Abstract:
An electromagnetic relay having a moving contact plate and fixed contact plates juxtaposed with one another on a base. A moving iron plate is rotated during magnetization/demagnetization of a coil block put on the base to reciprocate a card in a horizontal direction. The moving contact plate is allowed to undergo elastic deformation so that a contact on the moving contact plate is brought into contact and out of contact with contacts on the fixed contact plates. The top corners of the moving contact plate is bent into an upper component and a lower components in such a fashion as to form card acceptance portions, and a distal end portion of the card is brought into contact with an inner surface of the card acceptance portions.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention relates to an electromagnetic relay. 
   2. Description of the Related Art 
   A known electromagnetic relay employs a construction in which a moving contact plate is allowed to undergo elastic deformation through a card to thereby open and close contacts (refer to patent reference 1, for example). 
   Patent reference 1: 
   Microfilm of Japanese Utility Model Application No.23090/1991 (JP-UM-A-4-119947) 
   In the electromagnetic relay of the prior art described above, however, first and second protuberances are formed on the card, the first protuberance is inserted through a through-hole formed in the moving contact plate to guide the card and the second protuberance can be pushed and brought into contact with the moving contact plate. The card is formed of a resin and the moving contact plate is formed of a metal. Therefore, the protuberances of the card come into sliding contact with the moving contact plate and generate wear dust, or the like. The wear dust adhering to contacts is likely to deteriorate contact reliability of the contacts. An inserting work of the first protuberance of the card through the through-hole of the moving contact plate is troublesome at the time of assembling. 
   It is therefore an object of the invention to provide an electromagnetic relay that can acquire a satisfactory operation without generating the wear dust though it has a simple construction. 
   SUMMARY OF THE INVENTION 
   To accomplish this object, the invention provides an electromagnetic relay in which a moving contact plate and fixed contact plates are juxtaposed with one another on a base, a moving iron plate is rotated on the basis of magnetization/demagnetization of a coil block put on the base to reciprocate a card in a horizontal direction, and the moving contact plate is allowed to undergo elastic deformation so that a moving contact provided to the moving contact plate is brought into contact with and out of contact from fixed contacts provided to the fixed contact plates, wherein a distal end portion of the moving contact plate is bent in such a fashion as to form card acceptance portions positioned at least at upper and lower positions, and a distal end portion of the card is brought into contact with an inner surface of the card acceptance portions. 
   This construction can bring the distal end portion of the card and the card acceptance portions of the moving contact plate at least into line contact, and can restrict the occurrence of the wear dust by diffusing a sliding contact range. Because it is only necessary to guide the distal end portion of the card by the card acceptance portions, an assembly work can be carried out extremely simply. 
   The card described above is preferably equipped with a guide portion for guiding from both sides the card acceptance portions formed on the moving contact plate because a contact switch operation can be conducted under a stable state. 
   Preferably, the card has a reduced thickness portion that is guided by the card acceptance portions. For, when ribs for reinforcing the reduced thickness portion guide the card acceptance portions, desired rigidity can be secured while reducing the weight of the card and the contact switch operation can be stabilized. 
   Preferably, the fixed contact plate is interposed between the moving contact plate and the coil block so that a bent portion at a distal end thereof is positioned above a push-in portion of the moving contact plate, and the card acceptance portion of the moving contact plate has an escape portion for allowing insertion of the fixed contact plate because each contact plate can be appropriately pushed in irrespective of the restrictive condition of the push-in position. 

   
     BRIEF DESCRIPTION OF THE DRAWING 
       FIG. 1  is a perspective view of an electromagnetic relay according to an embodiment of the invention when its case is removed; 
       FIG. 2  is a sectional view of the electromagnetic relay according to the embodiment of the invention; 
       FIG. 3A  is a perspective view of a first fixed contact plate; 
       FIG. 3B  is a perspective view of a moving contact plate; 
       FIG. 3C  is a perspective view of a second fixed contact plate; 
       FIG. 4  is an exploded perspective view of a coil block; 
       FIG. 5  is a perspective view of the coil block; 
       FIG. 6  is a perspective view of the coil block when it is viewed from a bottom side; 
       FIG. 7  is a perspective view of a card; 
       FIG. 8  is a perspective view of a base; 
       FIG. 9  is a perspective view showing the state where each contact plate is assembled to the base; 
       FIG. 10  is a perspective view showing the state before the coil block is assembled to the base to which each contact plate is assembled; 
       FIG. 11  is a perspective view showing the state where each contact plate and the coil block are assembled to the base; 
       FIG. 12  is a perspective view showing the state where each contact plate and the coil block are assembled to the base and the card is fitted; 
       FIG. 13  is a perspective view of an electromagnetic relay; 
       FIG. 14  is a partial plan view showing a contact switch mechanism; 
       FIG. 15  is a partial front view showing the contact switch mechanism; and 
       FIG. 16  is a perspective view of an electromagnetic relay according to another embodiment. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Embodiments of the invention will be hereinafter explained with reference to the accompanying drawings. 
     FIGS. 1 and 2  show an electromagnetic relay according to an embodiment. The electromagnetic relay briefly has a construction in which a contact switch mechanism  2  and a coil block  3  are arranged on a base  1  and these constituents are covered with a case  4 . 
   An insulating wall  5  divides the base  1  into a coil block-fitting portion  6  and a contact switch mechanism-fitting portion  7  as shown in  FIGS. 8 to 10 . 
   The insulating wall  5  has a partition portion  8  and both side portions  9 . Protuberance portions  10  are so formed at the center of the partition portion  8  as to extend in a vertical direction with a predetermined gap between them. The protuberance portions  10  reinforce the partition portion  8  and guide with their upper edge protuberance portions  10   a  a card  100  that will be later described. An auxiliary insulating wall  11  is formed at a lower part of each protuberance portion  10  in such a fashion as to define a recess in cooperation with the insulating wall  5 . A guide groove  11   a  extending in the vertical direction is formed at the center of the inner surface of the auxiliary insulating wall  11 . On the other hand, groove portions  9   a  and  9   b  extending in the vertical direction while their positions are deviated from each other are formed on the inner and outer surfaces of both side portions  9 , respectively. The inner surface groove portion  9   a  guides a yoke  30  to be later described. The outer surface groove portion  9   b  is a recession for molding the base  1 . 
   As particularly shown in  FIG. 10 , a partition wall  12  partitions the coil block-fitting portion  6 . An escape recess portion  13  is defined in the bottom surface on the side of the insulating wall so partitioned. A notch portion  14  is defined in both sidewalls. Through-holes  15  are defined in the remaining partitioned portions and coil terminals  42  are fitted into both end portions of the through-hole  15 . Three base reinforcement ribs  16  defined between both through-holes  15  connect the partition wall  12  to the sidewall on one of the sides. The base reinforcement ribs  16  allow a resin to smoothly fluidize when the base  1  is molded even when the thickness of the bottom surface is small and also play the role of reinforcement. The partition wall  12  and the base reinforcement ribs  16  together constitute a push-in acceptance portion  17  for pushing and fixing an increased thickness portion  41  of the coil block  3  that will be later described. 
   Incidentally, reference numeral la denotes a standoff. The standoff la forms a clearance with the bottom surface of the base when the electromagnetic relay is mounted to a printed board and eliminates influences of a solder at the time of soldering. 
   The contact switch mechanism-fitting portion  7  has contact plate push-in portions  18   a ,  18   b  and  18   c  at three positions as shown in  FIG. 8 . 
   The contact switch mechanism  2  includes a first fixed contact plate  19 , a moving contact plate  20  and a second fixed contact plate  21  that are serially pushed into the contact plate push-in portions  18   a ,  18   b  and  18   c  from one of the ends  18   a  of these contact plate push-in portions  18   a ,  18   b  and  18   c.    
   The first fixed contact plate  19  is substantially flat as shown in  FIG. 3C  and has at its upper end the first fixed contact  22  and at its lower end a protuberance  19   a  to be pushed into the contact plate push-in portion  18 . Terminal portions  19   b  and  19   c  extend downward from both sides of the first fixed contact plate  19 . 
   The moving contact plate  20  has on both surfaces of its upper end a moving contact  23  having a contact surface with respect to the fixed contacts  22  and  26  as shown in  FIG. 3B . Card acceptance portions  24   a  and  24   b  extending obliquely vertically are formed at the upper edge of the moving contact plate  20 . A protruding distance of the card acceptance portions  24   a  and  24   b  is set to a value at which the card  100  to be later described does not fall off even when the moving contact plate  20  undergoes elastic deformation. The intermediate part of each card acceptance portion  24   a ,  24   b  constitutes an escape portion  25  lest it becomes an obstacle when the second fixed contact plate  21  is inserted from above. Push-in protuberance portions  20   a  are formed at the lower end of the moving contact plate  20  in the same way as the first fixed contact plate  19 . Terminal portions  20   b  and  20   c  extend from both sides of the moving contact plate  20 . The center portion is bent into a crank shape and a slit  20   d  is formed at the center so that the moving contact plate  20  can easily undergo elastic deformation. 
   The second fixed contact  26  is fixed to the upper end of the second fixed contact plate  21 . The second fixed contact plate  21  is bent into a crank shape from its part in the proximity of the second fixed contact  26 . Push-in protuberance portions  21 a are formed at the lower end of the second fixed contact plate  21  in the same way as both contact plates  19  and  20 . The lower portion of the second fixed contact plate  21  below the push-in protuberance portions  21   a  is bent substantially at right angles in the horizontal direction and terminal portions  21   b  and  21   c  extend downward from both ends of the bent portion. The second fixed contact plate  21  is fitted to the base  1  under the state where it is guided by the guide groove  11   a  of the auxiliary insulating wall  11 . The auxiliary insulating wall  11  secures desired insulating performance (creep distance) with the moving contact plate  20  when the moving contact  23  is spaced apart from the second fixed contact  26 . 
   The coil block  3  is obtained by winding a coil  29  onto a core  27  through a spool  28  as shown in  FIGS. 4 and 5 . 
   A yoke  30  is fixed to the upper end of the core  27 . A flange-like lower end of the core  27  operates as an attraction surface  27   a . The yoke  30  is constituted by a substantially L-shaped magnetic material and has at the center of one of its ends an opening  30   a  into which the core  27  is fitted and fixed. An anchor acceptance portion  30   b  for fitting a hinge spring  31  is formed at a side edge of the other end of the yoke  30 . The other end of the yoke  30  operates as a support point for rotation. A substantially L-shaped moving iron plate  32  is supported in such a fashion that a bent portion  33  can freely rock while being held by the hinge spring  31 . One of the ends of the moving iron plate  32  is an attracted portion  34  that is attracted to the attraction surface  27   a  of the core  27 , and an anchor portion  35   a  is formed at the upper end of a reduced width portion  35  at the other end of the moving iron plate  32 . The hinge spring  31  includes an anchor portion  31   a  anchored to the anchor acceptance portion  30   b  of the yoke  30  described above and a rectangular pressure contact portion  31   b  into which the reduced width portion  35  of the moving iron plate  32  is fitted and which comes into pressure contact with the bent portion  33 . The rectangular pressure contact portion  31   b  comes into pressure contact with a step portion  32   a  and a curved surface  32   b  of the bent portion  33  of the moving iron plate  32  and urges the moving iron plate  32  counter-clockwise in  FIG. 2 , that is, in a direction in which the attracted portion  34   b  comes away from the attraction surface  27   a  of the core  27 . 
   The card  100  is interposed between the anchor portion  35   a  of the moving iron plate  32  and the card acceptance portion  24  of the moving contact plate  20 . As shown in  FIG. 7 , the card  100  has at one of its ends an anchor holding portion  36  to which the anchor portion  35   a  of the moving iron plate  32  is anchored and at its other end a push portion  37  into which the card acceptance portion  24  is pushed. The anchor holding portion  36  has a contact plate  38  that comes into contact with the anchor portion  35   a  of the moving iron plate  32 , and a flexible holding plate  39  that flexibly holds the anchor portion  35   a  from both sides. A clearance is defined between the contact plate  38  and the flexible holding plate  39 . When the upper end protuberance portion  10   a  formed on the insulating wall  5  of the base  1  is positioned, the card  100  is guided during its horizontal movement. The push-in portion  37  has a reduced thickness portion  37   a  and guide plates  37   b  and  37   b . The guide plates  37   b  and  37   b  are positioned on both sides of the reduced thickness portion  37   a  and are supported by the card acceptance portions  24   b  on the lower side. The distal end of the reduced thickness portion  37   a  is preferably shaped into a taper surface or a curve surface so that the reduced thickness portion  37   a  can come into surface contact with the card acceptance portions  24   a  and  24   b  of the moving contact plate  20 . A card reinforcement rib  40  having a substantial E shape when viewed on a plane reinforces the reduced thickness portion  37   a . Upper and lower card acceptance portions  24   a  and  24   b  of the moving contact plate  20  come into contact with the upper and lower surface edge portions of the reduced thickness portion  37   a , respectively. The card reinforcement rib  40  not only reinforces the reduced thickness portion  37   a  but also allows a resin to smoothly flow when the card  100  is molded and prevents the occurrence of problems such as short shot. The guide plates  37   b  and  37   b  guide from both sides the card acceptance portion  24   a  on the upper side. 
   As shown in  FIGS. 4 and 6 , the spool  28  has a cylindrical shape and the core  27  is inserted through the spool  28 . The spool  28  has flanges  28   a  and  28   b  at its both ends. Protuberances  28   c  are formed at three positions of the upper flange  28   a  and guide the yoke  30 . Increased thickness portions  41  are formed on both sides of the lower flange  28   b . Each increased thickness portion  41  has a terminal hole  41   a  into which the coil terminal  42  is pushed. A ring-like recess  43  is formed around the terminal hole  41   a  on the bottom surface side. Each increased thickness portion  41  is pushed into each push-in acceptance portion  17  of the base  1  when the coil block  3  is fitted to the base  1 , stores a sealant flowing from the through-hole  15  in its ring-like recess  43  and prevents further inflow. 
   The coil  29  is wound on a drum portion of the spool  28  and both of its ends are wound on the coil terminal  42 , respectively. 
   Referring to  FIG. 13 , the case  4  has substantially a box shape the lower surface of which is open. When the open edge of the lower surface of the case  4  is fitted to the side surfaces of the base  1 , the case  4  covers constituent components. A gas vent hole  44  is formed at a corner of the upper surface to emit the gas resulting from the seal work to the outside. The gas vent hole  44  is thermally sealed when the electromagnetic relay is completed. First and second protuberance portions  45  and  46  protruding inward are formed at a corner and substantially at a center portion of the ceiling surface of the base  1  as shown in  FIG. 2 , respectively. The first protuberance portion  45  guides the yoke  30  and the second protuberance portion  46  restricts the moving range of the card  100 . 
   An assembling method of the electromagnetic relay described above will be subsequently explained. 
   The coil block  3  is formed in a separate step. In other words, the coil  29  is wound on the core  27  through the spool  28  as shown in  FIG. 4  and both ends of the coil  29  are wound on the coil terminals  42  pushed into and fixed to the increased thickness portion  41 , respectively. One of the ends of the yoke  30  is fixed to the upper end of the core  27  and the moving iron plate  32  is arranged at the other end of the yoke  30  in such a fashion as to be capable of rocking. The moving iron plate  32  is fitted to the yoke  30  through the hinge spring  31  and is urged to come away from the attraction surface  27   a  of the core  27 . The coil block  3  shown in  FIG. 5  is thus completed. 
   The moving contact plate  20  and the first and second fixed contact plates  19  and  21  are pushed into and fixed to the base  1  as shown in  FIG. 9  and the completed coil block  3  is assembled to the base  1  as shown in  FIGS. 10 and 11 . The coil block  3  is fixed as the increased thickness portion  41  is pushed into the push-in acceptance portion  17  and both side portions  9  of the yoke  30  are pushed into the inner surface groove portion  9   a . A space is defined under this state between the base  1  and the coil block  3  and a rotation space of the moving iron plate  32  can be secured. However, the escape recess  13  formed in the base  1  restricts the height of the electromagnetic relay. Each contact plate is pushed into and fixed to the base  1  in the sequence of the first fixed contact plate  19 , the moving contact plate  20  and the second fixed contact plate  21 . When the second fixed contact plate  21  is first pushed in, its bent portion prevents the push-in operation of the moving contact plate  20 . Therefore, the moving contact plate  20  is first pushed in and then the second fixed contact plate  21  is pushed in and fixed. In this case, the escape portion  25  prevents the interference of the second fixed contact  26  though the card acceptance portion  24  is formed at the upper end of the moving contact plate  20 . 
   After the push-in and fixing operation of the coil block  3  and each contact plate  19 ,  20 ,  21  to the base  1  is completed, the anchor holding portion  36  of the card  100  is anchored to the anchor portion  35   a  of the moving iron plate  32  as shown in  FIG. 12 . In other words, when the anchor holding portion  36  is pushed from the side of the anchor portion  35   a , the flexible holding plate  39  undergoes elastic deformation and then returns to its original shape. In consequence, the flexible holding plate  39  and the contact plate  38  hold the anchor portion  35   a . After the moving contact plate  20  is allowed to undergo elastic deformation and then to return to its original shape, the reduced thickness portion  37   a  of the card  100  is positioned between the upper and lower card acceptance portions  24  formed at the upper end of the moving contact plate  20 . As shown in  FIGS. 14 and 15 , the card acceptance portions  24  prevent fall-off of the card  100  in the vertical direction and the guide plate  37   b  formed on the card  100  prevents a positioning error of the card  100  in the transverse direction. 
   After fitting of the card  100  is completed, power is applied to the coil  29  through the coil terminals  42  and the coil block  3  is magnetized and demagnetized to thereby rotate the moving iron plate  32 . Whether or not the moving iron plate  32  is appropriately attracted to the attraction surface  27   a  of the core  27  is confirmed with eye or by use of laser through the notch portion  14  formed in the base  1 . Whether or not switching of the contacts is appropriately conducted is also confirmed at this time to inspect the absence/existence of an operation defect. When any operation defect exists, the shape of the moving contact plate  20  is deformed for adjustment, for example. 
   When the operation is satisfactory, the case  4  is fitted to the base  1  as shown in  FIG. 13  to cover the constituent components. The base  1  is turned upside down so that its bottom surface faces upward, and the terminal holes and the fitting portion between the base  1  and the case  4 , and so forth, are sealed with the sealant by use of a nozzle, or the like. The sealant enters the inside due to capillary. The sealant entering from the clearance between each terminal portion  19   b ,  19   c ,  20   b ,  20   c ,  21   b ,  21   c  of each contact plate  19 ,  20 ,  21  and the terminal hole is far from the region in which the contacts are opened and closed, and improves the fixing strength of the contact plates to the base  1 . The sealant entering from the clearance between the coil terminal  42  and the through-hole  15  is stored in the ring-like recess  43  formed in the increased thickness portion  41  of the coil block  3  and its further invasion is checked. Even when the sealant enters beyond the ring-like recess portion  43 , the partition wall  12  prevents the sealant from reaching the driving region of the moving iron plate  32 . Therefore, even when the driving region of the moving iron plate  32  is positioned in the proximity of the region that the sealant enters, the problem due to adhesion, etc does not occur. 
   The electromagnetic relay is completed in the manner described above. However, the gas vent hole  44  formed in the case  4  may well be used while left open or under the sealed state after it is thermally sealed depending on the environment of use. Even when impact force acts on the internal constituent components due to fall, or the like, no problem occurs because each component is firmly fixed to the base  1 . The card  100 , in particular, has the simple construction in which the moving iron plate  32  and the moving contact plate  20  are merely interconnected. One of the ends of the card is interconnected to the moving iron plate  32  through the anchor holding portion  36  and the other end guides the reduced thickness portion  37   a  of the push-in portion  37  within the range in which the moving contact plate  20  can undergo deformation. The upper end protuberance portion  10   a  formed on the insulating wall  5  of the base  1  is positioned between the contact plate  38  and the flexible holding plate  39  constituting the anchor holding portion  36  and the second protuberance portion  46  formed on the case  4  is positioned above the card  100 . Therefore, even when any impact force operates, the card  100  does not fall off. 
   Next, the operation of the electromagnetic relay described above will be explained. 
   While power is not applied to the coil  29  and the coil block  3  is demagnetized, the moving iron plate  32  rotates counter-clockwise in  FIG. 2  due to the urging force of the hinge spring  31  with the rotation support point at the distal end of the yoke  30  being the center. In consequence, the moving contact plate  20  is under the erected state due to its own flexible force and keeps the moving contact  23  under the closed state relative to the second fixed contact  26 . 
   When power is applied to the coil  29  and the coil block  3  is excited, one of the ends of the moving iron plate  32  is attracted to the attraction surface  27   a  of the core  27  and the moving iron plate  32  rotates clockwise in  FIG. 2  with the rotation support point at the distal end of the yoke  30  being the center. In consequence, the card  100  moves to the right and the moving contact plate  20  undergoes elastic deformation. In this case, since the distal end of the reduced thickness portion  37   a  of the card  100  pushes the card acceptance portion  24  of the moving contact plate  20 , contact becomes line contact or surface contact and wear dust does not develop. Movement of the card  100  closes the moving contact  23  relative to the first fixed contact  22  and the contact is thus switched. 
   In the embodiment described above, the fixed contact plates  19  and  20  are disposed on both sides of the moving contact plate  20 , but they may be disposed on only one side. In other words, it is possible to employ a construction in which only the second fixed contact plate  21  is not disposed but the rest of the constituent components is as such used as shown in  FIG. 16 . 
   In the embodiment described above, the guide plate  37   b  of the card  100  is disposed separately from the card reinforcement rib  40 . However, it is also possible to employ a construction in which the card reinforcement rib  40  operates also as the guide plate  37   b . In other words, the card reinforcement ribs  40  positioned on both sides guide both sides  9  of the upper card acceptance portion  24 . At least one each card acceptance portion  24  of the moving contact plate  20  may well exist at the upper and lower positions. In the construction in which the second fixed contact plate  21  is not disposed, the card acceptance portion  24  may well be formed at the center. 
   As is obvious from the explanation given above, the invention forms the card acceptance portions positioned at least at the upper and lower positions by bending the upper end portion of the moving contact plate. Therefore, even when the moving contact plate is driven through the card, wear dust does not easily occur, and the assembly work of the card can be easily carried out.