Abstract:
A polar electromagnet device has a drive shaft comprising an axis center supported so as to reciprocate in an axis center direction at a center hole of a spool wound with a coil, and a movable iron core attached to a lower end of the drive shaft on the axis center. The drive shaft is reciprocated with the movable iron core which reciprocates based on excitation and demagnetization of the coil. A permanent magnet is integrally arranged at the movable iron core on the same axis center.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Technical Field 
         [0002]    The present invention relates to electromagnet devices, and in particular, to a polar electromagnet device including a permanent magnet. 
         [0003]    2. Related Art 
         [0004]    Conventionally, as a polar electromagnet device, a release electromagnet device has been known including a movable armature held in a freely projecting manner in a predetermined direction, a fixed armature arranged facing the movable armature, a tripping spring for biasing the movable armature in the projecting direction, a permanent magnet for holding the tripping spring in an accumulated state, a yoke configuring a magnetic path of the magnetic flux from the permanent magnet through the movable armature and the fixed armature, and an electromagnet for generating a demagnetizing field with respect to the magnetic field by the permanent magnet based on the detection result of an abnormal current, where the magnetic flux density that passes the contacting surface when the movable armature and the fixed armature contact is greater than or equal to one tesla. 
       SUMMARY 
       [0005]    However, as shown in FIG. 1 of Japanese Unexamined Patent Publication No. 2007-258150, the polar electromagnet device has a permanent magnet  5  arranged on the lower end side of a coil bobbin  1 . Thus, a movable armature  6  needs to be driven with the magnetic force of a coil  2  against the magnetic force of the permanent magnet  5  in time of operation, and power consumption is large. 
         [0006]    In the release electromagnet device, a space for winding the coil  2  is small, and the device enlarges when attempting to obtain high magnetic force with the coil  2 . 
         [0007]    In view of the above problems, the present invention aims to provide a small polar electromagnet device of small power consumption. 
         [0008]    In accordance with one aspect of the present invention, to achieve the above object, there is provided a polar electromagnet device in which a drive shaft is supported so as to reciprocate in an axis center direction at a center hole of a spool wound with a coil, a movable iron core is attached to a lower end of the drive shaft on the same axis center, and the drive shaft is reciprocated with the movable iron core which reciprocates based on excitation and demagnetization of the coil; wherein a permanent magnet is integrally arranged at the movable iron core on the same axis center. 
         [0009]    According to the present invention, the permanent magnet integrally arranged on the movable iron core acts repulsively to the magnetic force generated by the excitation of the coil in time of operation, and the movable iron core integrally arranged with the permanent magnet operates, whereby the operation voltage becomes lower than in the related art, and a polar electromagnet device with small power consumption is obtained. 
         [0010]    Since the permanent magnet is integrally arranged on the same axis center on the movable iron core, the winding space of the coil becomes larger than in the related art. Thus, more coils can be wound even in the housing having the same outer shape dimension as the related art, and consequently, a smaller polar electromagnet device is obtained. 
         [0011]    According to an embodiment of the present invention, an annular auxiliary yoke may be arranged at a position for exerting repulsive force based on a magnetic force generated by the excitation of the coil to the movable iron core in time of operation of an inner circumferential surface of the center hole of the spool. 
         [0012]    According to the present embodiment, the movable iron core is driven by the large repulsive force with respect to the permanent magnet in time of operation, and thus a polar electromagnet device with smaller power consumption is obtained. 
         [0013]    According to another embodiment of the present invention, an annular auxiliary yoke may be arranged at a position for enhancing a returning force of the movable iron core based on a magnetic force generated by the permanent magnet arranged at the movable iron core in time of returning of the inner circumferential surface of the center hole of the spool. 
         [0014]    According to the present embodiment, the magnetic force of the permanent magnet is efficiently utilized as the returning force by the annular auxiliary yoke, and thus a polar electromagnet device having quick operation characteristics is obtained. As the returning force is maintained even after returning is completed, mistaken operation is less likely to occur even by the impact force from the outside, and a polar electromagnet device having high reliability can be obtained. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIGS. 1A and 1B  are perspective views each showing a first embodiment of a power load electromagnetic relay applied with a polar electromagnet device according to the present invention; 
           [0016]      FIG. 2  is a front cross-sectional view of the power load electromagnetic relay shown in  FIGS. 1A and 1B ; 
           [0017]      FIG. 3  is a side cross-sectional view of the power load electromagnetic relay shown in  FIGS. 1A and 1B ; 
           [0018]      FIG. 4  is an exploded perspective view of the power load electromagnetic relay shown in  FIGS. 1A and 1B ; 
           [0019]      FIG. 5  is an exploded perspective view of the main parts of  FIG. 4 ; 
           [0020]      FIG. 6  is a partial enlarged cross-sectional view of  FIG. 2 ; 
           [0021]      FIG. 7  is an exploded perspective view of the main parts of  FIG. 4 ; 
           [0022]      FIG. 8  is an exploded perspective view of the main parts of  FIG. 7 ; 
           [0023]      FIG. 9  is an exploded perspective view of the main parts of  FIG. 7 ; 
           [0024]      FIG. 10  is an exploded perspective view of the main parts of  FIG. 9 ; 
           [0025]      FIG. 11  is an exploded perspective view of the main parts of  FIG. 4 ; 
           [0026]      FIG. 12  is a front cross-sectional view showing a second embodiment of a power load electromagnetic relay applied with a polar electromagnet device according to the present invention; 
           [0027]      FIG. 13  is a front cross-sectional view showing a third embodiment of a polar electromagnet device according to the present invention; and 
           [0028]      FIG. 14  is an exploded perspective view of the main parts of the polar electromagnet device shown in  FIG. 13 . 
       
    
    
     DETAILED DESCRIPTION 
       [0029]    Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings  FIGS. 1A to 14 . 
         [0030]    As shown in  FIGS. 1A to 11 , a power load electromagnetic relay applied with a first embodiment of the polar electromagnet device according to the present invention, in brief, has a drive mechanism unit  20  and a contact mechanism unit  50 , which are integrated one above the other, accommodated in a case  10 , and a cover  70  is fitted to cover the case  10 . 
         [0031]    As shown in  FIG. 4 , the case  10  has a box-shape capable of accommodating the drive mechanism unit  20  and the contact mechanism unit  50 , to be hereinafter described, where a fit-in recessed portion  11  ( FIGS. 2 and 3 ) for positioning the drive mechanism unit  20  is formed at the middle of the bottom surface. The case  10  has mounts  12 ,  13  arranged in a projecting manner towards the side from the lower edge of the outer peripheral corners positioned on a diagonal line. The mounts  12 ,  13  are respectively formed with attachment holes  14 ,  14 , where a terminal block  15  is integrally molded to the mount  12 . Furthermore, the case  10  has a slit  16  for pulling out a lead wire  33   a,  to be hereinafter described, formed at the corner of the opening edge, and an engagement hole  17  for preventing the cover  70 , to be hereinafter described, from coming off formed at the opening edge of the opposing side walls. 
         [0032]    As shown in  FIGS. 5 to 7 , the drive mechanism unit  20  has an electromagnet block  30 , in which a coil  32  is wound around a spool  31 , fixed between a first yoke  21  having a substantially U-shaped cross section and a second yoke  22  bridged over both ends of the first yoke  1 . 
         [0033]    As shown in  FIG. 5 , the first yoke  21  has an insertion hole  21   a  for inserting a bottomed tubular body  34 , to be hereinafter described, formed at the middle of the bottom surface, and cutouts  21   b  for fitting the second yoke  22  formed at both ends. 
         [0034]    As shown in  FIG. 10 , the second yoke  22  has both ends formed to a planar shape that can engage to and bridge over the cutouts  21   b  of the first yoke  21 , and has a caulking hole  22   a  formed at the middle. The second yoke  22  has a counterbore hole  22   b  formed at the corner on the upper surface, where a gas sealing pipe  23  is air-tightly joined to the counterbore hole  22   b  by brazing. 
         [0035]    As shown in  FIG. 5 , the electromagnet block  30  is formed by wounding the coil  32  around the spool  31  having collar portions  31   a,    31   b  at both ends, where a pull-out line of the coil  32  is engaged and soldered to a pair of relay terminals  33  (relay terminal on far side is not shown) arranged on the collar portion  31   a.  Lead wires  33   a  are connected to the relay terminals  33 ,  33 . As shown in  FIGS. 5 and 6 , the bottomed tubular body  34  is inserted to a center hole  31   c  passing through the collar portions  31   a,    31   b  of the spool  31 . The upper opening of the bottomed tubular body  34  is air-tightly joined to the lower surface of the second yoke  22  by laser welding. The bottomed tubular body  34  has an annular auxiliary yoke  35  fitted to the lower end projecting out from the insertion hole  21   a  of the first yoke  21  ( FIG. 6 ). 
         [0036]    According to the present embodiment, the annular auxiliary yoke  35  is sandwiched by the bottomed tubular body  34  and the first yoke  21 . Thus, the opposing area of an outer circumferential surface of a movable iron core  42 , to be hereinafter described, and the first yoke  21  and the annular auxiliary yoke  35  increases and the magnetic resistance reduces, and thus the magnetic efficiency improves and the power consumption reduces. 
         [0037]    A shown in  FIG. 2 , a fixed iron core  40 , a returning coil spring  41 , and the movable iron core  42  are accommodated in the bottomed tubular body  34 . As shown in  FIG. 6 , the fixed iron core  40  has the upper end caulked and fixed to the caulking hole  22   a  of the second yoke  22 . Thus, the movable iron core  42  is biased to the lower side with the spring force of the returning coil spring  41 . As shown in  FIG. 7 , the bottomed tubular body  34  has an adhesion prevention metal sheet  48  and a shock eliminating circular plate  49  made of rubber arranged between the bottom surface and the movable iron core  42 . 
         [0038]    As shown in  FIGS. 6 and 8 , the movable iron core  42  has a first movable iron piece  44  inserted into a connection pipe  43  made of non-magnetic material, and a ring-shaped permanent magnet  45  and a second movable iron piece  46  fitted to and integrated with the outer peripheral surface of the connection pipe  43 . Thus, a desired magnetic circuit can be formed by shielding the magnetic power of the ring-shaped permanent magnet  45  with the connection pipe  43 . In time of returning, the second movable iron piece  46  is positioned above the opening edge of the annular auxiliary yoke  35 .  FIGS. 6 and 7  do not show the returning coil spring  41  for the sake of convenience of explanation. 
         [0039]    As shown in  FIG. 9 , the contact mechanism unit  50  has a shield member  55  and a movable contact block  60  arranged in a sealed space formed by connecting and integrating a ceramic sealing container  51  to the upper surface of the second yoke  22 . 
         [0040]    The sealing container  51  has fixed contact terminals  52 ,  53  having a substantially T-shaped cross section brazed to terminal holes  51   a,    51   b  formed at the roof surface by way of washers  51   c,    51   c,  and a connection annular skirt portion  54  brazed to the lower opening edge. The fixed contact terminals  52 ,  53  have screw holes  52   a,    53   a  formed at the upper surface, and fixed contacts  52   b,    53   b  arranged at the lower end face. The annular skirt portion  54  is positioned on the upper surface of the second yoke  22 , and then welded and integrated with laser to form the sealed space. 
         [0041]    As shown in  FIG. 10 , the shield member  55  is integrated by fitting a metal shield ring  57  to a box-shaped resin molded article  56  having a shallow bottom with a pass-through hole  56   a  at the middle, and caulking a caulking projection  56   b  arranged in a projecting manner at the bottom surface of the box-shaped resin molded article  56 . The metal shield ring  57  draws the arc generated in time of contact opening/closing, and prevents the brazed part of the sealing container  51  and the connection annular skirt portion  54  from melting. 
         [0042]    As shown in  FIG. 10 , the movable contact block  60  has an upper end of a drive shaft  61  inserted to a caulking hole  62   c  of the movable contact  62  formed with movable contact points  62   a,    62   b  at both ends, and caulked and fixed by way of a washer  63 . A contact-pressure coil spring  64  is inserted to the drive shaft  61  from the lower side, and an E ring  65  is engaged and assembled to an annular groove  61   a  formed on the outer circumferential surface of the drive shaft  61 . Thus, the movable contact  62  is biased upward by way of the pressure-contact coil spring  64 . 
         [0043]    The pressure-contact coil spring  64  applies contact pressure to the movable contact  62 . Thus, the attractive force characteristics can be adjusted and the degree of freedom in design can be extended by appropriately selecting the contact-pressure coil spring  64 . 
         [0044]    As shown in  FIG. 4 , the cover  70  has a plan shape that can be fitted to the case  10 . As shown in  FIG. 11 , the cover  70  is fitted at the inner side surface with a holding member  90  made of magnetic material and having a substantially U-shape in plan view. 
         [0045]    The cover  70  has terminal holes  72 ,  73  formed on both sides of an insulation protrusion  71  formed at the middle of the roof surface. The cover  70  also has a rotation-preventing projection  74  for an external terminal (not shown) arranged in a projecting manner at the corner of the roof surface, and an engagement projection  75  arranged in a projecting manner to the side from both side surfaces on the short side. 
         [0046]    The holding member  90  has a positioning nail  91  raised from the lower edge on the opposing inner side surface, and a positioning recessed portion  92  formed through extrusion processing. Two permanent magnets  93  are arranged facing each other by way of the positioning projection  91 . The permanent magnet  93  pulls the arc generated between the movable contact  62  and the fixed contact terminals  52 ,  53  with the magnetic force and allows the arc to be easily extinguished, prevents contact adhesion, and protects the brazed portion of the sealed container  51 . 
         [0047]    A method of assembling the seal contact device according to the present embodiment will now be described. 
         [0048]    First, the electromagnet block  30  in which the coil  32  is wound around the spool  31  is placed and positioned at the first yoke  21 . The shield member  55  is positioned at the middle of the upper surface of the second yoke  22  caulked and fixed with the fixed iron core  40  in advance, and the drive shaft  61  of the movable contact block  60  is inserted to the pass-through hole  56   a  of the shield member  55  and the shaft hole  40   a  of the fixed iron core  40 . The inner peripheral edge of the sealed container  51  brazed with the fixed contact terminals  52 ,  53  and the annular skirt portion  54  is fitted to the shield ring  57  of the shield member  55 . The annular skirt portion  54  is laser welded and integrated to the upper surface of the second yoke  22  while pushing the box-shaped molded article  56  with the lower end face of the opening edge of the sealed container  51 . 
         [0049]    The drive shaft  61  projecting out from the lower surface of the fixed iron core  40  is then inserted to the returning coil spring  41  and the shaft hole  42   a  of the movable iron core  42 . The movable iron core  42  is pushed in against the spring force of the returning coil spring  41  until contacting the fixed iron core  40 . Furthermore, the drive shaft  61  is pushed in until obtaining a predetermined contact pressure, a state in which the movable contact  62  contacts the fixed contacts  52   a,    53   a  of the fixed contact terminals  52 ,  53  with a predetermined contact pressure is maintained, and the lower end of the drive shaft  61  is welded and integrated with the movable iron core  42 . Thereafter, the bottomed tubular body  34  sequentially accommodating the shock eliminating circular plate  49  made of rubber and the adhesion prevention metal sheet  48  is placed over the movable iron core  42 , and the opening edge thereof is welded and integrated through laser welding to the lower surface of the second yoke  22 . After releasing the air in the sealed space from the gas sealing pipe  23 , inactive gas is injected, and the gas sealing pipe  23  is caulked and sealed. 
         [0050]    Furthermore, the bottomed tubular body  34  is inserted to the center hole  31   c  of the spool  31 , and both ends of the second yoke  22  are fitted to and caulked and fixed to the cutouts  21   b  of the first yoke  22 . The annular auxiliary yoke  35  is fitted to and prevented from coming off from the lower end of the bottomed tubular body  34  projecting out from the insertion hole  21   a  of the first yoke  21 . 
         [0051]    As shown in  FIG. 4 , the drive mechanism unit  20  and the contact mechanism unit  50  integrated one above the other are then inserted into the base  10 . The lower end of the projecting bottomed tubular body  34  is fitted to and positioned in the recessed portion  11  of the base  10  and the lead wire  33   a  is pulled out from the cutout  16  of the base  10 . The engagement nail  75  of the cover  70  is then engaged and fixed to the engagement hole  17  of the base  10 . The power load electromagnetic relay according to the present embodiment is thereby obtained. 
         [0052]    The operation of the contact device according to the present embodiment will now be described. 
         [0053]    As shown in  FIG. 2 , when voltage is not applied to the coil  32 , the movable iron core  42  is separated from the fixed iron core  40  by the spring force of the returning coil spring  41  and the magnetic force of the permanent magnet  45  of the movable iron core  42 . Thus, movable contacts  62   a,    62   b  positioned at both ends of the movable contact  62  are separated from the fixed contacts  52   b,    53   b  of the fixed contact terminals  52 ,  53 . 
         [0054]    When voltage is applied to the coil  32 , and the movable iron core  42  moves towards the fixed iron core  40  against the spring force of the returning coil spring  41  by the combined force of the attractive force of the fixed iron core  40  with respect to the movable iron core  42  and the repulsive force of the ring-shaped permanent magnet  45  of the movable iron core  42  on the magnetic flux of the coil  32 . Thus, the drive shaft  61  integral with the movable iron core  42  moves in the axis center direction, and the movable contacts  62   a,    62   b  of the movable contact  62  contact the fixed contacts  52   b,    53   b  of the fixed contact terminals  52 ,  53 . 
         [0055]    According to the present embodiment, the magnetic force of the ring-shaped permanent magnet  45  can be effectively used during the operation, and thus the movable iron core  42  can be driven with small power consumption. Furthermore, the magnetic flux generated at the coil  32  can pass through the annular auxiliary yoke  35 , the magnetic efficiency improves, and greater repulsive force can be obtained, whereby the electromagnetic relay with smaller power consumption is obtained. 
         [0056]    The movable iron core  42  is attracted towards the fixed iron core  40 , the movable iron core  42  moves against the spring force of the returning coil spring  41 , and the contact pressure increases. The movable contacts  62   a,    62   b  of the movable contact  62  then contact the fixed contacts  52   b,    53   b  of the fixed contact terminals  52 ,  53  at a predetermined pressure against the spring force of the returning coil spring  41 , and thereafter, the movable iron core  42  is attracted to the fixed iron core  40 , and such a state is maintained. 
         [0057]    Finally, when application of voltage on the coil  32  is stopped, the magnetic force of the coil  32  disappears, and the movable iron core  42  separates from the fixed iron core  40  by the spring force of the returning coil spring  41 . Then, the movable iron core  42  returns to the original position after the movable contact  62  separates from the fixed contact terminals  52 ,  53 . In returning, the movable iron core  42  impacts the shock eliminating circular plate  49  by way of the adhesion prevention metal sheet  48 , whereby the impact force is absorbed and alleviated. 
         [0058]    According to the present embodiment, the magnetic flux of the ring-shaped permanent magnet  45  forms a magnetic circuit by way of the annular auxiliary yoke  35  in time of returning. Thus, the returning operation of the movable iron core  42  becomes quick by effectively using the magnetic force of the ring-shaped permanent magnet  45  even in time of returning, and an electromagnetic relay excelling in operation characteristics can be obtained. 
         [0059]    A second embodiment is substantially the same as the first embodiment but differs in the structure of the movable iron core  42 , as shown in  FIG. 12 . 
         [0060]    In other words, the movable iron core  42  has a shaft hole of an inner diameter capable of receiving the drive shaft  61 , and has the first movable iron piece  44 , the ring-shaped permanent magnet  45 , and the second movable iron piece  46  fitted to and integrated with the connection pipe  43  made of non-magnetic material. 
         [0061]    According to the present embodiment, the ring-shaped permanent magnet  45  is arranged so as to be directly sandwiched by the first movable iron piece  44  and the second movable iron piece  46 , and thus an electromagnetic relay in which the assembly precision is high and the operation characteristics are not varied is obtained. 
         [0062]    Others are the same as the first embodiment, and thus same reference numbers are denoted for the same portions and the description will not be given. 
         [0063]    A third embodiment is substantially the same as the first embodiment but differs in the structure of the movable iron core  42 , as shown in  FIGS. 13 and 14 . 
         [0064]    In other words, the movable iron core  42  has the first movable iron piece  44  fitted to the outer peripheral surface of the connection pipe  43  made of magnetic material, and has the ring-shaped permanent magnet  45  having a shaft hole of an inner diameter capable of receiving the drive shaft  61  and the second movable iron piece  46  fitted and integrated at the interior. 
         [0065]    According to the present embodiment, the outermost side surface of the movable iron core  42  is covered by the first movable iron piece  44 , and the first movable iron piece  44  is shielded by the connection pipe  43  made of non-magnetic material. Thus, the magnetic force generated at the coil  32  easily passes through the first movable iron piece  44  and the magnetic circuit can be formed, whereby an electromagnetic relay obtaining large attractive force and having high magnetic efficiency can be obtained. 
         [0066]    Others are the same as the first embodiment, and thus same reference numbers are denoted for the same portions and the description will not be given. 
         [0067]    It should be recognized that the polar electromagnet device according to the present invention is not limited to the electromagnetic relay described above, and can be applied to other electric devices.