Patent Publication Number: US-11398362-B2

Title: Terminal and relay

Description:
This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2018-225916, filed Nov. 30, 2018, the entire contents of which are incorporated herein by reference. 
     TECHNICAL FIELD 
     The present invention relates to a terminal and a relay. 
     BACKGROUND 
     Relays (electromagnetic relays), in which contacts are opened and closed by an electromagnet, comprise an electromagnet, an armature, a movable terminal including a movable contact, and a fixed terminal including a fixed contact. In such relays, the armature is moved by the excitation of the electromagnet, whereby the armature is pressed against the movable terminal, and contact between the movable contact and the fixed contact come is established. 
     JP 5741679 B discloses a relay comprising a terminal in which a first member including a movable contact and a second member including a leg are affixed thereto by crimping in three locations. 
     JP 3959894 B discloses a relay in which an insulated pressing member, which presses a movable terminal, is attached to an armature to secure the insulation distance between the movable terminal and the armature. 
     JP 2008-053152 A discloses a relay in which an electromagnet and an armature are surrounded with an insulating wall, so as to secure the insulation distance for a movable terminal and a fixed terminal. 
     SUMMARY 
     In relays comprising a terminal in which two members are affixed in a plurality of locations, when outside forces are applied to the terminal, there is a risk that the locations of fixation between the members could become damaged due to non-uniform stress concentration. 
     An aspect of the present invention provides a terminal of a relay comprising a first member having a leg, and a second member combined with the first member and having a contact, wherein the second member has at least three holes, the first member has at least three protrusions which are individually inserted into and crimped in the at least three holes, and an intermediate hole among the at least three holes is arranged so as to be positioned on the side opposite the contact with respect to a straight line that contacts the edges of the outermost holes on the side close to the contact. 
     According to the terminal of the aspect, when a force is applied to the pressing location, the difference between the stress concentrated around a single hole and the stress concentrated around the holes adjacent thereto is reduced, and the stress is uniformly distributed to prevent deformation of the second member. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view of a relay according to an embodiment; 
         FIG. 2  is an exploded perspective view of the relay; 
         FIG. 3  is a front view of a movable terminal; 
         FIG. 4  is a perspective view of the movable terminal; 
         FIG. 5  is a front view of a second member having a different hole arrangement; 
         FIG. 6  is a front view of the second member; 
         FIG. 7  is a front view of a modified example of the movable terminal; 
         FIG. 8  is a front view of the second member according to the modified example; 
         FIG. 9  is a perspective view of a base; 
         FIG. 10  is a perspective view of a first member; 
         FIG. 11  is a cross-sectional view of the relay; 
         FIG. 12  is an enlarged cross-sectional view of the relay; 
         FIG. 13  is a perspective view of an armature to which a pressing member is attached; 
         FIG. 14  is a perspective view detailing attachment of the pressing member to the armature; 
         FIG. 15  is a front view of the pressing member; 
         FIG. 16  is a side view of the pressing member; 
         FIG. 17  is a plan view of the pressing member; 
         FIG. 18  is a side view showing the positional relationship between the armature, the pressing member, and the movable terminal; 
         FIG. 19  is a cross-section view of the pressing member and the armature; 
         FIG. 20  is a perspective view of the armature; 
         FIG. 21A  is a view detailing the crimped parts of the pressing member; 
         FIG. 21B  is a view detailing the crimped parts of the pressing member; 
         FIG. 22  is a cross-sectional view of a modified example of the relay; 
         FIG. 23  is a perspective view of the coil assembly and a metal part of the modified example; and 
         FIG. 24  is a bottom view of the relay. 
     
    
    
     DETAILED DESCRIPTION 
     The relays according to the embodiments will be described below with reference to the attached drawings.  FIG. 1  is a perspective view of a relay  2  according to an embodiment, and  FIG. 2  is an exploded perspective view. The relay  2  comprises a base  4  in which the constituent parts are assembled, and a cover  6  which encloses the base  4 . The base  4  and the cover  6  may be, for example, molded parts made of resin. 
     The constituent parts assembled in the base  4  include a movable terminal  20 , a fixed terminal  26 , an electromagnet  7 , a hinge spring  8 , an armature  10 , and a pressing member  12  made of a resin or the like. 
     The movable terminal  20  comprises a first member  14  including two legs  14   a ,  14   b , and a second member  18  including a movable contact  16 . The fixed terminal  26  comprises two legs  22   a ,  22   b , and a fixed contact  24 . The electromagnet  7  comprises a coil assembly  27 , an iron core  30 , and a yoke  32 . The coil assembly  27  comprises two coil terminals  28  comprising respective legs  28   a ,  28   b , a coil  34  which is connected to the coil terminals  28 , and a bobbin  36  on which the coil  34  is wound. 
     The electromagnet  7  is excited by applying a voltage to the terminals  28 . Due to the excitation of the electromagnet  7 , the armature  10  pivots and contacts the iron core  30 . The pressing part  12  attached to the armature  10  presses the movable terminal  20  in accordance with the pivoting of the armature  10 , and the movable contact  16  comes into contact with the fixed contact  24 . The hinge spring  8  is attached to the armature  10  and the yoke  32 , and biases the armature  10  in a direction away from the iron core  30 . 
     When the application of voltage to the coil terminal  28  is stopped, the armature  10  returns to a position spaced from the iron core  30  by the biasing of the hinge spring  8 . Then, the pressing force from the pressing part  12  to the movable terminal  20  is released as the armature  10  returns, and the movable contact  16  separates from the fixed contact  24 . 
     The movable contact  16  and the fixed contact  24  open and close with the above configuration. The aforementioned configuration is merely exemplary, and any configuration may be used. For example, the fixed terminal  26  may comprise a member including the contact  24 , and a member including the legs  22   a ,  22   b.    
       FIG. 3  is a front view of the movable terminal  20 . The movable terminal  20  is constituted by an assembly of the first member  14  and the second member  18 . 
     The first member  14  comprises legs  14   a ,  14   b  for electrical connection with external components, and a plurality (three in the drawings) of protrusions  36   a ,  36   b , and  36   c  (collectively “protrusions  36 ”). The second member  18  comprises the contact  16 , and a plurality (three in the drawings) of holes  38   a ,  38   b , and  38   c  (collectively “holes  38 ”). The second member  18  is a plate-like member which is elastically displaceable. The first member  14  and the second member  18  are made of, for example, a metal. 
     The protrusions  36  are individually inserted into the corresponding holes  38  and the tips thereof are crimped to formed crimped parts  40   a ,  40   b , and  40   c  (collectively “crimped parts  40 ”). 
     The first member  14  and the second member  18  are electrically connected and mutually affixed by the crimped parts  40 . Though a voltage drop occurs when current flows through the movable terminal  20 , the internal resistance of the movable terminal  20  is reduced by providing crimped parts  40 , so as to reduce the voltage drop. If high current of 30 A or more flows, it is preferable that three or more crimped parts  30  be provided. 
     The three crimped parts  40  shown in  FIG. 3  are arranged in a line. Since the protrusion  36   b  is arranged lower than the protrusions  36   a  and  36   c  by a distance H 1 , and the hole  38   b  is arranged lower than the holes  38   a  and  38   c  by distance H 1 , the center crimped part  40   b  is arranged lower than the outermost crimped parts  40   a  and  40   c  by distance H 1 . Distance H 1  is, for example, approximately 0.3 mm. 
     The holes  38  may be circular, elliptical, triangular, or rectangular, and the protrusions may be shaped so as to be capable of being inserted into the respective holes. 
       FIG. 4  is a perspective view of the movable terminal  20 . The second member  18  is pressed in direction A by the pressing part  12 , and is elastically displaced. When the second member  18  is displaced in direction A, the stress is concentrated around holes  38  in which protrusions  36  of the second member  18  are affixed. 
       FIG. 5  is a front view of a second member  19  in which holes  38   d ,  38   e , and  38   f  (collectively “holes  38 ”) are arranged in positions different than those of  FIG. 4 . In the second member  19 , the position of the hole  38   e  differs from that of the second member  18 , and the three holes  38 ′ are arranged at the same height. 
     A pressed part  42   a  is an area which is pressed by the pressing member  12 . The stress in the vicinity of the holes  38 ′ will be described using the center point  44   a  of the pressing part  42   a . The center  44   a  is arranged in the geometrical center of the second member  19 , and the force with which the pressing member  12  presses the second member  19  will be assumed as being received at a single point. 
     The magnitude of the stress occurring around the holes  38 ′ due to the force applied to the center  44   a  depends on the distance from the center  44   a . As the distance between the center  44   a  and the holes  38 ′ decreases, the bending angle in the vicinity of the hole of the second member  19  increases and the stress increases. 
     In  FIG. 5 , a line L 11  connecting the center  44   a  and the center  39   d  of the hole  38   d  and a line L 22  connecting the center  44   a  and the center  39   f  of the hole  38   f  have substantially the same lengths. In this case, the stress in the vicinity of the hole  38   d  and the stress in the vicinity of the hole  38   f  due to the application of outside forces to the center  44   a  are approximately equal. 
     Conversely, a line L 33  connecting the center  44   a  and the center  39   e  of the hole  38   e  is shorter than the lines L 11  and L 22 . In  FIG. 5 , the three holes  38 ′ are arranged in a horizontal row, and a line L 44  passing along the edges  46   a ,  48   a ,  50   a  on the pressing location  42   a  side of the holes  38 ′ is perpendicular to the line L 33 . 
     Under such a positional relationship, the stress around the hole  38   e  is greater than the stresses around the holes  38   d  and  38   f.    
       FIG. 6  is a front view of the second member  18  according to the present embodiment. The stresses in the vicinities of the holes  38  will be described using  FIG. 6 . 
     The center hole  38   b  is arranged lower than the holes  38   a  and  38   c . A line L 10  contacts edges  46  and  50  on the contact  16  side of the holes  38   a ,  38   c . When the holes  38   a  and  38   c  are circular, the line L 10  is tangent to the circles. 
     The hole  38   b  is arranged on the side opposite the contact  16   b  with respect to the line L 10 . 
     A line L 1  connecting the center  44  and the center  39   a  of the hole  38   a  and a line L 2  connecting the center  44  and the center  39   c  of the hole  38   c  have substantially the same lengths. 
     The hole  38   b  is arranged lower than the holes  38   a  and  38   c , and the hole  38   b  is arranged on the side opposite the contact  16  with respect to the line L 10 . 
     In the present embodiment, a line L 3  connecting the center  44  and the center  39   b  of the hole  38   b  is longer than the line L 33  of  FIG. 5 , and the length thereof is close to the lengths of the lines L 1 , L 2 . Thus, in the present embodiment, the stress in the vicinity of the hole  38   b  is comparatively reduced. 
     By arranging the hole  38   b  in a position which minimizes the difference between the lengths of the lines L 1  and L 2  and the length of the line L 3 , when a force is applied to the pressing location  42 , the difference between the stress around one hole and the stresses around the other holes is minimized, and by uniformly distributing the stress, deformation of the second member  18  can be prevented. 
       FIG. 7  is a front view of a movable terminal  20 B according to a modified example. The hole  38   b  shown in  FIG. 7  is smaller than the holes  38   a  and  38   c , and the protrusion  36   b  is smaller than the protrusions  36   a  and  36   c . As a result, the hole  38   b  is arranged lower than the holes  38   a  and  38   c  by distance H 2 , and the protrusion  36   b  is arranged lower than the protrusions  36   a  and  36   c  by distance H 2 . Distance H 2  is, for example, 0.3 mm. 
       FIG. 8  is a front view of a second member  18 B. The stresses around the holes  38  of the second member  18 B will be described using  FIG. 8 . 
     The centers  39   a ,  39   b , and  39   c  of the holes  38   a ,  38   b , and  38   c  are arranged on the same line, the edge of the hole  38   b  on the contact  16  side is lower than those of the holes  38   a  and  38   c.    
     A line L 10  contacts edges  46 ,  50  of the holes  38   a ,  38   c  on the contact  16  side. The hole  38   b  is arranged so as to be positioned on the side opposite the contact  16  with respect to the line L 10 . 
     A line L 1  connecting the center  44  and the center  39   a  and a line L 2  connecting the center  44  and the center  39   c  have substantially the same lengths. 
     When the hole  38   b  is arranged lower than the holes  38   a  and  38   c , the hole  38   b  is arranged on the side opposite the contact  16  with respect to the line L 10 . The length of a line L 3  connecting the center  44  and the center  39   b  is longer than that of the line L 33  in  FIG. 5 , and is close to the lengths of the lines L 1 , L 2 . Thus, in the present embodiment, the stress concentrated in the vicinity of the hole  38   b  is reduced as compared to the case shown in  FIG. 5 . 
     By arranging the hole  38   b  in a position in which the difference between the lengths of the lines L 1  and L 2  and the length of the line L 3  is minimized, when a force is applied to the pressing location  42 , the difference between the stress around a single hole and the stress around the other holes is reduced, and by uniformly distributing the stress, deformation of the second member  18 B can be prevented. 
     The movable terminal  20 B is designed so as to minimize the difference between the lengths of the line L 3  and the lines L 1  and L 2  by reducing the diameter of the hole  38   b . Thus, since the lower end of the hole  38   b  is arranged higher as compared with the case shown in  FIG. 3 , the hole  38   b  can be formed without extending the edge  52   a . Therefore, an increase in size of the movable terminal  20 B can be prevented. 
     The crimped parts  40  can also be applied to the fixed terminal  26  comprising the first member including the contact  24  and the second member including the legs  22   a  and  22   b.    
     Though the movable terminals  20  and  20 B having three crimped parts  40  have been described, a terminal may have four or more crimped parts as long as the second member has at least three holes, and the edge of an intermediate hole on the contact side is arranged so as to be positioned on the side opposite the contact with respect to a line which contacts the edges of the outermost holes. 
       FIG. 10  is a perspective view of the first member  14 . 
     When high current is flowed through the terminal, reducing internal resistance may be reduced by increasing the sizes of the legs. When a terminal such as a blade terminal is used in order to increase the size of the legs, it is necessary to form square holes in the substrate to which the legs are connected. 
     Conversely, when internal resistance is reduced by providing a plurality of comparatively small legs, such as legs  14   a  and  14   b  shown in  FIG. 10 , comparatively small circular holes may be formed in the substrate rather than square holes, and the design of the board is easier than when a blade terminal is used. 
     The first member  14  comprises a support  56  having a flat surface  56   a . Three protrusions  36  are formed on the surface  56   a . As shown in  FIG. 4 , the support  56  is arranged on the second member  18  on the side on which the contact  16  is provided, and supports the second member  18 . 
     By contacting the surface  56   a  to a surface  18   a  on which the contact  16  is provided, the surface  56   a  can absorb the force imparted to the second member  18  which is pressed by the pressing member  12 . 
     If the first member is arranged on a side opposite the position shown in  FIG. 4  to support the second member, when the second member is pressed by the pressing member, there is a risk that high stress will be generated since the stress is concentrated in the crimped part, particularly its upper end. 
     Conversely, in the present embodiment, the first member  14  is arranged on the side of the second member  18  that is pressed by the pressing part  12 , and the lower part of the second member  18  is supported by the straight upper end  56   b  of the surface  56   a . Therefore, the range across which the second member  18  is supported is widened. Further, as the upper end  56   b  supporting the second member  18  is separated from the crimped parts  40  by a certain distance, the stresses generated in the second member  18  in the vicinity of the crimped parts  40  can be distributed, and concentration of stress in the crimped parts  40  can be prevented. Thus, the stresses around the holes  38  when the second member  18  is pressed toward the first member  14  are reduced as compared to the case in which the support  56  is not provided. 
     The legs  14   a  and  14   b  will be described using  FIGS. 4 and 10 . The leg  14   a  comprises a base  58   a  which connects with the support  56 . The base  58   a  protrudes from the side opposite the side on which the contact  16  is provided. 
     The leg  14   a  comprises an end  60   a  which is bent away from the base  58   a . The end  60   a  is formed so that the bottom thereof extends in a direction away from the second member  18 . The base  58   a  is bent so that the portion thereof which connects with the end  60   a  is arranged above the portion thereof which connects with the support  56 . The leg  14   b  is configured in the same manner as the leg  14   a , and comprises a base  58   b  and an end  60   b.    
       FIG. 11  is a cross-sectional view of the relay  2  taken along line A 1 -A 1  of  FIG. 1 .  FIG. 12  is an enlarged cross-sectional view of area XII of  FIG. 11 , which is an enlarged view of the vicinity of the first member  14 . The legs  14   a  and  14   b  will be described using  FIG. 12 . 
     The base  4  houses the movable terminal  20  and the fixed terminal  26 , and comprises a bottom  61  to which an adhesive  71  such as an epoxy resin is applied. The bottom  61  comprises a first adhesion part  62  having a hole  64  from which the end  60   a  of the leg  14   a  protrudes outside. 
     By applying the adhesive  71  to the surface  62   a  outside the first adhesion part  62  and occluding the hole  64 , the intrusion of foreign matter such as solder or flux into the interior of the relay  2  can be prevented. 
     The bottom  61  comprises a second adhesion part  70  including a hole  72  from which the leg  22   a  protrudes outside. The adhesive  71  is applied to the surface  70   a  of the second adhesion part  70  to occlude the hole  72 . The surface  62   a  and the surface  70   a  are arranged on the same plane. In order to ensure space for applying the adhesive  71 , the surface  62   a  and the surface  70   a  are arranged above the lower end  6   a  of the cover  6 . 
     The bottom  61  includes a raised part  66 . The raised part  66  includes a recess  68  and bulges downward in  FIG. 12 , and protrudes more outwardly from the relay  2  at the position of the recess  68  than the first adhesion part  62  and the second adhesion part  70 . The surface  62   a  and the surface  70   a  are arranged on the back side as viewed from below the raised part  66 . 
     The base  58   a  is housed within the recess  68 . The end  60   b  is arranged outside the recess  68 , and protrudes from the hole  64 . The end  60   b  does not protrude to the outside of the relay  2  from below the crimped part  40   b . Regarding the unillustrated leg  14   b , the base  58   b  thereof is also housed within the recess  60 , and the first adhesion part  62  has an unillustrated hole from which the end  60   b  of the leg  14   b  protrudes. The adhesive  71  is applied to the hole. 
     By housing the bases  58   a ,  58   b  in the recess  68 , and arranging the ends  60   a ,  60   b  so as to protrude to the outside of the relay  2  at positions separated from the crimped parts  40 , it is not necessary to ensure space below the crimped parts  40  for applying the adhesive  71 , whereby the accommodation space of the second member  18  can be expanded by the height of the recess  68 . Thus, the second member  18  can be lengthened to increase the allowable current while maintaining the low profile of the relay  2 . 
       FIG. 13  is a perspective view of the armature  10  to which the pressing member  12  is attached. The armature  10  comprises a first portion  74  which can be attracted by the iron core  30 , and a second portion  76  which extends from the first portion  74 . The second portion  76  comprises a bent part  78  which connects with the first portion  74 . The pressing member  12  is attached to the tip of the second portion  76  and is affixed to the armature  10 . The armature  10  is made of metal, and the pressing member  12  is made of resin. 
     The iron core  30  is arranged below the first portion  74  as shown in  FIG. 11 . The first portion  74  moves in direction B by the excitation of the electromagnet  7 , and the surface  74   a  comes into contact with the iron core  30 . 
     The armature  10  pivots about an axis  80 , correspond to the position of the bent part  78 , while deforming the hinge spring  8 . When the first portion  74  moves in direction B, the second portion  76  moves in direction A, whereby the pressing part  12  presses the movable terminal  20 . The movable terminal  20  is displaced in accordance with the movement of the armature  10 . 
       FIG. 14  is a perspective view of the armature  10  and the pressing member  12 . The second portion  76  includes a plate-like insertion  82  provided on the tip which is inserted into the pressing part  12  and a groove  84  formed in the upper side of the insertion  82 . The insertion  82  and the groove  84  extend in the direction parallel to the axis  80 , and the pressing member  12  is inserted into the groove  84 . Note that the “direction parallel to the axis” encompasses substantially parallel directions in consideration of manufacturing tolerances and the like. 
       FIG. 15  is a front view of the pressing member  12 .  FIG. 16  is a side view of the pressing member  12  as viewed from the right side of  FIG. 14 . The pressing member  12  comprises a pressing part  86  which protrudes toward the movable terminal  20 . The tip  86   a  of the pressing part  86  extends in a straight line, and is arranged parallel to the axis  80  in a state in which the pressing member  12  is attached to the armature  10 . 
     The pressing member  12  comprises a receiving part  88  which receives the insertion  82  in an enclosure  90  one end of which is open. The receiving part  88  has four inner surfaces  88   a ,  88   b ,  88   c , and  88   d , a bottom surface  88   e , and an aperture  91  positioned on the side opposite the bottom surface  88   e.    
       FIG. 17  is a top view of the pressing member  12 . The pressing member  12  comprises an insertion  92  which is inserted into the groove  84 . The insertion  92  is a part of the enclosure  90 . 
       FIG. 19  is a cross-sectional view of the pressing member  12  taken along line B 1 -B 1  of  FIG. 16 , showing a front surface of the armature  10 . The length of the inner surface  88   d  from the bottom surface  88   e  is shorter as compared to the other inner surfaces  88   a ,  88   b , and  88   c , and the aperture  91  is open to the right and the top of  FIG. 19 . 
     When the pressing member  12  is attached to the armature  10 , the insertion  82  is inserted into the receiving part  88 . By guiding the insertion  92  along the groove  84 , the pressing member  12  is attached to the armature  10  along direction C which is parallel to the axis  80 . 
     In order to facilitate insertion of the insertion  82  into the receiving part  88 , tapered guide surfaces  93 ,  95  are formed on the portion of the surface  88   d  close to the aperture  91 , and on the tip of the insertion part  82 , respectively. When the insertion  82  is fully received in the receiving part  88 , the receiving part  88  covers the insertion  82  with the enclosure  90 . 
     By inserting the insertion  82  into the receiving part  88  in direction C and attaching the pressing member  12  to the armature  10  by inserting the insertion  92  into the groove  84 , the pressing member is not misaligned in the vertical directions relative to the armature  10 . Thus, even if misalignment of the armature  10  and the pressing member  12  occurs, the direction thereof is limited to the direction parallel to the axis  80  along the groove  84 . 
       FIG. 18  shows the relationship between the armature  10 , the pressing member  12 , and the movable terminal  20 . Even if the pressing member  12  is displaced from the direction parallel to the axis  80  relative to the armature  10 , a distance L 21  from the axis  80  to the abutment tip  86   a  in which the pressing member  12  and the movable terminal  20  abut does not change. 
     Thus, in the relay  2 , even if the position of the pressing member  12  is displaced relative to the armature  10  due to impact or the like, the distance L 21  does not change since the direction of displacement is limited to the direction parallel to the axis  80 . As long as the distance L 21  does not change, the position in the vertical direction at which the pressing member  12  presses the movable terminal  20  does not change, and thus, the moment of the pressing force imparted to the movable terminal  20  from the pressing member  12  does not change. Thus, it is not necessary to change the voltage applied to the coil  34  to bring the first portion  74  of the armature  10  into contact with the iron core  30 , and changes in the characteristics of the relay  2  such as operating voltage can be prevented. 
     The enclosure  90  covers the insertion  82  to insulate the armature  10  and the movable terminal  20  from each other. Further, a pressing part  86  protruding toward the movable terminal  20  is provided outside the enclosure  90 . Therefore, the armature  10  and the movable terminal  20  are arranged in positions which are spaced from the left and right directions of  FIG. 18 . As a result, the creepage distance between the armature  10  and the movable terminal  20 , which is represented by the dotted arrow in  FIG. 18 , can be ensured. 
     As shown in  FIGS. 16 and 19 , the pressing member  12  includes, on the surface  88   b , a first protrusion  94  which engages with an end surface  98  of the insertion  82 . 
     The first protrusion  94  has a shape which protrudes in a straight line extending in the direction parallel to the inner surfaces  88   a ,  88   c  from the vicinity of the aperture  91  to the bottom surface  88   e . When the pressing member  12  is attached to the armature  10 , the first protrusion  94  is arranged parallel to the axis  80 . 
     The first protrusion  94  includes a high part  94   a  and a low part  94   b  which differ in height from the inner surface  88   b . The high part  94   a  is formed on the side close to the bottom surface  88   e , and the low part  94   b , which is shorter in height from the inner surface  88   b  than the high part  94   a , is formed on the side close to the aperture  91 . 
       FIG. 20  is a perspective view of the armature  10 . The armature  10  has an end surface  98  on the end of the insertion  82 , which is parallel to the axis  80 . The end surface  98  has a step-shaped end surface  98   a  near the axis  80  which engages with the high part  94   a , and the end surface  98   b  distant from the axis  80  which engages with the low part  94   b.    
     When the insertion  82  is inserted into the receiving part  88  in direction C to attach the pressing member  12  to the armature  10 , the end surface  98  slides on the first protrusion  94 . As the insertion  82  is pushed into the receiving part  88 , the end surface  98   a  engages so as to be wedged into the high part  94   a  after passing through the low back part  94   b , and the end surface  98   b  engages so as to be wedged into the low part  94   b.    
     The first protrusion  94  positions the pressing member  12  relative to the longitudinal direction of the armature  10 . By engaging the end surface  98  with the first protrusion  94 , the other edge  99  of the insertion  82  is pressed against the inner surface  88   d . As a result, the insertion  82  is inserted into and press-fit in the receiving part  88 , whereby misalignment of the armature  10  and the pressing member  12  in the vertical direction is prevented. 
     Furthermore, the end surfaces  98   a ,  98   b  engage with the high part  94   a  and the low part  94   b  at two points. Therefore, inclination of the insertion  82  relative to the pressing member  12  toward the direction in which the degree of parallel alignment between the end surface  98  and the inner surface  88   b  is deteriorated can be prevented. As a result, a high level of parallel alignment between the tip  86   a  and the axis  80  can be secured. 
     The pressing member  12  comprises a second protrusion  96  which engages with a surface  100  of the insertion  82 . 
     The second protrusion  96  has a shape which extends from the vicinity of the aperture  91  to the bottom surface  88   e  in a straight line extending in the direction parallel to the inner surfaces  88   b ,  88   d . When the pressing member  12  is attached to the armature  10 , the second protrusion  96  is arranged parallel to the axis  80 . 
     The second protrusion  96  has a high part  96   a  and a low part  96   b  which differ in height from the inner surface  88   c . The high part  96   a  is formed on the side close to the bottom surface  88   e , and the low part  96   b , which is shorter than the high part  94   a , is formed on the side close to the aperture  91 . 
     The armature  10  has a surface  100  and an end surface  106 . The surface  100  has a back-side  100   a  distant from the end surface  106 , and a front side  100   b  close to the end surface  106 . The back-side  100   a  has a recess  102  which is parallel to the axis  80 , and a stepped shape is formed on the surface  100  by the recess  102 . The surface  100  engages with the high part  96   a  in the recess  102 , and engages with the low part  96   b  on the front side  100   b.    
     When the insertion  82  is inserted into the receiving part  88  in direction C to attach the pressing member  12  to the armature  10 , the surface  100  slides on the protrusion  96 . As the insertion  82  is pressed into the receiving part  88 , the recess  102  passes the low part  96   b  and then engages with the high part  96   a , and the front side  100   b  engages with the low part  96   b.    
     The second protrusion  96  positions the pressing member  12  relative to the direction in which the second portion  76  moves. By engaging the surface  100  with the second protrusion  96 , the surface  100  is pressed against the inner surface  88   a . As a result, the insertion  82  is inserted into and press-fit in the receiving part  88 , whereby misalignment of the armature  10  and the pressing member  12  in direction A is prevented. 
     Since the surface  100  of the insertion  82  engages with the high part  96   a  and the low part  96   b  at two points, the recess  102  and the front side  100   b , inclination of the insertion  82  relative to the pressing member  12  toward the direction in which the degree of parallel alignment between the surface  100  and the inner surface  88   c  is deteriorated can be prevented. As a result, a high level of parallel alignment between the tip  86   a  and the axis  80  can be secured. 
     The end surface  98  and the surface  100  may not have a stepped shape. The first protrusion  94  may be shaped so as to have a constant height without forming the high part  94   a  and the low part  94   b . Likewise, the second protrusion  96  may be formed so as to have a constant height without forming the high part  96   a  and the low part  96   b.    
     In this case, by engaging the end surface  98  with the first protrusion  94 , the other edge  99  is pressed against the inner surface  88   d . As a result, the insertion  82  can be inserted into and press-fit in the receiving part  88 , and misalignment between the armature  10  and the pressing member  12  in the vertical directions is prevented. 
     Further, by engaging the surface  100  with the second protrusion  96 , the surface  101  is pressed against the inner surface  88   a . As a result, the insertion  82  can be inserted into and press-fit in the receiving part  88 , and misalignment between the armature  10  and the pressing member  12  in direction A is prevented. 
       FIGS. 21A and 21B  are views showing the crimp structure which secures the pressing member in the armature. The pressing member  12  includes a crimped part  104  which is adjacent to the aperture  91  and which is positioned toward the right of the receiving part  88 . The armature  10  has an end surface  106  formed by cutting one end thereof. 
     The crimped part  104  is deformed by applying heat.  FIG. 21A  shows the crimped part  104  prior to deformation, and  FIG. 21B  shows the crimped part  104  after deformation. 
     The deformed crimped part  104  shown in  FIG. 21B  engages with the end surface  106 . By engaging the crimped part  104  with the end surface  106 , the pressing member is secured in the armature, and misalignment of the pressing member  12  can be prevented even when an external shock is received. 
     The insulation structure of the relay  2  will be described with reference to  FIGS. 9 and 11 .  FIG. 9  is a perspective view of the base  4 . In the relay  2 , insulation distances are maintained for each of the parts while the size of the device is reduced. Note that the insulation distances include gap distance and creepage distance. 
     The relay  2  comprises a first area  110  in which the coil  34  and the iron core  30  are arranged, and a second area  112  in which the movable terminal  20 , the fixed terminal  26 , and the pressing member  12  are arranged. The base  4  includes a wall  108  which is positioned between the first area  110  and the second area  112  and which extends in the upwards and downwards directions. 
     The wall  108  is formed from, for example, a resin, and insulates the coil  34  from the movable terminal  20  and the fixed terminal  26 . Since the wall  108  is formed so as to separate the first area  110  and the second area  112  and so as to cover the portion of the coil  34  in the vicinity of the second area  112 , the insulation distance between the coil  34  and the movable terminal  20  and the fixed terminal  26  can be maintained. 
     The first portion  74  is arranged in the first area  110  above the coil  34  and the iron core  30 . The second portion  76  is arranged in the second area  112  extending from the first portion  74 . 
     Since the pressing member  12  is attached to the second portion  76 , the insulation distance between the armature  10  and the movable terminal  20  can be maintained by the pressing member  12 . 
     The bobbin  36  has a first flange  118 , a second flange  120 , and a cavity  121  into which the iron core  30  is inserted. The bobbin  36  is formed from, for example, a resin. The first flange  118  and the second flange  120  insulate the iron core  30  and the coil  34 . Since the first flange  118  and the second flange  120  cover the upper surface  34   a  and the lower surface  34   b  of the coil  34 , the insulation distance between the iron core  30  and the coil  34  can be maintained. 
     The base  4  includes a first extending part  114  and a second extending part  116  arranged in the first area  110  which extend from the wall  108 . The first extending part  114  is connected to the wall  108 , and protrudes toward the first area  110 . The second extending part  116  is connected to the wall  108 , and protrudes toward the first area  110 . The first extending part  114  is opposed to an upper portion of the first flange  118 . The second extending part  116  is opposed to a lower portion of the second flange  120 . The first extending part  114  and the second extending part  116  insulate the coil  34 , the armature  10 , and the yoke  32 . Since the upper surface  34   a  is covered by the first extending part  114  and the first flange  118 , the insulation distance between the coil  34  and the first portion  74  can be maintained. Likewise, since the lower surface  34   b  is covered by the second extending part  116  and the second flange  120 , the insulation distance between the coil  34  and the first portion  122  can be maintained. 
     The yoke  32  comprises a first portion  122  arranged in the first area  110 , and a second portion  124  arranged in the second area  112  which extends so as to bend away from the first portion  122 . The second portion  124  is present along the wall  108 , and supports the bend part  78  along the end  126 . The wall  108  insulates the second portion  124  and the coil  34 . Since the wall  108  covers the coil  34 , the insulation distance between the coil  34  and the second portion  124  can be maintained. 
     By using the bobbin  36  and the base  4  of the present embodiment, the insulation distance between the coil  34  and the other parts can be maintained. Since it is not necessary to provide additional elements for maintaining insulation, an increase of the space within the relay can be prevented, and the insulation properties between the components can be maintained while maintaining the small size of the relay. 
     The yoke  32  includes an aperture  128  in the first portion  122 . The iron core  30  includes a protrusion  130  on an end thereof. By inserting and crimping the protrusion  130  in the aperture  128 , the iron core  30  and the yoke  32  are connected to form a magnetic path. 
     The iron core  30  comprises a shaft  132  which is inserted into the cavity  121 , and a head  124  which is arranged outside of the first flange  118 . A head  134  includes a surface  134   a  which extends outwardly from the tip of the shaft  132  on the outside of the coil  34  and which faces outside in the axial direction of the iron core  30 . The attractable surface  74   a  is attracted to the surface  134   a  by the excitation of the coil  34 . 
     The head  134  includes a surface  134   b  which projects outwardly from the outer circumference of the shaft  132  on the side opposite the surface  134   a . The first extending part  114  extending from the wall  108  has a thin portion  114   a  at the tip thereof which is inserted between the head  134  and the coil  34 , and more specifically, between the surface  134   b  of the head  134  and the first flange  118 . 
     The assembly of the relay  2  will be described with reference to  FIGS. 2, 11, and 24 .  FIG. 24  is a bottom view of the relay  2 . After housing the bobbin  36  on which the coil  34  is wound into the base  4 , the iron core  30  is inserted from above, the head  134  is inserted between the first extending part  114  and the second extending part  116  with a posture adjacent to the first extending part  114 . 
     An aperture  148  through which the second extending part  116  is exposed is provided in the bottom  61  of the base  4 . The second portion  124  is inserted from the aperture  148 , and the first portion  122  is arranged outside the second extending part  116 . Thereafter, the protrusion  130  protruding from the bobbin  36  is inserted into and crimped in the aperture  128 . 
     As a result, the thin portion  114   a  is interposed between the surface  134   b  and the first flange  118 , and the second extending part  116  is interposed between the first portion  122  and the second flange  120 . Thus, the electromagnet  7  and the base  4  are firmly secured without looseness. 
     As shown in  FIG. 24 , the first portion  122  is exposed from the aperture  148 . The adhesive  71 , which is represented by the hatched lines, is applied to the bottom  61 . In the present embodiment, the adhesive  71  covers the first portion  122  and the bottom  61  around the first portion  122 . 
     By inserting the yoke  32  from the aperture  148 , assembly of the relay  2  is simplified, and by covering the bottom  61  with adhesive  71 , the relay  2  is sealed so that the intrusion of foreign matter into the interior of the relay  2  can be prevented. Further, the insulation between the relay  2  and external devices is maintained. 
       FIG. 22  is a cross-sectional view of a modified example of the relay  2  taken along line A 1 -A 1  of  FIG. 1 . In the present embodiment, the iron core  30  and the yoke  32  are integrally formed in the metal part  138 , whereby the production cost of the relay  2  can be reduced. 
     The metal part  138  comprises an iron core  140  which is inserted into the cavity  121 , and a yoke  142  which extends so as to bend away from the iron core  140 . The iron core  140  has a surface  140   a  outside and above the coil  34 . The surface  140   a  attracts the contact surface  74   a  by the excitation of the coil  34 . 
     The yoke  142  comprises a first portion  144  arranged in the first area  110  which extends so as to bend away from the iron core  140 , and a second portion  146  arranged in the second area  112  which extends away from the first portion  144 . The second portion  146  extends along the wall  108 , and supports the bent part  78  on the end  147 . The wall  108  insulates the second portion  146  and the coil  34 . 
       FIG. 23  is a perspective view of the coil assembly  27  and the metal part  138  according to a modified example. As shown in  FIG. 23 , the iron core  140  and the cavity  121  are formed so as to be, for example, rectangular parallelepipeds. 
     The embodiments described above can be appropriately combined. Furthermore, in the drawings described above, identical or corresponding portions are assigned the same reference signs. Note that the embodiments described above are merely exemplary and do not limit the invention.