JP4564161B2 - refrigerator - Google Patents

Description

【００７２】
上記表１に示す結果から明らかなように、磁性粒子の円形度係数Ｒおよびその標準偏差σを適正な範囲に調製した磁性粒子群で構成した各実施例の蓄冷材を充填した冷却機においては、４．２Ｋにおける冷凍能力の初期値が高く、また、１０００時間連続運転後の冷凍能力も高く、長時間運転した後も冷凍能力の低下が少なく、安定した冷凍性能が確認できた。さらに、運転終了後に蓄冷器を分解して蓄冷材を取り出して外観を観察したが、破壊された磁性粒子や微粉の発生は認められなかった。
【００７３】
一方、磁性粒子の円形度係数Ｒおよびその標準偏差σの少なくとも一方が、本発明で規定する範囲外である磁性粒子群で構成した各比較例に係る蓄冷材を充填した冷凍機においては、４．２Ｋにおける冷凍能力の初期値が実施例と比較して低下した。また、１０００時間連続運転後の冷凍能力も大幅に低下しており、冷凍性能の低下が顕著であった。さらに、運転終了後に蓄冷器から蓄冷材を取り出して外観を観察したところ、粉々に破壊された粒子や微粉の発生が認められた。
そしてその一部の冷凍機のシール部が破損していることも確認された。
【００７４】
以上の実施例および比較例から明らかなように、円形度係数Ｒの平均値およびその標準偏差を適正に規定した各実施例に係る蓄冷材を使用した冷凍機によれば、運転中に蓄冷材が破損して微粉化することが少なく、安定した冷凍能力を長期間に亘って維持できる冷凍機が実現できる。
【００７５】
以上説明した各実施例では、本発明で使用する蓄冷材をＧＭ冷凍機に適用した例を示しているが、本発明で使用する蓄冷材は図２に示すようなパルス管型冷凍機７０にも適用可能である。
【００７６】
図２に１段式パルスチューブ冷凍機の基本構成を示す。このパルスチューブ冷凍機７０の最大の構造的特徴は、前述したＧＭ冷凍機では必須となっている寒冷発生用の往復動ピストンを具備しないことである。そのため、機械的信頼性および低振動性に優れる長所を有し、特に素子やセンサー冷却用冷凍機として期待を担っている。
【００７７】
パルスチューブ冷凍機７０は蓄冷式冷凍機の一種であり、冷媒ガスとして一般にヘリウムガスが用いられる。基本的な構成として、冷凍機は蓄冷器１の他にヘリウムガスを圧縮する圧力振動源７１、および冷媒ガスの圧力変動と位置変動（変位）の時間差を制御する位相調節機構７２から成る。
【００７８】
ＧＭ冷凍機やスターリング冷凍機においては、上記位相調節機構７２は低温部に配置された往復動ピストン機構であるのに対して、パルスチューブ冷凍機７０では、それが室温部に配置され、蓄冷器１の低温端と室温部の位相調節機構７２との間がパルス管と呼ばれる配管で連結され、冷媒ガスの圧力波の位相の遠隔制御がなされる。そして圧力変動による冷媒ガスと蓄冷材との間のエントロピー授受が変位との適当なタイミングで進行することにより、エントロピーが一方向へ順次汲み上げられ、蓄冷器１の低温部において、より低温度の冷熱が得られる。
【００７９】
次に、本発明に係る蓄冷式冷凍機を使用した超電導ＭＲＩ装置、磁気浮上列車用超電導磁石、クライオポンプ、および磁界印加式単結晶引上げ装置の実施例について述べる。
【００８０】
図４は、本発明を適用した超電導ＭＲＩ装置の概略構成を示す断面図である。
図４に示す超電導ＭＲＩ装置３０は、人体に対して空間的に均一で時間的に安定な静磁界を印加する超電導静磁界コイル３１、発生磁界の不均一性を補正する図示を省略した補正コイル、測定領域に磁界勾配を与える傾斜磁界コイル３２、およびラジオ波送受信用プローブ３３等により構成されている。そして、超電導静磁界コイル３１の冷却用として、前述したような本発明に係る蓄冷式冷凍機３４が用いられている。なお、図中３５はクライオスタット、３６は放射断熱シールドである。
【００８１】
本発明に係る蓄冷式冷凍機３４を用いた超電導ＭＲＩ装置３０においては、超電導静磁界コイル３１の動作温度を長期間に亘って安定に保証することができるため、空間的に均一で時間的に安定な静磁界を長期間に亘って得ることができる。したがって、超電導ＭＲＩ装置３０の性能を長期間に亘って安定して発揮させることが可能となる。
【００８２】
図５は、本発明に係る蓄冷式冷凍機を使用した磁気浮上列車用超電導磁石の要部概略構成を示す斜視図であり、磁気浮上列車用超電導マグネット４０の部分を示している。図５に示す磁気浮上列車用超電導マグネット４０は、超電導コイル４１、この超電導コイル４１を冷却するための液体ヘリウムタンク４２、この液体ヘリウムタンクの揮散を防ぐ液体窒素タンク４３および本発明に係る蓄冷式冷凍機４４等により構成されている。なお、図中４５は積層断熱材、４６はパワーリード、４７は永久電流スイッチである。
【００８３】
本発明に係る蓄冷式冷凍機４４を用いた磁気浮上列車用超電導マグネット４０においては、超電導コイル４１の動作温度を長期間に亘って安定に保証することができるため、列車の磁気浮上および推進に必要な磁界を長期間に亘って安定して得ることができる。特に、磁気浮上列車用超電導マグネット４０では加速度が作用するが、本発明に係る蓄冷式冷凍機４４は加速度が作用した場合においても長期間に亘って優れた冷凍能力を維持できることから、磁界強度等の長期安定化に大きく貢献する。したがって、このような超電導マグネット４０を用いた磁気浮上列車は、その信頼性を長期間に亘って発揮させることが可能となる。
【００８４】
図６は、本発明に係る蓄冷式冷凍機を使用したクライオポンプの概略構成を示す断面図である。図６に示すクライオポンプ５０は、気体分子を凝縮または吸着するクライオパネル５１、このクライオパネル５１を所定の極低温に冷却する本発明に係る蓄冷式冷凍機５２、これらの間に設けられたシールド５３、吸気口に設けられたバッフル５４、およびアルゴン、窒素、水素等の排気速度を変化させるリング５５等により構成されている。
【００８５】
本発明に係る蓄冷式冷凍機５２を用いたクライオポンプ５０においては、クライオパネル５１の動作温度を長期間に亘って安定に保証することができる。したがって、クライオポンプ５０の性能を長期間に亘って安定して発揮させることが可能となる。
【００８６】
図７は、本発明に係る蓄冷式冷凍機を使用した磁界印加式単結晶引上げ装置の概略構成を示す斜視図である。図７に示す磁界印加式単結晶引上げ装置６０は、原料溶融用るつぼ、ヒータ、単結晶引上げ機構等を有する単結晶引上げ部６１、原料融液に対して静磁界を印加する超電導コイル６２、および単結晶引上げ部６１の昇降機構６３等により構成されている。そして、超電導コイル６２の冷却用として、前述したような本発明に係る蓄冷式冷凍機６４が用いられている。なお、図中６５は電流リード、６６は熱シールド板、６７はヘリウム容器である。
【００８７】
本発明に係る蓄冷式冷凍機６４を用いた磁界印加式単結晶引上げ装置６０においては、超電導コイル６２の動作温度を長期間に亘って安定に保証することができるため、単結晶の原料融液の対流を抑える良好な磁界を長期間に亘って得ることができる。したがって、磁界印加式単結晶引上げ装置６０の性能を長期間に亘って安定して発揮させることが可能となる。
【００８８】
【発明の効果】
以上説明の通り、本発明で使用する蓄冷材によれば、磁性粒子の円形度係数およびその標準偏差を所定の範囲に規定しているため、機械的強度や熱伝導率が高く、耐熱衝撃性が優れており、微粉化のおそれも少ない。そのため、スターリング冷凍機やパルスチューブ冷凍機などの高速運転を行う冷凍機用の蓄冷材として使用した場合においても、圧力損失が小さく、長期間に亘り安定した冷凍特性を示す蓄冷材が得られる。そして、その蓄冷材を冷凍機の少なくとも一部の蓄冷材として使用することにより、冷凍能力が高く、かつ長期間に亘って安定した冷凍性能が維持できる冷凍機を提供することができる。
【００８９】
そして、ＭＲＩ装置、クライオポンプ、磁気浮上列車用超電導磁石、および磁界印加式単結晶引上げ装置は、いずれも冷凍機性能が各装置の性能を左右することから、上述したような冷凍機を用いた本発明のＭＲＩ装置、クライオポンプ、磁気浮上列車用超電導磁石、および磁界印加式単結晶引上げ装置は、いずれも長期間に亘って優れた性能を発揮させることができる。
【図面の簡単な説明】
【図１】蓄冷式冷凍機（ＧＭ冷凍機）の要部構成を示す断面図。
【図２】パルス管冷凍機の要素構成および温度分布を模式的に示す図。
【図３】熱プラズマ装置の構成を示す図。
【図４】本発明の一実施例による超電導ＭＲＩ装置の概略構成を示す断面図。
【図５】本発明の一実施例による超電導磁石（磁気浮上列車用）の要部概略構成を示す斜視図。
【図６】本発明の一実施例によるクライオポンプの概略構成を示す断面図。
【図７】本発明の一実施例による磁界印加式単結晶引上げ装置の要部概略構成を示す斜視図。
【符号の説明】
１ 蓄冷器
１０ ＧＭ冷凍機（蓄冷式冷凍機）
１１ 第１シリンダ
１２ 第２シリンダ
１３ 真空容器
１４ 第１蓄冷器
１５ 第２蓄冷器
１６，１７ シールリング
１８ 第１蓄熱材
１９ 第２蓄熱材（極低温用蓄冷材）
２０ 第１膨張室
２１ 第２膨張室
２２ 第１冷却ステージ
２３ 第２冷却ステージ
２４ コンプレッサ
３０ 超電導ＭＲＩ装置
３１ 超電導静磁界コイル
３２ 傾斜磁界コイル
３３ ラジオ波送受信用プローブ
３４ 蓄冷式冷凍機
３５ クライオスタット
３６ 放射断熱シールド
４０ 超電導磁石（マグネット）
４１ 超電導コイル
４２ 液体ヘリウムタンク
４３ 液体窒素タンク
４４ 蓄冷式冷凍機
４５ 積層断熱材
４６ パワーリード
４７ 永久電流スイッチ
５０ クライオポンプ
５１ クライオパネル
５２ 蓄冷式冷凍機
５３ シールド
５４ バッフル
５５ リング
６０ 磁界印加式単結晶引上げ装置
６１ 単結晶引上げ部
６２ 超電導コイル
６３ 昇降機構
６４ 蓄冷式冷凍機
６５ 電流リード
６６ 熱シールド板
６７ ヘリウム容器
７０ パルス管型冷凍機
７１ 圧力振動源
７２ 位相調節機構
８０ 熱プラズマ装置
８１ 反応容器
８２ 高周波発信器
８３ コイル
８４ プラズマ発生部外囲筒
８５ プラズマフレーム
８６ 粉体供給口
８７ 粉体供給器
８８ キャリアガス供給ボンベ
８９ プラズマ発生用ガス源
９０ サイクロン
９１ 冷却ガス源[0001]
BACKGROUND OF THE INVENTION
  The present invention is cold storageMaterialRefrigerating machine that can be used for refrigerating machines, etc., and that has excellent mechanical strength and durability with little risk of being pulverized, and that can exhibit remarkable refrigerating capacity in low temperature range.MaterialIt relates to the refrigerator used.
[0002]
[Prior art]
In recent years, the development of superconducting technology has been remarkable, and the development of compact and high-performance refrigerators has become indispensable as the field of application expands. Such small refrigerators are required to be lightweight, small and have high thermal efficiency, and are being put to practical use in various application fields.
[0003]
For example, in a superconducting MRI apparatus, a cryopump, and the like, a refrigerator using a refrigeration cycle such as a Gifford McMahon (GM) system, a Stirling system, or a pulse tube refrigerator is used. Further, a high-performance refrigerator is indispensable in order to generate a magnetic force using a superconducting magnet in a magnetic levitation train. Furthermore, recently, high-performance refrigerators are also used in superconducting power storage devices (SMES) and single-crystal pulling devices in a magnetic field for producing high-quality silicon wafers. The development and commercialization of pulse tube refrigerators that are expected to have higher reliability are also being actively promoted.
[0004]
In such a refrigerator, a working medium such as compressed He gas flows in one direction in the regenerator filled with the regenerator material, supplies the heat energy to the regenerator material, and the operation expanded here. The medium flows in the opposite direction and receives heat energy from the cold storage material. As the recuperation effect in such a process becomes better, the thermal efficiency in the working medium cycle is improved, and a lower temperature can be realized.
[0005]
Conventionally, Cu, Pb, etc. have been mainly used as the regenerator material used in the refrigerator as described above. However, such a regenerator material has a remarkably small specific heat at an extremely low temperature of 20K or less, so that the above-described recuperation effect does not function sufficiently, and the regenerator material is operated every cycle at a very low temperature when operating in a refrigerator. Sufficient heat energy cannot be stored, and the working medium cannot receive sufficient heat energy from the cold storage material. As a result, there has been a problem that a refrigerator incorporating a regenerator filled with the regenerator material cannot reach an extremely low temperature.
[0006]
Therefore, recently, in order to improve the recuperative characteristics at the cryogenic temperature of the regenerator and realize a refrigeration temperature closer to absolute zero, it has a maximum value of volume specific heat particularly in an extremely low temperature region of 20K or less, and Er with a large value₃Ni, ErNi, HoCu₂For example, magnetic regenerators mainly composed of intermetallic compounds composed of rare earth elements and transition metal elements are used. By using such a magnetic regenerator material for a GM refrigerator, refrigeration at 4K is realized.
[0007]
As the above-mentioned refrigerators are actually applied to various cooling systems, it is necessary to stably cool larger-scale objects to be cooled. Improvement is demanded.
[0008]
[Problems to be solved by the invention]
However, in refrigerators that operate at high speed, such as Stirling refrigerators and pulse tube refrigerators, the pressure loss in the regenerator filled with magnetic regenerator particles increases, and sufficient refrigeration capacity cannot be realized. It was. In GM refrigerators, etc., the magnetic particles are damaged or pulverized by the pressure vibration of the high-pressure helium gas that acts during operation of the refrigerator, various stresses, and impact force, and the ventilation resistance of the refrigerant gas is increased. There is a problem that defects such as abrupt decrease are likely to occur.
[0009]
In particular, in the case of a GM refrigerator, the stress due to the reciprocating motion of the displacer (refrigerant compression piston) acts on the cold storage material, and the influence is great. In addition, when the refrigerator is started, the temperature drops in a short time from near room temperature to a cryogenic temperature near 4K, so a large thermal shock acts on the cold storage material.
[0010]
However, in general, magnetic particles exhibit brittleness, mechanical strength is not sufficient, and they are also vulnerable to thermal shock, so the regenerator material breaks down during operation of the refrigerator, or a part of the regenerator material surface peels off. Then, fine powder is generated. This fine powder damages the seal part of the refrigerator, and as a result, there is a problem that the capacity of the refrigerator is significantly reduced in a short operation.
[0011]
  The present invention has been made to solve the above-mentioned problems, and has particularly high strength, low risk of pulverization, excellent thermal shock resistance and durability, and a remarkable refrigeration capacity in a low temperature range for a long time. Cold storage that can be demonstrated overMaterialIt aims at providing the used cool storage type refrigerator etc.
[0012]
[Means for Solving the Problems]
  To achieve the above object, according to the present invention.refrigeratorIsThe regenerator is filled in a refrigerating machine that obtains a lower temperature on the downstream side of the regenerator through heat exchange between the refrigerant gas and the regenerator material filled in the regenerator by flowing the refrigerant gas from the upstream high temperature side of the regenerator. At least some of the regenerator materialA cold storage material consisting of many magnetic particles,The magnetic particles contain a rare earth element and have a particle size of 0.01 to 3 mm;When the area of the projected image on the plane of each magnetic particle is A, and the perimeter of the projected image is L, 4πA / L²The average value of the circularity coefficient R defined by the above is 0.7 or more, and the standard deviation of the circularity coefficient R is 0.1 or less.The decrease in the refrigeration capacity after continuously operating the refrigerator for 1000 hours is 0.02 W or less..
[0013]
In the cold storage material, the magnetic particles preferably include a rare earth element.
[0014]
  In addition, the refrigerator according to the present invention has a lower temperature on the downstream side of the regenerator through heat exchange between the refrigerant gas and the regenerator material filled in the regenerator by flowing the refrigerant gas from the upstream high temperature side of the regenerator. In the obtained refrigerator, at least a part of the regenerator material charged in the regenerator is the present invention.Use inIt is a cold storage material.
[0015]
Furthermore, the MRI (Magnetic Resonance Imaging) device, the superconducting magnet for the magnetic levitation train, the cryopump, and the magnetic field application type single crystal pulling device according to the present invention are all characterized by including the above-described refrigerator according to the present invention. Yes.
[0016]
  The present inventionUse inThe composition of the regenerator material is not particularly limited, but it is preferable that at least a part of the particulate regenerator material contains a rare earth element. Specifically, the particulate regenerator material is
  General formula RMz (1)
  (However, R is at least one rare earth element selected from Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm and Yb, and M is Ni. , Co, Cu, Ag, Al, Ru, In, Ga, Ge, Si, and Rh, and z is an atomic ratio satisfying 0 ≦ z ≦ 9.0.) It is preferable to comprise a rare earth element represented by the formula or an intermetallic compound containing a rare earth element. Of the above cold storage materials, HoCu₂Is particularly preferred.
[0017]
  The present inventionUse inThe regenerator material may be composed of a large number of magnetic particles mainly composed of an oxide having a specific heat peak in an extremely low temperature region of 20K or less. As the oxide constituting the magnetic particles, for example, compositions represented by the following general formulas (2), (3), and (4) can be preferably used.
[0018]
That is, the general formula: RMO₃    (2)
(However, R is at least one rare earth element selected from Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm and Yb, and M is A perovskite-based oxide represented by at least one element selected from Group 3B elements;
General formula: AB₂O₄    ...... (3)
(Wherein A is at least one element selected from group 2B elements, and B is a transition metal element containing at least Cr); and
General formula: CD₂O₆    (4)
An oxide or the like represented by (wherein C is at least one element selected from Mn and Ni, and D is at least one element selected from Nb and Ta) is preferably used.
[0019]
The regenerator material composed of these rare earth element-based magnetic particles has a maximum specific heat of 20K or less, and the value is sufficiently large as the specific heat per unit volume (volume specific heat), so it can reach a much lower temperature. Therefore, the cold storage material is suitable for the present invention.
[0020]
  The present inventionUse inThe average value of the circularity coefficient R of the magnetic particles constituting the cold storage material is set to a range of 0.7 or more. Here, the circularity coefficient R is 4πA / L when the area of the projected image of the magnetic particle on the plane is A and the peripheral length of the projected image is L.²Defined as the value given by.
[0021]
The circularity coefficient R (= 4πA / L²) Is a coefficient representing the degree of roundness of the magnetic particle. The closer the coefficient value is to 1, the closer the particle cross-sectional shape is to a perfect circle. When the particle shape is completely a sphere, the value is 1. It is. However, when a fine protrusion is formed on the surface of a substantially spherical magnetic particle, a certain degree of circularity coefficient R can be obtained, but the vibration and impact force that the protrusion acts during operation of the refrigerator. There is still a high possibility that the seal part of the refrigerator is damaged by acting like the pulverized powder of magnetic particles.
[0022]
The presence or absence of the protrusion is measured as the degree of variation in the circularity coefficient R. Therefore, in the regenerator material according to the present invention, in order to prevent pulverization and increase the mechanical strength and durability, the average value of the circularity coefficient R of a large number of magnetic particles constituting the regenerator material is set to a predetermined value (0.7 ) And the standard deviation of the circularity coefficient R is specified to be 0.1 or less. The standard deviation of the circularity coefficient R is a value indicating variation in the degree of roundness of the magnetic particles, and the smaller the standard deviation, the more uniform the magnetic particle group is.
[0023]
And the structure as a regenerator when the projected image shape on the plane of each magnetic particle is close to a perfect circle, and there are few protrusions and recesses that are the starting point of destruction and the standard deviation is small. The strength is increased, and the durability as an aggregate of magnetic particles in a state where the regenerator is filled is also increased.
[0024]
When the average value of the circularity coefficient R is less than 0.7, the shape of the magnetic particles constituting the regenerator material is irregularly separated from the true spherical state. For this reason, the contact area between the magnetic particles is not constant, it becomes difficult to uniformly fill the regenerator with a high packing density, and the contact efficiency with the refrigerant gas also becomes uneven, so that the efficiency of cold heat exchange is reduced. In addition, the capacity as a refrigerator is reduced. Therefore, the average value of the circularity coefficient R is defined as 0.7 or more, more preferably 0.8 or more, and further preferably 0.9 or more.
[0025]
In addition, the ratio of the magnetic particles having a circularity coefficient R of 0.7 or more to the total magnetic particles constituting the cold storage material is preferably 70% by mass or more. Furthermore, 80 mass% or more is more preferable, and 90 mass% or more is desirable.
[0026]
In addition, the magnetic particles in which the variation in the circularity coefficient R is large so that the standard deviation σ of the circularity coefficient R of the magnetic particles constituting the cold storage material exceeds 0.1 are formed with protrusions or the like that are the starting points of fracture. Is. When such a magnetic particle is filled in a regenerator, a tendency to form a bridge (crosslinked structure) in a spherical magnetic particle is high, and in an aggregate including such a bridged magnetic particle, breakage occurs at the bridge portion. Is likely to occur, and the reliability as a cold storage material is reduced. For this reason, the standard deviation of the circularity coefficient R is defined to be 0.1 or less. However, in order to ensure durability and strength as a cold storage material, the standard deviation is more preferably 0.06 or less, and further 0 0.03 or less is more preferable.
[0027]
The circularity coefficient R of the magnetic particles and the standard deviation σ thereof are obtained by photographing a projected image with an optical microscope in a state where about 100 randomly selected magnetic particles are placed on a flat plate. Can be measured quickly by image processing. As an image processing apparatus for performing the image processing, for example, an image processing apparatus manufactured by Pierce (model number: PIAS-III) can be preferably used.
[0028]
In addition, since the particle size of the magnetic particles constituting the cold storage material has a great influence on the heat transfer characteristics and the like, in the present invention, 70% by weight or more of the whole particle has a particle size of 0.01 to 3 mm. It is preferable to comprise cold storage material particles. Here, the particle diameter referred to in the present invention means the diameter of the smallest sphere that can enclose the particles. If the particle size of the regenerator material particles is less than 0.01 mm, the packing density becomes too high, which may cause an increase in pressure loss. If the particle size exceeds 3.0 mm, the heat transfer area is small. Therefore, the heat transfer efficiency is likely to be lowered. Therefore, when such particles exceed 30% by weight of the whole granules, there is a risk of causing a decrease in cold storage performance. A more preferable particle size is in the range of 0.03 to 1.0 mm. More preferably, it is the range of 0.05-5 mm. The ratio of the particles having a particle size in the range of 0.01 to 3.0 mm in the whole particle is more preferably 80% by weight or more, and still more preferably 90% by weight or more.
[0029]
  Further, the present invention comprising a large number of magnetic particlesUse inIn the cold storage material, the mass ratio of the magnetic particles having two or more cracks having a length of 10 μm or more on the surface of the magnetic particles to the total magnetic particles is preferably 20% or less.
[0030]
If there are a plurality of cracks on the surface of the magnetic particles constituting the cold storage material, the cracks are likely to develop due to vibrations or impact forces acting during the operation of the refrigerator, and the possibility that the particles are destroyed increases. Specifically, when the abundance ratio (number ratio) of magnetic particles in which two or more cracks having a length of 10 μm or more are present on the surface of the magnetic particles exceeds 20%, the fracture ratio of the particles increases. As a result, the generated fine powder damages the seal part of the refrigerator, and the performance of the refrigerator is significantly reduced.
[0031]
Accordingly, the abundance ratio of particles having two or more cracks having a length of 10 μm or more is preferably 20% or less, more preferably 10% or less, and further preferably 5% or less. The crack to be measured is more preferably a crack having a length of 5 μm or more, and more preferably a crack having a length of 3 μm or more.
[0032]
In the regenerator material composed of a large number of magnetic particles, it is preferable that the mass ratio of the magnetic particles having a maximum surface roughness of the magnetic particles of 10 μm or more to the total magnetic particles is defined as 30% or less.
[0033]
When the surface roughness of the magnetic particles is large, stress concentration is likely to occur at the portions where the protrusions and steps are formed, and the particles are destroyed starting from the stress concentration portions. In order to prevent this phenomenon, it is preferable to regulate the ratio of magnetic particles having a maximum height indicating the degree of surface roughness of 10 μm or more to 30% or less. The proportion of particles having the maximum height of 10 μm or more is preferably 20% or less, and more preferably 10% or less. Further, the maximum height of the surface roughness to be evaluated is preferably 5 μm or more, and more preferably 3 μm or more. The surface roughness can be measured in accordance with Japanese Industrial Standard (JIS-B0601) from a cross-sectional curve of the surface texture obtained by photographing the surface texture with observation means such as an electron microscope.
[0034]
  The present inventionUse inThe method for producing the regenerator material is not particularly limited, and the rotating disk method, the rotating electrode method, the gas atomizing method, the water atomizing method, the twin roll method, the single roll method, etc. that are conventionally used when preparing metal powders. It is possible to produce the molten metal by rapid solidification method. In addition, according to the molten metal rapid solidification method, magnetic particles having a relatively high degree of circularity (sphericity) can be obtained. However, depending on manufacturing conditions, magnetic particles having a large variation (standard deviation) in the circularity factor R are formed. It is easy to be done. In this case, shape selection is performed on the magnetic particles obtained as appropriate, and a particle group having a circularity coefficient R and a standard deviation only within a predetermined range is selected as the cold storage material according to the present invention.
[0035]
  In addition, the present inventionUse inThe regenerator material can also be manufactured according to the following powder metallurgy method. For example, raw material powder is mixed using a ball mill to prepare a raw material mixture, and the obtained raw material mixture is tumbled granulated, stirred granulated, extruded, sprayed (sprayed), or pressed. It can manufacture by sintering the obtained spherical molded object after shape | molding (granulation) spherically by the method etc.
[0036]
The raw material powder used in the above production method is desirably a powder having a particle size of 0.3 to 30 μm. A more preferable particle size range is 0.4 to 10 μm, and a particle size range of 0.5 to 8 μm is more preferable.
[0037]
Note that particles formed by various granulation methods such as the rolling granulation method, the stirring granulation method, the extrusion method, and the spraying method (spray method) have a low molding density and are excellent when sintered as they are. It may be difficult to tie.
[0038]
Therefore, in the present invention, the following manufacturing method can be adopted.
[0039]
That is, the raw material powder is granulated to form granulated particles, and the resulting granulated particles are subjected to cold isostatic pressure (CIP) pressure treatment to prepare spherical densified particles, and the obtained dense particles It is also possible to employ a method for manufacturing a regenerator material such as preparing a regenerator material composed of a large number of magnetic particles by sintering the activated particles.
[0040]
In the said manufacturing method, you may implement a hot isostatic pressure (HIP) pressurization process as a sintering process. That is, the density of the compact can be further improved by subjecting the granulated particles to cold isostatic pressing (CIP) treatment or hot isostatic pressing (HIP) treatment. Furthermore, by sintering this high-density molded body, magnetic particles with high density and few cracks and voids can be effectively obtained.
[0041]
Moreover, in the said manufacturing method, it is possible to raise a shaping | molding density more by granulating by adding 5-30 weight% of binders with respect to oxide powder.
[0042]
As the binder, water, ethyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, polyvinyl alcohol, polyvinyl butyral, polyethylene glycol, polyacrylic acid ester and the like can be suitably used.
[0043]
When the amount of the binder added to the raw material powder is too small, less than 5% by weight, the effect of increasing the density by bonding the powders with high strength becomes insufficient. On the other hand, when the addition amount is excessive so as to exceed 30% by weight, the ratio of the regenerator material powder in the molded body becomes excessively low, and the molding density decreases. Therefore, the addition amount of the binder is specified in the range of 5 to 30% by weight.
[0044]
The added binder is removed by degreasing treatment of the molded body after granulation, and further, the cold storage material according to the present invention is prepared by sintering the degreased molded body.
[0045]
As a method for preparing spherical magnetic particles, in addition to the method in which the raw material powder is granulated spherically by the rolling granulation method as described above and then sintered, the following thermal plasma is used to spheroidize It is also possible to adopt a method of
[0046]
That is, a method for producing a regenerator material that prepares a regenerator material composed of a large number of magnetic particles by melting raw material powder through thermal plasma and solidifying it in a spheroidized state by the surface tension of the melt. Can also be adopted.
[0047]
Here, the thermal plasma means a state in which a high-temperature gas is discharged, and can be generated by discharging a gas by a high frequency electromagnetic wave of several MHz to several GHz or a direct current.
[0048]
FIG. 3 shows the configuration of the thermal plasma apparatus. This thermal plasma device 80 is a powder that opens to face a reaction vessel 81, a high-frequency transmitter 82, a coil 83, a plasma generation unit outer cylinder 86, and a plasma frame 85 generated at the top of the reaction vessel 81. A body supply port 86, a carrier gas supply cylinder 88 transported to a reaction container 81 stored in a powder supplier 87, a plasma generating gas source 89, a cyclone 90 for separating generated particles, and a reaction container 81 And a cooling gas source 91 for cooling.
[0049]
In the thermal plasma device 80, the electromagnetic wave transmitted from the high-frequency transmitter 82 is amplified by the coil 83, while high temperature plasma is generated at the top of the reaction vessel 81 by the discharge of the gas supplied from the plasma generating gas source 89. A frame 85 is formed. The gas temperature of the frame portion 85 reaches several thousand degrees Celsius to about 10,000 degrees Celsius. When the raw material powder supplied from the powder supplier 87 together with the carrier gas is put into the plasma flame 85 in a high temperature state, the whole particle or a part including the surface is melted. The melted raw material powder is spheroidized by its surface tension. Then, it is rapidly solidified by the cooling gas supplied from the cooling gas source 91. The generated spherical magnetic particles are separated and collected by the cyclone 90. In this way, at least part of it is melted and spheroidized and rapidly solidified, so there is no crack on the particle surface, the surface is smooth, the surface roughness is small, and there is no void inside Particles are obtained.
[0050]
Even in the case of magnetic particles formed by the powder metallurgy method or the thermal plasma method as described above, depending on the manufacturing conditions, magnetic particles having a large variation (standard deviation) in the circularity coefficient R may be formed. In that case, shape selection may be performed on the obtained magnetic particle group using a shape separation device using an inclined belt conveyor as shown below.
[0051]
That is, the shape separation device has a configuration in which a belt conveyor inclined so that the conveyor belt is driven obliquely upward is arranged in a plurality of stages as necessary, and rolls according to the shapes of the spherical object and the deformed object. A spherical object and a deformed object are separated based on the difference in ease. In addition, a vibration device that attaches vibration to a spherical object and a deformed object, which are objects to be processed, in a direction different from the rolling direction is attached. That is, when a magnetic particle group in which spherical objects and irregular shapes are mixed is supplied onto a conveyor belt driven obliquely upward, spherical magnetic particles having a larger circularity coefficient R and easier to roll roll down on the conveyor belt surface. On the other hand, irregularly shaped magnetic particles having a small circularity coefficient R that are difficult to roll are transported upward by frictional force with the transport belt. Even when the circularity coefficient R is large, the magnetic particles having protrusions on the surface are caught upward between the protrusions and the transport belt and are transported upward. As a result, the spherical object and the deformed object are separated on the lower side and the upper side of the conveyor. In particular, the separation accuracy can be changed by appropriately adjusting the inclination angle of the belt conveyor, the number of arrangement stages, the material of the conveyance belt, the conveyance speed, and the like. By carrying out shape selection using the above-described shape separation device, a group of magnetic particles having the circularity coefficient R defined by the present invention and its standard deviation can be selected as the regenerator material.
[0052]
The regenerator type refrigerator according to the present invention is configured by using a regenerator filled with the regenerator material as at least a part of the regenerator material. In addition, while the regenerator filled with the regenerator material according to the present invention is loaded as the regenerator of the predetermined cooling stage, as the other regenerator, another regenerator material having specific heat characteristics according to its temperature distribution is filled. A regenerator may be used in combination.
[0053]
According to the regenerator material according to the above configuration, the circularity coefficient and standard deviation of the magnetic particles are defined within a predetermined range, so that the mechanical strength and thermal conductivity are high, the thermal shock resistance is excellent, and the pulverization is performed. There is little fear of it. Therefore, even when used as a regenerator material for a refrigerating machine that performs high-speed operation such as a Stirling refrigerating machine or a pulse tube refrigerating machine, a regenerator material that exhibits low pressure loss and stable refrigerating characteristics over a long period of time can be obtained.
And by using the cool storage material as at least a part of the cool storage material of the refrigerator, it is possible to provide a refrigerator having a high refrigeration capacity and capable of maintaining a stable refrigeration performance over a long period of time.
[0054]
The MRI apparatus, the cryopump, the superconducting magnet for the magnetic levitation train, and the magnetic field application type single crystal pulling apparatus all use the refrigerator as described above because the refrigerator performance affects the performance of each device. The MRI apparatus, cryopump, magnetic levitation train superconducting magnet, and magnetic field application type single crystal pulling apparatus of the present invention can all exhibit excellent performance over a long period of time.
[0055]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be specifically described based on the following examples.
[0056]
Examples 1-5
HoCu₂A raw material alloy having the following composition was melted by a high frequency melting method, and the obtained molten alloy was processed by a centrifugal spray quenching method to prepare spherical magnetic particles. The obtained magnetic particles were sieved by a sieving method to obtain magnetic particles having a particle size range as shown in Table 1.
[0057]
  Subsequently, the magnetic particles were supplied onto a conveyor belt of a shape separation device in which three inclined belt conveyors as described above were arranged in series. In order to change the circularity coefficient R and the standard deviation of the magnetic particles obtained at this time, the shape sorting of the magnetic particles is performed by adjusting the inclination angle of the belt conveyor and the belt conveying speed of the shape separation device, Examples 1 to 5 comprising spherical magnetic particlesUse inEach cold storage material was manufactured.
[0058]
  [Example 6]
  Er₃Example 6 was processed under the same conditions as in Example 1 except that a raw material alloy having a composition of Ni was used.Use inA cold storage material was produced.
[0059]
Example 7
Al with an average particle size of 1.5 μm₂O₃Powder and Gd₂O₃The powder was mixed and ground in ethyl alcohol using a ball mill for 24 hours to prepare a raw material mixture. Next, after drying the obtained raw material mixture, it was pre-sintered at a temperature of 1500 ° C. for 12 hours to obtain GdAlO as an oxide sintered body.₃Was synthesized.
[0060]
  Next, the obtained sintered body was further pulverized in ethyl alcohol for 6 hours using a ball mill. The pulverized powder was dried and then granulated using a rolling granulator to prepare granulated particles having a particle size of 0.1 to 0.4 mm. Further, the obtained granulated particles were sintered at a temperature of 1700 ° C. for 12 hours to obtain Example 7 comprising substantially spherical magnetic particles.Use inA cold storage material was produced.
[0061]
Comparative Example 1
On the other hand, except that the magnetic particles prepared by the centrifugal spray quenching method were employed as they were without carrying out the shape fractionation treatment, the treatment was performed under the same conditions as in Example 1 to obtain the cold storage material from the magnetic particle group according to Comparative Example 1. Was prepared.
[0062]
Comparative Example 2
HoCu with an average particle size of 10 μm₂Granulated particles having a particle size of 0.1 to 0.4 mm were prepared by granulating the alloy powder using a rolling granulator. Further, the obtained granulated particles are supplied into a plasma flame generated by the thermal plasma apparatus shown in FIG. 3 and melted, and further rapidly cooled and solidified in a spherical state, so that Comparative Example 2 composed of substantially spherical magnetic particles. The cold storage material which concerns on was manufactured.
[0063]
Comparative Example 3
HoCu with an average particle size of 10 μm₂The cold storage material according to Comparative Example 3 was manufactured by processing the alloy powder by the gas atomization method.
[0064]
  Next, each Example and Comparative Example prepared as described aboveUse inRandomly selecting 100 magnetic particles from the regenerator, taking a projected image with an optical microscope in a state of being placed on a flat glass, and for each of the obtained projected images, an image processing apparatus (Pierce, model number) The circularity coefficient (R) and its standard deviation (σ) were measured by performing image analysis using: PIAS-III). The measurement results are shown in Table 1.
[0065]
Next, in order to evaluate the characteristics of the regenerator material prepared as described above, a two-stage expansion GM refrigerator as shown in FIG. 1 was prepared. The two-stage GM refrigerator 10 shown in FIG. 1 shows an embodiment of the refrigerator of the present invention. A two-stage GM refrigerator 10 shown in FIG. 1 includes a vacuum vessel 13 in which a large-diameter first cylinder 11 and a small-diameter second cylinder 12 connected coaxially to the first cylinder 11 are installed. Have. A first regenerator 14 is disposed in the first cylinder 11 so as to be able to reciprocate, and a second regenerator 15 is disposed in the second cylinder 12 so as to be capable of reciprocating. Seal rings 16 and 17 are disposed between the first cylinder 11 and the first regenerator 14, and between the second cylinder 12 and the second regenerator 15, respectively.
[0066]
The first regenerator 14 accommodates a first regenerator material 18 such as Cu mesh. In the second regenerator 15, a plate-like cryogenic regenerator material used in the regenerator of the present invention is accommodated as the second regenerator material 19. The first regenerator 14 and the second regenerator 15 each have a passage for a working medium (refrigerant gas) such as He gas provided in a gap between the first regenerator 18 and the cryogenic regenerator 19. .
[0067]
A first expansion chamber 20 is provided between the first regenerator 14 and the second regenerator 15. A second expansion chamber 21 is provided between the second regenerator 15 and the tip wall of the second cylinder 12. A first cooling stage 22 is formed at the bottom of the first expansion chamber 20, and a second cooling stage 23 having a temperature lower than that of the first cooling stage 22 is formed at the bottom of the second expansion chamber 21.
[0068]
A high-pressure working medium (for example, He gas) is supplied from the compressor 24 to the two-stage GM refrigerator 10 as described above. The supplied working medium passes between the first regenerators 18 accommodated in the first regenerator 14, reaches the first expansion chamber 20, and is further stored in the second regenerator 15. (Second cool storage material) 19 passes through and reaches the second expansion chamber 21. At this time, the working medium is cooled by supplying heat energy to the regenerator materials 18 and 19. The working medium that has passed between the regenerators 18 and 19 expands in the expansion chambers 20 and 21 to generate cold, and the cooling stages 22 and 23 are cooled. The expanded working medium flows in the opposite direction between the regenerator materials 18 and 19. The working medium is discharged after receiving thermal energy from each of the cold storage materials 18 and 19. As the recuperating effect is improved in such a process, the thermal efficiency of the working medium cycle is improved, and an even lower temperature is realized.
[0069]
  And Examples and Comparative Examples prepared as described aboveUse inEach cold storage material was filled in the second-stage regenerator (inner diameter: 38 mm) of the two-stage expansion GM refrigerator 10 shown in FIG. That is, in Examples 1-5 and Comparative Examples 1-3, each HoCu₂A regenerator material consisting of On the other hand, in Example 6, 200 g of Er is placed on the high temperature side of the regenerator.₃While filling the cold storage material made of Ni, on the low temperature side, 200 g of HoCu prepared in Example 1₂Filled with cold storage material. Further, in Example 7, 200 g of HoCu prepared in Example 1 on the high temperature side.₂While filling cold storage material, the low temperature side is GdAlO₃200 g of cold storage material was filled and the refrigerators according to the examples and comparative examples were assembled and subjected to a refrigeration test, and the refrigeration capacity at 4.2 K was measured.
[0070]
The refrigeration capacity in this example was defined as a heat load when a heat load was applied to the second cooling stage by the heater during the operation of the refrigerator and the temperature increase of the second cooling stage stopped at 4.2K. The refrigeration capacity was measured by both the initial value immediately after the start of operation and the value after 1000 hours of continuous operation. The measurement results are shown in Table 1 below.
[0071]
[Table 1]

[0072]
As is clear from the results shown in Table 1 above, in the cooler filled with the regenerator material of each example composed of a group of magnetic particles prepared with the circularity coefficient R and the standard deviation σ of the magnetic particles in an appropriate range. The initial value of the refrigeration capacity at 4.2 K was high, the refrigeration capacity after 1000 hours of continuous operation was also high, and the refrigeration capacity did not decrease even after long time operation, and stable refrigeration performance could be confirmed. Furthermore, after the operation was completed, the regenerator was disassembled, the regenerator material was taken out and the appearance was observed, but generation of broken magnetic particles and fine powder was not observed.
[0073]
On the other hand, in the refrigerator filled with the regenerator material according to each comparative example, in which at least one of the circularity coefficient R of the magnetic particles and the standard deviation σ thereof is outside the range defined in the present invention, The initial value of the refrigerating capacity at 2K was lower than that of the example. In addition, the refrigeration capacity after 1000 hours of continuous operation was significantly reduced, and the refrigeration performance was significantly reduced. Furthermore, when the regenerator material was taken out from the regenerator after the operation was completed and the appearance was observed, generation of finely broken particles and fine powder was observed.
And it was also confirmed that the seal part of some refrigerators was damaged.
[0074]
As is clear from the above examples and comparative examples, according to the refrigerator using the regenerator material according to each example in which the average value of the circularity coefficient R and the standard deviation thereof are properly defined, the regenerator material during operation It is possible to realize a refrigerator capable of maintaining a stable refrigeration capacity over a long period of time.
[0075]
  In each of the embodiments described above, the present inventionUse inAlthough the example which applied the cool storage material to GM refrigerator is shown, this inventionUse inThe regenerator material can also be applied to a pulse tube refrigerator 70 as shown in FIG.
[0076]
FIG. 2 shows the basic configuration of a single-stage pulse tube refrigerator. The greatest structural feature of the pulse tube refrigerator 70 is that it does not have a reciprocating piston for generating cold, which is essential in the GM refrigerator described above. For this reason, it has an advantage of excellent mechanical reliability and low vibration, and is particularly expected as an element and a sensor cooling refrigerator.
[0077]
The pulse tube refrigerator 70 is a kind of a regenerative refrigerator, and generally helium gas is used as a refrigerant gas. As a basic configuration, the refrigerator includes, in addition to the regenerator 1, a pressure vibration source 71 that compresses helium gas, and a phase adjustment mechanism 72 that controls a time difference between pressure fluctuation and position fluctuation (displacement) of the refrigerant gas.
[0078]
In the GM refrigerator and Stirling refrigerator, the phase adjusting mechanism 72 is a reciprocating piston mechanism disposed in the low temperature portion, whereas in the pulse tube refrigerator 70, it is disposed in the room temperature portion, and the regenerator The low temperature end of 1 and the phase adjustment mechanism 72 in the room temperature portion are connected by a pipe called a pulse tube, and the phase of the pressure wave of the refrigerant gas is remotely controlled. Entropy exchange between the refrigerant gas and the regenerator material due to pressure fluctuation proceeds at an appropriate timing of the displacement, so that entropy is sequentially pumped in one direction, and in the low-temperature part of the regenerator 1, lower temperature cold heat Is obtained.
[0079]
Next, examples of a superconducting MRI apparatus using a regenerative refrigerator according to the present invention, a superconducting magnet for a magnetic levitation train, a cryopump, and a magnetic field application type single crystal pulling apparatus will be described.
[0080]
FIG. 4 is a cross-sectional view showing a schematic configuration of a superconducting MRI apparatus to which the present invention is applied.
A superconducting MRI apparatus 30 shown in FIG. 4 includes a superconducting static magnetic field coil 31 that applies a spatially uniform and temporally stable static magnetic field to a human body, and a correction coil that is not shown to correct nonuniformity of the generated magnetic field. A gradient magnetic field coil 32 that applies a magnetic field gradient to the measurement region, a radio wave transmission / reception probe 33, and the like. In addition, as described above, the regenerative refrigerator 34 according to the present invention is used for cooling the superconducting static magnetic field coil 31. In the figure, 35 is a cryostat, and 36 is a radiation heat shield.
[0081]
In the superconducting MRI apparatus 30 using the regenerative refrigerator 34 according to the present invention, the operating temperature of the superconducting static magnetic field coil 31 can be assured stably over a long period of time. A stable static magnetic field can be obtained over a long period of time. Therefore, the performance of the superconducting MRI apparatus 30 can be exhibited stably over a long period of time.
[0082]
FIG. 5 is a perspective view showing a schematic configuration of a main part of a superconducting magnet for a magnetic levitation train using a regenerative refrigerator according to the present invention, and shows a portion of a superconducting magnet 40 for a magnetic levitation train. A superconducting magnet 40 for a magnetic levitation train shown in FIG. 5 includes a superconducting coil 41, a liquid helium tank 42 for cooling the superconducting coil 41, a liquid nitrogen tank 43 for preventing volatilization of the liquid helium tank, and a regenerative type according to the present invention. It is comprised by the refrigerator 44 grade | etc.,. In the figure, 45 is a laminated heat insulating material, 46 is a power lead, and 47 is a permanent current switch.
[0083]
In the superconducting magnet 40 for a magnetically levitated train using the regenerative refrigerator 44 according to the present invention, the operating temperature of the superconducting coil 41 can be assured stably over a long period of time. A necessary magnetic field can be stably obtained over a long period of time. In particular, the superconducting magnet 40 for a magnetic levitation train acts on acceleration, but the regenerative refrigerator 44 according to the present invention can maintain excellent refrigeration capacity over a long period of time even when acceleration acts, so that the magnetic field strength, etc. Greatly contribute to the long-term stabilization of Therefore, the magnetic levitation train using such a superconducting magnet 40 can exhibit its reliability over a long period of time.
[0084]
FIG. 6 is a cross-sectional view showing a schematic configuration of a cryopump using the regenerative refrigerator according to the present invention. A cryopump 50 shown in FIG. 6 includes a cryopanel 51 that condenses or adsorbs gas molecules, a regenerator chiller 52 according to the present invention that cools the cryopanel 51 to a predetermined cryogenic temperature, and a shield provided therebetween. 53, a baffle 54 provided at the intake port, and a ring 55 for changing the exhaust speed of argon, nitrogen, hydrogen or the like.
[0085]
In the cryopump 50 using the regenerative refrigerator 52 according to the present invention, the operating temperature of the cryopanel 51 can be stably guaranteed over a long period of time. Therefore, the performance of the cryopump 50 can be exhibited stably over a long period of time.
[0086]
FIG. 7 is a perspective view showing a schematic configuration of a magnetic field application type single crystal pulling apparatus using a regenerative refrigerator according to the present invention. A magnetic field application type single crystal pulling device 60 shown in FIG. 7 includes a raw material melting crucible, a heater, a single crystal pulling unit 61 having a single crystal pulling mechanism, a superconducting coil 62 for applying a static magnetic field to the raw material melt, and It is constituted by an elevating mechanism 63 of the single crystal pulling unit 61 or the like. Then, as described above, the regenerative refrigerator 64 according to the present invention is used for cooling the superconducting coil 62. In the figure, 65 is a current lead, 66 is a heat shield plate, and 67 is a helium vessel.
[0087]
In the magnetic field application type single crystal pulling apparatus 60 using the regenerative refrigerator 64 according to the present invention, the operating temperature of the superconducting coil 62 can be stably guaranteed over a long period of time. A good magnetic field that suppresses the convection can be obtained over a long period of time. Therefore, the performance of the magnetic field application type single crystal pulling apparatus 60 can be exhibited stably over a long period of time.
[0088]
【The invention's effect】
  As described above, the present inventionUse inAccording to the cold storage material, the circularity coefficient and the standard deviation of the magnetic particles are defined within a predetermined range, so that the mechanical strength and thermal conductivity are high, the thermal shock resistance is excellent, and there is a risk of pulverization. Few. Therefore, even when used as a regenerator material for a refrigerating machine that performs high-speed operation such as a Stirling refrigerating machine or a pulse tube refrigerating machine, a regenerator material that exhibits low pressure loss and exhibits stable refrigerating characteristics over a long period of time can be obtained. And by using the cold storage material as a cold storage material of at least a part of the refrigerator, it is possible to provide a refrigerator having a high refrigeration capacity and capable of maintaining a stable refrigeration performance over a long period of time.
[0089]
The MRI apparatus, the cryopump, the superconducting magnet for the magnetic levitation train, and the magnetic field application type single crystal pulling apparatus all use the refrigerator as described above because the refrigerator performance affects the performance of each device. The MRI apparatus, cryopump, magnetic levitation train superconducting magnet, and magnetic field application type single crystal pulling apparatus of the present invention can all exhibit excellent performance over a long period of time.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a main configuration of a regenerative refrigerator (GM refrigerator).
FIG. 2 is a diagram schematically showing an element configuration and a temperature distribution of a pulse tube refrigerator.
FIG. 3 is a diagram showing a configuration of a thermal plasma apparatus.
FIG. 4 is a cross-sectional view showing a schematic configuration of a superconducting MRI apparatus according to an embodiment of the present invention.
FIG. 5 is a perspective view showing a schematic configuration of a main part of a superconducting magnet (for a magnetic levitation train) according to an embodiment of the present invention.
FIG. 6 is a cross-sectional view showing a schematic configuration of a cryopump according to an embodiment of the present invention.
FIG. 7 is a perspective view showing a schematic configuration of a main part of a magnetic field application type single crystal pulling apparatus according to an embodiment of the present invention.
[Explanation of symbols]
1 Regenerator
10 GM refrigerator (cool storage type refrigerator)
11 First cylinder
12 Second cylinder
13 Vacuum container
14 1st regenerator
15 Second regenerator
16, 17 Seal ring
18 First heat storage material
19 Second heat storage material (cold storage material for cryogenic temperature)
20 First expansion chamber
21 Second expansion chamber
22 First cooling stage
23 Second cooling stage
24 Compressor
30 Superconducting MRI system
31 Superconducting static magnetic field coil
32 Gradient coil
33 Probe for radio wave transmission / reception
34 Regenerative refrigerator
35 Cryostat
36 Radiation insulation shield
40 Superconducting magnet
41 Superconducting coil
42 Liquid helium tank
43 Liquid nitrogen tank
44 Regenerative refrigerator
45 Laminated insulation
46 Power Lead
47 Permanent current switch
50 cryopump
51 Cryopanel
52 Regenerative refrigerator
53 Shield
54 Baffle
55 ring
60 Magnetic field application type single crystal pulling device
61 Single crystal pulling part
62 Superconducting coil
63 Lifting mechanism
64 Cold storage type refrigerator
65 Current lead
66 Heat shield plate
67 Helium container
70 Pulse tube refrigerator
71 Pressure vibration source
72 Phase adjustment mechanism
80 Thermal plasma device
81 reaction vessel
82 High frequency transmitter
83 coils
84 Outer cylinder of plasma generation
85 Plasma flame
86 Powder supply port
87 Powder feeder
88 Carrier gas supply cylinder
89 Gas source for plasma generation
90 Cyclone
91 Cooling gas source

Claims (7)

The regenerator is filled in a refrigerating machine that obtains a lower temperature on the downstream side of the regenerator through heat exchange between the refrigerant gas and the regenerator material filled in the regenerator by flowing the refrigerant gas from the upstream high temperature side of the regenerator. At least a part of the regenerator material is a regenerator material composed of a large number of magnetic particles , the magnetic particles contain a rare earth element, and have a particle size of 0.01 to 3 mm . When the area of the projected image is A and the peripheral length of the projected image is L, the average value of the circularity coefficient R defined by 4πA / L ² is 0.7 or more, and the circularity coefficient R Refrigeration machine using a regenerator material having a standard deviation of 0.1 or less, wherein the reduction in refrigeration capacity after continuous operation of the refrigerator for 1000 hours is 0.02 W or less . The refrigerator according to claim 1, wherein the refrigerator is a GM refrigerator. The refrigerator according to claim 1, wherein the refrigerator is a pulse tube refrigerator. A superconducting magnet comprising the refrigerator according to claim 1 . An MRI (nuclear magnetic resonance imaging) apparatus comprising the refrigerator according to claim 1 . A cryopump comprising the refrigerator according to claim 1 . A magnetic field application type single crystal pulling apparatus comprising the refrigerator according to claim 1 .

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