Abstract:
A contact mechanism with long contact lifetime comprises a base; a movable touch piece that comprises a movable contact and stands in the base; and a fixed touch piece that comprises a fixed contact and stands in the base, wherein the movable contact is opposed to the fixed contact and configured to come into contact with and separate from the fixed contact, an operation member configured to move reciprocally in a horizontal direction is configured to press and release an upper end edge of the movable touch piece, and the movable touch piece is configured to turn to cause the movable contact to come into contact with and separate from the fixed contact, and the movable contact is fixed to a turning tongue piece that is formed cut out by providing a curved cutout groove in the movable touch piece.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of priority from Japanese Patent Application No. 2013-166950, filed on 8 Aug. 2013, the entire contents of which is incorporated herein by reference for all purposes. 
       BACKGROUND 
       [0002]    The present invention relates to a contact mechanism, for example, a contact mechanism assembled in an electromagnetic relay. 
         [0003]    Japanese Unexamined Patent Publication No. 2004-164948 discloses an electromagnetic relay in which a conventional contact mechanism is assembled. In a conventional contact mechanism, a movable touch piece and a fixed touch piece are provided in parallel in a base, a card is reciprocally moved in a horizontal direction by turning a movable iron piece based on excitation and demagnetization of a coil block placed on the base, the movable touch piece is elastically deformed to cause a movable contact provided in the movable touch piece to come into contact with and separate from a fixed contact provided in the fixed touch piece. In a configuration of the electromagnetic relay, card receiving portions located at upper and lower portions are formed by bending leading end portions of the movable touch piece, and a leading end portion of the card abuts on inner surfaces of the card receiving portions. 
         [0004]    However, in the contact mechanism assembled in the electromagnetic relay, when card  70  presses an upper end edge of movable touch piece  52  to turn movable contact  51  as illustrated in  FIG. 7A , movable contact  51  abuts on fixed contact  42  ( FIG. 7B ). When movable touch piece  52  is further pushed in, movable contact  51  wipes on fixed contact  42 , and fixed touch piece  52  is bent rearward ( FIG. 7C ). Although movable contact  51  seems to be in total contact with fixed contact  42  at a position where movable contact  51  abuts on fixed contact  42 , actually only a lower end edge of movable contact  51  is in one-sided contact with fixed contact  42  at a pinpoint. As a result, in the case that the contact mechanism is used in an electromagnetic relay through which a large amount of current is passed, the contacts are possibly abraded at an early stage resulting in shortening of contact lifetimes. 
         [0005]    On the other hand, as illustrated in  FIG. 7D , when a pressing force on card  70  is released, movable touch piece  52  is returned by a force (such as a self-spring force), and movable contact  51  moves in a tensile direction because movable contact  51  is displaced while wiping on fixed contact  42 . Therefore, in the case that welding of the contacts is generated, unfortunately a large tensile opening force is required to open the contacts, and since fixed touch piece  43  is also bent on a side of movable touch piece  52 , an even larger tensile opening force is required. 
         [0006]    A purpose of the present invention is to provide a long-contact-lifetime contact mechanism in which a large force is not required to open the contact at the time of return. 
       SUMMARY 
       [0007]    In accordance with an embodiment of the present invention, there is provided a contact mechanism in which a base, a movable touch piece that comprises a movable contact and stands in the base, and a fixed touch piece that comprises a fixed contact and stands in the base, wherein the movable contact is opposed to the fixed contact and configured to come into contact with and separate from the fixed contact, an operation member configured to move reciprocally in a horizontal direction is configured to press and release an upper end edge of the movable touch piece, and the movable touch piece is configured to turn to cause the movable contact to come into contact with and separate from the fixed contact, and the movable contact is fixed to a turning tongue piece that is formed by providing a cutout groove in the movable touch piece. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIGS. 1A and 1B  are schematic perspective views illustrating an electromagnetic relay in which a contact mechanism according to an embodiment of the present invention is assembled when the electromagnetic relay is viewed from different angles; 
           [0009]      FIG. 2  is an exploded perspective view of the electromagnetic relay in  FIG. 1A ; 
           [0010]      FIG. 3  is an exploded perspective view of the electromagnetic relay in  FIG. 1B ; 
           [0011]      FIG. 4  is an enlarged front view of a movable contact terminal in  FIGS. 2 and 3 ; 
           [0012]      FIGS. 5A and 5B  are sectional views illustrating the electromagnetic relay in  FIGS. 1A and 1B  before and after an operation; 
           [0013]      FIGS. 6A to 6F  are schematic views illustrating the electromagnetic relay in  FIGS. 5A and 5B  before and after the operation; and 
           [0014]      FIGS. 7A to 7F  are schematic views illustrating a conventional electromagnetic relay before and after the operation. 
       
    
    
     DETAILED DESCRIPTION 
       [0015]    A self-holding electromagnetic relay in which a contact mechanism according to an embodiment of the present invention is applied will be described with reference to  FIGS. 1A to 6F . In the following description, a term (such as terms including “up”, “down”, “side”, and “end”) indicating a specific direction or position is used as needed basis. However, the use of the term is aimed only at easy understanding of the present invention with reference to the accompanying drawings, but the technical scope of the present invention is not restricted to the meaning of the term. 
         [0016]    The embodiment is provided only as an example, and the present invention is not limited to the embodiment. 
         [0017]    As illustrated in  FIGS. 2 and 3 , the electromagnetic relay of the embodiment includes base  10 , electromagnetic block  20 , movable iron piece  30 , contact mechanism  40 , card  70 , and box type cover  80 . 
         [0018]    In base  10 , as illustrated in  FIG. 2 , insulating wall  11  having a gate shape in planar view is provided to stand in a center of an upper surface to form storage portion  12 , and coil terminal holes  12   a  ( FIG. 3 ) are made in a bottom surface of storage portion  12 . 
         [0019]    In base  10 , fitting wall  13  having a gate shape in planar view is integrally molded so as to be adjacent to an outside surface of insulating wall  11 , thereby forming fitting recess  14 . A pair of latching holes  14   a  are made in the bottom surface of fitting recess  14 . 
         [0020]    In base  10 , position restriction rib  15  is projected at an upper edge located on a side opposite to insulating wall  11 , and a pair of L-shape position restriction ribs  16  and  17  are projected at positions opposed to each other at edges on both sides of position restriction rib  15 . Therefore, base  10  has a structure in which fixed contact terminal  41  can be fixed by press-fitting. Terminal holes  16   a  and  16   a  are made in the bottom surface located between fitting wall  13  and L-shape position restriction ribs  16  and  17 , and terminal holes  17   a  and  17   a  are made in the bottom surface located between position restriction rib  15  and L-shape position restriction ribs  16  and  17 . 
         [0021]    In electromagnetic block  20 , as illustrated in  FIGS. 5A and 5B , iron core  23  having a T-shape in section is inserted in spool  22  around which coil  21  is wound, one projecting end portion  23   a  is fixed to auxiliary yoke  24  by caulking, permanent magnet  26  is sandwiched between a leading end surface of one end portion  23   a  and a horizontal portion of yoke  25  having a substantial L-shape in section, and a second projecting end portion of iron core  23  constitutes magnetic pole portion  23   b.  Coil terminal  27  is press-fitted in spool  22 , and leads of coil  21  are soldered to coil terminal  27  while tied up. Auxiliary yoke  24  abuts on a side surface of yoke  25  to form a magnetic circuit together with yoke  25  and permanent magnet  26  at the time of return such that movable iron piece  30  does not malfunction due to an external vibration. 
         [0022]    Movable iron piece  30  is made of a magnetic material bent into a substantial L-shape. Movable iron piece  30  is turnably supported with lower end  25   a  of yoke  25  as fulcrum by hinge spring  31  attached to the edges on both the sides of a perpendicular portion of yoke  25 . Therefore, horizontal end portion  30   a  of movable iron piece  30  is opposed to magnetic pole portion  23   b  of iron core  23  so as to be able to come into contact with and separate from magnetic pole portion  23   b.  Notches  32  are provided in upper end edge of the perpendicular portion of movable iron piece  30  ( FIG. 2 ). 
         [0023]    Contact mechanism  40  includes fixed contact terminal  41  to which fixed contact  42  is fixed by caulking, movable contact terminal  50  to which movable contact  51  is fixed by caulking, and elastic touch piece  60  that comes into press contact with movable contact  51  at the time of return. 
         [0024]    In fixed contact terminal  41 , aligning projections  44  are formed to protrude at the edges on both the sides of fixed touch piece  43  in which fixed contact  42  is provided. A pair of terminals  45  and  45  extending downward from fixed touch piece  43  is inserted in terminal holes  17   a  and  17   a  of base  10  ( FIG. 3 ), and fixed touch piece  43  is press-fitted between position restriction rib  15  and L-shape position restriction ribs  16  and  17  ( FIG. 2 ). This enables fixed touch piece  43  to be elastically deformed using aligning projections  44  as the fulcrums, thereby fixed contact terminal  41  having a short inter-fulcrum distance and a large rigidity is obtained. 
         [0025]    In movable contact terminal  50 , as illustrated in  FIG. 4 , a pair of terminals  53  and  53  extend downward from bent movable touch piece  52  in which movable contact  51  is provided. In movable touch piece  52 , position restriction tongue pieces  54  and  54  are provided by cutting and bending edges on both sides in an upper end edge of movable touch piece  52 , and retaining tongue pieces  55  and  55  are cut and bent between position restriction tongue pieces  54  and  54  so as to be higher than the surroundings of retaining tongue pieces  55  and  55 . In movable touch piece  52 , a wide portion which includes cutout groove  56  (such as a curved cutout groove) that is a substantially U-shaped or substantially V-shaped opening formed toward the upper end side of movable touch piece  52 . Cutout groove  56  is formed so as to surround turning tongue piece  57  and movable contact  51 , which is fixed to turning tongue piece  57  by caulking. Slit  58  communicating with cutout groove  56  is provided on a lower side of movable touch piece  52  in order to adjust a spring constant. 
         [0026]    Width X of a base portion of turning tongue piece  57  is larger than a total of widths Y 1  and Y 2 , each width Y 1  and Y 2  is measured across an edge portion of movable touch pieces  52  located on a side of turning tongue piece  57 . Therefore, a spring constant of turning tongue piece  57  is larger than a spring constant of the edge portions on the sides of movable touch piece  52 , and when an increasing force is applied to the movable touch piece, the edge portions on the sides of movable touch piece  52  are elastically deformed before turning tongue piece  57  is elastically deformed. At this point, by virtue of C-planes  54   a  and  54   a  formed toward the edges on both the sides of movable touch piece  52  at the edge portions on both the sides of position restriction tongue pieces  54  and  54 , the edge portions on both the sides of movable touch piece  52  located below C-planes  54   a  and  54   a  are easily elastically deformed. 
         [0027]    Terminals  53  and  53  are press-fitted in terminal holes  16   a  and  16   a  of base  10  ( FIG. 3 ), whereby movable contact  51  is opposed to fixed contact  42  thereby allowing movable contact  51  to come into contact with and separate from fixed contact  42 . 
         [0028]    In elastic touch piece  60 , elastically-curved portion  61  extends outward from the upper end edge, and latching claws  62  and  62  extend laterally from the lower end edge. Latching claws  62  and  62  are inserted in latching holes  14   a  and  14   a  formed in the bottom surface of fitting recess  14 , whereby elastically-curved portion  61  extends outward from fitting wall  13  to come into press contact with a rear surface of movable contact  51 . 
         [0029]    Card  70  has a substantial T-shape in planar view. In card  70 , a pair of elastic arms  72  and  72  extend in parallel with each other along a narrow end portion  71  so as to be able to be engaged with notches  32  and  32  of movable iron piece  30 . In card  70 , aligning projections  74  and  74  are projected at edges on both sides of wide end portion  73 . Wide end portion  73  engages movable contact terminal  50  between position restriction tongue pieces  54  and retaining tongue pieces  55  of movable contact terminal  50  while a pair of elastic arms  72  and  72  are engaged with notches  32  and  32  of movable iron piece  30 . 
         [0030]    Box type cover  80  which has an outer shape, is fitted in base  10  and houses components of the electromagnetic relay such as electromagnetic block  20 . To complete the assembly work of the electromagnetic relay, box type cover  80  is fitted in base  10 , sealing material  81  ( FIG. 1B ) is injected into the bottom surface of base  10  and on solidification, seals the electromagnetic relay, inner air is sucked and removed through degassing hole  82  ( FIG. 1A ) of box type cover  80 , and degassing hole  82  is heat-sealed. 
         [0031]    Operation of the electromagnetic relay will be described below with reference to  FIGS. 5A to 6F . 
         [0032]    In the case that a voltage is not applied to coil  21 , movable iron piece  30  is pressed by a spring force of movable touch piece  52  with card  70  interposed between movable touch piece  52  and movable iron piece  30 , and movable contact  51  separates from fixed contact  42  and comes into press contact with elastically-curved portion  61  of elastic touch piece  60 . 
         [0033]    Then, in the case that the voltage is applied to excite coil  21 , as illustrated in  FIG. 5B , horizontal end portion  30   a  of movable iron piece  30  is attracted to magnetic pole portion  23   b  of iron core  23 , and movable iron piece  30  turns with perpendicularly lower end portion  25   a  of yoke  25  as the fulcrum against the spring force of movable touch piece  52 . Card  70  pressed by the upper end portion of movable iron piece  30  moves horizontally, and presses the upper end edge of movable touch piece  52 . Therefore, movable contact  51  turns to abut on fixed contact  42  ( FIG. 6B ). When the upper end edge of movable touch piece  52  is further pushed, the edge portions of movable touch piece  52 , having the spring constant smaller than that of turning tongue piece  57 , are elastically deformed prior to turning tongue piece  57  becoming elastically deformed. Therefore, movable contact  51  is displaced while rolling on the surface of fixed contact  42  ( FIG. 6C ). Since horizontal end portion  30   a  of movable iron piece  30  is attracted to magnetic pole portion  23   b  of iron core  23 , as a result, iron core  23 , permanent magnet  26 , yoke  25 , and movable iron piece  30  form a closed magnetic circuit, and an operating state of movable touch piece  52  is retained by a magnetic force from magnetic flux of permanent magnet  26  even if the voltage application to coil  21  is stopped. 
         [0034]    As described above, cutout groove  56  includes the opening formed toward the upper end side of movable touch piece  52 , and cutout groove  56  is formed so as to surround movable contact  51 . Therefore, the force pressing the upper end edge of movable touch piece  52  is efficiently transmitted to movable contact  51  through turning tongue piece  57  by card  70  irrespective of the elastic deformation at the edge portions of movable touch piece  52 . 
         [0035]    When the voltage is applied to coil  21  in a direction canceling out the magnetic force caused by the magnetic flux of permanent magnet  26 , movable iron piece  30  turns in an opposite direction by a magnetic force of coil  21  and the spring force of movable touch piece  52 . Therefore, card  70  is drawn back to release the deformation at the edge portions of movable touch piece  52  as illustrated in  FIG. 6D , turning tongue piece  57  turns in the opposite direction, and movable contact  51  rolls on the surface of fixed contact  42  ( FIG. 6E ) and the contact between movable contact  51  and fixed contact  42  is opened ( FIG. 6F ). Movable contact  51  comes into press contact with elastically-curved portion  61  of elastic touch piece  60  to absorb and release a rapid returning force of movable contact  51 , and movable contact  51  is returned to an original position. 
         [0036]    At this point, magnetic leakage is not generated because permanent magnet  26 , auxiliary yoke  24 , and yoke  25  form the magnetic circuit. As a result, even if movable iron piece  30  turns due to the external vibration, horizontal end portion  30   a  of movable iron piece  30  is not attracted to magnetic pole portion  23   b  of iron core  23 , and there is no malfunction. Accordingly, high-reliability in the electromagnetic relay is achieved. 
         [0037]    In the embodiment, movable contact  51  is displaced so as to roll on the surface of the fixed contact. Even if movable contact  51  is welded to fixed contact  42 , welded movable contact  51  is separated from fixed contact  42  by not a tensile force but a shearing force, so that the welded movable contact can forcedly be separated from the fixed contact by a small opening force. 
         [0038]    Because fixed contact terminal  41  turns with aligning projections  44  provided in fixed touch piece  43  as the fulcrums, the inter-fulcrum distance is short and the rigidity is large. Therefore, the contact is further easily opened. 
         [0039]    In accordance with one aspect of an embodiment of the present invention, the movable contact rolls on the surface of the fixed contact when the turning tongue piece turns, hence one-sided contact of the movable contact at the pinpoint is eliminated and even if a large amount of current is passed, the movable contact and the fixed contact are not abraded and contact lifetimes are lengthened. 
         [0040]    Since the movable contact rolls on the surface of the fixed contact, a shearing force and not a tensile force acts between the movable contact and the fixed contact. Therefore, if the movable contact is welded to the fixed contact, the welded movable contact can forcedly be separated from the fixed contact by a small opening force and a high-reliability contact mechanism is obtained. 
         [0041]    In the contact mechanism, because the cutout groove may include an opening formed toward an upper end side of the movable touch piece, and the cutout groove may be formed so as to surround the movable contact, the force pressing on the upper end edge of the movable touch piece is efficiently transmitted to the movable contact by the operation member. Additionally, the movable contact rolls on the surface of the fixed contact because the turning tongue piece turns as the movable touch piece comes into operation or returns to an original position. 
         [0042]    In accordance with an aspect of an embodiment of the present invention, a shape of the cutout groove is selected based on requirements of the application. Therefore, greater flexibility in designing of the contact mechanism is achieved. 
         [0043]    In accordance with an aspect of an embodiment of the present invention, both sides of the turning tongue piece include the movable touch piece, and a spring constant of the turning tongue piece may be larger than spring constants of edge portions of the movable touch piece. 
         [0044]    Accordingly, because the edge portions on both the sides of the turning tongue piece are easily elastically deformed compared with the turning tongue piece, the turning tongue piece turns without the elastic deformation, and the movable contact rolls easily on the surface of the fixed contact. 
         [0045]    In an aspect of an embodiment of the present invention, the width of the base portion of the turning tongue piece may be larger than a total of the two widths, each width is measured across the edge portion of the movable touch piece located at the side of the turning tongue piece. 
         [0046]    Accordingly, because the edge portions on both the sides of the turning tongue piece are harder easily elastically deformed compared with the turning tongue piece, the turning tongue piece turns without elastic deformation, and the movable contact rolls more easily on the surface of the fixed contact. 
         [0047]    In accordance with an aspect of an embodiment of the present invention, a slit communicating with the cutout groove may extend downward in the movable touch piece. 
         [0048]    Accordingly, the spring constant of the movable touch piece is easily adjusted and an easy-to-design movable touch piece is obtained. 
         [0049]    In accordance with an aspect of an embodiment of the present invention, the fixed touch piece may be held in the base such that the turning fulcrum of the fixed touch piece is located above the turning fulcrum of the movable touch piece. 
         [0050]    Accordingly, the fixed touch piece is more rigid than the movable touch piece, and hence the movable contact will roll more easily on the fixed contact. 
       INDUSTRIAL APPLICABILITY 
       [0051]    The contact mechanism of the present invention can be applied to not only the self-holding electromagnetic relay, but also other electromagnetic relays such as a self-returning electromagnetic relay.