Patent Publication Number: US-2023145550-A1

Title: Gas filling structure, hermetically sealed electromagnetic contactor, and gas filling method

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation Application, filed under 35 U.S.C. § 111(a), of International Patent Application No. PCT/JP2021/044679 filed on Dec. 6, 2021, which claims priority benefit from Japanese Patent Application No. 2021-008373 filed on Jan. 22, 2021, the contents of each of which are incorporated herein by reference in their entireties. 
    
    
     TECHNICAL FIELD 
     The present invention relates to a gas filling structure, a hermetically sealed electromagnetic contactor, and a gas filling method. 
     BACKGROUND ART 
     In hermetically sealed electromagnetic contactors, by housing a contact unit in a hermetically sealed container and filling the hermetically sealed container with pressurized insulating gas, such as hydrogen, breaking performance or a contact is improved. In a gas filling method described in PTL 1, insulating gas is supplied through a pipe made of metal that communicates with the inside of a hermetically sealed container, and, when the supply of insulating gas is stopped, ultrasonic welding is performed with the opening portion of the pipe closed and, subsequently, the pipe is cut. 
     CITATION LIST 
     Patent Literature 
     PLT 1: JP2014110095 A 
     SUMMARY OF INVENTION 
     Technical Problem 
     The configuration in which a pipe made of metal is used has been applicable only to a hermetically sealed container using a metal as a base material and has been inapplicable to a hermetically sealed container made of resin. Therefore, there has been a limit to miniaturization and weight reduction and a degree of freedom in design. 
     An object of the present invention is to enable a gas filling structure to be applied to a hermetically sealed container made of resin and not only achieve miniaturization and weight reduction but also improve a degree of freedom in design of the gas filling structure. 
     Solution to Problem 
     A gas filling structure according to one aspect of the present invention includes a through-hole formed in a hermetically sealed container made of resin to fill the hermetically sealed container with gas, and a fastener fastened to the through-hole to seal the through-hole. 
     A hermetically sealed electromagnetic contactor according to another aspect of the invention includes the gas filling structure and a main contact unit configured to open and close an electrical path or a main circuit, the main contact unit is hermetically sealed in the hermetically sealed electromagnetic contactor and the hermetically sealed container is filled with the hermetically sealed container insulating gas. 
     A gas filling method according to another aspect of the invention includes performing evacuation with a fastener half-fastened to a through-hole formed in a hermetically sealed container made of resin, filling the hermetically sealed container with gas after performing the evacuation, and completing fastening of the fastener after performing filling of the hermetically sealed container with the gas. 
     Advantageous Effects of Invention 
     According to the present invention, since the gas filling structure is a structure in which a through-hole is sealed by a fastener, the gas filling structure is applicable to a hermetically sealed container made of resin and enables not only miniaturization and weight reduction to be achieved but also a degree of freedom in design to be improved. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is an external view of a hermetically sealed container; 
         FIG.  2    is an exploded view of the hermetically sealed container; 
         FIG.  3    is a cross-sectional view of the hermetically sealed container; 
         FIG.  4    is another cross-sectional view of the hermetically sealed container; 
         FIG.  5    is a cross-sectional view of a coil contact piece; 
         FIG.  6    is a diagram illustrative of the coil contact pieces, support springs, and relay contact pieces; and 
         FIGS.  7 A,  7 B, and  7 C  are enlarged cross-sectional views of a gas filling structure. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, embodiments of the present invention are described with reference to the drawings. It should be noted that each drawing is schematic and may not be the same as actual one. Additionally, the embodiments given below exemplify devices and methods for embodying the technological concept of the present invention, and do not limit components of the invention to those below. In other words, various modifications can be added to the technological concept of the present invention without departing from the technological scope described in the appended claims. 
     Embodiment 
     In the following description, for descriptive purposes, three directions orthogonal to one another are assumed to be the vertical direction, the width direction, and the depth direction. 
       FIG.  1    is an external view of a hermetically sealed container. 
     A hermetically sealed container  11  is used, housed in a case of a not-illustrated hermetically sealed electromagnetic contactor, and opens and closes an electrical path of a main circuit and also opens and closes an electrical path of an auxiliary circuit in an interlocking manner with opening and closing of the main circuit. The hermetically sealed container  11  is made of a resin having electrical insulation and includes a container body  12  and an auxiliary contact housing portion  13 . The container body  12  includes a container portion  14  and a lid portion  15 . 
     The container portion  14  is formed in a square box shape that has the far side in the depth direction, both sides in the vertical direction, and both sides in the width direction closed and the near side in the depth direction opened. 
     The lid portion  15  fits into the open end of the container portion  14  and closes the near side in the depth direction of the container portion  14 . It is assumed that a protruding line portion and a recessed line portion are formed on one and the other of the container portion  14  and the lid portion  15 , respectively and the protruding line portion and the recessed line portion are fitted to each other. 
     The auxiliary contact housing portion  13  is disposed at the center of the lid portion  15 , is formed in a square small-box shape that has the near side in the depth direction, both sides in the vertical direction, and both sides in the width direction closed and the far side in the depth direction opened, and communicates with the inside of the container body  12 . 
     The hermetically sealed container  11  is filled with pressurized insulating gas, such as hydrogen and nitrogen. Therefore, the hermetically sealed container  11  not only has the container portion  14 , the lid portion  15 , and the auxiliary contact housing portion  13  fixed to each other with epoxy resin-cased adhesive, but also has gas barrier coating applied to the entire outer peripheral surface including boundary portions, using laminated films of clay crystals. Specifically, exchanging interlayer ions in purified smectite and joining the laminated films with an organic binder, such as polyvinyl alcohol (PVA) and water-soluble nylon, causes the laminated films to exhibit labyrinth effect and thereby prevent permeation of gas molecules, such as hydrogen and nitrogen. The laminated films are stacked in the thickness direction, and the thickness thereof is, for example, 2 μm. The gas barrier coating is applied by a spray method in which coating liquid is formed into mist and applied to the hermetically sealed container  11 , and is completed by being burned at a temperature at which interlayer ions are incorporated into clay crystals, for example, a temperature greater than or equal to 150° C. Since, as described above, gas barrier coating is applied to the entire outer peripheral surface, the outer peripheral shape of the hermetically sealed container  11  is preferably formed in a polygon that is composed or planes that are flat and linear to the extent possible. 
       FIG.  2    is an exploded view of a hermetically sealed container. 
       FIG.  3    is a cross-sectional view of the hermetically sealed container. 
     In this drawing, a cross section passing the center in the width direction and taken along the vertical direction and the depth direction is illustrated. 
       FIG.  4    is another cross-sectional view of the hermetically sealed container. 
     In this drawing, a cross section passing the center the vertical direction and taken along the width direction and the depth direction is illustrated. 
     In the hermetically sealed container  11 , a main contact unit  21 , an auxiliary contact unit  22 , and an electromagnet unit  23  are housed. Specifically, the auxiliary contact unit  22  is arranged in the auxiliary contact housing portion  13 , the main contact unit  21  is arranged on the near side in the depth direction in the container body  12 , and the electromagnet unit  23  is arranged on the far side in the depth direction in the container body  12 . In the container portion  14 , a gas filling structure  16  for filling of the hermetically sealed container  11  with insulating gas is formed at the center of the bottom surface. 
     The main contact unit  21  is a contact unit connected to a main circuit via crimp terminals and configured to open and close an electrical path of the main circuit, and the container body  12  includes a pair of main fixed contact pieces  31  and a main movable con tact piece  32 . 
     The pail of main fixed contact pieces  31  are belt-shaped metals having conductivity and are arranged with a gap interposed therebetween in the vertical direction. Each of the main fixed contact pieces  31  includes a side plate portion  33 , an upper plate portion  34 , and a lower plate portion  35  and is formed in a substantially U-shape opening to the inner side in the vertical direction when viewed from the width direction. The side plate portion  33  is formed in a plate shape extending in the depth direction and aligned with the width direction and the depth direction on the outer side in the vertical direction, and penetrates through the lid portion  15 . The upper plate portion  34  is formed in a plate shape aligned with the vertical direction and the width direction and extends from the near side in the depth direction of the side plate portion  33  toward the inner side in the vertical direction outside the container body  12 . The lower plate portion  35  is formed in a plate shape aligned with the vertical, direction and the width direction and extends from the far side in the depth direction of the side plate portion  33  toward the inner side in the vertical direction inside the container body  12 . 
     The pair of lower plate portions  35  are disposed with a gap interposed between the tip ends thereof, which face each other in the vertical direction, inside the container body  12  and respectively have main fixed contacts  36  formed on surfaces on the near side in the depth direction. The pair of upper plate portions  34  are arranged with a gap interposed between the tip ends thereof, which face each other in the vertical direction, outside the container body  12  and are disposed in such a manner that surfaces thereof on the far side in the depth direction come into contact with the lid portion  15 . In each of the pair of upper plate portions  34 , a threaded hole penetrating in the depth direction is formed and a terminal bolt  37  is fitted into an internal threaded portion of the threaded hole. Each of the terminal bolts  37  is made of a metal having conductivity and is a stud bolt that does not have a head and on which an external threaded portion is formed over the entire length in the depth direction. The terminal bolt  37  has the far side in the depth direction embedded in the lid portion  15  and the near side in the depth direction, which projects out of the upper plate portion  34 , serving as a main terminal. One and the other of the pair of terminal bolts  37  are connected to the primary side and the secondary side of the main circuit, respectively. 
     The pair of main fixed contact pieces  31  and terminal bolts  37  are integrated with the lid portion  15  with the side plate portions  33  penetrating through the lid portion  15  by insert molding. Specifically, after fine micron-sized protruding and recessed shapes are formed on the surfaces of the main fixed contact pieces  31  and the surfaces of the terminal bolts  37  by chemical etching, insert molding is performed. Through this processing, melted resin enters the inside of the protruding and recessed shapes and solidification of the resin causes the metal and the resin to be joined at the interface level and produces complex junctions exhibiting labyrinth effect, which prevents gas molecules, such as hydrogen and nitrogen, from leaking. Examples of the metal surface treatment technology include “AMALPHA” (registered trademark) by MEC COMPANY LTD. 
     The main movable contact piece  32  is made of a metal having conductivity, is formed in a plate shape extending in the vertical direction and aligned with the vertical direction and the width direction, and is arranged on the near side in the depth direction of the pair of lower plate portions  35 . On both end sides of the main movable contact piece  32 , main movable contacts  38  are brazed on a surface on the far side in the depth direction. The main movable contact piece  32  causes the main movable contacts  38  to be respectively separated from the main fixed contacts  36  when the main movable contact piece  32  retreats to the near side in the direction, and causes the main movable contacts  38  to respectively come into contact with the main fixed contacts  36  when the main movable contact piece  32  advances to the far side in the depth direction. The main contact unit  21  is formed by the main fixed contacts  36  and the main movable contacts  38 . Since the main movable contact piece  32  opens and closes an electrical path of the main circuit by moving in the depth direction, the depth direction serves as an opening/closing direction for the main contact unit  21 . 
     The auxiliary contact unit  22  is a contact unit connected to an auxiliary circuit via connector terminals and configured to open and close an electrical path of the auxiliary circuit, and the auxiliary contact housing portion  13  includes a pair of auxiliary fixed contact pieces  41  and an auxiliary movable contact piece  42  (see  FIG.  4   ). 
     The pair of auxiliary fixed contact pieces  41  are belt-shaped metals having conductivity and are arranged with a gap interposed therebetween in the vertical direction. Each of the auxiliary fixed contact pieces  41  includes a lower plate portion  43  and a side plate portion  44  and is formed in a substantially L-shape when viewed from the vertical direction. The lower plate portion  43  is formed in a plate shape extending in the width direction and aligned with the width direction and the vertical direction, and penetrates through a sidewall of the auxiliary contact housing portion  13 . The side plate portion  44  is formed in a plate shape aligned with the vertical direction and the depth direction and extends from the outer side in the width direction of the lower plate portion  43  toward the near side in the depth direction outside the auxiliary contact housing portion  13 . 
     The pair of lower plate portions  43  are disposed with a gap interposed between the tip ends thereof, which face each other in the width direction, inside the auxiliary contact housing portion  13  and respectively have auxiliary fixed contacts  46  brazed on surfaces on the far side in the depth direction. On the auxiliary contact housing portion  13 , a recessed portion  47 , which is recessed toward the inner side in the width direction, is formed on each of outer peripheral surfaces on both sides in the width direction, and the side plate portions  44  are exposed by the recessed portions  47 . The pair of side plate portions  44 , which are exposed by the recessed portions  47 , serve as auxiliary terminals, and one and the other of the auxiliary terminals are connected to the primary side and the secondary side of the auxiliary circuit, respectively. The pair of auxiliary fixed contact pieces  41  are integrated with the auxiliary contact housing portion  13  in such a manner as to penetrate through side-walls of the auxiliary contact housing portion  13  by insert molding. As for a method of insert molding, the same method as that used for the afore-described main fixed contact pieces  31  can be used. 
     The auxiliary movable contact piece  42  is made of a metal having conductivity, is formed in a plate shape extending in the width direction and aligned with the width direction and the vertical direction, and is arranged on the far side in the depth direction of the pair of auxiliary fixed contact pieces  41 . Both end sides of the auxiliary movable contact piece  42  bifurcate and form dual contacts, and auxiliary movable contacts  48  are brazed on a surface on the near side in the depth direction of the auxiliary movable contact piece  42 . The auxiliary movable contact piece  42  causes the auxiliary movable contacts  48  to respectively come into contact with the auxiliary fixed contacts  46  when the auxiliary movable contact piece  42  retreats to the near side in the depth direction, and causes the auxiliary movable contacts  48  to be respectively separated from the auxiliary fixed contacts  46  when the auxiliary movable contact piece  42  advances to the far side in the depth direction. The auxiliary contact unit  22  is formed by the auxiliary fixed contacts  46  and the auxiliary movable contacts  48 . Since the auxiliary movable contact piece  42  opens and closes an electrical path of the auxiliary circuit by moving in the depth direction, the depth direction serves as an opening/closing direction for the auxiliary contact unit  22 . 
     The main movable contact piece  32  and the auxiliary movable contact piece  42  are supported by a contact support  51 . The contact support  51  is made of a resin having electrical insulation and is arranged between the pair of main fixed contact pieces  31 . In the lid portion  15 , an opening portion  17  penetrating in the depth direction is formed between the pair of upper plate portions  34 . The contact support  51  has the far side in the depth direction, which serves as the base end side, elastically supporting the main movable contact piece  32  via a main contact spring  52  inside the container body  12 . The main contact spring  52  maintains contact pressure of the main contact unit  21  constant by biasing the main movable contact piece  32  to the far side in the depth direction. 
     The contact support  51  has the near side in the depth direction, which serves as the tip end side, passing the opening portion  17  and elastically supporting the auxiliary movable contact piece  42  via an auxiliary contact spring  53  inside the auxiliary contact housing portion  13 . The auxiliary contact spring  53  maintains contact pressure of the auxiliary contact unit  22  constant by biasing the auxiliary movable contact piece  42  to the near side in the depth direction. 
     On the lid portion  15 , a recessed portion  18  that is recessed toward the far side in the depth direction and into which the far side in the depth direction of the auxiliary contact housing portion  13  can be fitted is formed between the pair of upper plate portions  34  within a surface on the near side in the depth direction. The auxiliary contact housing portion  13  covers the tip end side of the contact support  51  and hermetically seals the opening portion  17  by being fixed to the recessed portion  18 . 
     In the container body  12 , a partition wall member  54  is disposed around the contact support  51 . The partition wall member  54  is made of a resin having electrical insulation and is formed in a square cylindrical shape that surrounds both sides in the vertical direction and both sides in the width direction. On the partition wall member  54 , a plate-shaped permanent magnet  55  is fitted into each of surfaces on both sides in the vertical direction and surfaces on both sides in the width direction of the outer peripheral surfaces, and belt-shaped yokes  56  are further disposed over the circumference of the partition wall member  54 . A pair of permanent magnets  55  arranged on both sides in the vertical direction have the inner sides in the vertical direction magnetized to the S-pole, and a pair of permanent magnets  55  arranged on both sides in the width direction have the inner sides in the width direction magnetized to the N-pole. Because of this configuration, when viewed from the depth direction, magnetic flux flowing from the respective permanent magnets  55  arranged on both sides in the vertical direction to the respective permanent magnets  55  arranged on both sides in the width direction is formed. The yokes  56  are halved at the center the vertical direction and each of the yokes  56  is formed in a substantially U-shape opening to the inner side in the vertical direction when viewed from the depth direction, and fitting the pair of yokes  56  to each other from both sides in the vertical direction causes the yokes  56  to surround the entire circumference of the partition wall member  54  viewed from the depth direction. 
     The electromagnet unit  23  is housed on the far side in the depth direction in the container portion  14  and switches opening/closing of the main contact unit  21  and opening/closing of the auxiliary contact unit  22 . The electromagnet unit  23  includes a spool  61 , a plunger  62 , an upper armature  63 , a lower armature  64 , yokes  65 , and a return spring  66  (see  FIG.  4   ). 
     The spool  61  is made of a resin having electrical insulation, and a coil  72  is wound around a cylindrical winding shaft  71 , which extends in the depth direction. The plunger  62  is a columnar movable iron core, which extends in the depth direction, and is inserted into the winding shaft  71 . The plunger  62  has the near side in the depth direction coupled to the contact support  51  via a plate spring. The upper armature  63  is a flat plate-shaped yoke aligned with the vertical direction and the width direction and is fixed to the near side in the depth direction of the plunger  62 . The lower armature  64  is a flat plate-shaped yoke aligned with the vertical direction and the width direction and is fixed to the far side in the depth direction of the plunger  62 . 
     The pair of yokes  65  are plate-shaped yokes, and each of the yokes  65  is fixed to one of one side and the other side in the width direction of the spool  61 . Each of the yokes  65  includes a side piece portion  73 , an upper piece portion  74 , and a lower piece portion  75  and is formed in a substantially U-shape opening to the inner side in the width direct when viewed from the vertical direction. 
     The side piece portion  73  is formed in a plate shape aligned with the vertical direction and the depth direction and covers the outer side in the width direction of the spool  61 . 
     The upper piece portion  74  is formed in a plate shape aligned with the vertical direction and the width direction and extends from the near side in the depth direction of the side piece portion  73  toward the inner side in the width direction. 
     The lower piece portion  75  is formed in a plate shape aligned with the vertical direction and the width direction and extends from the far side in the depth direction of the side piece portion  73  toward the inner side in the width direction. 
     Separation distance between the upper piece portion  74  and the lower piece portion  75  is the same as separation distance between the upper armature  63  and the lower armature  64 . The upper piece portion  74  is disposed on the far side in the depth direction of the upper armature  63 , and the lower piece portion  75  is disposed on the far side in the depth direction of the lower armature  64 . 
     The return spring  66  is sandwiched between the lower armature  64  and the bottom surface of the container portion  14  and biases the plunger  62  to the near side in the depth direction. 
       FIG.  5    is a cross-sectional view of a coil contact piece. 
     In this drawing, a cross section passing a coil contact piece  81  and taken along the vertical direction and the depth direction is illustrated. 
     A pair of coil contact pieces  81  are made of a metal having conductivity, are formed in plate shapes aligned with the vertical direction and the width direction, and are arranged in parallel with a gap interposed therebetween in the width direction (see  FIG.  6   ). One of the coil contact pieces  81  has the inner side in the vertical direction arranged inside the container body  12  and the outer side in the vertical direction connected to the positive side of a control circuit outside the container body  12 . The other of the coil contact pieces  81  has the inner side in the vertical direction arranged inside the container body  12  and the outer side in the vertical direction connected to the negative side of the control circuit outside the container body  12 . The pair of coil contact pieces  81  are integrated with the container portion  14  in such a manner as to penetrate through a sidewall of container portion  14  by insert molding. As for a method of insert molding, the same method as that used for the afore-described main fixed contact pieces  31  can be used. 
     On the inner peripheral surface of the container portion  14 , a step-shaped spool receiving portion  82  is formed on each of both end sides in the vertical direction. On each of the spool receiving portions  82 , two deep recessed portions  83 , each of which is recessed toward the far side in the depth direction, are formed on a surface on the near side in the depth direction. A pair of deep recessed portions  83  are arranged in parallel with a gap interposed therebetween in the width direction, and, on one side in the vertical direction, the inner sides in the vertical direction of the coil contact pieces  81  are exposed by the deep recessed portions  83 . The front surfaces of the coil contact pieces  81  that are exposed on one side in the vertical direction and the bottom surfaces of the deep recessed portions  83  formed on the other side in the vertical direction are located at the same position in the depth direction. 
     On the spool  61 , an arm piece  84 , which projects toward the outer side in the vertical direction, is formed on the near side in the depth direction and each of both sides in the vertical direction (see  FIG.  3   ). Each or the arm pieces  84  is formed in a substantially plate shape aligned with the vertical direction and the width direction and serves as a cantilever. On one side in the vertical direction, a pair of relay contact pieces  85  are insert-molded in the arm piece  84  (see  FIG.  6   ). The pair of relay contact pieces  85  are made of a metal having conductivity and are formed in plate shapes aligned with the vertical direction and the width direction. Since the relay contact pieces  85  are not components that penetrate through the hermetically sealed container  11 , the method of insert molding does not require a special metal surface treatment technology as in a case of the afore-described main fixed contact pieces  31 . 
     On each of the arm pieces  84 , two shallow recessed portions  86 , each of which is recessed toward the near side in the depth direction, are formed on a surface on the far side in the depth direction. Each pair of shallow recessed portions  86  are arranged in parallel with a gap interposed therebetween in the width direction, and, on one side in the vertical direction, the outer sides in the vertical direction of the relay contact pieces  85  are exposed by the shallow recessed portions  86 . The front surfaces of the relay contact pieces  85  that are exposed on one side in the vertical direction and the bottom surfaces of the shallow recessed portions  86  formed on the other side in the vertical direction are located at the same position in the depth direction. On each of the relay contact pieces  85 , a projecting portion  87 , which projects from an end portion on the inner side in the vertical direction toward the outer side in the width direction, is formed (see  FIG.  6   ). Each of the projecting portions  87  projects from a side surface in the width direction of the arm piece  84  and is inclined to the far side in the depth direction. To one of the projecting portions  87 , one end of a winding wire of the coil  72  is soldered, and, to the other of the projecting portions  87 , the other end of the winding wire of the coil  72  is soldered. 
     In each of the deep recessed portions  83  and corresponding one of the shallow recessed portions  86 , a support spring  88  (spring member) is housed. Each of the support springs  88  has a feature that free height when no load is applied in the compression direction is greater than a dimension obtained by adding depth of a shallow recessed portion  86  to depth of a deep recessed portion  83 . Although, when all the components are housed in the hermetically sealed container  11 , a load in the compression direction is applied to the support springs  88 , the support springs  88  are set to keep the arm pieces  84  separated upward from the spool receiving portions  82  even on this occasion (see  FIG.  3   ). Therefore, the spool  61  has the pair of arm pieces  84  suspended on two pairs of support springs  88 , each pair of which is disposed on one side. When the lid portion  15  is fixed to the container portion  14 , the spool  61  being pressed to the lid portion  15  via the partition wall member  54  due to repulsive force of the support springs  88  causes backlash to be suppressed. 
       FIG.  6    is a diagram illustrative of the coil contact pieces, the support springs, and the relay contact pieces. 
     In this drawing, a configuration in which only the coil contact pieces  81 , the relay contact pieces  85 , and the support springs  88  are picked out and the container portion  14 , the arm pieces  84 , and the spool receiving portions  82  are omitted is illustrated. The support springs  88  are made of a metal having conductivity. On one side in the vertical direction, the support springs  88  are sandwiched between the coil contact pieces  81  and the relay contact piece  85  while being compressed, and the support springs  88  are in contact with both the coil contact pieces  81  and the relay contact pieces  85 . This configuration causes the coil contact pieces  81  and the coil  72  to be electrically connected. Therefore, on the one side in the vertical direction, the support springs  88  serve as both a support of the spool  61  and an electrical connection for the coil contact pieces  81 . 
     According to the above description, when the coil  72  is in a non-excited state in which no current is applied to the coil  72 , the plunger  62  has retreated to the near side in the depth direction due to repulsive force of the return spring  66  and, in association therewith, the contact support  51  also retreats to the near side in the depth direction. Because of this configuration, the main contact unit  21  is opened and, at the same time, the auxiliary contact unit  22  is closed. On this occasion, the upper armature  63  is separated from the upper piece portions  74 , and the lower armature  64  is separated from the lower piece portions  75 . 
     When, while the coil  72  is in this state, current is applied to the coil  72  and the coil  72  is excited, the upper armature  63  attracted and stuck to the upper piece portions  74  and, at the same time, the lower armature  64  is attracted and stuck to the lower piece portions  75 . Therefore, the plunger  62  advances to the far side in the depth direction against the repulsive force of the return spring  66  and, in association therewith, the contact support  51  also advances to the far side in the depth direction. Because of this configuration, the main contact unit  21  is closed and, at the same time, the auxiliary contact unit  22  is opened. 
     Next, the gas filling structure  16  will be described. 
       FIG.  7    is enlarged cross-sectional views of the gas filling structure. 
     The gas filling structure  16  includes a through-hole  91  and a screw  92  (fastener).  FIGS.  7 A,  7 B, and  7 C  illustrate a state before the screw  92  is fitted, a state in which the screw  92  is fastened by substantially half of the length thereof, and a state in which the fastening of the screw  92  is completed, respectively. 
     At the center of the bottom of the container portion  14 , a small-diameter boss  14   a,  which protrudes toward the near side in the depth direction, is formed on the inner peripheral surface, and a large-diameter boss  14   b,  which protrudes toward the far side in the depth direction, is formed on the outer peripheral surface. The small-diameter boss  14   a  is configured to be located inside the lower end side of the return spring  66 . The through-hole  91  penetrates the bottom of the container portion  14  in the depth direction from the small-diameter boss  14   a  to the large-diameter boss  14   b,  and includes a threaded hole  93  (first through-hole), a tapered hole  94  (second through-hole), and a countersunk hole  95 . 
     The screw  92  is, for example, made of stainless steel and is a truss head screw that has a cross hole formed on the spherically-shaped head thereof. In addition, the shaft of the shank has a uniform diameter, and an external threaded portion is formed over the entire length of the shank. Material, the shape of the head, the shape of a groove or a hole formed on the head, and the like of the screw  92  can be arbitrarily determined. 
     The threaded hole  93  is mainly formed at a part corresponding to the small-diameter boss  14   a  and the bottom of the container portion  14 , is a bottomed hole that is recessed toward the near side in the depth direction, and has an internal threaded portion, to which the screw  92  fits, formed on the inner peripheral surface. The depth dimension of the threaded hole  93  is greater than the length of the shank (nominal length) of the screw  92 . Therefore, even when the screw  92  is fastened until the bearing surface of the head of the screw  92  is tightly fastened to the bottom surface of the countersunk hole  95 , there is no possibility that the tip of the screw  92  reaches the bottom of the threaded hole  93 . 
     The tapered hole  94  is formed at part corresponding to the small-diameter boss  14   a,  is connected in such a manner that the inside of the container portion  14  communicates with the bottom of the threaded hole  93 , and is formed in a shape having diameter becoming smaller toward the threaded hole  93 . The tapered hole  94  has the diameter dimension of the far side end in the depth direction set to be smaller than that of the threaded hole  93  and the diameter dimension of the near side end in the depth direction set to be substantially equal to that of the threaded hole  93 . 
     The countersunk hole  95  is mainly formed at a part corresponding to the large-diameter boss  14   b,  is connected to the threaded hole  93  from the outside of the container portion  14 , and is formed in a shape having a larger diameter than that of the head of the screw  92  and having a depth greater than the height of the head of the screw  92 . 
     Next, an insulating gas filling method will be described. 
     First, the hermetically sealed container  11  is assembled, the hermetically sealed container  11  is housed in a not-illustrated chamber with the screw  92  half-fastened to the threaded hole  93 , and evacuation is performed. Being half-fastened is a state in which only a tip portion or approximately half on the tip end side of the external threaded portion of the screw  92  is fitted into the internal threaded portion of the threaded hole  93 . 
     Succeedingly, by supplying pressurized insulating gas into the chamber, the hermetically sealed container  11  is filled with insulating gas through the threaded hole  93 . 
     Succeedingly, by operating a bit disposed in the chamber, fastening of the screw  92  to the threaded hole  93  is completed. The completion of fastening is a state in which the bearing surface of the head of the screw  92  is tightly fastened to the bottom surface of the countersunk hole  95  and has a load applied thereto. 
     Succeedingly, the hermetically sealed container  11  is taken out from the chamber, the head of the screw  92  is buried in epoxy resin-based adhesive  96  by injecting the adhesive  96  into the countersunk hole  95 , and the adhesive  96  is dried. It is preferable to inject the adhesive  96  in such a way that, when the adhesive  96  has dried, the adhesive  96  in the countersunk hole  95  has a surface substantially flush with the undersurface of the large-diameter boss  14   b.  There is no possibility that, at room temperature, the insulating gas is discharged from the hermetically sealed container  11  in a short time. 
     Succeedingly, gas barrier coating is applied to the hermetically sealed container  11 , using laminated films of clay crystals, and, as a consequence, the hermetically sealed container  11  to be used in a hermetically sealed electromagnetic contactor is completed. 
     Advantageous Effects 
     Next, main advantageous effects of the embodiment will be described. 
     In conventional gas filling methods, insulating gas is supplied through a pipe made of metal that communicates with the inside of a hermetically sealed container, and, when the supply of insulating gas is stopped, ultrasonic welding is performed with the opening portion of the pipe closed and, subsequently, the pipe is cut. However, the configuration in which a pipe made of metal is used has been applicable only to a hermetically sealed container using a metal as a base material and has been inapplicable to a hermetically sealed container made of resin. Therefore, there has been a limit to miniaturization and weight reduction and a degree of freedom in design. Accordingly, in the present embodiment, the through-hole  91  is formed in the container portion  14  made of resin to fill the container portion  14  with gas and the screw  92  is fastened to the through-hole  91  to seal the through-hole  91 . Since, as described above, a structure in which the through-hole  91  is sealed by the screw  92  is employed, the present embodiment is applicable to the hermetically sealed container  11  made of resin and enables not only miniaturization and weight reduction to be achieved but also a degree of freedom in design to be improved. 
     The through-hole  91  includes the threaded hole  93  to which the screw  92  is fastened and the tapered hole  94  connected to the threaded hole  93  from the inside of the container portion  14 . The tapered hole  94  is formed in a shape having diameter becoming smaller toward the threaded hole  93 . In mold forming, it is generally difficult to form a small hole due to difficulty in ensuring strength of a mold. Forming a hole connected to the threaded hole  93  in a tapered shape enables the strength of a mold for molding the container portion  14  to be improved. 
     The tapered hole  94  is formed in such a manner that the diameter of one end that is connected to the threaded hole  93  is smaller than the diameter of the threaded hole  93 . This configuration enables dust and foreign objects to be prevented from entering the hermetically sealed container  11 . In addition, the hermetically sealed container  11  is pressurized to approximately 5 atmosphere, the tapered hole  94 , which is smaller than the threaded hole  93 , serves as a choke, which is preferable for safety reasons. In particular, although pressure sometimes increases due to increase in temperature at the time of breaking, the tapered hole  94  functioning as a choke enables pressure that the tip of the screw  92  receives to be reduced. 
     Since a structure in which the screw  92  is fitted into the threaded hole  93  is employed, fastening work is easy to perform. 
     Since the screw  92  has the head buried by the adhesive  96 , a concave-convex surface can be easily flattened. 
     Since the main contact unit  21 , which opens and closes an electrical path of the main circuit, is hermetically sealed in the hermetically sealed container  11 , which has the gas filling structure  16 , and the hermetically sealed container  11  is filled with insulating gas, which improves breaking performance, it is possible to prevent the arc-extinguishing space from becoming larger in size. 
     To the hermetically sealed container  11 , gas barrier coating is applied using laminated films of clay crystals. This configuration can suppress permeation of gas molecules, such as hydrogen and nitrogen, and thereby prevent leakage of pressurized insulating gas. 
     In the gas filling method, first, evacuation is performed with the screw  92  half-fastened to the through-hole  91 , and, succeedingly, the hermetically sealed container  11  is filled with insulating gas and, succeedingly, fastening of the screw  92  is completed. Although, when the screw  92  is half-fastened, passage of insulating gas is allowed, when the fastening of the screw  92  is completed, there is no possibility that, at room temperature, the insulating gas is discharged in a short time. Therefore, when the screw  92  is half-fastened, it is possible to easily perform filling of the hermetically sealed container  11  with insulating gas, and, when the fastening of the screw  92  is completed, it is possible to prevent insulating gas from leaking. 
     Since it is only required to completely fasten the screw  92  having been half-fastened, the work is easy to perform. 
     After the fastening of the screw  92  is completed, the head of the screw  92  is buried by the adhesive  96 , and, succeedingly, gas barrier coating is applied to the hermetically sealed container  11 , using laminated films of clay crystals. This configuration can suppress permeation or gas molecules, such as hydrogen and nitrogen, and thereby prevent leakage of pressurized insulating gas. 
     Next, other advantageous effects of the embodiment will be described. 
     Although hermetically sealed containers, which house a main contact unit and an auxiliary contact unit, have been hitherto containers made of metal and covered by a lid made of ceramic, it has been difficult to lead out auxiliary terminals while maintaining electrical insulation and increase in the number of components and cost have been brought about. Accordingly, in the present embodiment, first, the main contact unit  21  and the electromagnet unit  23  are hermetically sealed in the container body  12  made of resin. Further, the auxiliary contact unit  22  is disposed outside the container body  12  on the near side in the depth direction of the main contact unit  21 , and the auxiliary contact unit  22  is hermetically sealed in the auxiliary contact housing portion  13 , which is made of resin and communicates with the inside of the container body  12 . The container body  12  and the auxiliary contact housing portion  13  are filled with insulating gas. Employing the container body  12  and the auxiliary contact housing portion  13  that are made of resin as described above enables the auxiliary contact housing portion  13  to be easily disposed on one side in the opening/closing direction of the container body  12 , while enabling electrical insulation to be secured. Therefore, it is possible to dispose an auxiliary contact with a simpler structure at a low cost. 
     To the container body  12  and the auxiliary contact housing portion  13 , gas barrier coating is applied using laminated films of clay crystals. This configuration can suppress permeation of gas molecules, such as hydrogen and nitrogen, and thereby prevent leakage of pressurized insulating gas. 
     In the container body  12 , the opening portion  17  is formed on the near side in the depth direction. The contact support  51 , which is capable of advancing and retreating in the depth direction, has the base end side supporting the movable side of the main contact unit  21  inside the container body  12  and the tip end side passing the opening portion  17  and supporting the movable side of the auxiliary contact unit  22  inside the auxiliary contact housing portion  13 . Disposing the opening portion  17  on a line along which the contact support  51  advances and retreats and causing the tip end side of the contact support  51  to enter the inside of the auxiliary contact housing portion  13  via the opening portion  17  as described above enable a structure that is easy to assemble and is inexpensive to be achieved. 
     The auxiliary contact housing portion  13  covers the tip end side of the contact support  51  and hermetically seals the opening portion  17 . Hermetically sealing the container body  12  and the auxiliary contact housing portion  13  as described above enables breaking performance of the main contact unit  21  and the auxiliary contact unit  22  to be improved. Therefore, it is possible to prevent an arc-extinguishing space from becoming larger in size and achieve miniaturization and weight reduction. 
     The auxiliary contact housing portion  13  is fixed to the recessed portion  18  of the lid portion  15  by epoxy resin-based adhesive. Using adhesive for bonding between the lid portion  15  and the auxiliary contact housing portion  13  as described above enable a structure that is easy to assemble and is inexpensive to be achieved. 
     The pair of auxiliary fixed contact pieces  41  are arranged with a gap interposed between one end sides thereof inside the auxiliary contact housing portion  13 , the auxiliary fixed contact  46  is formed on one end side of each of the auxiliary fixed contact pieces  41 , and the other end side of each of the auxiliary fixed contact pieces  41  is connected to the auxiliary circuit outside the auxiliary contact housing portion  13 . The auxiliary movable contact piece  42  has the auxiliary movable contacts  48  formed on both end sides and causes the auxiliary movable contacts  48  to respectively come into contact with and be separated from the auxiliary fixed contacts  46 . The auxiliary contact unit  22  is formed by the auxiliary fixed contacts  46  and the auxiliary movable contacts  48 . The pair of auxiliary fixed contact pieces  41  are subjected to surface treatment by chemical etching and are integrated with the auxiliary contact housing portion  13  by insert molding. This processing causes the metal and the resin to be joined at the interface level and produces complex junctions exhibiting labyrinth effect, which enables gas molecules, such as hydrogen and nitrogen, to be prevented from leaking. 
     The pair of main fixed contact pieces  31  are arranged with a gap interposed between one end sides thereof inside the container body  12 , the main fixed contact  36  is formed on one end side of each of the main fixed contact pieces  31 , and the other end side of each of the main fixed contact pieces  31  is connected to the main circuit outside the container body  12 . The main movable contact piece  32  has the main movable contacts  38  formed on both end sides and causes the main movable contacts  38  to respectively come into contact with and be separated from the main fixed contacts  36 . The main contact unit  21  is formed by the main fixed contacts  36  and the main movable contacts  38 . The pair of main fixed contact pieces  31  are subjected to surface treatment by chemical etching and are integrated with the lid portion  15  by insert molding. This processing causes the metal and the resin to be joined at the interface level and produces complex junctions exhibiting labyrinth effect, which enables gas molecules, such as hydrogen and nitrogen, to be prevented from leaking. 
     Each of the coil contact pieces  81  has one end side arranged inside the container body  12  and the other end side connected to the control circuit outside the container body  12 . The relay contact pieces  85  are fixed to the spool  61  of the electromagnet unit  23 , and the coil  72  of the electromagnet unit  23  is connected to the relay contact pieces  85 . The support springs  88  are made of metal and are sandwiched between the coil contact pieces  81  and the relay contact pieces  85  inside the container body  12 . Because of this configuration, it is possible to maintain an excellent contact state between the coil contact pieces  81  and the relay contact pieces  85  by expansion and contraction of the support springs  88  even in an environment in which the electromagnetic contactor is vibrated, which enables reliability of the product to be improved. The coil contact pieces  81  are subjected to surface treatment by chemical etching and are integrated with the container portion  14  by insert molding. This processing causes the metal and the resin to be joined at the interface level and produces complex junctions exhibiting labyrinth effect, which enables gas molecules, such as hydrogen and nitrogen, to be prevented from leaking. 
     The support springs  88  press the electromagnet unit  23  to the container body  12 . Specifically, when the lid portion  15  is fixed to the container portion  14 , the spool  61  is pressed to the back surface of the lid Portion  15  via the partition wall member  54  due to repulsive force of the support springs  88 . This configuration can prevent backlash from occurring to the electromagnet unit  23  and the partition wall member  54  inside the container body  12 . Two support springs  88  on one side and two support springs  88  on the other side in the vertical direction, that is, in total, four support springs  88  are disposed, and are arranged in such a way that repulsive force equally acts on both sides in the vertical direction of the spool  61 . Because of this configuration, deviation of the center of gravity is reduced and stability is improved. In addition, workability when the container body  12  is assembled is also improved. 
     Note that, differing from alternating current in which current zero crossing periodically occurs, in breaking of direct current in which no current zero crossing occurs, it is required to forcibly generate current zero crossing by increasing arc voltage, which is generated between the contacts of the main contact unit  21 , to a voltage greater than or equal to power source voltage and restore insulation between the contacts. Thus, by stretching an arc to an arc-extinguishing space using the permanent magnets  55  in order to increase arc voltage, it is possible to improve breaking performance. Further, by arranging the main contact unit  21  and the auxiliary contact unit  22  in the hermetically sealed container  11  and filling the inside of the hermetically sealed container  11  with insulating gas, which improves breaking performance, it is possible to prevent the arc-extinguishing space from becoming larger in size. 
     Variations 
     Although, in the present embodiment, the hermetically sealed container  11  of the hermetically sealed electromagnetic contactor was described, the present invention is not limited thereto, and the present embodiment is applicable to any other hermetically sealed containers that are filled with gas. 
     Although, in the present embodiment, the gas filling structure  16  is disposed on a surface on the far side in the depth direction of the hermetically sealed container  11 , the present invention is not limited thereto, and the gas filling structure  16  may be disposed on a side surface in the vertical direction or the width direction or a surface on the near side in the depth direction. 
     Although, in the present embodiment, the screw  92  made of stainless steel is used, the present invention is not limited thereto, and, for example, a screw made of resin may be used. 
     Although, in the present embodiment, the screw  92  is used as a fastener, the present invention is not limited thereto, and a rivet may be used. 
     Although, in the embodiment, it is assumed that the auxiliary contact unit  22  is a b-contact of the normally-closed type, the present invention is not limited thereto, and the auxiliary contact unit  22  may be an a-contact of the normally-open type. 
     Although, in the embodiment, gas barrier coating is applied only to the outer peripheral surface of the hermetically sealed container  11 , the present invention is not limited thereto, and gas barrier coating may also be applied to the inner peripheral surface of the hermetically sealed container  11 . 
     Although, in the embodiment, the support springs  88  serve as both a support of the spool  61  and an electrical connection for the coil contact pieces  81 , the present invention is not limited thereto. That is, the roles may be separated by disposing a spring member to support the spool  61  and a spring member to electrically connect the coil contact pieces  81 . 
     While the present invention has been described with reference to the limited number of embodiments, the scope of the rights of the invention is not limited thereto. It will be obvious to those skilled in the art that various changes and modifications may be made in the embodiments based on the above disclosure. 
     REFERENCE SIGNS LIST 
       11  Hermetically sealed container 
       12  Container body 
       13  Auxiliary contact housing portion 
       14  Container portion 
       14   a  Small diameter boss 
       14   b  Large-diameter boss 
       15  Lid portion 
       16  Gas filling structure 
       17  Opening portion. 
       18  Recessed portion 
       21  Main contact unit 
       22  Auxiliary contact unit 
       23  Electromagnet unit 
       31  Main fixed contact piece 
       32  Main movable contact piece 
       33  Side plate portion 
       34  Upper plate portion 
       35  Lower plate portion 
       36  Main fixed contact 
       37  Terminal bolt 
       38  Main movable contact 
       41  Auxiliary fixed contact piece 
       42  Auxiliary movable contact piece 
       43  Lower plate portion 
       44  Side plate portion 
       46  Auxiliary fixed contact 
       47  Recessed portion 
       48  Auxiliary movable contact 
       51  Contact support 
       52  Main contact spring 
       53  Auxiliary contact spring 
       54  Partition wall member 
       55  Permanent magnet 
       56  Yoke 
       61  Spool 
       62  Plunger 
       63  Upper armature 
       64  Lower armature 
       65  Yoke 
       66  Return spring 
       71  Winding shaft 
       72  Coil 
       73  Side piece portion 
       74  Upper piece portion 
       75  Lower piece portion 
       81  Coil contact piece 
       82  Spool receiving portion 
       83  Deep recessed portion 
       84  Arm piece 
       85  Relay contact piece 
       86  Shallow recessed portion 
       87  Projecting portion 
       88  Support spring 
       91  Through-hole 
       92  Screw 
       93  Threaded hole 
       94  Tapered hole 
       95  Countersunk hole 
       96  Adhesive