnetic regenerator material 36d are arranged so as to be closest packed. Indicates. From the symmetry of the sphere, the center of gravity of the tetrahedron formed by the centers of the second nonmagnetic regenerator material 36a, the second nonmagnetic regenerator material 36b, the second nonmagnetic regenerator material 36c, and the second nonmagnetic regenerator material 36d is determined. A void is generated in the containing space. If this gap can be filled with the first nonmagnetic cold storage material 35, the porosity of the first region 24a can be reduced.

  FIG. 5 schematically shows a state in which the first nonmagnetic regenerator material 35 is arranged so as to be in contact with the four second nonmagnetic regenerator materials 36 in the gaps of the four second nonmagnetic regenerator materials 36 that are closely packed. FIG. From the symmetry of the figure, the center 39 of the sphere constituting the first nonmagnetic regenerator material 35 has a second nonmagnetic regenerator material 36a, a second nonmagnetic regenerator material 36b, a second nonmagnetic regenerator material 36c, and a second nonmagnetic regenerator material 36c. This coincides with the center of gravity w of a regular tetrahedron having the center of the magnetic regenerator material 36d as a vertex.

  The radius of the sphere constituting the first nonmagnetic regenerator material 35 is r. At this time, the distance L from the apex of the regular tetrahedron to the center of gravity w is equal to the sum of the radius R of the second nonmagnetic regenerator material 36 and the radius r of the first nonmagnetic regenerator material 35.

  Since the length of one side of the regular tetrahedron is 2R, the height H of the regular tetrahedron is 2√6R / 3. Since the distance L from the apex of the regular tetrahedron to the center of gravity w is 2/3 of the height H of the regular tetrahedron, L = 4√6R / 9. Therefore, r = LR = (4√6 / 9-1) R≈0.08866R. From the above, when the radius r of the first nonmagnetic regenerator material 35 is 8.8% or less of the radius R of the second nonmagnetic regenerator material 36, the second nonmagnetic regenerator material 36 is packed most closely. Even so, the gap of the second nonmagnetic regenerator material 36 can be filled. In addition, 8.8% is a theoretical value when it is assumed that the radii of the second nonmagnetic regenerator material 36 are completely the same. Actually, it is considered that the radius of the second non-magnetic regenerator material 36 is likely to cause processing accuracy, so that the radius r of the first non-magnetic regenerator material 35 is 8.8% of the radius R of the second non-magnetic regenerator material 36. Is preferably less than 8%, and more preferably less than 5%.

  The radius of the third nonmagnetic regenerator material 37 is larger than the radius r of the first nonmagnetic regenerator material 35 and smaller than the radius R of the second nonmagnetic regenerator material 36. Therefore, the radius of the third nonmagnetic regenerator material 37 is 10% or more of the radius R of the second nonmagnetic regenerator material 36, and is 50% to 60% of the radius R of the second nonmagnetic regenerator material 36. preferable.

  As described above, in the second regenerator 34 according to the embodiment, the first region 24a is filled with nonmagnetic regenerator materials having different particle diameters. Thereby, the smaller nonmagnetic regenerator material can enter the gap between the larger nonmagnetic regenerator material, and the porosity of the first region 24a can be reduced. The first region 24a includes a temperature range in which the density difference between the high pressure helium gas and the low pressure helium gas is maximized. Therefore, in the second regenerator 34 according to the embodiment, helium gas stays in a region where the density difference between the high-pressure helium gas and the low-pressure helium gas is maximized. As a result, the pressure difference of the regenerator type refrigerator 1 is increased, and the refrigerating capacity can be improved.

  Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various modifications and substitutions are made to the above-described embodiments without departing from the scope of the present invention. be able to.

(First modification)
In the above description, the case where the porosity of the first region 24a is reduced by filling the first region 24a of the second regenerator 34 according to the embodiment with nonmagnetic regenerator materials having different particle diameters has been described. In order to reduce the porosity of the first region 24a, instead of filling nonmagnetic regenerator material having different particle diameters, a sintered body of nonmagnetic regenerator material may be filled.

  FIGS. 6A to 6B are diagrams schematically illustrating a sintered body of a nonmagnetic regenerator material that is filled in the first region 24a by the second regenerator 34 according to the first modification of the embodiment. is there. More specifically, FIG. 6A is a diagram showing a nonmagnetic regenerator material before sintering. FIG. 6B is a diagram schematically showing a sintered body of a nonmagnetic regenerator material obtained by sintering FIG. 6A. In FIG. 6 (a)-(b), the hatched areas are voids, and the other areas are areas where the nonmagnetic regenerator material is present.

  FIG. 6A shows a state in which a plurality of non-magnetic regenerator materials that are spherical metals are filled. The nonmagnetic regenerator materials in contact with each other are hardened by sintering, and as a whole, become denser than before sintering as shown in FIG. As a result, the porosity of the nonmagnetic regenerator material is reduced. By filling the first region 24a of the second regenerator 34 with a sintered body of a nonmagnetic regenerator material, helium gas convection to the first region 24a can be reduced.

  Here, when the nonmagnetic regenerator material is sintered, the nonmagnetic regenerator material becomes a large mass as compared with before sintering. For this reason, the shape of the sintered body of the nonmagnetic regenerator material may not match the shape of the container that is the second regenerator 34. Therefore, the first region 24a of the second regenerator 34 may be filled with the sintered body of the nonmagnetic regenerator material, and the gap between the container and the sintered body may be filled with an unsintered regenerator material. . The cold storage material that fills the gap is, for example, a spherical nonmagnetic cold storage material before sintering. As a result, the gap between the container that is the second regenerator 34 and the sintered body of the nonmagnetic regenerator material is filled with the spherical nonmagnetic regenerator material before sintering, and the porosity of the first region 24a is increased. It can be further reduced.

(Second modification)
In the above, the first region 24a of the second regenerator 34 is filled with nonmagnetic regenerator materials having different particle diameters or filled with a sintered body of nonmagnetic regenerator material, whereby the voids in the first region 24a are filled. The case of reducing the rate has been described. In addition, the porosity of the first region 24a can be reduced by accommodating a punching plate provided with a helium gas flow hole in the first region 24a of the second regenerator 34.

  FIG. 7 is an enlarged schematic view of a part of the second regenerator 34 according to the second modification of the embodiment. As shown in FIG. 7, the second regenerator 34 according to the second modification accommodates a plurality of punching plates 40 in the first region 24 a instead of the spherical nonmagnetic regenerator material.

  The punching plate is a thin plate made of metal or the like, and is a member provided with a plurality of holes penetrating from the front surface to the back surface. In FIG. 7, to avoid complication, not all punching plates 40 are labeled, but the second regenerator 34 accommodates the plurality of punching plates 40 in layers in the first region 24 a. doing. Each punching plate 40 is provided with a plurality of helium gas flow holes 41.

  As shown in FIG. 7, when a plurality of punching plates 40 are accommodated in the first region 24 a of the second regenerator 34, the porosity of the first region 24 a is the size of the flow holes 41 provided in the punching plate 40 and Determined by density. The size and density of the flow holes 41 can be freely designed when the punching plate 40 is processed. Therefore, by providing the flow hole 41 so that the porosity of the first region 24a is less than 26%, the first region 24a is filled with a spherical nonmagnetic regenerator material having the same radius as the first region 24a. The porosity of the region 24a can be reduced.

  In the assembly process of the regenerator type refrigerator 1, the punching plate 40 is accommodated in the second regenerator 34. At this time, it is preferable to make the punching plate 40 smaller than the cross section of the container of the second regenerator 34 from the viewpoint of easy accommodation. However, if the punching plate 40 is made smaller than the cross section of the container of the second regenerator 34, a gap is generated between the container of the second regenerator 34 and the punching plate 40, so the porosity of the first region 24a is large. Become.

  Therefore, a plurality of punching plates 40 may be accommodated in the first region 24a of the second regenerator 34 and further filled with a nonmagnetic regenerator material made of spherical particles. As a result, the gap between the container that is the second regenerator 34 and the punching plate 40 is filled with the spherical nonmagnetic regenerator material, and the porosity of the first region 24a can be reduced. Further, when the spherical nonmagnetic regenerator material enters the flow hole 41 of the punching plate 40, the porosity of the first region 24a is further reduced. Thereby, the simplification of the assembly process of the regenerator type refrigerator 1 and the reduction of the porosity of the first region 24a can both be achieved.

  In the above description, in the regenerator type refrigerator 1, the GM refrigerator having two stages is mainly described. However, the number of stages can be appropriately selected to be three or more. In the embodiment, an example in which the regenerator type refrigerator 1 is a displacer type GM refrigerator has been described, but the present invention is not limited thereto. For example, the present invention can be applied to a pulse tube type GM refrigerator, a Stirling refrigerator, a Solvay refrigerator, and the like.

  DESCRIPTION OF SYMBOLS 1 Regenerator type refrigerator, C1 1st clearance, 2 1st displacer, C2 2nd clearance, 3 2nd displacer, 4 pins, 5 connectors, 6 pins, 7 1st cylinder, 8 2nd cylinder, 9 1st cool storage 10, 11 rectifier, 12 room temperature chamber, 13 first opening, 14 compressor, 15 supply valve, 16 return valve, 17 seal, 18 first expansion space, 19 second opening, 20 first cooling stage, 21, 22 rectifier, 23 partition material, 24 high temperature side region, 24a first region, 24b second region, 25 low temperature side region, 26 second expansion space, 27 third opening, 28 second cooling stage, 29, 30 lid, 31, 32 Press-fit pins, 34 Second regenerator, 35 First non-magnetic regenerator, 36 Second Magnetic regenerator material, 37 third nonmagnetic regenerator material, 40 punching plate, 41 communication holes.

Claims (6)

A regenerator refrigerator,
A non-magnetic regenerator and a magnetic regenerator that accumulates the cold generated by the expansion of helium gas;
A regenerator including a container filled with the non-magnetic regenerator material on a higher temperature side than the partition material and filled with the magnetic regenerator material on a lower temperature side than the partition material ;
The portion of the container that contains the non-magnetic regenerator material is
A first region where the temperature during operation of the regenerator refrigerator is 6K or more and 15K or less, and a second region which is a temperature range higher than the first region ,
A regenerator type refrigerator having a porosity in the first region smaller than a porosity in the second region. The non-magnetic regenerator material is composed of spherical particles,
The regenerator type refrigerator according to claim 1, wherein the container is filled with nonmagnetic regenerator materials having different particle diameters in the first region. The container is
Filling the first region with a first nonmagnetic regenerator material and a second nonmagnetic regenerator material having a particle size larger than the particle size of the first nonmagnetic regenerator material,
The second region is filled with a third nonmagnetic regenerator material having a particle diameter larger than that of the first nonmagnetic regenerator material and smaller than that of the second nonmagnetic regenerator material. The regenerator type refrigerator according to claim 1 or 2.   The regenerator refrigerator according to claim 1, wherein the container is filled with a sintered body of a nonmagnetic regenerator material in the first region.   The regenerator-type refrigerator according to claim 1, wherein the container accommodates a punching plate having a plurality of helium gas flow holes provided in the first region.   The regenerator type refrigerator according to claim 4 or 5, wherein the container is filled with a nonmagnetic regenerator material made of spherical particles in the first region.

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