Abstract:
A method for manufacturing an electromagnetic relay includes: forming an iron core that has an end face and a groove which goes across the end face; fitting a shading coil that is fitted in the groove; and fixing the shading coil to the iron core by applying caulking processing to a plurality of areas in the end face which sandwich the groove.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is based upon and claims the benefit of priority under 35 U.S.C. §119 of the prior Japanese Patent Application No. 2012-261398 filed on Nov. 29, 2012, and is a continuation application filed under USC §§ 111 and 120 of U.S. Ser. No. 14/067,571, filed Oct. 30, 2013, the entire contents of which are incorporated herein by reference. 
     
    
     FIELD 
       [0002]    A certain aspect of the embodiments is related to an electromagnetic relay. 
       BACKGROUND 
       [0003]    There is an alternating-current electromagnetic relay which applies an alternating voltage to a coil as an electromagnetic relay that drives a switch with an electromagnet. In order to keep an attractive force of the electromagnet constant and to restrain a beat, a shading coil is attached to an iron core. Since the beat is restrained with the shading coil, the rectification of the alternating voltage is unnecessary. Japanese Laid-open Patent Publication No. 2008-171639 discloses a technique using a permanent magnet and an auxiliary yoke as a member which assists the attractive force. Japanese Laid-open Patent Publication No. 6-53027 discloses a technique which attaches the shading coil to the iron core with a screw mechanism. Japanese Laid-open Patent Publication No. 1-283904 discloses a technique which presses the shading coil toward the iron core and fixes the shading coil. Japanese Unexamined Utility Model Publication No. 62-114411 discloses a technique which fixes the shading coil by applying caulking processing to a pole face of the iron core. 
       SUMMARY 
       [0004]    According to an aspect of the present invention, there is provided an electromagnetic relay including: an iron core that has an end face and a groove which goes across the end face; and a shading coil that is fitted in the groove; wherein the shading coil is fixed to the iron core by applying caulking processing to a plurality of areas in the end face which sandwich the groove. 
         [0005]    The object and advantages of the invention will be realized and attained by the elements and combinations particularly pointed out in the claims. 
         [0006]    It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention, as claimed. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0007]      FIG. 1  is an exploded perspective view illustrating an electromagnetic relay; 
           [0008]      FIG. 2A  is an exploded perspective view illustrating an electromagnet; 
           [0009]      FIG. 2B  is a perspective view illustrating the composition in which a bobbin, an armature, and the electromagnet are assembled; 
           [0010]      FIG. 3A  is a perspective view illustrating the composition in which a card, the bobbin, the armature, the electromagnet and a contact member are assembled; 
           [0011]      FIG. 3B  is a perspective view illustrating an electromagnetic relay; 
           [0012]      FIG. 4A  is a cross-section view illustrating caulking processing; 
           [0013]      FIG. 4B  is a top view illustrating the electromagnet; 
           [0014]      FIG. 5A  is a cross-section view illustrating the caulking processing according to a first embodiment; 
           [0015]      FIG. 5B  is a top view illustrating the electromagnet; 
           [0016]      FIG. 6A  is a cross-section view illustrating the caulking processing according to a second embodiment; 
           [0017]      FIG. 6B  is a top view illustrating the electromagnet; 
           [0018]      FIG. 7A  is a cross-section view illustrating a caulking punch and a supporting unit; 
           [0019]      FIGS. 7B and 7C  are cross-section views illustrating the caulking processing; 
           [0020]      FIG. 8A  is a cross-section view illustrating the caulking punch and a flattening unit; 
           [0021]      FIG. 8B  is a cross-section view illustrating flattening processing; 
           [0022]      FIG. 8C  is a cross-section view illustrating the caulking processing; 
           [0023]      FIG. 9A  is a top view illustrating the electromagnet after the flattening processing and the caulking processing; 
           [0024]      FIG. 9B  is a cross-section view illustrating another example of the flattening processing and the caulking processing; 
           [0025]      FIG. 10A  is a perspective view illustrating the bobbin of the electromagnetic relay according to a fifth embodiment; 
           [0026]      FIG. 10B  is a front view illustrating the bobbin; 
           [0027]      FIG. 11A  is a perspective view illustrating the electromagnet; and 
           [0028]      FIG. 11B  is a front view illustrating the electromagnet. 
       
    
    
     DETAILED DESCRIPTION 
       [0029]    A description will now be given of the composition of an electromagnetic relay.  FIG. 1  is an exploded perspective view illustrating an electromagnetic relay  100 .  FIG. 2A  is an exploded perspective view illustrating an electromagnet  32 R.  FIG. 2B  is a perspective view illustrating the composition in which a bobbin  16 , an armature  24 , and the electromagnet  32 R are assembled.  FIG. 3A  is a perspective view illustrating the composition in which a card  14 , the bobbin  16 , the armature  24 , the electromagnet  32 R and contact members (i.e., a movable contact member  18  and fixed contact members  20  and  22 ) are assembled.  FIG. 3B  is a perspective view illustrating the electromagnetic relay  100 . 
         [0030]    As illustrated in  FIG. 1 , the electromagnetic relay  100  includes a cover  10 , a housing  12 , the card  14 , the bobbin  16 , the contact members, the armature  24 , and the electromagnet  32 R. 
         [0031]    As illustrated in  FIGS. 2A and 2B , the electromagnet  32 R includes the bobbin  16 , a coil  26  and an iron core  28 . The coil  26  is wound on an area  16   a  of the bobbin  16 . An air hole  16   b  is formed inside the area  16   a . The iron core  28  is inserted into the air hole  16   b . As described later, an end face  28   a  of the iron core  28  serves as an attractive surface of the electromagnet  32 R. A groove  28   b  going across the end face  28   a  is provided on the end face  28   a . It is assumed that one area in the end face  28   a  divided by the groove  28   b  is a first area  28   c , and another area by the end face  28   a  is a second area  28   d . As illustrated by a dashed line of  FIG. 2A , the iron core  28  also penetrates a hole  30   a  of a shading coil  30 . The shading coil  30  is fitted into the groove  28   b  so as to surround the first area  28   c , for example. The caulking processing is applied to the first area  28   c , so that the shading coil  30  is fixed to the iron core  28 , as described below. A terminal  16   c  of the bobbin  16  is electrically connected to the coil  26 . The armature  24  is provided in opposition to the end face  28   a . The bobbin  16  is inserted into an air hole  12   a  of the housing  12 . 
         [0032]    As illustrated in  FIGS. 1 and 3A , the movable contact member  18  includes terminals  18   a , and a movable contact  18   b  electrically connected to the terminals  18   a . The fixed contact member  20  ( 22 ) includes a terminal  20   a  ( 22   a ), and a fixed contact  20   b  ( 22   b ) electrically connected to the terminal  20   a  ( 22   a ). Each of the terminals  18   a ,  20   a  and  22   a  is a terminal for performing electric connection between the electromagnetic relay  100  and an external device. As illustrated in  FIG. 3A , the contact members are mounted on the housing  12  so as to be located at a side opposite to the end face  28   a  via the bobbin  16 . From a position near the bobbin  16 , the fixed contact member  20 , the movable contact member  18  and the fixed contact member  22  are arranged in turn. The card  14  is disposed on the housing  12 , and is coupled with the armature  24 . As illustrated in  FIG. 3B , the cover  10  is provided so as to cover the housing  12  through the card  14 . 
         [0033]    When a voltage is not applied to the coil  26 , the electromagnet  32 R does not generate a magnetic force. Therefore, the armature  24  is not attracted to the end face  28   a , and separates from the end face  28   a . The movable contact member  18  is a member including a plate spring, for example, and causes a force in a Z1 direction to the movable contact  18   b . Therefore, the movable contact  18   b  contacts the fixed contact  20   b , and separates from a fixed contact  22   b . When a voltage is applied to the coil  26  via the terminal  16   c , the electromagnet  32 R generates the magnetic force. The armature  24  moves in a Z2 direction, and is attracted to the end face  28   a  (see  FIG. 2B ). The armature  24  presses the card  14  in the Z2 direction, and the card  14  presses the movable contact member  18  in the Z2 direction (see  FIG. 3A ). That is, the card  14  transfers a press force of the armature  24  to the movable contact member  18 . The movable contact  18   b  moves in the Z2 direction, separates from the fixed contact  20   b , and contacts the fixed contact  22   b . Thereby, the electromagnetic relay  100  can be switched. 
         [0034]    The curvature and the distortion which occur in the iron core  28  are explained.  FIG. 4A  is a cross-section view illustrating the caulking processing, and  FIG. 4B  is a top view illustrating the electromagnet  32 R. Here, a direction in which the groove  28   b  goes across the end face  28   a  is set as an X-direction, and a direction perpendicular to the X-direction in the end face  28   a  is set as a Y-direction. 
         [0035]    As illustrated in  FIG. 4A , a caulking punch  40  disposed on the iron core  28  descends in the Z2 direction. The caulking punch  40  presses the first area  28   c  and the shading coil  30  to perform the caulking processing. As illustrated by a dashed rectangles in  FIG. 4B , caulking areas  42  are formed on both ends of the first area  28   c  and the shading coil  30 . Each of the caulking areas  42  is an area where the caulking processing has been performed. In the caulking areas  42 , the end face  28   a  and the shading coil  30  are pressed. Thus, the shading coil  30  is fixed to the iron core  28 . The caulking areas  42  are not formed on the second area  28   d . That is, the caulking processing is not applied to the second area  28   d.    
         [0036]    The press force of the caulking punch  40  is unevenly applied to the first area  28   c . Therefore, as illustrated by an arrow of  FIG. 4A , the first area  28   c  of the iron core  28  curves in the Y-direction. In addition, as illustrated by a lattice hatching of  FIG. 4B , distortion  28   e  (deviation of thickness) occurs in the first area  28   c . The distortion  28   e  is roughness of the first area  28   c . The distortion  28   e  is easily generated in areas which adjoin the caulking areas  42 , for example. The magnetic force of the electromagnet  32 R varies by the curvature and the distortion  28   e . As a result, the beat is not restrained, and the function of the electromagnetic relay  100  is spoiled. Next, a description will be given of embodiments of the present invention with reference to the drawings. 
       First Embodiment  
       [0037]    A first embodiment indicates an example in which the caulking processing is applied to the first area  28   c  and the second area  28   d . The composition of the electromagnetic relay is the same as that of the above-mentioned electromagnetic relay except for an electromagnet  32 .  FIG. 5A  is a cross-section view illustrating the caulking processing according to a first embodiment.  FIG. 5B  is a top view illustrating the electromagnet  32 . 
         [0038]    As illustrated in  FIG. 5A , the caulking processing is applied to two areas (i.e., the first area  28   c  and the second area  28   d ) sandwiching the groove  28   b . As a result, the caulking areas  42  are formed on both of the first area  28   c  and the second area  28   d , as illustrated in  FIG. 5B . Thereby, the shading coil  30  is fixed to the iron core  28 . 
         [0039]    The caulking punch  40  presses both of the first area  28   c  and the second area  28   d . Thereby, the press force of the caulking punch  40  is hard to be biased, and is almost evenly added to both of the first area  28   c  and the second area  28   d . Therefore, the curvature of the iron core  28  is restrained. Thereby, the beat can be restrained. 
         [0040]    In order to apply the caulking processing to the first area  28   c  and the second area  28   d , the caulking punch  40  may have a width which straddles the groove  28   b  and overlaps with the first area  28   c  and the second area  28   d . The caulking punch  40  may be shifted from the position of the comparative example, and may be arranged at a position which overlaps with the first area  28   c  and the second area  28   d . For example, a part of the first area  28   c  included in each of the caulking areas  42  may have a size different from a part of the second area  28   d  included in each of the caulking areas  42 . Moreover, the part of the first area  28   c  included in each of the caulking areas  42  may have the same size as the part of the second area  28   d  included in each of the caulking areas  42 . Thereby, the press force to be added to the first area  28   c  is substantially equal to the press force to be added to the second area  28   d , and hence the curvature is restrained. It is desirable that the caulking areas  42  are located at both ends  28   b - 1  of the groove  28   b . That is, it is desirable that the caulking processing is applied to the first area  28   c  and the second area  28   d  in positions which sandwich the both ends  28   b - 1  of the groove  28   b . Thereby, the press force is added evenly and the curvature is restrained effectively. When a plurality of grooves are provided on the end face  28   a  and the end face  28   a  is divided into three or more areas, the caulking punch  40  may apply the caulking processing to the areas sandwiching the grooves. 
       Second Embodiment  
       [0041]    A second embodiment indicates an example in which the caulking processing is performed while the iron core  28  is being supported.  FIG. 6A  is a cross-section view illustrating the caulking processing according to a second embodiment.  FIG. 6B  is a top view illustrating the electromagnet  32 . 
         [0042]    As illustrated in  FIGS. 6A and 6B , a supporting unit  41  sandwiches the iron core  28  and the shading coil  30  in the Y-direction. The caulking processing is performed in a state where the supporting unit  41  supports the side surfaces of the iron core  28  in the Y-direction. Thereby, the curvature can be restrained. 
         [0043]    The supporting unit  41  may support the side surface of the iron core  28  in a radial direction of the end face  28   a  (i.e., a direction toward the center of the iron core  28  from the outside of the iron core  28 ). As illustrated in  FIG. 4A , a curvature occurs in the Y-direction easily. Therefore, the supporting unit  41  supports the iron core  28  in the Y-direction, so that the curvature can be restrained effectively. The supporting unit  41  may support the side surface of the iron core  28  in a direction crossing the X-direction other than the Y-direction, and may support the side surface of the iron core  28  so as to surround the end face  28   a,  for example. The supporting unit  41  is provided on a jig for fixing the bobbin  16 , for example. 
       Third Embodiment  
       [0044]    A third embodiment indicates another example in which the caulking processing is performed while the iron core  28  is being supported.  FIG. 7A  is a cross-section view illustrating the caulking punch  40  and a supporting unit  44 .  FIGS. 7B and 7C  are cross-section views illustrating the caulking processing. The bobbin  16  is omitted. Oblique lines are added to the caulking punch  40 . 
         [0045]    As illustrated in  FIG. 7A , the supporting unit  44  is provided so as to surround the caulking punch  40 . The caulking punch  40  can descend and rise independently of the supporting unit  44 . The supporting unit  44  has a shape like a dome which covers the end face  28   a,  for example. Next, the caulking processing is explained. 
         [0046]    As illustrated in  FIG. 7B , the supporting unit  44  descends ahead of the caulking punch  40 , and contacts the edge of the end face  28   a.  Thereby, the supporting unit  44  supports the edge of the end face  28   a  in the radial direction of the end face  28   a . At this time, the caulking punch  40  does not contact the end face  28   a.  As illustrated in  FIG. 7C , the caulking punch  40  performs the caulking processing. That is, the caulking processing is performed in a state where the supporting unit  44  supports the edge of the end face  28   a.  Therefore, the curvature of the iron core  28  is restrained. 
         [0047]    It is desirable that, in order to restrain the curvature effectively, the supporting unit  44  contacts the iron core  28  before the caulking punch  40  contacts the iron core  28 . The supporting unit  44  completely surrounds the end face  28   a  in the radial direction of the end face  28   a.  Therefore, the curvature in all directions can be restrained. Here, the supporting unit  44  does not need to completely surround the end face  28   a,  and may surround a part of the end face  28   a,  for example. Especially, it is desirable that the supporting unit  44  supports the end face  28   a  in the Y-direction. This is because the curvature to be easily generated in the Y-direction can be restrained. The shape of the supporting unit  44  may be a shape other than the dome shape, and the supporting unit  44  needs to have an area which contacts the edge of the end face  28   a  and the side surface of the iron core  28 . 
         [0048]    The second and the third embodiments may be combined with the first embodiment. That is, the caulking processing may be applied to both of the first area  28   c  and the second area  28   d  while the iron core  28  is being supported in the radial direction of the end face  28   a.  Thereby, the curvature can be restrained effectively. 
       Fourth Embodiment  
       [0049]    A fourth embodiment indicates an example in which flattening processing is performed.  FIG. 8A  is a cross-section view illustrating the caulking punch  40  and a flattening unit  46 .  FIG. 8B  is a cross-section view illustrating the flattening processing.  FIG. 8C  is a cross-section view illustrating the caulking processing. The bobbin  16  is omitted. 
         [0050]    As illustrated in  FIG. 8A , the caulking punch  40  is located inside the flattening unit  46 . The caulking punch  40  can descend and rise independently of the flattening unit  46 . Next, the caulking processing and the flattening processing are explained. 
         [0051]    As illustrated in  FIG. 8B , the caulking punch  40  descends ahead of the flattening unit  46 , and performs the caulking processing. As illustrated in  FIG. 8C , after the caulking processing, the flattening unit  46  descends and presses the end face  28   a.  Thereby, the flattening processing is performed, and the end face  28   a  becomes flat. 
         [0052]      FIG. 9A  is a top view illustrating the electromagnet  32  after the flattening processing and the caulking processing. As illustrated in  FIG. 9A , the distortion  28   e  (see  FIG. 4B ) is removed by the flattening processing, and a flattening area  28   f  is formed on the end face  28   a.  The flattening area  28   f  is flatter than the distortion  28   e . Therefore, the beat can be restrained effectively. 
         [0053]    To remove the distortion, the flattening unit  46  flattens at least a part of an area other than the caulking areas  42  in the end face  28   a.  Especially, it is desirable that the flattening unit  46  flattens an area which adjoins the caulking areas  42 . This is because the distortion  28   e  is easily generated in the area which adjoins the caulking areas  42 . In addition, the flattening unit  46  may flatten the whole area other than the caulking areas  42 . Thereby, the flattening of the end face  28   a  can be improved more. 
         [0054]      FIG. 9B  is a cross-section view illustrating another example of the flattening processing and the caulking processing. As illustrated in  FIG. 9B , the flattening unit  46  contacts the end face  28   a  before the caulking punch  40  contacts the end face  28   a,  and then the flattening processing may be performed in a state where the flattening unit  46  presses the end face  28   a.  That is, the caulking processing and the flattening processing may be performed at the same time. Thereby, the generation of the distortion can be restrained. 
         [0055]    The first to the third embodiments may be combined with the fourth embodiment. Thereby, the curvature can be restrained and the distortion can be removed. Therefore, the beat can be restrained effectively. 
       Fifth Embodiment  
       [0056]    A fifth embodiment indicates that an example in which the shading coil  30  is fixed to the iron core  28  by pushing an outer circumferential surface of the shading coil  30 .  FIG. 10A  is a perspective view illustrating the bobbin  16  of the electromagnetic relay according to the fifth embodiment.  FIG. 10B  is a front view illustrating the bobbin  16 . The iron core  28  and the shading coil  30  are not provided on the bobbin  16 .  FIG. 11A  is a perspective view illustrating the electromagnet  32 .  FIG. 11B  is a front view illustrating the electromagnet  32 . 
         [0057]    As illustrated in  FIGS. 10A to 11B , an air hole  16   d  (i.e., a storage unit) is formed in the bobbin  16 . Five projections  16   e  (i.e., a holding unit) are formed in an inner wall of the bobbin  16  surrounding the air hole  16   d.  The projections  16   e  are projected to the inside of the air hole  16   d  from the inner wall. 
         [0058]    As illustrated in  FIGS. 11A and 11B , the iron core  28  is inserted into the bobbin  16 , and the shading coil  30  is fitted on the iron core  28 . The shading coil  30  is located in the air hole  16   d.  The projections  16   e  are projected toward the shading coil  30 , and hold the outer circumferential surface of the shading coil  30 . Thereby, the shading coil  30  is fixed to the iron core  28 . According to the fifth embodiment, the caulking processing is not required. Therefore, the curvature and the distortion caused by the caulking processing can be restrained. 
         [0059]    It is desirable that the projections  16   e  hold the shading coil  30  in order to fix the shading coil  30  solidly. It is also desirable that the projections  16   e  hold the shading coil  30  from a plurality of directions. In the fifth embodiment, since the projections  16   e  hold the shading coil  30  from the X-direction and the Y-direction, the shading coil  30  can be fixed solidly. Thus, it is desirable that the projections  16   e  hold the shading coil  30  from a plurality of directions. The projections  16   e  may hold the shading coil  30  from any one of the X-direction and the Y-direction. Alternatively, the projections  16   e  may hold the shading coil  30  from a direction other than the X-direction and the Y-direction. Although the number of projections  16   e  is five, the number of projections  16   e  may be equal to or less than four, or equal to or more than six. 
         [0060]    Also in the fifth embodiment, the caulking processing may be performed as with the first to the fourth embodiments, for example. Thereby, the shading coil  30  is fixed more solidly. 
         [0061]    All examples and conditional language recited herein are intended for pedagogical purposes to aid the reader in understanding the invention and the concepts contributed by the inventor to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a showing of the superiority and inferiority of the invention. Although the embodiments of the present invention have been described in detail, it should be understood that the various change, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention.