Patent Publication Number: US-10784055-B2

Title: Contact piece unit and relay

Description:
TECHNICAL FIELD 
     The present invention relates to a contact piece unit and a relay. 
     BACKGROUND ART 
     There is known a contact piece unit incorporated in a relay, and including a terminal and a contact piece connected to the terminal. For example, a relay disclosed in Patent Document 1 includes a contact piece extending in a lengthwise direction of a terminal, and disposed at a position facing the terminal. A proximal end portion of the contact piece is connected with a proximal end portion of the terminal. A leading end portion of the contact piece is disposed with a space left from the terminal. A movable contact is attached to the contact piece. 
     A link member is attached to the leading end portion of the contact piece. The link member is driven by a coil unit to press the contact piece. The pressed contact piece elastically deforms, whereby the movable contact moves toward a fixed contact. The movable contact thus comes into contact with the fixed contact. As a result, conduction is achieved between a terminal connected with the movable contact and a terminal connected with the fixed contact. 
     PRIOR ART DOCUMENT 
     Patent Document 
     
         
         Patent Document 1: U.S. Pat. No. 7,659,800 
       
    
     SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
     According to the contact piece unit described above, the contact piece and the terminal face each other. In this case, current i flows in a contact piece  101  and a terminal  102  in opposite directions. Accordingly, electromagnetic repulsion force F acts on the contact piece  101  in a direction away from the terminal  102  as illustrated in  FIG. 11 . The electromagnetic repulsion force F acts in such a direction as to press a movable contact  103  toward a fixed contact  104 . The contact piece unit described above is therefore capable of improving stability of contact between the contacts  103  and  104  by generating the electromagnetic repulsion force F in the contact piece  101  and utilizing the electromagnetic repulsion force F as assisting force for assisting contact force between the contacts  103  and  104  at the time of overcurrent. 
     Electromagnetic repulsion force increases in accordance with increase in current density. Accordingly, it is preferable to increase current density of current flowing in a terminal to raise strength of assisting force. However, high current density produces a problem of a temperature rise in the terminal. 
     An object of the present invention is to provide a contact piece unit and a relay capable of improving assisting force produced by electromagnetic repulsion force for assisting contacts while suppressing a temperature rise of a terminal. 
     Means for Solving the Problem 
     A contact piece unit according to an aspect of the present invention includes a terminal, a contact piece, and a contact. The contact piece is connected with the terminal, and disposed at a position facing the terminal. The contact is attached to the contact piece. The terminal includes a connection portion, a body, and a narrow portion. The connection portion is connected with the contact piece. The body extends in a lengthwise direction of the contact piece from the connection portion. The narrow portion has a width smaller than a width of the body and smaller than a width of the contact piece. 
     In the contact piece unit according to the aspect, the width of the narrow portion is smaller than the width of the body and smaller than the width of the contact piece. In this case, the current density can be increased in the narrow portion. Accordingly, assisting force produced by electromagnetic repulsion force for assisting the contact can be improved. Moreover, the width of the terminal is partially reduced at the narrow portion. Accordingly, a temperature rise of the terminal can be suppressed, compared to the case that the entire width of the terminal is reduced. 
     The narrow portion may overlap with the contact as viewed in a direction perpendicular to a surface of the narrow portion. In this case, electromagnetic repulsion force generated in the narrow portion can effectively act on the contact as assisting force. 
     The contact piece may include a contact attaching portion to which the contact is attached. The narrow portion may overlap with a portion of the contact piece on a side where the connection portion is disposed with respect to the contact attaching portion as viewed in the direction perpendicular to the surface of the narrow portion. In this case, large electromagnetic repulsion force is generated in the portion of the contact piece on side where the connection portion is disposed with respect to the contact attaching portion, and accordingly, assisting force can be improved. 
     The terminal may include a recess recessed in a widthwise direction. The recess may overlap with a portion of the contact piece on a leading end side with respect to the contact. In this case, a link member provided to operate the contact piece is allowed to be positioned via the recess. 
     The narrow portion may be located between the body and the recess in the lengthwise direction of the terminal. 
     A length of the narrow portion may be smaller than a length of the recess in the lengthwise direction of the terminal. In this case, a temperature rise of the terminal can be suppressed, compared to the case that the narrow portion is excessively long. 
     The terminal may further include a projection that projects widthwise on a side opposite to the recess. The projection thus provided secures a sufficient width of the terminal in a portion including the recess. Accordingly, a temperature rise of the terminal can be suppressed. 
     The contact may include a first contact and a second contact. A height of the second contact from the contact piece may be smaller than a height of the first contact from the contact piece. The contact piece may include a first plate and a second plate. The first contact may be attached to the first plate. The second plate may be divided from the first plate by a slit that extends in the lengthwise direction of the contact piece. The second contact may be attached to the second plate. The narrow portion may overlap with the first plate as viewed in the direction perpendicular to the surface of the narrow portion. 
     In this case, the height of the second contact is smaller than the height of the first contact. Accordingly, at the time of contact between the contacts, the first contact comes into contact with a paired contact prior to contact of the second contact. In addition, at the time of separation between the contacts, the first contact separates from the paired contact after separation of the second contact. Accordingly, a load produced at the time of contact between the contacts or separation between the contacts is chiefly applied to the first contact. The narrow portion is therefore overlapped with the first plate to allow electromagnetic repulsion force generated in the narrow portion to effectively act on the first contact as assisting force. Accordingly, contact stability of the contact can be improved. 
     The narrow portion may be so disposed as not to overlap with the second plate as viewed in the direction perpendicular to the surface of the narrow portion. This configuration reduces the width of the narrow portion, thereby improving the assisting force. 
     The width of the narrow portion may be equal to or larger than the width of the first plate. In this case, electromagnetic repulsion force generated in the narrow portion can effectively act on the first contact as assisting force. Accordingly, contact stability of the contact can be improved. 
     The length of the narrow portion may be smaller than a dimension of the first contact in the lengthwise direction of the terminal. In this case, a temperature rise of the terminal can be suppressed, compared to the case that the narrow portion is excessively long. 
     A relay according to a second aspect of the present invention includes the contact piece unit described above. The relay according to the aspect can improve assisting force generated by electromagnetic repulsion force for assisting the contact, similarly to the contact piece unit described above. In addition, a temperature rise of the terminal can be suppressed. 
     Effect of the Invention 
     According to the present invention, a contact piece unit and a relay capable of improving assisting force produced by electromagnetic repulsion force for assisting a contact while suppressing a temperature rise of a terminal. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a relay according to an embodiment. 
         FIG. 2  is a plan view of the relay in a reset state. 
         FIG. 3  is a plan view of the relay in a set state. 
         FIG. 4  is a plan view of a contact piece unit according to the embodiment. 
         FIG. 5  is a perspective view of the contact piece unit. 
         FIG. 6  is a perspective view of the contact piece unit. 
         FIG. 7  is an exploded perspective view of the contact piece unit. 
         FIG. 8  is a side view of the contact piece unit. 
         FIG. 9  is a side view of the contact piece unit. 
         FIG. 10  is a side view of a first terminal. 
         FIG. 11  is an explanatory view of electromagnetic repulsion force acting on a contact piece. 
     
    
    
     MODE FOR CARRYING OUT THE INVENTION 
     A relay according to an embodiment is hereinafter described with reference to the drawings.  FIG. 1  is a perspective view of a relay  1  according to the embodiment.  FIG. 2  is a plan view of the relay  1  in a reset state.  FIG. 3  is a plan view of the relay  1  in a set state. The relay  1  includes a base  2 , a driving unit  3 , a movable unit  4 , a support member  5 , a link member  6 , a contact piece unit  7 , and a fixed contact terminal unit  8 . The support member  5  is not shown in  FIGS. 2 and 3 . 
     The base  2  houses the driving unit  3 , the movable unit  4 , the link member  6 , the contact piece unit  7 , and the fixed contact terminal unit  8 . A not-shown cover member is attached to the base  2 . 
     The driving unit  3  drives the movable unit  4 . The driving unit  3  generates electromagnetic force for rotating the movable unit  4 . As illustrated in  FIG. 2 , the driving unit  3  includes a coil  11 , a spool  12 , a first yoke  13 , and a second yoke  14 . The coil  11  is wound around the spool  12 . A coil terminal  15  is attached to the coil  11  such that the coil  11  can be energized via the coil terminal  15 . A not-shown iron core is inserted into the spool  12 . The first yoke  13  is connected with one end of the iron core, while the second yoke  14  is connected with the other end of the iron core. 
     The movable unit  4  is rotatably supported relative to the base  2 . The movable unit  4  is disposed between the first yoke  13  and the second yoke  14 . The movable unit  4  includes a first armature  16 , a second armature  17 , a permanent magnet  18 , and a movable body  19 . The first armature  16 , the second armature  17 , and the permanent magnet  18  are attached to the movable body  19 . The movable body  19  is rotatably supported on the base  2  around a rotation shaft  191 . The movable body  19  includes an arm  192 . The arm  192  extends toward the link member  6 . 
     The first armature  16  includes a first end  161  and a second end  162 . The second armature  17  includes a third end  171  and a fourth end  172 . The first end  161  and the third end  171  project in the same direction from the movable body  19 . The second end  162  and the fourth end  172  project in the direction opposite to the projection direction of the first end  161  and the third end  171  from the movable body  19 . 
     The link member  6  connects the movable body  19  and the contact piece unit  7 . The link member  6  is so disposed as to cross a first terminal  21  of the contact piece unit  7  described below in plan view. One end of the link member  6  is connected with the movable body  19 . The other end of the link member  6  is connected with the contact piece unit  7 . More specifically, the link member  6  includes a connection hole  601 . A leading end of the arm  192  of the movable body  19  is disposed in the connection hole  601 . This configuration latches the arm  192  to the link member  6  during driving of the link member  6  by the movable body  19 . The link member  6  further includes a pressing portion  602 . The pressing portion  602  is so disposed as to surround a leading end of a contact piece  22  of the contact piece unit  7  described below. This configuration latches the pressing portion  602  to the leading end of the contact piece  22  during driving of the link member  6  by the movable body  19 . 
     The contact piece unit  7  includes a first terminal  21 , the contact piece  22 , and movable contacts  23  and  24 . The contact piece  22  is connected with the first terminal  21 . The contact piece  22  is disposed at a position facing the first terminal  21 . The movable contacts  23  and  24  are attached to the contact piece  22 . The contact piece unit  7  will be detailed below. 
     The fixed contact terminal unit  8  includes a second terminal  25  and fixed contacts  26  and  27 . The fixed contacts  26  and  27  are attached to the second terminal  25 . The fixed contacts  26  and  27  are disposed at positions facing the movable contacts  23  and  24 , respectively. 
     Next, an operation of the relay  1  is described. In the reset state illustrated in  FIG. 2 , the first end  161  of the first armature  16  contacts the first yoke  13 , while the second end  162  separates from the second yoke  14 . The fourth end  172  of the second armature  17  contacts the second yoke  14 , while the third end  171  separates from the first yoke  13 . The movable contacts  23  and  24  separate from the fixed contacts  26  and  27 , respectively. 
     When the coil  11  is energized in a predetermined direction, electromagnetic force is generated to rotate the movable unit  4  in a predetermined forward direction (clockwise in  FIG. 2 ). The movable unit  4  therefore rotates in the forward direction. The link member  6  moves in the left direction in  FIG. 2  in accordance with rotation of the movable unit  4  in the forward direction. In this case, a leading end of the contact piece  22  moves in the left direction in  FIG. 2 , and accordingly, the movable contacts  23  and  24  move toward the fixed contacts  26  and  27 . The movable contacts  23  and  24  therefore come into contact with the fixed contacts  26  and  27 . As a result, the reset state of the relay  1  illustrated in  FIG. 2  is switched to the set state illustrated in  FIG. 3 . 
     In the set state, the first end  161  of the first armature  16  separates from the first yoke  13 , while the second end  162  contacts the second yoke  14  as illustrated in  FIG. 3 . In addition, the fourth end  172  of the second armature  17  separates from the second yoke  14 , while the third end  171  contacts the first yoke  13 . The set state is maintained by magnetic force of the permanent magnet  18  even at a stop of energization of the coil  11  in this state. 
     When the coil  11  is subsequently energized in the direction opposite to the foregoing predetermined direction, electromagnetic force is generated to rotate the movable unit  4  in the direction opposite to the foregoing forward direction (anticlockwise in  FIG. 3 ). As a result, the movable unit  4  rotates in the opposite direction. The link member  6  moves in the right direction in  FIG. 3  in accordance with the rotation of the movable unit  4  in the opposite direction. In this case, the leading end of the contact piece unit  7  moves in the right direction in  FIG. 3 , and accordingly, the movable contacts  23  and  24  move away from the fixed contacts  26  and  27 , respectively. The movable contacts  23  and  24  therefore separate from the fixed contacts  26  and  27 , respectively. As a result, the set state of the relay  1  illustrated in  FIG. 3  is switched to the reset state illustrated in  FIG. 2 . The reset state is maintained by magnetic force of the permanent magnet  18  even at a stop of energization of the coil  11  in this state. 
     The contact piece unit  7  according to the embodiment is now described.  FIG. 4  is a plan view of the contact piece unit  7 .  FIGS. 5 and 6  are perspective views of the contact piece unit  7 .  FIG. 7  is an exploded perspective view of the contact piece unit  7 .  FIG. 8  is a side view of the contact piece unit  7  as viewed from the first terminal  21  side.  FIG. 9  is a side view of the contact piece unit  7  as viewed from the contact piece  22  side. 
     As illustrated in  FIGS. 4 to 7 , the first terminal  21  has an elongate plate shape. The first terminal  21  has a leading end portion  31  and a proximal end portion  32 . As illustrated in  FIG. 2 , the leading end portion  31  of the first terminal  21  is so disposed as to project from the base  2  to the outside. The proximal end portion  32  of the first terminal  21  is disposed inside the base  2 . 
     According to the embodiment, a direction in parallel to a direction extending from the proximal end portion  32  toward the leading end portion  31  is referred to as a lengthwise direction. The lengthwise direction corresponds to an up-down direction in  FIG. 4 . A direction perpendicular to the lengthwise direction and a plate thickness direction of the first terminal  21  is referred to as a widthwise direction. The plate thickness direction of the first terminal  21  corresponds to a right-left direction in  FIG. 4 . The widthwise direction is a direction perpendicular to the sheet of  FIG. 4 , and corresponds to a right-left direction in  FIGS. 8 and 9 . 
     The movable contacts  23  and  24  include the first movable contact  23  and the second movable contact  24 , respectively. A height of the second movable contact  24  from the contact piece  22  is smaller than a height of the first movable contact  23  from the contact piece  22 . Accordingly, at the time of contact between the contacts, the first movable contact  23  comes into contact with the first fixed contact  26  prior to contact between the second movable contact  24  and the second fixed contact  27 . At the time of separation between the contacts, the first movable contact  23  separates from the first fixed contact  26  after separation of the second movable contact  24  from the second fixed contact  27 . Accordingly, an electric load produced at the time of contact between the contacts or separation between the contacts is chiefly applied to the first movable contact  23 . 
     The first movable contact  23  and the second movable contact  24  are separated from each other in the lengthwise direction of the contact piece  22 . More specifically, the first movable contact  23  is located at the leading end side of the contact piece  22  with respect to the second movable contact  24 . The number of the movable contacts is not limited to two, but may be a number larger than two. Alternatively, only the single movable contact may be provided. 
     The contact piece  22  is connected to the proximal end portion  32  of the first terminal  21 . The contact piece  22  has a plate shape elongated in the lengthwise direction of the first terminal  21 . The contact piece  22  has a proximal end portion  33  and a leading end portion  34 . The proximal end portion  33  of the contact piece  22  is joined to the first terminal  21 . The leading end portion  34  of the contact piece  22  is a free end located on the side opposite to the proximal end portion  33 . Accordingly, the proximal end portion  33  of the contact piece  22  is supported on the first terminal  21  in a cantilevered manner. 
     As illustrated in  FIG. 5 , the contact piece  22  includes a first plate  35  and a second plate  36 . The contact piece  22  includes a slit  37  formed between the first plate  35  and the second plate  36 . The slit  37  divides the first plate  35  and the second plate  36  from one another. The slit  37  extends lengthwise from the leading end portion  34  of the contact piece  22  toward the proximal end portion  33 . The slit  37  does not reach the proximal end portion  33 , and therefore the first plate  35  and the second plate  36  are connected with each other on the proximal end side of the slit  37 . The first movable contact  23  is attached to the first plate  35 . The second movable contact  24  is attached to the second plate  36 . The first plate  35  includes a slit  38 . The slit  38  is disposed between the first movable contact  23  and a portion connected with the first terminal  21 . The first plate  35  has a width larger than a width of the second plate  36 . A leading end of the first plate  35  is located on the leading end side of the first terminal  21  with respect to a leading end of the second plate  36 . 
     The contact piece  22  includes an expanded portion  39 . The expanded portion  39  has a curved shape protruding in a direction away from the first terminal  21 . The expanded portion  39  projects from the movable contacts  23  and  24  toward the fixed contacts  26  and  27 . The expanded portion  39  extends in the widthwise direction of the contact piece  22 . The expanded portion  39  is located between the proximal end portion  33  of the contact piece  22  and the movable contacts  23  and  24  in the lengthwise direction of the contact piece  22 . 
     As illustrated in  FIG. 7 , the contact piece unit  7  includes a plurality of leaf springs  41  to  43 . The plurality of leaf springs  41  to  43  are laminated on each other. More specifically, the contact piece unit  7  includes the first leaf spring  41 , the second leaf spring  42 , and the third leaf spring  43 . In the plurality of leaf springs  41  to  43 , the first leaf spring  41  is disposed at a position farthest from the first terminal  21 . In the plurality of leaf springs  41  to  43 , the second leaf spring  42  is disposed at a position closest to the first terminal  21 . The third leaf spring  43  is disposed between the first leaf spring  41  and the second leaf spring  42 . 
     The number of the leaf springs is not limited to three, but may be a number smaller than three. Alternatively, the number of the leaf springs may be a number larger than three. 
     The first leaf spring  41  includes connection holes  411 . The second leaf spring  42  includes connection holes  421 . The third leaf spring  43  includes connection holes  431 . The first terminal  21  includes connection projections  211 . The connection projections  211  are inserted into the connection holes  411 ,  421 , and  431  of the first to third leaf springs  41  to  43  to connect the first to third leaf springs  41  to  43  and the first terminal  21  integrally. 
     The first leaf spring  41  includes a first plate  351  and a second plate  361 . The second leaf spring  42  includes a first plate  352  and a second plate  362 . The third leaf spring  43  includes a first plate  353  and a second plate  363 . The plurality of first plates  351  to  353  are laminated on each other, and constitute the first plate  35  of the contact piece  22  described above. The plurality of second plates  361  to  363  are laminated on each other, and constitute the second plate  36  of the contact piece  22  described above. 
     The first leaf spring  41 , the second leaf spring  42 , and the third leaf spring  43  include first contact attaching portions  441 ,  442 , and  443 , respectively. The first contact attaching portions  441  to  443  are attachment holes formed in the first to third leaf springs  41  to  43 , respectively, and are so disposed as to overlap with each other. The first movable contact  23  is attached to the first contact attaching portions  441  to  443 . 
     The first leaf spring  41 , the second leaf spring  42 , and the third leaf spring  43  include second contact attaching portions  451 ,  452 , and  453 , respectively. The second contact attaching portions  451  to  453  are attachment holes formed in the first to third leaf springs  41  to  43 , respectively, and are so disposed as to overlap with each other. The second movable contact  24  is attached to the second contact attaching portions  451  to  453 . 
     The first leaf spring  41  includes a first slit  461 . The first slit  461  is formed around the first contact attaching portion  441 . The first slit  461  has a shape curved along a part of the first contact attaching portion  441 . The second leaf spring  42  includes a second slit  462 . The second slit  462  is formed around the first contact attaching portion  442 . The second slit  462  has a shape curved along a part of the first contact attaching portion  442 . The third leaf spring  43  includes a third slit  463 . The third slit  463  has a shape similar to the shape of the first slit  461 . 
     The first leaf spring  41 , the second leaf spring  42 , and the third leaf spring  43  include slits  371  to  373 , respectively. The slits  371  to  373  are so disposed as to overlap with each other, and constitute the slit  37  described above. The first leaf spring  41 , the second leaf spring  42 , and the third leaf spring  43  include slits  381  to  383 , respectively. The slits  381  to  383  are so disposed as to overlap with each other, and constitute the slit  38  described above. 
     The first leaf spring  41 , the second leaf spring  42 , and the third leaf spring  43  include expanded portions  391  to  393 , respectively. The expanded portions  391  to  393  are so disposed as to overlap with each other, and constitute the expanded portion  39  described above. 
     The first leaf spring  41  includes a first contact portion  412  and a second contact portion  413 . The first contact portion  412  is provided at a leading end portion of the first plate  351 . The second contact portion  413  is provided at a leading end portion of the second plate  361 . The link member  6  presses the first contact portion  412  and the second contact portion  413  to move the movable contacts  23  and  24  in directions away from the fixed contacts  26  and  27  and thereby separate the movable contacts  23  and  24  from the fixed contacts  26  and  27 . As a result, the set state of the relay  1  is switched to the reset state. 
     The second leaf spring  42  includes a first contact portion  422  and a second contact portion  423 . The first contact portion  422  is provided at a leading end portion of the first plate  352 . The second contact portion  423  is provided at a leading end portion of the second plate  362 . The link member  6  presses the first contact portion  422  and the second contact portion  423  to move the movable contacts  23  and  24  toward the fixed contacts  26  and  27  and thereby bring the movable contacts  23  and  24  into contact with the fixed contacts  26  and  27 . As a result, the reset state of the relay  1  is switched to the set state. 
     A leading end portion of the second leaf spring  42  is bent toward the first terminal  21 . This configuration stabilizes a contact pressure of the contacts in the set state of the relay  1 . 
     A rib  432  is provided on the third leaf spring  43 . The rib  432  disposed at an edge of the second plate  363  of the third leaf spring  43  extends in the lengthwise direction of the contact piece  22 . The rib  432  has a shape bent toward the first terminal  21 . 
     The first terminal  21  is now detailed.  FIG. 10  is a side view of the first terminal  21 . As illustrated in  FIG. 10 , the first terminal  21  includes a connection portion  51 , a body  52 , a narrow portion  53 , a recess  54 , and a distal end portion  55 . The connection portion  51  includes the proximal end portion  32  of the first terminal  21 . As illustrated in  FIG. 9 , the connection projections  211  described above are provided on the connection portion  51 . The proximal end portion  33  of the contact piece  22  is connected with the connection portion  51 . 
     The body  52  extends in the lengthwise direction of the contact piece  22  from the connection portion  51 . A width W 52  of the body  52  is equivalent to a width W 51  of the connection portion  51 . As illustrated in  FIGS. 4 to 6 , the body  52  faces the expanded portion  39  of the contact piece  22 . The body  52  faces the second contact attaching portions  451  to  453 . The body  52  includes a bent portion  521  having a bent shape. A proximal end side of the body  52  with respect to the bent portion  521  is inclined toward the contact piece  22  with nearness to the proximal end portion  32 . 
     As illustrated in  FIG. 10 , the narrow portion  53  is located on a leading end side of the body  52 . The narrow portion  53  is located between the body  52  and the recess  54  in the lengthwise direction of the first terminal  21 . One edge  531  of the narrow portion  53  in the widthwise direction of the first terminal  21  is recessed widthwise from an edge  522  of the body  52 . Accordingly, a step  57  is formed by the edge  531  of the first terminal  21  and the edge  522  of the body  52 . An edge  532  that is the other edge of the narrow portion  53  in the widthwise direction of the first terminal  21  is continuously formed from an edge  523  of the body  52  and arranged in a line in the lengthwise direction. 
     The narrow portion  53  has a width W 53  smaller than the width W 52  of the body  52 . The width W 53  of the narrow portion  53  is smaller than a width W 55  of the distal end portion  55 . The width W 53  of the narrow portion  53  is larger than a width W 54  of the first terminal  21  at a portion including the recess  54 . The width W 53  of the narrow portion  53  is smaller than a width of the contact piece  22 . The width W 53  of the narrow portion  53  is larger than a width of the second plate  36 . The width W 53  of the narrow portion  53  is substantially equivalent to the width of the first plate  35 . Alternatively, the width W 53  of the narrow portion  53  may be larger than the width of the first plate  35 . 
     As illustrated in  FIG. 9 , the narrow portion  53  overlaps with the first movable contact  23  as viewed in a direction perpendicular to a surface of the narrow portion  53 . As illustrated in  FIG. 8 , the narrow portion  53  overlaps with a portion of the contact piece  22  located on a side where the connection portion  51  is disposed with respect to the first contact attaching portion  442  as viewed in the direction perpendicular to the surface of the narrow portion  53 . The narrow portion  53  overlaps with the first plate  35  as viewed in the direction perpendicular to the surface of the narrow portion  53 . The narrow portion  53  does not overlap with the second plate  36  as viewed in the direction perpendicular to the surface of the narrow portion  53 . The narrow portion  53  overlaps with the second slit  462  as viewed in the direction perpendicular to the surface of the narrow portion  53 . 
     As illustrated in  FIG. 10 , a length L 53  of the narrow portion  53  is smaller than a length L 52  of the body  52  in the lengthwise direction of the first terminal  21 . The length L 53  of the narrow portion  53  is smaller than a length L 54  of the recess  54  in the lengthwise direction of the first terminal  21 . The length L 53  of the narrow portion  53  is smaller than a length L 55  of the distal end portion  55  in the lengthwise direction of the first terminal  21 . The length L 53  of the narrow portion  53  is smaller than a dimension, i.e., a diameter of the first movable contact  23  in the lengthwise direction of the first terminal  21 . The length L 53  of the narrow portion  53  is larger than a diameter of the first contact attaching portion  442  in the lengthwise direction of the first terminal  21 . 
     The recess  54  is recessed widthwise from the edge  531  of the narrow portion  53 . The recess  54  overlaps with a portion of the contact piece  22  on the leading end side with respect to the first movable contact  23 . The first terminal  21  includes a projection  56  located on the side opposite to the recess  54  in the widthwise direction of the first terminal  21 . The projection  56  projects widthwise from the edge  532  of the narrow portion  53 . 
     The distal end portion  55  is located on a leading end side of the recess  54 . The distal end portion  55  includes the leading end portion  31  of the first terminal  21 . The distal end portion  55  is a portion of the first terminal  21 , which projects from the base  2  to the outside. 
     In the contact piece unit  7  according to the embodiment described above, the width W 53  of the narrow portion  53  is smaller than the width W 52  of the body  52 , and smaller than the width of the contact piece  22 . In this case, the current density can be increased in the narrow portion  53 . Accordingly, assisting force produced by electromagnetic repulsion force for assisting the movable contacts  23  and  24  can be improved. Moreover, the width of the first terminal  21  is partially reduced at the narrow portion  53 . Accordingly, a temperature rise of the first terminal  21  can be suppressed, compared to the case that the entire width of the first terminal  21  is reduced. 
     The narrow portion  53  overlaps with the first movable contact  23  as viewed in the direction perpendicular to the surface of the narrow portion  53 . Accordingly, electromagnetic repulsion force generated in the narrow portion  53  can effectively act on the first movable contact  23  as assisting force. 
     The narrow portion  53  overlaps with the portion of the contact piece  22  on the side where the connection portion  51  is disposed with respect to the first contact attaching portions  441  to  443 , as viewed in the direction perpendicular to the surface of the narrow portion  53 . Thus, large electromagnetic repulsion force is generated in the portion of the contact piece  22  on the side where the connection portion  51  is disposed with respect to the first contact attaching portion  442 , so that assisting force can be improved. 
     The recess  54  formed in the first terminal  21  overlaps with the portion of the contact piece  22  on the leading end side with respect to the first movable contact  23 . Accordingly, the link member  6  is allowed to be positioned via the recess  54  and connected with the leading end portion  34  of the contact piece  22 . 
     The length L 53  of the narrow portion  53  is smaller than the length L 54  of the recess  54  in the lengthwise direction of the first terminal  21 . Accordingly, a temperature rise of the first terminal  21  can be suppressed, compared to the case that the narrow portion  53  is excessively long. 
     The first terminal  21  includes the projection  56  on the side opposite to the recess  54 . In this case, a large width of the first terminal  21  can be secured in the portion including the recess  54 . Accordingly, a temperature rise of the first terminal  21  can be suppressed. 
     The narrow portion  53  overlaps with the first plate  35  as viewed in the direction perpendicular to the surface of the narrow portion  53 . Accordingly, electromagnetic repulsion force generated in the narrow portion  53  can effectively act on the first movable contact  23  as assisting force. Accordingly, contact stability of the contacts can be improved. 
     The narrow portion  53  does not overlap with the second plate  36  as viewed in the direction perpendicular to the surface of the narrow portion  53 . In this case, the width W 53  of the narrow portion  53  can be reduced as compared to the case that the narrow portion  53  overlaps with the second plate  36 . Accordingly, the assisting force can be improved. The width W 53  of the narrow portion  53  is equal to or larger than the width of the first plate  35 . Accordingly, electromagnetic repulsion force generated in the narrow portion  53  can effectively act on the first movable contact  23  as assisting force. Accordingly, contact stability of the contacts can be improved. 
     The length L 53  of the narrow portion  53  is smaller than the diameter of the first movable contact  23  in the lengthwise direction of the terminal. In this case, a temperature rise of the first terminal  21  can be suppressed, compared to the case that the narrow portion  53  is excessively long. 
     The present invention is not limited to the embodiment described herein as a specific embodiment of the present invention. Various modifications may be made without departing from the scope of the subject matters of the invention. 
     The shape of the first terminal  21  may be modified from the shape described above in the embodiment. For example, the recess  54  may be eliminated depending on the structure of the link member  6 . The width W 53  or the length L 53  of the narrow portion  53  may be changed from the width or the length described above in the embodiment. The position of the narrow portion  53  may be changed from the position described above in the embodiment. 
     The shape of the contact piece  22  may be modified from the shape described above in the embodiment. For example, the contact piece  22  divided into the first plate  35  and the second plate  36  in the embodiment may be provided as one piece component. The positions of the first movable contact  23  and the second movable contact  24  shifted lengthwise in the embodiment may be aligned in a line. 
     Configurations of the relay  1  other than the contact piece unit  7  may be modified from the corresponding configurations described above in the embodiment. 
     INDUSTRIAL APPLICABILITY 
     According to the present invention, a contact piece unit and a relay capable of improving assisting force produced by electromagnetic repulsion force for assisting a contact while suppressing a temperature rise of a terminal. 
     DESCRIPTION OF SYMBOLS 
     
         
         
           
               21  first terminal 
               22  contact piece 
               23 ,  24  movable contact 
               51  connection portion 
               52  body 
               53  narrow portion 
               7  contact piece unit 
               442  first contact attaching portion 
               54  recess 
               56  projection 
               23  first movable contact 
               24  second movable contact 
               35  first plate 
               36  second plate