Abstract:
There is provided a coaxial connector that can ensure high airtightness without using a costly hermetic sealing component. An airtight coaxial connector includes: a resin filling space portion formed more to a coaxial cable connection side than to an insulator in an outer shell; a resin inlet that is open more to a target connector connection side than to the insulator in the outer shell and communicates with the resin filling space portion; and an airtightness resin that is filled in the resin filling space portion through the resin inlet and seals between a central conductor and the outer shell and between a dielectric of a coaxial cable and the outer shell.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to Japanese Application No. 2014-109668 filed May 28, 2014 which is assigned to the assignee of the present application and is incorporated by reference herein. 
       BACKGROUND 
       [0002]    1. Technical Field 
         [0003]    The present invention mainly relates to an airtight coaxial connector which is used to connect a coaxial cable used to transmit high-frequency signals, to a precision instrument such as broadcasting equipment or an electron microscope. 
         [0004]    2. Related Art 
         [0005]    Precision instruments such as broadcasting equipment and electron microscopes may require airtightness. There is developed a coaxial connector that connects such precision instruments to a coaxial cable for transmitting high-frequency signals and that also has airtightness (see, for example, JP 2001-257510 A). 
         [0006]    This airtight coaxial connector has, for example, a central terminal to which a central conductor of a coaxial cable is connected; and a metal shell disposed outside the central terminal. The airtight coaxial connector uses a hermetic component that seals a gap between the central terminal and the metal shell by an airtight sealing material such as glass. The hermetic component is incorporated into a metal outer shell, and the outer shell and the metal shell are soldered to each other with no gap therebetween and are thereby hermetically sealed. 
       SUMMARY 
       [0007]    However, a conventional airtight coaxial connector such as that described above requires a special technique for manufacturing a hermetic sealing component, which causes problems that it is very costly and there are only a limited number of people who can manufacture the hermetic sealing component. 
         [0008]    In addition, when a technique for manufacturing a hermetic sealing component is not available, a manufacturer of a coaxial connector purchases a general-purpose hermetic sealing component from other companies and incorporates the hermetic sealing component into a coaxial connector manufactured thereby, which causes problems of an increase in assembling manhours, resulting in poor work efficiency, and limited flexibility in design. 
         [0009]    In view of such conventional problems, an object of the present invention is therefore to provide an airtight coaxial connector capable of ensuring high airtightness without using a costly hermetic sealing component. 
         [0010]    To solve the conventional problems described above and achieve the intended purpose, the invention according to a first aspect provides an airtight coaxial connector that has a cylindrical outer shell to which an outer conductor of a coaxial cable is connected; a central contact concentrically disposed inside the outer shell and having a central conductor of the coaxial cable connected thereto; and an insulator interposed between the outer shell and the central contact, and that has the coaxial cable connected to one of two sides in an axial direction thereof and has a target connector connected to an other side, the insulator in the outer shell being placed between the two sides, the airtight coaxial connector including: a resin filling space portion formed more to a coaxial cable connection side than to the insulator in the outer shell; a resin inlet that is open more to a target connector connection side than to the insulator in the outer shell and communicates with the resin filling space portion; and an airtightness resin that is filled in the resin filling space portion through the resin inlet and seals between the central conductor and the outer shell and between a dielectric of the coaxial cable and the outer shell. 
         [0011]    In the invention according to a second aspect, in addition to the configuration of the first aspect, the airtight coaxial connector further includes an air release opening that is open on a target connector connection side in the outer shell and communicates with the resin filling space portion. 
         [0012]    In the invention according to a third aspect, in addition to the configuration of the first or second aspect, the resin inlet and/or the air release opening are/is formed in a shape of a hole or a groove passing through the insulator in the axial direction. 
         [0013]    In the invention according to a fourth aspect, in addition to the configurations of the first to third aspects, the central contact and the central conductor are connected to each other by soldering. 
         [0014]    In the invention according to a fifth aspect, in addition to the configuration of the fourth aspect, the central contact has: a conductor insertion hole into which the central conductor is inserted; and a block hole that is open in an outer surface of the central contact and disposed so as to communicate with the conductor insertion hole, and the central conductor inserted into the conductor insertion hole is soldered to the central contact, and the block hole is sealed by solder. 
         [0015]    As described above, an airtight coaxial connector according to the present invention has a cylindrical outer shell to which an outer conductor of a coaxial cable is connected; a central contact concentrically disposed inside the outer shell and having a central conductor of the coaxial cable connected thereto; and an insulator interposed between the outer shell and the central contact, and has the coaxial cable connected to one of two sides in an axial direction thereof and has a target connector connected to an other side, the insulator in the outer shell being placed between the two sides. The airtight coaxial connector includes: a resin filling space portion formed more to a coaxial cable connection side than to the insulator in the outer shell; a resin inlet that is open more to a target connector connection side than to the insulator in the outer shell and communicates with the resin filling space portion; and an airtightness resin that is filled in the resin filling space portion through the resin inlet and seals between the central conductor and the outer shell and between a dielectric of the coaxial cable and the outer shell. By this, high airtightness can be easily ensured without using a costly general-purpose hermetic sealing component. Moreover, the degree of flexibility in connector design is high. 
         [0016]    In addition, in the present invention, an air release opening is provided that is open on the target connector connection side in the outer shell and communicates with the resin filling space portion. By this, air in the resin filling space portion is pushed out, by which the inside of the resin filling space portion can be filled with the airtightness resin, enabling to ensure high airtightness. 
         [0017]    Furthermore, in the present invention, the resin inlet and/or the air release opening are/is formed in the shape of a hole or a groove passing through the insulator in the axial direction. By this, the resin inlet and the air release opening can be easily formed. 
         [0018]    In addition, in the present invention, the central contact and the central conductor are connected to each other by soldering. By this, even if the central conductor is a stranded wire having a plurality of wire materials stranded to each other, the solder penetrates between the wire materials, enabling to achieve high airtightness. 
         [0019]    Furthermore, in the present invention, the central contact has a conductor insertion hole into which the central conductor is inserted; and a block hole that is open in an outer surface of the central contact and disposed so as to communicate with the conductor insertion hole. The central conductor inserted into the conductor insertion hole is soldered to the central contact, and the block hole is sealed by solder. By this, high airtightness can be ensured by the solder. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0020]      FIG. 1  is a lateral cross-sectional view showing a state in which an airtight coaxial connector according to the present invention and a target connector are connected to each other; 
           [0021]      FIG. 2  is a perspective view of the airtight coaxial connector of  FIG. 1 ; 
           [0022]      FIG. 3  is a longitudinal cross-sectional view of the airtight coaxial connector; 
           [0023]      FIG. 4  is an exploded perspective view of the airtight coaxial connector; 
           [0024]      FIG. 5A  is a perspective view showing an outer shield member of the airtight coaxial connector and  FIG. 5B  is a longitudinal cross-sectional view of the outer shield member; 
           [0025]      FIG. 6A  is a perspective view showing an outer contact member of the airtight coaxial connector and  FIG. 6B  is a longitudinal cross-sectional view of the outer contact member; 
           [0026]      FIG. 7A  is a perspective view showing a cable holding member of the airtight coaxial connector and  FIG. 7B  is a longitudinal cross-sectional view of the cable holding member; 
           [0027]      FIG. 8A  is a perspective view showing an insulator of the airtight coaxial connector,  FIG. 8B  is a front view of the insulator, and  FIG. 8C  is a longitudinal cross-sectional view of the insulator; and 
           [0028]      FIG. 9A  is a perspective view showing a central contact of the airtight coaxial connector and  FIG. 9B  is a longitudinal cross-sectional view of the central contact. 
       
    
    
     DETAILED DESCRIPTION 
       [0029]    Next, an embodiment of an airtight coaxial connector according to the present invention will be described based on an implementation example shown in  FIGS. 1 to 9A  and  9 B. Note that in the drawings reference numeral  1  indicates a coaxial cable, reference numeral  2  indicates an airtight coaxial connector to which the coaxial cable  1  is connected, and reference numeral  3  indicates a target connector connected to the airtight coaxial connector  2 . 
         [0030]    As shown in  FIG. 1 , the target connector  3  has a pin-like target-side central contact  4 , a cylindrical target-side outer shell  5  which is concentrically disposed outside the target-side central contact  4 , and a target-side insulator  6  made of an insulating resin and interposed between the target-side central contact  4  and the target-side outer shell  5 . 
         [0031]    The airtight coaxial connector  2  has a cylindrical outer shell  10  to which an outer conductor  1   c  of the coaxial cable  1  is connected, a central contact  11  which is concentrically disposed inside the outer shell  10 , and an insulator  12  interposed between the outer shell  10  and the central contact  11 . The airtight coaxial connector  2  has the coaxial cable  1  connected to one of two side thereof, between which the insulator  12  in the outer shell  10  is provided, and has the target connector  3  connected to the other side. 
         [0032]    In addition, the airtight coaxial connector  2  has a resin filling space portion  13  formed more to the coaxial cable connection side than to the insulator  12  in the outer shell  10 ; a resin inlet  14  which is open more to the target connector connection side than to the insulator  12  in the outer shell  10  and communicates with the resin filling space portion  13 ; and an airtightness resin  15  which is filled in the resin filling space portion  13  through the resin inlet  14  and seals between a central conductor  1   a  of the coaxial cable  1  and the outer shell  10  and between a dielectric  1   b  of the coaxial cable  1  and the outer shell  10 . By this, airtightness is maintained between the coaxial cable connection side and the target connector connection side in the outer shell  10 . 
         [0033]    Note that in the present implementation example an outer housing  16  made of an insulating resin is provided outside the outer shell  10  and holds therein the outer shell  10  and an end portion of the coaxial cable  1 , and a gap between the outer housing  16  and the outer shell  10  is sealed by a sealing member  17  such as an O-ring. 
         [0034]    The outer shell  10  has a cylindrical outer shield member  20 , a concentric cylindrical outer contact member  21  disposed inside the outer shield member  20 , and a cable holding member  22  which fits into the coaxial cable connection side of the outer shield member  20 . The outer shield member  20 , the outer contact member  21 , and the cable holding member  22  are assembled together so as to have continuity therebetween. The outer shell  10  forms a bottomed cylindrical shape with one side closed and the other side open. 
         [0035]    As shown in  FIGS. 5A and 5B , the outer shield member  20  is formed of a conductive metal material and in a cylindrical shape. The outer shield member  20  has an expanded diameter portion  23  with an expanded inside diameter on its coaxial cable connection side. The cable holding member  22  fits into the expanded diameter portion  23 . 
         [0036]    The outer shield member  20  has, at an end portion on the coaxial cable connection side thereof, an annular stopper portion  24  which hangs over from an inner surface thereof. A contact fitting portion  25  into which an expanded-diameter fitting portion  26  of the outer contact member  21  which will be described later fits is formed on the coaxial cable connection side of the stopper portion  24 . 
         [0037]    In addition, a flange  20   a  which hangs over outwardly is protrudingly and integrally formed with an outer surface of the outer shield member  20 . A sealing member  17  is held on the target connector connection side of the flange  20   a.    
         [0038]    The outer contact member  21  is integrally formed of an elastic, conductive metal material and is formed in a cylindrical form with both ends in an axial direction open. 
         [0039]    The outer contact member  21  is formed such that the outside diameter thereof is smaller than the inside diameter of the outer shield member  20 . The expanded-diameter fitting portion  26  whose outside diameter is substantially the same as the inside diameter of the outer shield member  20  is protrudingly and integrally formed around an end portion on the coaxial cable connection side of the outer contact member  21 . 
         [0040]    In addition, the outer contact member  21  has a plurality of slits  27 ,  27  . . . which are provided at intervals in a circumferential direction and whose ends on the target connector connection side are open. By the slits  27 ,  27  . . . , the cylindrical target connector connection side is divided, forming a plurality of cantilever spring-like elastic contact piece portions  28 ,  28  . . . . 
         [0041]    A contact point portion  29  bulging inwardly is integrally formed with each of the elastic contact piece portions  28 ,  28  . . . . When the target connector  3  is connected, the contact point portion  29  comes into contact with an outer surface of the target-side outer shell  5  of the target connector  3 . 
         [0042]    By pressing the cable holding member  22  against the end portion on the coaxial cable connection side of the outer contact member  21  with the outer contact member  21  inserted into the outer shield member  20  from the coaxial cable connection side and the expanded-diameter fitting portion  26  fitting into the contact fitting portion  25  and stopped by the stopper portion  24 , the expanded-diameter fitting portion  26  is fixed and the elastic contact piece portions  28 ,  28  . . . are held in a deformable state in a radius direction. 
         [0043]    As shown in  FIGS. 7A and 7B , the cable holding member  22  is integrally formed of a conductive metal material, and has a cylindrical airtight fitting portion  30 ; a disc-like cover portion  31  that closes an end surface on the coaxial cable connection side of the airtight fitting portion  30 ; and a cylindrical cable connecting portion  32  projecting toward the coaxial cable connection side from the center of the cover portion  31 . 
         [0044]    The airtight fitting portion  30  forms a multistep shape where the inside diameter of its inner hole portion gradually decreases from the target connector connection side. The airtight fitting portion  30  has a holding stepped portion  33  into which an end on the coaxial cable connection side of the outer contact member  21  fits; a flange holding stepped portion  34  into which a flange portion  43  of the insulator  12  which will be described later fits; and the recessed resin filling space portion  13 , which are continuously formed. 
         [0045]    In addition, a recessed groove  35  in a circumferential direction is formed around the airtight fitting portion  30 . A sealing member  36  such as an O-ring fits into the recessed groove  35 . By the sealing member  36 , a gap between the airtight fitting portion  30  and the outer shield member  20  is sealed. 
         [0046]    The cover portion  31  is formed such that the diameter thereof has substantially the same size as the outside diameter of the outer shield member  20 . By fitting the airtight fitting portion  30  into the expanded diameter portion  23 , the cover portion  31  abuts against an end surface of the outer shield member  20 , closing an opening on the coaxial cable connection side of the outer shield member  20 . 
         [0047]    The cable connecting portion  32  is formed in a cylindrical shape where the cable connecting portion  32  passes through the cover portion  31  and communicates with the resin filling space portion  13 . The end portion of the coaxial cable  1  whose outer sheath  1   d  and outer conductor  1   c  are removed is inserted into the cable connecting portion  32 , and an end surface of the dielectric  1   b  is exposed within the resin filling space portion  13 . 
         [0048]    In addition, the outer conductor  1   c  of the coaxial cable  1  is connected and fixed on the outer side of the cable connecting portion  32  by crimping, etc. 
         [0049]    As shown in  FIGS. 8A to 8C , the insulator  12  is formed in a circular cylindrical shape with a plurality of steps where a circular cylindrical insulator main body portion  40  and a circular cylindrical contact accommodation projection portion  41  projecting from the center of one end surface of the insulator main body portion  40  are concentrically continued. 
         [0050]    In addition, a contact accommodation hole  42  passing through the center in an axial direction of the contact accommodation projection portion  41  and the insulator main body portion  40  is made in the insulator  12 . The central contact  11  is inserted and accommodated into the contact accommodation hole  42 , by which the outer shell  10  and the central contact  11  are concentrically disposed and the insulator  12  is interposed between the outer shell  10  and the central contact  11 . 
         [0051]    The insulator main body portion  40  is formed in a circular cylindrical shape where the flange portion  43  is integrally formed around an end portion on the coaxial cable connection side of the insulator main body portion  40 . The insulator main body portion  40  fits into the inside of the outer shell  10 , i.e., the inside of the outer contact member  21 , and the flange portion  43  fits into the flange holding stepped portion  34  and is sandwiched between an end surface of the outer contact member  21  and the flange holding stepped portion  34 , and the insulator  12  is fixed within the outer shell  10  and the resin filling space portion  13  is disposed on the coaxial cable connection side of the insulator  12 . 
         [0052]    In addition, an outer region of the insulator main body portion  40  has a recessed grooved resin inlet groove  14   a  passing through the insulator  12  in the axial direction; and a plurality of air release opening grooves  44   a ,  44   a  . . . disposed at intervals in a circumferential direction and passing through the insulator  12  in the axial direction. By the insulator main body portion  40  fitting into the outer contact member  21 , the resin inlet groove  14   a  forms the resin inlet  14 , and the air release opening grooves  44   a ,  44   a  . . . form air release openings  44  and  44  which are open more to the target connector connection side than to the insulator  12  in the outer shell  10  and which communicate with the resin filling space portion  13 . 
         [0053]    For the size of the resin inlet  14 , a size (cross-sectional area) suitable for resin injection, i.e., a size suitable for use of a resin injection apparatus such as a dispenser, is secured. More specifically, a cross-sectional area is secured that allows a needle-like inlet of a dispenser to be inserted into the resin filling space portion  13  through the resin inlet  14 . 
         [0054]    The air release openings  44  and  44  are configured such that, when the airtightness resin  15  is filled in the resin filling space portion  13  through the resin inlet  14 , air in the resin filling space portion  13  is pushed by the airtightness resin  15  and is thereby discharged from the air release openings  44  and  44 . 
         [0055]    The resin filling space portion  13  is a closed space that is enclosed by the airtight fitting portion  30  and that is sandwiched between the cover portion  31  and the end surface on the coaxial cable connection side of the insulator main body portion  40 . The cable connecting portion  32 , the resin inlet  14 , and the air release openings  44  and  44  are in a state of communicating with the outside. 
         [0056]    Then, the airtightness resin  15  is filled and cured into the resin filling space portion  13  through the resin inlet  14 . By the airtightness resin  15 , a gap between the central conductor  1   a  exposed within the resin filling space portion  13  through the cable connecting portion  32  and the outer shell  10  and a gap between the dielectric  1   b  of the coaxial cable  1  and the outer shell  10  are sealed. 
         [0057]    In addition, by the airtightness resin  15 , the opening portions on the space side of the resin inlet  14  and the air release openings  44  and  44  are also sealed. 
         [0058]    For the airtightness resin  15 , a resin is used that has high flowability and excellent filling properties before curing and exerts high airtightness after curing. For example, an epoxy-based resin is used. 
         [0059]    The central contact  11  is formed of a conductive metal material and in a rod shape. The central contact  11  has, on the one-end side in an axial direction thereof, an elastic connecting portion  50  into which the target-side central contact  4  of the target connector  3  fits. The central contact  11  has, on the other-end side in the axial direction thereof, a conductor insertion hole  51  into which the central conductor  1   a  of the coaxial cable  1  fits. 
         [0060]    The elastic connecting portion  50  has a pair of slits  52  and  52  whose ends on the target connector connection side are open. The pin-like target-side central contact  4  of the target connector  3  fits into the elastic connecting portion  50 , by which the two central contacts  4  and  11  are connected to each other with a desired contact pressure. 
         [0061]    The central contact  11  has a block hole  53  which is open in an outer surface of the central contact  11  and disposed so as to communicate with the conductor insertion hole  51 . The central conductor  1   a  inserted into the conductor insertion hole  51  is soldered to the central contact  11 , and the block hole  53  is sealed by solder  54 . 
         [0062]    Thus, since the block hole  53  is sealed by the solder  54 , high airtightness between the central conductor  1   a  and the insulator  12  is ensured. Furthermore, even if the central conductor  1   a  of the coaxial cable  1  is a stranded wire made up of a plurality of cores, since the solder  54  penetrates between the cores, airtightness between the coaxial cable  1  and the central contact  11  can be increased. 
         [0063]    The airtight coaxial connector  2  thus configured has the resin filling space portion  13  formed more to the coaxial cable connection side than to the insulator  12  in the outer shell  10 . The airtightness resin  15  is filled into the resin filling space portion  13  through the resin inlet  14 , sealing between the central conductor  1   a  and the outer shell  10  and between the dielectric  1   b  of the coaxial cable  1  and the outer shell  10  by the airtightness resin  15 . By this, the more to the coaxial cable connection side than the insulator  12  in the outer shell  10  and the target connector connection side are hermetically sealed. 
         [0064]    Note that the modes of the resin inlet  14  and the air release openings  44  and  44  are not limited to those of the above-described implementation example, and the resin inlet  14  and the air release openings  44  and  44  may be formed in the shape of circular holes passing through the insulator main body portion  40  of the insulator  12  in the axial direction, or grooves that communicate with the resin filling space portion  13  in the axial direction may be formed in an inner surface of the outer shell  10  in the axial direction and may be used as the resin inlet  14  and the air release openings  44  and  44 . 
       REFERENCE SIGNS LIST 
       [0000]    
       
           1  coaxial cable 
           2  airtight coaxial connector 
           3  target connector 
           4  target-side central contact 
           5  target-side outer shell 
           6  target-side insulator 
           10  outer shell 
           11  central contact 
           12  insulator 
           13  resin filling space portion 
           14  resin inlet 
           15  airtightness resin 
           16  outer housing 
           17  sealing member 
           20  outer shield member 
           21  outer contact member 
           22  cable holding member 
           23  expanded diameter portion 
           24  stopper portion 
           25  contact fitting portion 
           26  expanded-diameter fitting portion 
           27  slit 
           28  elastic contact piece portion 
           29  contact point portion 
           30  airtight fitting portion 
           31  cover portion 
           32  cable connecting portion 
           33  holding stepped portion 
           34  flange holding stepped portion 
           35  recessed groove 
           36  sealing member 
           40  insulator main body portion 
           41  contact accommodation projection portion 
           42  contact accommodation hole 
           43  flange portion 
           44  air release opening 
           50  elastic connecting portion 
           51  conductor insertion hole 
           52  slit 
           53  block hole 
           54  solder