Patent Publication Number: US-2023134636-A1

Title: Hermetically sealed electromagnetic contactor

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation application filed under 35 U.S.C. § 111(a) of International Patent Application No. PCT/JP2021/044681, filed on Dec. 6, 2021, the contents of which are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present invention relates to a hermetically sealed electromagnetic contactor. 
     BACKGROUND ART 
     In a hermetically sealed electromagnetic contactor described in JP 2018-163761 A, by housing a contact unit in a hermetically sealed container, which is made of metal and is covered by a lid made of ceramic, and filling the hermetically sealed container with pressurized insulating gas, such as hydrogen, breaking performance of the contact is improved without causing an arc-extinguishing space to become larger in size. 
     SUMMARY OF INVENTION 
     Technical Problem 
     There has been a limit to miniaturization and weight reduction and a degree of freedom in design for a configuration in which a hermetically sealed container made of metal and covered by a lid made of ceramic is used. 
     An object of the present invention is to, in a hermetically sealed electromagnetic contactor, not only achieve miniaturization and weight reduction but also improve a degree of freedom in design. 
     Solution to Problem 
     According to an aspect of the present invention, there is provided a hermetically sealed electromagnetic contactor including: a main contact unit including a pair of main fixed contact pieces, each of the main fixed contact pieces having a main fixed contact at one end and a terminal portion to be connected to a main circuit at the other end, and a main movable contact piece having a pair of main movable contacts configured to come into contact with and be separated from the main fixed contacts and configured to open and close an electrical path of the main circuit; a contact support configured to support the main movable contact piece; an electromagnet unit configured to switch opening/closing of the main contact unit via the contact support; and a hermetically sealed container made of resin on an inside of which the main contact unit and the electromagnet unit are arranged, the hermetically sealed container having the inside filled with insulating gas. 
     Advantageous Effects of Invention 
     According to the present invention, by using a hermetically sealed container made of resin, it is possible to not only achieve miniaturization and weight reduction but also improve a degree of freedom in design. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is an external view of a hermetically sealed electromagnetic contactor (single pole); 
         FIG.  2    is an external view of a hermetically sealed container (single pole); 
         FIG.  3    is an exploded view of the hermetically sealed container (single pole); 
         FIG.  4    is a cross-sectional view of the hermetically sealed container (single pole); 
         FIG.  5    is another cross-sectional view of the hermetically sealed container (single pole); 
         FIG.  6    is a cross-sectional view of a coil contact piece; 
         FIG.  7    is a diagram illustrative of the coil contact pieces, support springs, and relay contact pieces; 
         FIG.  8    is a cross-sectional view of an auxiliary contact unit; 
         FIGS.  9 A and  9 B  are diagrams illustrative of a nut member; 
         FIG.  10    is an external view of a hermetically sealed electromagnetic contactor (double poles); 
         FIG.  11    is an external view of a hermetically sealed container (double poles); 
         FIG.  12    is an exploded view of the hermetically sealed container (double poles); 
         FIG.  13    is a diagram illustrative of a partition wall member, a contact support, and an electromagnet unit after assembly; and 
         FIG.  14    is a cross-sectional view of the hermetically sealed container (double poles). 
     
    
    
     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. 
     FIRST EMBODIMENT 
     Configuration 
     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 electromagnetic contactor (single pole). 
     A hermetically sealed electromagnetic contactor  11  is of a single pole type and opens and closes an electrical path of a main circuit, and includes an auxiliary contact that 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 electromagnetic contactor  11  includes a case  12 , a main terminal cover  13 , an auxiliary terminal cover  14 , and a hermetically sealed container  15 . 
     The case  12  is made of a resin having electrical insulation and is mounted via mounting holes, which are formed at four corners on the far side in the depth direction. 
     The main terminal cover  13  is made of a resin having electrical insulation and, by being attached to the near side in the depth direction of the case  12  and preventing exposure of main terminals, improves safety at the time of maintenance and inspection performed by a worker. The main terminal cover  13  is formed by integrating a primary side portion and a secondary side portion, and both the primary side portion and the secondary side portion are fixed by fitting resin nuts  16  to ends of through bolts, which are fastened to main terminals. Each of the resin nuts  16  is made of a resin having electrical insulation, has the near side in the depth direction closed in a bag shape, and has a cross groove formed on a head. 
     The auxiliary terminal cover  14  is made of a resin having electrical insulation and, by preventing exposure of auxiliary terminals, improves safety at the time of maintenance and inspection performed by a worker. The auxiliary terminal cover  14  includes a primary side portion and a secondary side portion that are formed in separate bodies, and is fixed by being fitted to the hermetically sealed container  15 . 
     The hermetically sealed container  15  is made of a resin having electrical insulation and is housed in and fixed to the case  12 . 
       FIG.  2    is an external view of a hermetically sealed container (single pole). 
       FIG.  3    is an exploded view of the hermetically sealed container (single pole). 
       FIG.  4    is a cross-sectional view of the hermetically sealed container (single pole). 
     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. 
     The hermetically sealed container  15  houses a main contact unit  21 , an auxiliary contact unit  22 , and an electromagnet unit  23  and is further filled with pressurized insulating gas, such as hydrogen and nitrogen. The hermetically sealed container  15  not only has a container portion  24 , a lid portion  25 , and a cap portion  26  fixed to each other with epoxy resin-based 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  15 , 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  15  is preferably formed in a polygon that is composed of planes that are flat and linear to the extent possible. 
     The container portion  24  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  25  fits into the open end of the container portion  24  and closes the near side in the depth direction of the container portion  24 . The lid portion  25  is formed in a substantially hat-shape by a small cylinder portion  27 , which protrudes toward the near side in the depth direction, being formed at the center of the lid portion  25 . The small cylinder portion  27  is formed in a square cylinder shape that has the far side in the depth direction communicating with the inside of the container portion  24  and the near side in the depth direction opened. 
     The cap portion  26  fits into the open end of the small cylinder portion  27  and closes the near side in the depth direction of the small cylinder portion  27 . 
      The main contact unit  21  is a contact unit connected to a main circuit via the through bolts and configured to open and close an electrical path of the main circuit, and the hermetically sealed container  15  includes a pair of main fixed contact pieces  31  and a main movable contact piece  32 . 
     The pair of main fixed contact pieces  31  are made of a metal having conductivity, are long flat plates extending in the vertical direction and aligned with the vertical direction and the width direction, and are arranged in series with a gap interposed therebetween in the vertical direction inside the hermetically sealed container  15 . That is, the pair of main fixed contact pieces  31  extend along a surface orthogonal to a direction in which the main contact unit  21  is opened and closed. On one end sides of the pair of main fixed contact pieces  31 , which are the sides facing each other, main fixed contacts  33  are respectively brazed on surfaces on the far side in the depth direction. On the other end sides of the pair of main fixed contact pieces  31 , which are the sides turning away from each other, main terminal portions are formed outside the hermetically sealed container  15 , and one and the other of the main terminal portions are connected to the primary side and the secondary side of the main circuit, respectively. 
      The pair of main fixed contact pieces  31  are integrated with the lid portion  25  in such a manner as to penetrate through sidewalls of the lid portion  25  by insert molding. Specifically, after fine micron-sized protruding and recessed shapes are formed on the surfaces of the main fixed contact pieces  31  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 a long flat plate extending in the vertical direction and aligned with the vertical direction and the width direction, and is arranged on the far side in the depth direction of the pair of main fixed contact pieces  31 . On both end sides of the main movable contact piece  32 , main movable contacts  34  are brazed on a surface on the near side in the depth direction. The main movable contact piece  32  causes the main movable contacts  34  to be respectively separated from the main fixed contacts  33  when the main movable contact piece  32  retreats to the far side in the depth direction, and causes the main movable contacts  34  to respectively come into contact with the main fixed contacts  33  when the main movable contact piece  32  advances to the near side in the depth direction. The main contact unit  21  is formed by the main fixed contacts  33  and the main movable contacts  34 . 
     The auxiliary contact unit  22  is a contact unit connected to an auxiliary circuit via terminal screws and configured to open and close an electrical path of the auxiliary circuit, and the hermetically sealed container  15  includes a pair of auxiliary fixed contact pieces  41  and an auxiliary movable contact piece  42 . 
     The pair of auxiliary fixed contact pieces  41  are made of a metal having conductivity, are long flat plates extending in the vertical direction and aligned with the vertical direction and the width direction, and are arranged in series with a gap interposed therebetween in the vertical direction inside the hermetically sealed container  15 . On one end sides of the pair of auxiliary fixed contact pieces  41 , which are the sides facing each other, auxiliary fixed contacts  43  are respectively brazed on surfaces on the near side in the depth direction. On the other end sides of the pair of auxiliary fixed contact pieces  41 , which are the sides turning away from each other, auxiliary terminal portions are formed outside the hermetically sealed container  15 , and one and the other of the auxiliary terminal portions 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 small cylinder portion  27  in such a manner as to penetrate through sidewalls of the small cylinder portion  27  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 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 auxiliary fixed contact pieces  41 . That is, when viewed from the depth direction, the long-length directions of the main movable contact piece  41  and the auxiliary movable contact piece  42  are the same as each other. Both end sides of the auxiliary movable contact piece  42  bifurcate and form dual contacts, and auxiliary movable contacts  44  are brazed on a surface on the far side in the depth direction of the auxiliary movable contact piece  42 . The auxiliary movable contact piece  42  causes the auxiliary movable contacts  44  to respectively come into contact with the auxiliary fixed contacts  43  when the auxiliary movable contact piece  42  retreats to the far side in the depth direction, and causes the auxiliary movable contacts  44  to be respectively separated from the auxiliary fixed contacts  43  when the auxiliary movable contact piece  42  advances to the near side in the depth direction. The auxiliary contact unit  22  is formed by the auxiliary fixed contacts  43  and the auxiliary movable contacts  44 . 
     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, is formed in a substantially inverted-T shape when viewed from the vertical direction, and is arranged between the pair of main fixed contact pieces  31 . The contact support  51  elastically supports the main movable contact piece  32  via a main contact spring  52  on the far side in the depth direction of the main fixed contact pieces  31 . 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 near side in the depth direction. The contact support  51  elastically supports the auxiliary movable contact piece  42  via an auxiliary contact spring  53  on the near side in the depth direction of the auxiliary fixed contact pieces  41 . 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 far side in the depth direction. The contact support  51  is held by a partition wall member  54  (see  FIG.  3   ). The partition wall member  54  is made of a resin having electrical insulation and is housed on the near side in the depth direction in the container portion  24 . 
       FIG.  5    is another cross-sectional view of the hermetically sealed container (single pole). 
     In this drawing, a cross section passing the center in the vertical direction and taken along the width direction and the depth direction is illustrated. 
     The electromagnet unit  23  is housed on the far side in the depth direction in the container portion  24  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 . 
     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 direction 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 projects 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 projects 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 near side in the depth direction of the upper armature  63 , and the lower piece portion  75  is disposed on the near side in the depth direction of the lower armature  64 . 
     The return spring  66  is inserted onto the plunger  62  while being sandwiched between the lower armature  64  and the lower piece portions  75  and biases the plunger  62  to the far side in the depth direction with respect to the spool  61 . 
       FIG.  6    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.  7   ). One of the coil contact pieces  81  has the inner side in the vertical direction arranged inside the hermetically sealed container  15  and the outer side in the vertical direction connected to the positive side of a control circuit outside the hermetically sealed container  15 . 
     The other of the coil contact pieces  81  has the inner side in the vertical direction arranged inside the hermetically sealed container  15  and the outer side in the vertical direction connected to the negative side of the control circuit outside the hermetically sealed container  15 . The pair of coil contact pieces  81  are integrated with the container portion  24  in such a manner as to penetrate through a sidewall of container portion  24  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  24 , 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 of the arm pieces  84  is formed in a substantially plate shape aligned with the vertical direction and the vertical 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.  7   ). 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  15 , 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.  7   ). 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  15 , 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.  4   ). 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  25  is fixed to the container portion  24 , the spool  61  being pressed to the pair of main fixed contact pieces  31  via the partition wall member  54  due to repulsive force of the support springs  88  causes backlash to be suppressed. 
       FIG.  7    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  24 , the arm pieces  84 , the spool receiving portions  82 , and the like 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 pieces  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 far 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 far 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  is 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 near 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 near 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. 
       FIG.  8    is a cross-sectional view of the auxiliary contact unit. 
     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. 
     On the small cylinder portion  27 , terminal receiving portions  91  are formed on the back surface side, that is, on the far side in the depth direction, of the auxiliary fixed contact pieces  41 , which are located on the outer sides in the vertical direction of the small cylinder portion  27 . Each of the terminal receiving portions  91  is a portion projecting from a sidewall of the small cylinder portion  27  toward the outer side in the vertical direction, and a nut member  92  is integrated with the terminal receiving portion  91  by insert molding. Each of the nut members  92  is made of a metal having conductivity and is formed in a cylindrical shape, and, on the near side in the depth direction, a bottomed threaded hole  94 , into which a terminal screw  93  is fitted, is formed in the depth direction. 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. 
       FIGS.  9 A and  9 B  are diagrams illustrative of the nut member. 
       FIG.  9 A  illustrates fitting between a nut member  92  and an auxiliary fixed contact piece  41 , and  FIG.  9 B  illustrates fitting between the nut member  92  and a terminal screw  93 . In the auxiliary fixed contact piece  41 , a circular hole  96  (insertion hole), which has a larger diameter than the outer diameter of an external threaded portion  95  on the terminal screw  93 , is formed on the other end side, which is located outside the small cylinder portion  27 , and, on the nut member  92 , a small-diameter portion  97 , which fits into the circular hole  96 , is formed on the near side in the depth direction. Height in the depth direction of the small-diameter portion  97  is the same as plate thickness of the auxiliary fixed contact piece  41 . To the terminal screw  93 , a square washer for wire holding and a spring washer are attached. 
     Advantageous Effects 
     Next, main advantageous effects of the first 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, there has been a limit to miniaturization and weight reduction and a degree of freedom in design. Accordingly, in the present embodiment, the main contact unit  21 , the auxiliary contact unit  22 , and the electromagnet unit  23  are hermetically sealed in the hermetically sealed container  15 , which is made of resin, and the hermetically sealed container  15  is filled with pressurized insulating gas. Using the hermetically sealed container  15  made of resin enables not only miniaturization and weight reduction to be achieved but also a degree of freedom in design to be improved. In addition, by arranging the main contact unit  21  and the auxiliary contact unit  22  in the hermetically sealed container  15  and causing the hermetically sealed container  15  to be filled with insulating gas, which improves breaking performance, it is possible to prevent an arc-extinguishing space from becoming larger in size. 
     To the hermetically sealed container  15 , 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. 
     The main contact unit  21  includes the pair of main fixed contact pieces  31  and the main movable contact piece  32 . The main fixed contact pieces  31  have the main fixed contacts  33  at one ends, and the other ends serve as main terminal portions to be connected to the main circuit. The main movable contact piece  32  has the pair of main movable contacts  34 , which come into contact with and are separated from the main fixed contacts  33 , and is supported by the contact support  51 . The auxiliary contact unit  22  includes the pair of auxiliary fixed contact pieces  41  and the auxiliary movable contact piece  42 . The pair of auxiliary fixed contact pieces  41  have the auxiliary fixed contacts  43  at one ends, and the other end sides serve as auxiliary terminal portions to be connected to the auxiliary circuit. The auxiliary movable contact piece  42  has the pair of auxiliary movable contacts  44 , which come into contact with and are separated from the auxiliary fixed contacts  43 , and is supported by the contact support  51 . The electromagnet unit  23  switches opening/closing of the main contact unit  21  and opening/closing of the auxiliary contact unit  22  via the contact support  51 . This configuration enables opening/closing of the main contact unit  21  and opening/closing of the auxiliary contact unit  22  to be easily switched. 
     The support springs  88  press the electromagnet unit  23  to the main contact unit  21  side with respect to the hermetically sealed container  15 . Specifically, when the lid portion  25  is fixed to the container portion  24 , the spool  61  is pressed to the pair of main fixed contact pieces  31  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 hermetically sealed container  15 . 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 hermetically sealed container  15  is assembled is also improved. 
     Each of coil contact pieces  81  has one end side arranged inside the hermetically sealed container  15 , and the other end side of the coil contact piece  81  is connected to the control circuit outside the hermetically sealed container  15 . 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 arranged between the coil contact pieces  81  and the relay contact pieces  85  inside the hermetically sealed container  15 . 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 hermetically sealed container  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. 
     The pair of main fixed contact pieces  31  are formed in flat plate shapes and extend along a surface orthogonal to the direction in which the main contact unit  21  is opened and closed. Specifically, the pair of main fixed contact pieces  31  are arranged with a gap interposed between one end sides thereof inside the hermetically sealed container  15 , the main fixed contact  33  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 hermetically sealed container  15 . In addition, the main movable contact piece  32  has the main movable contacts  34  formed on both end sides and causes the main movable contacts  34  to respectively come into contact with and be separated from the main fixed contacts  33 . The main contact unit  21  is formed by the main fixed contacts  33  and the main movable contacts  34 . The pair of main fixed contact pieces  31  are subjected to surface treatment by chemical etching and are integrated with the hermetically sealed container  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. 
     The pair of auxiliary fixed contact pieces  41  are arranged with a gap interposed between one end sides thereof inside the hermetically sealed container  15 , the auxiliary fixed contact  43  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 hermetically sealed container  15 . The auxiliary movable contact piece  42  has the auxiliary movable contacts  44  formed on both end sides and causes the auxiliary movable contacts  44  to respectively come into contact with and be separated from the auxiliary fixed contacts  43 . The auxiliary contact unit  22  is formed by the auxiliary fixed contacts  43  and the auxiliary movable contacts  44 . The pair of auxiliary fixed contact pieces  41  are subjected to surface treatment by chemical etching and are integrated with the hermetically sealed container  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 pair of auxiliary fixed contact pieces  41  is formed in a flat plate shape, and the circular hole  96 , which has a larger diameter than the outer diameter of the external threaded portion  95  on the terminal screw  93 , is formed on the other end side, which is located outside the hermetically sealed container  15 . On the hermetically sealed container  15 , the terminal receiving portions  91  are formed on the back surface side of the auxiliary fixed contact pieces  41 , which are located outside the hermetically sealed container  15 , and, on the terminal receiving portions  91 , the nut members  92 , which are made of metal, in each of which the bottomed threaded hole  94 , into which the terminal screw  93  fits, is formed are disposed. Each of the nut members  92  is subjected to surface treatment by chemical etching and is integrated with the terminal receiving portion  91  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. 
     When a configuration in which the nut member  92  is omitted, an internal threaded portion is formed in the circular hole  96  of the auxiliary fixed contact piece  41 , and the terminal screw  93  is fitted into the internal threaded portion is employed, a threaded hole into which the external threaded portion  95  of the terminal screw  93  enters needs to be formed in the terminal receiving portion  91 . This threaded hole has a larger diameter than the external threaded portion  95  of the terminal screw  93 . Since it is required to apply gas barrier coating to the entire outer peripheral surface of the hermetically sealed container  15 , gas barrier coating also needs to be applied to the inner peripheral surface of the threaded hole formed in the terminal receiving portion  91 . However, since the auxiliary fixed contact piece  41  is disposed at the open end of the threaded hole, it is difficult to apply gas barrier coating to the inner peripheral surface of the threaded hole by spray method. Thus, by insert-molding the nut member  92  made of metal as described above, leakage of gas molecules, such as hydrogen and nitrogen, is prevented. 
     Variations 
     Although, in the first 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 first embodiment, gas barrier coating is applied only to the outer peripheral surface of the hermetically sealed container  15 , 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  15 . 
     Although, in the first 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 . 
     SECOND EMBODIMENT 
     Configuration 
     The second embodiment is a hermetically sealed electromagnetic contactor  11  configured into a double pole type that includes two main contact units  21 . That is, with the exception that the number of poles, that is, the number of main contact units  21 , is increased, the second embodiment has the same configuration as that in the afore-described first embodiment, and the same reference signs are assigned to the same constituent components as those in the first embodiment and detailed description thereof will be omitted. 
       FIG.  10    is an external view of a hermetically sealed electromagnetic contactor (double poles). 
     A main terminal cover  13  is fixed by two resin nuts  16 , and a resin nut  16  on a primary side portion of the main terminal cover  13  and the other resin nut  16  on a secondary side portion thereof are fixed to a main terminal of the first pole and a main terminal of the second pole, respectively. 
       FIG.  11    is an external view of a hermetically sealed container (double poles). 
     In the following description, when the first pole and the second pole are distinguished from each other, “a” and “b” are appended to a reference sign related to the first pole and a reference sign related to the second pole, respectively. A pair of main fixed contact pieces  31   a  in the first pole and a pair of main fixed contact pieces  31   b  in the second pole are disposed on one side and the other side in the width direction, respectively. 
       FIG.  12    is an exploded view of the hermetically sealed container (double poles). 
     A partition wall member  111  is made of a resin having electrical insulation and is housed on the near side in the depth direction in a container portion  24  while holding a contact support  51 . On the partition wall member  111 , on both sides in the vertical direction, inter-pole barriers  112  (partition wall members) that partition the first pole and the second pole, that is, the main contact units  21 , from each other are formed. 
       FIG.  13    is a diagram illustrative of the partition wall member, the contact support, and the electromagnet unit after assembly. 
       FIG.  14    is a cross-sectional view of the hermetically sealed container (double poles). 
     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. 
     The inter-pole barriers  112  are made of a resin having electrical insulation, are formed in plate shapes aligned with the vertical direction and the depth direction, and are disposed at the center in the width direction. Inside a hermetically sealed container  15 , the inter-pole barriers  112  partitioning the inside into a first pole side and a second pole side has improved electrical insulation between the respective poles in the main contact units  21 . 
     Advantageous Effects 
     Next, main advantageous effects of the second embodiment will be described. 
     In the second embodiment, the hermetically sealed electromagnetic contactor  11  is configured into the double pole type, and the inter-pole barriers  112  made of resin that partition the respective poles from each other are disposed on the partition wall member  111 . This configuration can improve electrical insulation between the respective poles in the main contact units  21 . Since hermetically sealed containers, which house main contact units, have been hitherto containers made of metal and covered by a lid made of ceramic, it has been difficult to secure electrical insulation between the respective poles inside a hermetically sealed container. In contrast, since use of the hermetically sealed container  15  made of resin enables the inter-pole barriers  112  to be easily formed even when the number of poles is multiple, it is possible to secure electrical insulation between the respective poles in the main contact units  21 . Use of the hermetically sealed container  15  made of resin as described above enables a degree of freedom in design to be improved and a request for increase in the number of poles to be easily coped with. 
     Variations 
     Although, in the second embodiment, the inter-pole barriers  112  are integrated with the partition wall member  111 , the present invention is not limited thereto, and the inter-pole barriers  112  may be disposed as separate members or integrated with a lid portion  25 . 
     Although, in the second embodiment, the hermetically sealed electromagnetic contactor  11  is configured into the double pole type, the present invention is not limited thereto, and the present embodiment is capable of adapting to a triple pole type or a quadruple pole type. Note, however, that the inter-pole barriers  112  are required to be disposed between respective poles for any pole type. 
     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 electromagnetic contactor 
           12  Case 
           13  Main terminal cover 
           14  Auxiliary terminal cover 
           15  Hermetically sealed container 
           16  Resin nut 
           21  Main contact unit 
           22  Auxiliary contact unit 
           23  Electromagnet unit 
           24  Container portion 
           25  Lid portion 
           26  Cap portion 
           27  Small cylinder portion 
           31  Main fixed contact piece 
           31   a  Main fixed contact piece 
           31   b  Main fixed contact piece 
           32  Main movable contact piece 
           33  Main fixed contact 
           34  Main movable contact 
           41  Auxiliary fixed contact piece 
           42  Auxiliary movable contact piece 
           43  Auxiliary fixed contact 
           44  Auxiliary movable contact 
           51  Contact support 
           52  Main contact spring 
           53  Auxiliary contact spring 
           54  Partition wall member 
           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  Terminal receiving portion 
           92  Nut member 
           93  Terminal screw 
           94  Threaded hole 
           95  External threaded portion 
           96  Circular hole 
           97  Small-diameter portion 
           111  Partition wall member 
           112  Inter-pole barrier