Patent Publication Number: US-2016223228-A1

Title: Regenerator and stirling cryocooler

Description:
RELATED APPLICATIONS 
     Priority is claimed to Japanese Patent Application No. 2015-015234, filed Jan. 29, 2015, the entire content of which is incorporated herein by reference. 
     BACKGROUND 
     1. Technical Field 
     Certain embodiments of the invention relate to a regenerator and a Stirling cryocooler. 
     2. Description of Related Art 
     For the regenerator elements in cryogenic refrigerators such as Stirling cryocoolers, a plurality of laminated wire-mesh sheets are sometimes used. The regenerator elements are packed into a container, which is then fitted into the refrigerator. 
     SUMMARY 
     According to an aspect of the present invention, there is provided a regenerator including an axially extending regenerator-element container, and a regenerator-element laminated structure accommodated in the regenerator-element container. The regenerator-element laminated structure includes a plurality of first regenerator-element members axially stacked in layers, and each extending along a plane perpendicular to the axis of regenerator extension. The plurality of first regenerator-element members each include a rim portion extending in a direction not lying in said plane, such as to fill a gap between the regenerator-element container and the regenerator-element laminated structure. 
     According to another aspect of the present invention, there is provided a Stirling cryocooler, furnished with: an axially extending displacer; and a regenerator arranged surrounding the displacer such as to guide axially reciprocating travel of the displacer. The regenerator includes a container inner cylinder extending axially and guiding the reciprocating travel of the displacer, a container outer cylinder extending axially and forming an accommodation space between the container inner and outer cylinders, and a regenerator-element laminated structure accommodated in the accommodation space. The regenerator-element laminated structure include a plurality of first regenerator-element members axially stacked in layers, and each extending along a plane perpendicular to the axis of regenerator extension. The plurality of first regenerator-element members each include an inner rim portion extending in a direction not lying in said plane, and an outer rim portion extending in a direction not lying in said plane, such as to fill an inner gap between the container inner cylinder and the regenerator-element laminated structure, and such as to fill an outer clearance between the container outer cylinder and the regenerator-element laminated structure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a view schematically showing a Stirling cryocooler according to a first embodiment of the present invention. 
         FIG. 2  is a view schematically showing an expander according to the first embodiment of the present invention. 
         FIG. 3  is a sectional view schematically showing a regenerator of a Stirling cryocooler. 
         FIG. 4  is a sectional view schematically showing a regenerator according to the first embodiment of the present invention. 
         FIG. 5  is a top view schematically showing a regenerator material member of the regenerator according to the first embodiment of the present invention. 
         FIG. 6  is a sectional view schematically showing a regenerator according to a second embodiment of the present invention. 
         FIG. 7  is a sectional view schematically showing a regenerator according to a third embodiment of the present invention. 
         FIG. 8  is a sectional view schematically showing a regenerator according to a fourth embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Due to a manufacturing tolerance, a slight gap may occur between regenerator materials and a vessel. The gap may be a passage of working gas. If the working gas flows to the gap, heat exchange between the regenerator materials and the working gas is not effectively performed. Accordingly, efficiency of a regenerator decreases. 
     It is desirable to decrease the gap between the regenerator materials and the vessel in the regenerator of a cryocooler. 
     In addition, certain embodiments of the invention include arbitrary combination of the above-described components, or components or expressions of the present invention which are replaced to each other between methods, devices, systems, or the like. 
     According to certain embodiment of the invention, it is possible to decrease a gap between a regenerator material and a vessel in a regenerator in a cryocooler. 
     It should be understood that the invention is not limited to the above-described embodiment, but may be modified into various forms on the basis of the spirit of the invention. Additionally, the modifications are included in the scope of the invention. 
     Hereinafter, certain embodiments of the invention will be described in detail with reference to the drawings. In addition, in descriptions thereof, the same reference numerals are assigned to the same elements, and overlapping descriptions are appropriately omitted. In addition, configurations described below are exemplified, and do not limit a scope of the present invention. 
       FIG. 1  is a view schematically showing a Stirling cryocooler  10  according to a first embodiment of the present invention. The Stirling cryocooler  10  includes a compressor  11 , a connection pipe  12 , and an expander  13 . 
     The compressor  11  includes a compressor case  14 . The compressor case  14  is a pressure vessel which is configured so as to airtightly hold a high-pressure working gas. For example, the working gas is helium gas. In addition, the compressor  11  includes a compressor unit which is accommodated in the compressor case  14 . The compressor unit includes a compressor piston and a compressor cylinder, one of the compressor piston and the compressor cylinder is a movable member  15  which is configured so as to reciprocate in the compressor case  14 , and the other is a stationary member which is fixed to the compressor case  14 . The compressor unit includes a drive source for driving the movable member  15  with respect to the compressor case  14  in a direction along the center axis of the movable member  15 . The compressor  11  includes a support portion  16  which supports movable member  15  to the compressor case  14  such that the movable member  15  can reciprocate. The movable member  15  is vibrated with respect to the compressor case  14  and the stationary member at certain amplitude and a frequency. As a result, a pressure of the working gas inside the compressor  11  is changed at specific amplitude and a specific frequency. 
     A working gas chamber is formed between the compressor piston and the compressor cylinder. The working gas chamber is connected to one end of the connection pipe  12  via communication passages which are formed in the above-described stationary member and the compressor case  14 . The other end of the connection pipe  12  is a working gas chamber of the expander  13 . Accordingly, the working gas chamber of the compressor  11  and the working gas chamber of the expander  13  are connected to each other by the connection pipe  12 . 
     As described below with reference to  FIG. 2 , the expander  13  includes an expander main body  20 , a displacer  22 , and at least one support portion  40 . 
       FIG. 2  is a view schematically showing the expander  13  according to the first embodiment of the present invention.  FIG. 2  schematically shows an inner structure of the expander  13 . 
     The expander main body  20  is a pressure vessel which is configured so as to airtightly hold a high-pressure working gas. The pressure vessel may be configured of a plurality of vessel portions which are connected to each other so as to airtightly hold the inner portion of the pressure vessel. The displacer  22  is a movable member which is configured so as to reciprocate in the expander main body  20 . The support portion  40  supports the displacer  22  to the expander main body  20  such that the displacer  22  can reciprocate. 
     The expander main body  20  includes a first section  24  and a second section  26 . The first section  24  is an expansion space  28  of working gas which is formed between the expander main body  20  and the displacer  22 . A cooling stage  29  for cooling an object is provided on the portion of the expander main body  20  adjacent to the expansion space  28 . The second section  26  is configured so as to support the displacer  22  to the expander main body  20  via elastic members  30 . 
     In the expander main body  20 , a portion of the first section  24  side is accommodated in a vacuum vessel (not shown). A vacuum layer inside the vacuum vessel and an atmospheric layer outside the vacuum vessel are separated from each other by a flange  47 . 
     The second section  26  is adjacent to the first section  24  in a reciprocation direction (shown by arrow C in  FIG. 1 ) of the displacer  22 . A seal portion  25  is provided between first section  24  and the second section  26 . Accordingly, the second section  26  is partitioned from the first section  24 . Accordingly, pressure variation of the working gas in the first section  24  is not transmitted to the second section  26 , or does not substantially influence the pressure of the working gas in the second section  26 . In addition, the same kind of gas as the working gas is sealed in the second section  26  such that the second section  26  has the same pressure as an average pressure of the working gas fed from the compressor  11 . 
     The displacer  22  includes a displacer head  32  which is accommodated in the first section  24 , and a displacer rod  34 . The displacer rod  34  is a shaft portion which is thinner than the displacer head  32 . The displacer  22  has a center axis (shown by a chain line A in  FIG. 1 ) which is parallel to the reciprocation direction, and the displacer head  32  and the displacer rod  34  are coaxially provided in the center axis of the displacer  22 . The displacer  22  is an inner space, and the inner space is filled with the same kind of gas as the working gas. 
     The displacer rod  34  extends from the displacer head  32  to the second section  26  via the seal portion  25 . The displacer rod  34  is supported by the expander main body  20  in the second section  26  such that the displacer  22  can reciprocate. For example, the above-described seal portion  25  may be a rod seal which is formed between the displacer rod  34  and the expander main body  20 . In addition, similarly to the displacer head  32 , the displacer rod  34  also has an inner space. The displacer rod  34  is connected to the displacer head  32 , and communicates with the inner spacer of the displacer head  32 . 
     The first section  24  forms a cylinder portion which surrounds the displacer head  32 . The expansion space  28  is formed between a bottom surface of the cylinder portion and a tip surface of the displacer head  32 . The expansion space  28  is formed on a side opposite to a joining portion between the displacer head  32  and the displacer rod  34  in the reciprocation direction of the displacer  22 . A gas space  36  which is connected to the connection pipe  12  is formed between the joining portion and the seal portion  25 . 
     A regenerator  38  is attached to the side surface of the cylinder portion of the expander main body  20  so as to be positioned on the outer circumferential portion of the displacer head  32 . More specifically, the regenerator  38  is provided on the side surface of the cylinder portion of the expander main body  20  so as to be positioned at a cylindrical region which has a longitudinal axis of the displacer  22  as the center axis in the outer circumferential portion of the displacer head  32 . For example, the regenerator  38  has a laminated structure of wire meshes. The flow of the working gas between the expansion space  28  and the gas space  36  can be performed through the regenerator  38 . 
     A water cooling type heat exchanger  37  can be provided between the regenerator  38  and the gas space  36 . The water cooling type heat exchanger  37  cools the working gas supplied from the compressor  11  and realizes heat exchange for discharging the heat from working gas to the outside of the expander  13 . In addition, a low-temperature heat exchanger  39  is attached to a portion between the regenerator  38  and the cooling stage  29 . 
     In the expander  13 , expander main body  20  supports the displacer  22  at a plurality of different positions in the reciprocation direction of the displacer  22  such that the displacer  22  can reciprocate. Accordingly, the expander  13  includes two support portions  40 . The two support portions  40  are provided in the second section  26 . Therefore, it is possible to prevent tilting of the displacer  22  with respect to the center axis. 
     The support portion  40  includes the above-described elastic member  30 . The elastic member  30  is disposed between the displacer rod  34  and the expander main body  20  such that an elastic restoring force is applied to the displacer  22  when the displacer  22  is displaced from a neutral position. Accordingly, the displacer  22  reciprocates at a natural frequency which is determined from an elastic coefficient of the elastic member  30 , an elastic coefficient due to the pressure of the working gas, and weight of the displacer  22 . 
     For example, the elastic member  30  has a spring mechanism which includes at least one plate spring. The plate spring is a spring referred to as a flexure spring, and the plate spring is flexible in the reciprocation direction of the displacer  22  and is rigid in a direction perpendicular to the reciprocation direction. Therefore, the movement of the displacer  22  along the direction along the center axis is allowed by the elastic member  30 . However, the movement of the displacer  22  in the direction orthogonal to the center axis is regulated by the elastic member  30 . The displacer rod  34  is fixed to the elastic member  30  via an elastic member attachment portion  51 . 
     In this way, a vibration system including the displacer  22  and the elastic member  30  is configured. The vibration system is configured such that the displacer  22  is vibrated so as to have the vibration and the phase difference at the same frequency as the vibration of the movable member  15  of the compressor  11 . The displacer  22  is driven by pulsation of a working gas pressure generated by the vibration of the movable member  15  of the compressor  11 . A reverse Stirling cycle is formed between the expansion space  28  and the working gas chamber of the compressor  11  by reciprocation of the displacer  22  and the movable member  15  of the compressor  11 . Accordingly, the cooling stage adjacent to the expansion space  28  is cooled, and it is possible to cool an object by the Stirling cryocooler  10 . 
     Subsequently, a regenerator material lamination structure of the Stirling cryocooler  10  according the first embodiment will be described. 
       FIG. 3  is a sectional view schematically showing a regenerator  138  of a Stirling cryocooler. In  FIG. 3 , the displacer is not shown, and the center axis is shown by a chain line. The regenerator  138  is disposed so as to be coaxial with the center axis of the displacer. 
     The regenerator  138  includes a regenerator material vessel  152  which has a vessel outer cylinder  154  and a vessel inner cylinder  156 . The vessel inner cylinder  156  functions as a cylinder which guides the displacer. A regenerator material laminated body  158  is accommodated between the vessel outer cylinder  154  and the vessel inner cylinder  156 . The regenerator material laminated body  158  is formed of a plurality of wire mesh members  160  which are laminated in the axial direction. Each of the wire mesh member  160  extends along a plane perpendicular to the axial direction. A pair of holders  162  is provided on both ends of the regenerator material laminated body  158  in the axial direction. The wire mesh member  160  has an annular shape or a doughnut shape. Similarly, the holder  162  also has an annular shape or a doughnut shape. 
     In general, the wire mesh members  160  are completely embedded to a space inside the regenerator material vessel  152 , and the sizes of the wire mesh members  160  are determined such that a gap is not generated between the regenerator material vessel  152  and the regenerator material laminated body  158 . However, in actual, as shown in the drawing, a slight gap is generated between the regenerator material laminated body  158  and the regenerator material vessel  152 . An outer gap  164   a  is generated between the vessel outer cylinder  154  and the regenerator material laminated body  158 , and an inner gap  164   b  is generated between the vessel inner cylinder  156  and the regenerator material laminated body  158 . The gap is generated due to the manufacturing tolerance of the wire mesh member  160 . The gap may be a passage of the working gas. If the working gas flows along the gap, heat exchange between the working gas and the regenerator material is not effectively performed. Accordingly, efficiency of the regenerator  138  decreases. Even when a slight gap is generated, performance of the regenerator  138  significantly decreases. 
     Accordingly, the regenerator  38  according to the first embodiment is configured so as to decrease or completely remove the gap between the regenerator material and the vessel. 
       FIG. 4  is a sectional view schematically showing the regenerator  38  according to the first embodiment of the present invention. In  FIG. 4 , the displacer  22  shown in  FIG. 2  is not shown, and similarly to  FIG. 2 , the center axis of the displacer  22  is shown by the chain line A. The displacer  22  extends in the axial direction. The regenerator  38  is disposed so as to be coaxial with the center axis of the displacer  22 . The regenerator  38  is disposed around the displacer  22  so as to guide the reciprocation of the displacer  22  in the axial direction. The upper portion in  FIG. 4  is a low temperature portion of the Stirling cryocooler  10 , and the lower portion is a normal temperature portion. Accordingly, the expansion space  28  shown in  FIG. 2  is formed above the regenerator  38  in  FIG. 2 . 
     The regenerator  38  includes a regenerator material vessel  52 , and a regenerator material laminated body  58  which is accommodated in the regenerator material vessel  52 . The regenerator material vessel  52  is an annular or a doughnut-shaped vessel which includes a vessel outer cylinder  54  and a vessel inner cylinder  56 . The vessel outer cylinder  54  extends in the axial direction, and forms an accommodation space of the regenerator material laminated body  58  between the vessel inner cylinder  56  and the vessel outer cylinder  54 . The vessel inner cylinder  56  extends in the axial direction, and functions as a cylinder portion which guides the reciprocation of the displacer  22 . 
     The regenerator material laminated body  58  is formed of a plurality of regenerator material members  60  which are laminated in the axial direction. Each of the regenerator material members  60  extends along a plane perpendicular to the axial direction. The regenerator material member  60  is a wire mesh member having an annular shape or a doughnut shape. 
     A pair of holders  62  is provided on both ends of the regenerator material laminated body  58  in the axial direction. One holder  62  is disposed on the low temperature portion, and the other holder  62  is disposed on the normal temperature portion. Similarly to the regenerator material member  60 , the holder  62  also has an annular shape or a doughnut shape. The pair of holder  62  clamps the regenerator material laminated body  58  from both ends in the axial direction so as to compress and hold the regenerator material laminated body  58  in the axial direction. The reason of compressing and holding the regenerator material is to prevent a positional variation of the regenerator material due to a flow of the working gas. In this way, the plurality of regenerator material members  60  which form the regenerator material laminated body  58  are fixed between the pair of holder  62 . 
       FIG. 5  is a top view schematically showing the regenerator material member  60  of the regenerator  38  according to the first embodiment of the present invention. Each of the regenerator material members  60  includes an outer rim portion  60   a  and an inner rim portion  60   b.  The outer rim portion  60   a  is formed on the outer circumference of the regenerator material member  60 , and the inner rim portion  60   b  is formed on the inner circumference of the regenerator material member  60 . The regenerator material member  60  includes a center flat portion  60   c  between the outer rim portion  60   a  and the inner rim portion  60   b.    
     The center flat portion  60   c  is annular region which occupies most of the wire mesh member which is the regenerator material member  60 , and extends along a plane perpendicular to the axial direction. The outer rim portion  60   a  is a ring-shaped portion which extends toward the outside in the radial direction from the center flat portion  60   c,  and forms a portion of the wire mesh member. The inner rim portion  60   b  is a ring-shaped portion which extends toward the inside in the radial direction from the center flat portion  60   c,  and forms a portion of the wire mesh member. In  FIG. 5 , a boundary line between the outer rim portion  60   a  and the center flat portion  60   c  is shown by a broken line. In addition, a boundary line between the inner rim portion  60   b  and the center flat portion  60   c  is shown by a broken line. 
     As shown in  FIG. 4 , each of the outer rim portions  60   a  and the inner rim portions  60   b  is formed in a curved shape (for example, a round shape or a tapered shape). The outer rim portion  60   a  extends from the center flat portion  60   c  in a direction (for example, axial direction) other than the direction of the plane perpendicular to the axial direction. The outer rim portion  60   a  comes into contact with the vessel outer cylinder  54 . Accordingly, an outer gap which is generated between the vessel outer cylinder  54  and the regenerator material laminated body  58  is filled with the outer rim portions  60   a.  Similarly, the inner rim portion  60   b  extends from the center flat portion  60   c  in a direction (for example, axial direction) other than the direction of the plane perpendicular to the axial direction. The inner rim portion  60   b  comes into contact with the vessel inner cylinder  56 . Accordingly, an inner gap which is generated between the vessel inner cylinder  56  and the regenerator material laminated body  58  is filled with the inner rim portions  60   b.    
     The size of outer rim portion  60   a  and/or the inner rim portion  60   b  may be significantly smaller than the size of the regenerator material member  60 . For example, a width in the radial direction and/or a height in the axial direction of the outer rim portion  60   a  and/or the inner rim portion  60   b  may be smaller than 1/10, 1/30, 1/50, or 1/100 of a width (for example, diameter) in the radial direction of the regenerator material member  60 . The width in the radial direction and/or the height in the axial direction of the outer rim portion  60   a  and/or the inner rim portion  60   b  may be less than 1 mm, 0.5 mm, or 0.1 mm. 
     A surface of the holder  62  which comes into contact with the regenerator material member  60  has a curved shape corresponding to the curved shape of the regenerator material member  60  so as to receive the regenerator material member  60 . Each of the pair of holders  62  includes an outer edge portion  63   a  which has a curved shape corresponding to the outer rim portion  60   a,  and an inner edge portion  63   b  which has a curved shaped corresponding to the inner rim portion  60   b.  In addition, each of the pair of holders  62  has a center portion  63   c  which is formed in a flat shape corresponding to the center flat portion  60   c . The holder  62  of the low temperature portion and the holder  62  of the normal temperature portion have shapes complementary to each other. Accordingly, the holder  62  of the low temperature portion can receive the holder  62  of the normal temperature portion. 
     The regenerator material member  60  has a slightly larger size than a size of a sectional area of the accommodation space in the regenerator material vessel  52  on the plane perpendicular to the axial direction. A length in the radial direction of the regenerator material member  60  is slightly longer than a length in the radial direction of the annular region or the doughnut-shaped region in the section of the regenerator material vessel  52 . Accordingly, in assembly work of the regenerator  38 , when the regenerator material members  60  are incorporated into the regenerator material vessel  52 , the outer circumferences and the inner circumferences of the regenerator material members  60  are curved by contact with the regenerator material vessel  52 , and the outer rim portions  60   a  and the inner rim portions  60   b  are formed. Since the regenerator material members  60  are laminated, and compressed and held by the holders  62 , the curved shapes formed on the outer rim portions  60   a  and the inner rim portions  60   b  are held. Accordingly, it is possible to effectively remove both the inner gap and the outer gap generated in the annular regenerator  38 . 
     Alternatively, the outer rim portions  60   a  and the inner rim portions  60   b  may be formed in advance. Before the assembly work of the regenerator  38 , the outer rim portions  60   a  and the inner rim portions  60   b  may be formed by rolling the wire mesh members. 
     Accordingly, in the regenerator  38 , it is possible to remove the gap generated between the regenerator material vessel  52  and the regenerator material laminated body  58 . Therefore, it is possible to prevent performance of the regenerator  38  from decreasing due to the flow of the working gas into the gap. 
       FIG. 6  is a sectional view schematically showing the regenerator  38  according to a second embodiment of the present invention. In the second embodiment, the lamination structure of the regenerator materials is different from that of the first embodiment. The others of the second embodiment are similar to the first embodiment. In descriptions below, in order to avoid redundant descriptions, descriptions with respect to the similar portions are appropriately omitted. 
     The regenerator material laminated body  58  includes at least one second regenerator material member  68  which is laminated in the axial direction along with the first regenerator material members  60 . The second regenerator material member  68  is alternately laminated with one or more (for example, ten or more) first regenerator material members  60 . The plurality of second regenerator material members  68  may be alternately laminated with one or more first regenerator material members  60 . 
     The second regenerator material member  68  is disposed between the inner rim portion  60   b  and the outer rim portion  60   a  of the first regenerator material member  60 . The second regenerator material member  68  has the shape corresponding to the center flat portion  60   c  of the first regenerator material member  60 . Accordingly, the second regenerator material member  68  extends along the plane perpendicular to the axial direction, and does not include a rim portion. Since the second regenerator material member  68  does not include the rim portion, the diameter dimension of the second regenerator material member  68  is smaller than that of the first regenerator material member  60 . 
     It is possible to press the center flat portion  60   c  of the first regenerator material member  60  by the second regenerator material member  68 . Since the first regenerator material members  60  and the second regenerator material member  68  are alternately laminated with each other, it is possible to laminate the plurality of first regenerator material members  60  in parallel to the plane perpendicular to the axial direction. 
       FIG. 7  is a sectional view schematically showing the regenerator  38  according to a third embodiment of the present invention. In the third embodiment, the regenerator material is different from that of the first embodiment. The others of the third embodiment are similar to the first embodiment. In descriptions below, in order to avoid redundant descriptions, descriptions with respect to the similar portions are appropriately omitted. 
     In the third embodiment, the regenerator material member is a felt-shaped sintered metal body  70 . Accordingly, the regenerator material laminated body  58  is formed of a plurality of sintered metal bodies  70  which are laminated in the axial direction. Each of the sintered metal bodies  70  extends along the plane perpendicular to the axial direction. The sintered metal body  70  has an annular shape or a doughnut shape. A thickness in the axial direction of the sintered metal body  70  is thicker than the thickness in the axial direction of the regenerator material member  60  in the first embodiment. 
     Similarly to the regenerator material member  60  in the embedment, the felt-shaped sintered metal body  70  includes an outer rim portion  70   a,  an inner rim portion  70   b,  and a center flat portion  70   c.  The center flat portion  70   c  is annular region which occupies most of the sintered metal body  70 , and extends along a plane perpendicular to the axial direction. The outer rim portion  70   a  extends toward the outside in the radial direction from the center flat portion  70   c,  and forms a portion of the sintered metal body  70 . The inner rim portion  70   b  extends toward the inside in the radial direction from the center flat portion  70   c,  and forms a portion of the sintered metal body  70 . 
     The pair of holders  62  is provided on both ends of the regenerator material laminated body  58  in the axial direction. The surface of the holder  62  which comes into contact with the sintered metal body  70  has a curved shape corresponding to the curved shape of the sintered metal body  70  so as to receive the sintered metal body  70 . 
     In order to remove a gap generated between the vessel inner cylinder  56  and the regenerator material laminated body  58 , the sintered metal body  70  has a slightly larger size than the size of the sectional area of the accommodation space in the regenerator material vessel  52  on the plane perpendicular to the axial direction. In assembly work of the regenerator  38 , when the sintered metal bodies  70  are incorporated into the regenerator material vessel  52 , the outer circumferences and the inner circumferences of the sintered metal bodies  70  are curved, and the outer rim portions  70   a  and the inner rim portions  70   b  are formed. Alternatively, the outer rim portions  70   a  and the inner rim portions  70   b  may be formed in advance. 
       FIG. 8  is a sectional view schematically showing the regenerator  38  according to a fourth embodiment of the present invention. In the fourth embodiment, the regenerator material vessel is different from that of the first embodiment. The others of the fourth embodiment are similar to the first embodiment. In descriptions below, in order to avoid redundant descriptions, descriptions with respect to the similar portions are appropriately omitted. 
     The regenerator material laminated body  58  is accommodated in a displacer  74  serving as the regenerator material vessel. A cylindrical accommodation space is formed in the inner portion of the displacer  74 . A plurality of regenerator material members  76  are laminated in the axial direction of the displacer  74  in the accommodation space. Each of the regenerator material members  76  is a circular wire mesh member or a felt-shaped sintered metal body. The regenerator material member  76  is formed in a tray shape or a flat dish shape. The regenerator material member  76  includes an outer rim portion  76   a  and a center flat portion  76   c.  The outer rim portion  76   a  extends from the center flat portion  76   c  in a direction (for example, axial direction) other than the direction of the plane perpendicular to the axial direction. The outer rim portion  76   a  comes into contact with the displacer  74 . Accordingly, a gap which is generated between the displacer  74  and the regenerator material laminated body  58  is filled with the outer rim portions  76   a.    
     Similarly to the second embodiment, the regenerator material laminated body  58  may include at least one second regenerator material member which is alternately laminated with one or more first regenerator material members  76  in the axial direction. The second regenerator material member may has a shape which is disposed inside the outer rim portion  76   a  and corresponds to the center flat portion  76   c.    
     The regenerator  38  according to the fourth embodiment may be used in a GM cryocooler, a Stirling cryocooler, or other regenerator-type cryocoolers. 
     Embodiments of the present invention may be described as follows. 
     1. A regenerator including: 
     an axially extending regenerator-element container; and 
     a regenerator-element laminated structure accommodated in the regenerator-element container; wherein 
     the regenerator-element laminated structure includes a plurality of first regenerator-element members axially stacked in layers, and each extending along a plane perpendicular to the axis of regenerator extension, and 
     the plurality of first regenerator-element members each include a rim portion extending in a direction not lying in said plane, such as to fill a gap between the regenerator-element container and the regenerator-element laminated structure. 
     2. The regenerator according to 1, wherein the first regenerator-element members include wire mesh components, and a part of each wire mesh component forms the rim portion of the respective first regenerator element member. 
     3. The regenerator according to 1, wherein the first regenerator-element members include felt-like sintered metal structures, and a part of each felt-like sintered metal structure forms the rim portion of the respective first regenerator element member. 
     4. The regenerator according to any one of 1 to 3, wherein the regenerator-element laminated structure includes the plurality of first regenerator-element members axially stacked together with at least one second regenerator-element member, and the second regenerator element member is disposed inward of the rim portions. 
     5. The regenerator according to any one of 1 to 3, wherein the regenerator-element container includes axially extending container inner and outer cylinders, and the regenerator-element laminated structure is accommodated in between the container inner and outer cylinders, and each of the plurality of first regenerator-element members includes an inner rim portion extending in a direction not lying in said plane, and an outer rim portion extending in a direction not lying in said plane such as to fill an inner gap between the container inner cylinder and the regenerator-element laminated structure, and such as to fill an outer gap between the container outer cylinder and the regenerator-element laminated structure. 
     6. The regenerator according to 5, wherein the regenerator-element laminated structure further includes the plurality of first regenerator-element members and axially stacked together with at least one second regenerator-element member, and the second regenerator-element member is disposed in between the first regenerator-element member inner and outer rim portions. 
     7. The regenerator according to any one of 1 to 6, further including a pair of holders clamping both of axial ends of the regenerator-element laminated structure such as to axially compressively retain the regenerator-element laminated structure, wherein the pair of holders each include an edge portion of form corresponding to that of the rim portions. 
     8. A cryocooler including the regenerator according to any one of 1 to 7. 
     9. A Stirling cryocooler, including: 
     an axially extending displacer; and 
     a regenerator arranged surrounding the displacer such as to guide axially reciprocating travel of the displacer; wherein 
     the regenerator includes a container inner cylinder extending axially and guiding the reciprocating travel of the displacer, a container outer cylinder extending axially and forming an accommodation space between the container inner and outer cylinders, and a regenerator-element laminated structure accommodated in the accommodation space; 
     the regenerator-element laminated structure include a plurality of first regenerator-element members axially stacked in layers, and each extending along a plane perpendicular to the axis of regenerator extension; and 
     the plurality of first regenerator-element members each include an inner rim portion extending in a direction not lying in said plane, and an outer rim portion extending in a direction not lying in said plane, such as to fill an inner gap between the container inner cylinder and the regenerator-element laminated structure, and such as to fill an outer gap between the container outer cylinder and the regenerator-element laminated structure. 
     10. The Stirling cryocooler according to 9, wherein the first regenerator-element members include wire mesh components, and parts of each wire mesh component form the inner and outer rim portions of the respective first regenerator element member. 
     11. The Stirling cryocooler according to 9, wherein the first regenerator-element members include felt-like sintered metal structures, and parts of each felt-like sintered metal structure form the inner and outer rim portions of the respective first regenerator element member. 
     12. The Stirling cryocooler according to any one of 9 to 11, wherein the regenerator-element laminated structure includes the plurality of first regenerator-element members axially stacked together with at least one second regenerator-element member, and the second regenerator element member is disposed inward of the rim portions. 
     13. The Stirling cryocooler according to any one of 9 to 12, further including a pair of holders clamping both of axial ends of the regenerator-element laminated structure such as to axially compressively retain the regenerator-element laminated structure, wherein the pair of holders each include an inner edge portion and an outer edge portion of form corresponding to that of the inner and outer rim portions. 
     Hereinbefore, certain embodiments of the invention are described. It should be understood that the invention is not limited to the above-described embodiment, but may be modified into various forms on the basis of the spirit of the invention. Additionally, the modifications are included in the scope of the invention.