Abstract:
Provided is a contact structure for a switch, in which a contact region is increased, a conduction failure can be more precluded, and the operational reliability of the switch can be improved by allowing contact points between contacts to be line contacts. The contact structure for a switch includes a pair of contacts that are opposed to each other to open or close the switch by allowing the contacts to come into contact with or to separate from each other, wherein a contact surface of a first contact is formed into a concave shape provided with a projection and a recess; a contact surface of a second contact is formed into a rounded surface; and the projection of the first contact and the rounded surface of the second contact are configured to come into contact with each other.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to contact structures for switches and to pressure switches using the contact structures, and particularly relates to a contact structure for a mechanical-type switch opened or closed by allowing contacts to come into contact with or to separate from each other, and to a pressure switch using the contact structure. 
       BACKGROUND ART 
       [0002]    Pressure switches have been conventionally used in order to detect the pressure of lubricating oil and to detect changes in the pressures of portions to be detected, such as the intake manifold pressures and exhaust pressures of engines, crank room pressures, and various controlling actuator working pressures, for example, in automobiles and the like. 
         [0003]      FIG. 9  is a cross-sectional view for explaining the configuration of a conventional pressure switch. 
         [0004]    In the pressure switch  100 , a diaphragm configuration member  107  comprising an upper cover  103 , a diaphragm  105 , and a lower cover  106  is arranged via an O-ring  108  in the interior of a body portion  102 . 
         [0005]    An O-ring  109  is placed on the upper portion of the upper cover  103 , a guide portion  111  is placed thereon, and a connector portion  112  is put so as to immobilize them. In addition, the outer circumferential stepped portion of the connector portion  112  is swaged with the open end of the body portion  102 , whereby they are integrated to form a pressure switch. 
         [0006]    An actuating shaft  116  that is slidably held in a through-hole  115  disposed in the center of the guide portion  111  is arranged on the upper part of the diaphragm  105 , and its upper end is opposed to an actuation portion  119  of a movable contact plate  117 . 
         [0007]    The bottom end of the actuating shaft  116  comes into contact with the diaphragm.  105  through an opening  120  in the upper cover  103 . A first connecting terminal  122  and a second connecting terminal  124  that are bent in generally L-shapes are disposed in the connector portion  112 , and one end of the movable contact plate  117  is fixed on an end of the first connecting terminal  122  by swaging. 
         [0008]    A movable contact  118  is mounted on the other end of the movable contact plate  117 , and a fixed contact  125  is fixed on an end of the second connecting terminal  124  so as to be opposed to the movable contact  118 . A micro switch is formed by the fixed contact  125  and the movable contact  118 . 
         [0009]    The pressure switch  100  configured in such a manner is mounted so that the pressure of the interior of an actuation room  123  in a portion beneath the diaphragm  105  is equal to the pressure of the above-mentioned portion to be detected, and is used. 
         [0010]    With increasing the pressure of the portion to be detected, the pressure of the interior of the actuation room  123  is also increased, and the center of the diaphragm  105  gradually rises with the increase. When the pressure becomes not less than predetermined pressure and the center of the diaphragm  105  rises over a neutral position and crosses an invertible region, the center of the diaphragm  105  is inverted and actuated upward, and the diaphragm  105  abuts on the lower end face of the upper cover  103  and stops. 
         [0011]    As a result, the actuating shaft  116  moves up to a raised position to push up the movable contact plate  117 , the movable contact  118  on its leading end is displaced upward, and the movable contact  118  and the fixed contact  125  become in a non-contact state. 
         [0012]    The pressure switch  100 , which is referred to as a normally closed type, becomes in a conduction state when the pressure of the portion to be detected is not more than the predetermined pressure (in a normal case) and becomes in a non-conduction state, only when the pressure of the portion to be detected is not less than the predetermined pressure, to thereby make it possible to detect a change in the pressure of the portion to be detected. 
         [0013]    Pressure switches include a pressure switch, referred to as a normally open type, which becomes in a non-conduction state when the pressure of a portion to be detected is not more than predetermined pressure (in a normal case) and becomes in a conduction state, only when the pressure of the portion to be detected is not less than the predetermined pressure, to thereby make it possible to detect a change in the pressure of the portion to be detected. 
         [0014]    In such a pressure switch, for example, a contact structure  200  in which rivet-type contacts  202   a  and  202   b  are places to be opposed to each other as illustrated in  FIG. 10  has been conventionally used. However, there has been a problem that a conduction failure between the contacts occurs due to adhesion of a foreign substance to the contacts, or the like. 
         [0015]    Therefore, Patent Literature 1 discloses a switch having a contact structure  300  in which a first contact is a doughnut-type contact  204   a , and a second contact is a crossbar-type contact  302   b  that extends in a direction crossing the doughnut-type contact  302   a  as illustrated in  FIG. 11 . 
         [0016]    A first contact is allowed to be the doughnut-type contact  302   a  in such a manner, whereby a conduction failure is precluded since the contact points between the contacts become many points and a foreign substance can be dissipated into the depression of the doughnut-type contact  302   a  even when entering between the contacts. 
         [0017]    Patent Literature 2 discloses that a body-ground-type pressure switch configured so that one or a plurality of recesses are disposed in the upper portion of a protrusion  121  disposed on a guide portion  111 , and electrical contact between a movable contact  118  and a protrusion  121  occurs on a plurality of contact points as illustrated in  FIG. 12 . 
       PRIOR ART REFERENCES 
     Patent Documents  
       [0018]    [Patent Document 1] JP-A-2000-322963 
         [0019]    [Patent Document 2] JP-A-2002-343207 
       SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
       [0020]    However, in the contact structure illustrated in  FIG. 11 , the doughnut-type contact  302   a  and the crossbar-type contact  302   b come into point contact with each other at two points of an a-point and a b-point, a contact region is therefore small, and a conduction failure has been able to occur. 
         [0021]    In addition, the contact structure of the pressure switch disclosed in Patent Literature 2 has been able to be utilized only as a normally closed type but has not been able to be used in a normally open type pressure switch. 
         [0022]    In view of such a current situation, an objective of the present invention is to provide a contact structure for a switch, in which a contact region is increased, a conduction failure can be more precluded, and the operational reliability of the switch can be improved by allowing contact points between contacts to be line contacts, and to provide a pressure switch using the contact structure. 
         [0023]    Furthermore, an objective of the present invention is to provide a contact structure for a switch, in which commonality of contact components in a normally closed type and a normally open type can be allowed to reduce the number of components by configuring movable contacts so as to be vertically symmetric with respect to a movable contact plate, and to provide a pressure switch using the contact structure. 
       Technical Soluition 
       [0024]    The present invention is achieved in order to solve such problems as mentioned above in the conventional art. A contact structure for a switch of the present invention is a contact structure for a switch comprising a pair of contacts that are opposed to each other to open or close the switch by allowing the contacts to come into contact with or to separate from each other, wherein 
         [0025]    a contact surface of a first contact is formed into a concave shape provided with a projection and a recess; 
         [0026]    a contact surface of a second contact is formed into a rounded surface; and 
         [0027]    the projection of the first contact and the rounded surface of the second contact are configured to come into contact with each other. 
         [0028]    In the present invention, at least one surface of a surface of the first contact and a surface of the second contact may be subjected to plating working with a material with good conductivity. 
         [0029]    At least one of the first contact and the second contact may also comprise a clad portion of a clad material. 
         [0030]    At least one of the first contact and the second contact may also be disposed by rivet swaging. 
         [0031]    The recess is preferably formed by crushing working by press forming. 
         [0032]    The present invention comprises a movable terminal comprising: 
         [0033]    a fixed portion formed of a conductive flat plate; 
         [0034]    a movable contact plate that is formed of an elastic material and connected to a first end of the fixed portion; and 
         [0035]    the movable contact disposed on a second end, which is not connected to the fixed portion, of the movable contact plate, 
         [0036]    wherein the movable contact is preferably either the first contact or the second contact. 
         [0037]    In this case, the movable contact plate can be configured so that a biasing force is exerted in a direction of touching the movable contact to the fixed contact. 
         [0038]    The movable contact plate may also be configured so that a biasing force is exerted in a direction of separating the movable contact from the fixed contact. 
         [0039]    In the present invention, the movable contacts are preferably symmetrically disposed on both surfaces with respect to the movable contact plate. 
         [0040]    A hole can also be disposed in the movable contact plate. 
         [0041]    A pressure switch of the present invention comprises any one contact structure for a switch mentioned above. 
       ADVANTAGEOUS EFFECTS OF INVENTION  
       [0042]    In accordance with the present invention, a contact region is increased, a conduction failure can be more precluded, and the operational reliability of the switch can be improved by allowing contact points between contacts to be line contacts. 
         [0043]    Furthermore, commonality of contact components in a normally closed type and a normally open type can be allowed to reduce the number of components by configuring movable contacts so as to be vertically symmetric with respect to a movable contact plate. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0044]      FIG. 1  is a schematic view illustrating the configuration of a contact structure for a switch of the present example. 
           [0045]      FIG. 2  is a cross-sectional view for explaining the configuration of a pressure switch having the contact structure of  FIG. 1 . 
           [0046]      FIG. 3  is a schematic view illustrating the configuration of another example of a contact structure for a switch of the present invention. 
           [0047]      FIG. 4  is a cross-sectional view for explaining the configuration of a pressure switch having the contact structure of  FIG. 3 . 
           [0048]      FIG. 5  is a schematic view for explaining a step of symmetrically disposing movable contacts on both surfaces with respect to a movable contact plate by press working. 
           [0049]      FIG. 6  is a schematic view for explaining the configuration of a movable contact plate in the contact structure of  FIG. 3 . 
           [0050]      FIG. 7  is a schematic view illustrating the configuration of a still another example of a contact structure for a switch of the present invention. 
           [0051]      FIG. 8  is a schematic view illustrating the configuration of a still another example of a contact structure for a switch of the present invention. 
           [0052]      FIG. 9  is a cross-sectional view for explaining the configuration of a conventional pressure switch. 
           [0053]      FIG. 10  is a schematic view for explaining the configuration of an example of a contact structure used in a conventional pressure switch. 
           [0054]      FIG. 11  is a schematic view for explaining the configuration of another example of a contact structure used in a conventional pressure switch. 
           [0055]      FIG. 12  is a cross-sectional view for explaining the configuration of a conventional body-ground-type pressure switch. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0056]    Embodiments (examples) of the present invention will now be described in more detail based on the drawings. 
         [0057]      FIG. 1  is a schematic view illustrating the configuration of a contact structure for a switch of the present example, and  FIG. 2  is a cross-sectional view for explaining the configuration of a pressure switch having the contact structure of  FIG. 1 . 
         [0058]    In the present example, the same components as those in a conventional pressure switch  100  illustrated in  FIG. 6  are denoted by the same reference characters, and the detailed description thereof is omitted. 
         [0059]    As illustrated in  FIGS. 1 and 2 , the contact structure  10  of the present example comprises a fixed terminal  12  and a movable terminal  18 . 
         [0060]    The fixed terminal  12  is formed by working a conductive flat plate such as, for example, brass into a generally L-shape, and a recess  14  is disposed in one end  12   a  of the fixed terminal  12 , for example, by crushing working by press forming. 
         [0061]    In addition, the one end  12   a  of the fixed terminal  12 , in which the recess  14  is disposed, is a fixed contact  16  to come into contact with a contact of the movable terminal  18 . The fixed contact  16  is subjected to plating with, for example, a material having excellent conductivity (referred to herein as “material with good conductivity”) such as a noble metal, such as gold or silver, or an alloy containing a noble metal, such as an alloy of silver and tin in order to improve conductivity with the movable terminal  18 . 
         [0062]    The recess  14  is disposed only on a surface coming into contact with a movable contact  24  of the movable terminal  18  mentioned later, and each of projections  17   a  and  17   b  of the fixed contact  16  comes into line contact with the movable contact  24 . 
         [0063]    The fixed contact  16  is formed into a concave shape in such a manner, whereby even when a foreign substance enters between the fixed contact  16  and the movable contact  24 , the foreign substance can be dissipated into the recess  14 , and a conduction failure is precluded. 
         [0064]    Meanwhile, the movable terminal  18  comprises a fixed portion  20 , a movable contact plate  22 , and the movable contact  24 . 
         [0065]    The fixed portion  20  is formed of a conductive flat plate such as, for example, brass, and the movable contact plate  22  is connected to a first end of the fixed portion  20 . 
         [0066]    The movable contact plate  22  is formed of an elastic material such as, for example, a flat spring, and the movable contact  24  is disposed on a second end that is not connected to the fixed portion  20 . 
         [0067]    The movable contact plate  22  is configured so that a biasing force is exerted in the direction of allowing the movable contact  24  to abut on the fixed contact  16  of the fixed terminal  12 . 
         [0068]    As a result, in a normal case, the fixed contact  16  and the movable contact  24  are in the state of coming into contact with each other, and the fixed terminal  12  and the movable terminal  18  are in a conduction state (normally closed). 
         [0069]    In addition, the movable contact  24  is disposed to protrude from the movable contact plate  22  in the direction of the fixed contact  16 , and a contact surface (surface coming into contact with the fixed contact  16 ) of the movable contact  24  is a rounded surface. The movable contact  24  has a crossbar shape to be configured to come into contact with the projections  17   a  and  17   b.    
         [0070]    The movable contact  24  as described above may be formed by joining a material with good conductivity to the movable contact plate  22  by welding or the like or may be formed by plating with a material with good conductivity. In addition, the movable contact plate  22  and the movable contact  24  can also be formed integrally with each other using, for example, a clad material referred to as an edgelay clad. 
         [0071]    The contact structure  10  for a switch of the present example, configured in such a manner, can be used as a component in a pressure switch  50  as illustrated in  FIG. 2 . 
         [0072]    The pressure switch  50  can be used as a normally closed type pressure switch. 
         [0073]    In the present example, the contact surface of the fixed contact  16  is formed into a concave shape, and the contact surface of the movable contact  24  is formed into a rounded surface. However, the contact surface of a first contact may have a concave shape, and the contact surface of a second contact may be a rounded surface. The contact surface of the fixed contact  16  may also be formed into a rounded surface, and the contact surface of the movable contact  24  may also be formed into a concave shape. 
         [0074]      FIG. 3  is a schematic view illustrating the configuration of another example of a contact structure for a switch of the present invention, and  FIG. 4  is a cross-sectional view for explaining the configuration of a pressure switch having the contact structure of  FIG. 3 . 
         [0075]    Since a contact structure  10  and a pressure switch  50  of the present example basically have configurations similar to those of the contact structure  10  and the pressure switch  50  illustrated in  FIGS. 1 and 2 , the same components are denoted by the same reference characters, and the detailed description thereof is omitted. 
         [0076]    In the contact structure  10  illustrated in  FIG. 3 , the movable contact plate  22  is configured so that a biasing force is exerted in the direction of allowing the movable contact  24  to abut on the fixed contact  16  of the fixed terminal  12 . However, in the contact structure  10  of the present example, a movable contact plate  22  is configured so that a biasing force is exerted in the direction of separating movable contacts  24  from a fixed contact  16  of a fixed terminal  12 . 
         [0077]    By such a configuration as described above, the fixed contact  16  and the movable contact  24  become in a non-contact state in a normal case, and the fixed terminal  12  and a movable terminal  18  become in a non-conduction state (normally open). 
         [0078]    In addition, the movable contacts  24  of this example are symmetrically disposed on both surfaces with respect to the movable contact plate  22 . 
         [0079]    The movable terminal  18  is configured in which the movable contacts  24  are symmetrically disposed on both surfaces with respect to the movable contact plate  22  in such a manner, whereby the same movable terminal  18  can be used even in the contact structure  10  used in the normally closed type pressure switch illustrated in  FIG. 1 . Therefore, commonality of the movable terminals  18  in a normally closed type and a normally open type can be allowed to reduce the number of components. 
         [0080]    The movable contacts  24  can also be easily symmetrically disposed on both surfaces with respect to the movable contact plate  22  in such a manner, for example, by forming a tri-metal wire rod  30  into a predetermined shape by press working as illustrated in  FIG. 5 . 
         [0081]    In  FIG. 5 , reference numeral  32  denotes a press upper die while reference numeral  34  denotes a press lower die. 
         [0082]    In the contact structure  10  illustrated in  FIG. 1 , the fixed contact  16  of the fixed terminal  12  is configured by subjecting the surface of the fixed terminal  12  to plating working. However, in the present example, a clad material referred to as an edgelay clad is worked in a generally L-shape to form the fixed terminal  12 , and a clad portion of the clad material is used as the fixed contact  16 . 
         [0083]    The fixed terminal  12  is formed of the clad material in such a manner, whereby time of plating working can be saved, and furthermore, the operational reliability of the switch can be further improved since peeling as in the case of plating is prevented. 
         [0084]    In addition, the movable contact plate  22  of the present example is provided with a hole  23  as illustrated in  FIG. 6 . The movable contact plate  22  is provided with the hole  23  in such a manner, whereby, for example, even when a foreign substance enters between a projection  17   a  of the fixed contact  16  and the movable contact  24 , the movable contact plate  22  inclines, a projection  17   b  of the fixed contact  16  and the movable contact  24  reliably come into contact with each other, and the malfunction of the switch is precluded. 
         [0085]      FIG. 7  is a schematic view illustrating the configuration of a still another example of a contact structure for a switch of the present invention. 
         [0086]    Since a contact structure  10  of the present example basically has a configuration similar to that of the contact structure  10  illustrated in  FIG. 1 , the same components are denoted by the same reference characters, and the detailed description thereof is omitted. 
         [0087]    In addition, the contact structure  10  of the present example is used as in the case of the contact structure  10  in the pressure switch  50  illustrated in  FIGS. 2 and 4 . 
         [0088]    In the contact structure  10  illustrated in  FIG. 7 , a contact surface (surface coming into contact with a movable contact  24 ) of a fixed contact  16  is a rounded surface, and the movable contact  24  is provided with a recess  14  and projections  17   a  and  17   b.    
         [0089]    As a method for manufacturing such a fixed contact  16 , the fixed contact  16  can be formed, for example, using means referred to as a toplay clad. 
         [0090]    As a method for forming the contact surface of the fixed contact  16  into a rounded surface, the surface may be rounded when the toplay clad is formed, or the surface may be rounded by post-working, for example, when the fixed terminal  12  is molded. 
         [0091]    By using a clad material in the fixed terminal  12 , the fixed terminal  12  can be shortened, the need for disposing the fixed contact  16  by post-working is eliminated, and the need of space for working is eliminated. 
         [0092]    Therefore, adoption of the contact structure of the present invention in a microswitch or the like can result in downsizing of the switch and in reduction in the constraints of designing other components used in the switch. 
         [0093]    Furthermore, since a step of joining a contact, such as, for example, swaging or welding, for disposing the fixed contact  16  on the fixed terminal  12  can be omitted, a manufacturing step can be simplified, mistakes and work time can be reduced, and a manufacture cost can be reduced. 
         [0094]      FIG. 8  is a schematic view illustrating the configuration of a still another example of a contact structure for a switch of the present invention. 
         [0095]    Since a contact structure  10  of the present example basically has a configuration similar to that of the contact structure  10  illustrated in  FIG. 1 , the same components are denoted by the same reference characters, and the detailed description thereof is omitted. 
         [0096]    In addition, the contact structure  10  of the present example is used as in the case of the contact structure  10  in the pressure switch  50  illustrated in  FIGS. 2 and 4 . 
         [0097]    In the contact structure  10  illustrated in  FIG. 8 , a fixed contact  16  of a fixed terminal  12  is disposed by rivet swaging. 
         [0098]    When the fixed contact  16  is disposed by rivet swaging in such a manner, a recess  14  and projections  17   a  and  17   b  may be pre-molded on a rivet  40 , or the recess  14  and the projections  17   a  and  17   b  may be molded by press working simultaneously with the rivet swaging. 
         [0099]    Although the movable contact  24  illustrated in FIG.  8  has a structure in which part of a surface coming into contact with the fixed contact  16  is provided with a rounded surface, the whole surface coming into contact with the fixed contact  16  can also be formed into a rounded surface. Such a configuration can result in reduction in the loss of a noble metal used in the contact and can result in inexpensive manufacture compared to the case of formation using a clad material. 
         [0100]    In the present example, only the fixed contact  16  is disposed by rivet swaging. However, movable contacts  24  of a movable terminal  18  can also be disposed by rivet swaging. In this case, the movable contacts  24  having symmetrical shapes can be disposed on both surfaces with respect to a movable contact plate  22  by molding the movable contacts  24  by press working simultaneously with the rivet swaging. 
         [0101]    The preferred embodiments of the present invention are explained above, but the present invention is not limited thereto. Various modifications, in which, for example, a material for the movable terminal, the fixed terminal, and the like can be appropriately selected from known materials, can be made without departing from the objectives of the present invention. 
       DESCRIPTION OF SYMBOLS 
       [0000]    
       
           10  Contact structure 
           12  Fixed terminal 
           12   a  End 
           14  Recess 
           16  Fixed contact 
           17   a ,  17   b  Projection 
           18  Movable terminal 
           20  Fixed portion 
           22  Movable contact plate 
           23  Hole 
           24  Movable contact 
           30  Tri-metal wire rod 
           32  Press upper die 
           34  Press lower die 
           40  Rivet 
           50  Pressure switch 
           100  Pressure switch 
           102  Body portion 
           103  Upper cover 
           105  Diaphragm 
           106  Lower cover 
           107  Diaphragm configuration member 
           108  O-ring 
           109  O-ring 
           111  Guide portion 
           112  Connector portion 
           115  Through-hole 
           116  Actuating shaft 
           117  Movable contact plate 
           118  Movable contact 
           119  Actuation portion 
           120  Opening 
           122  Connecting terminal 
           123  Actuation room 
           124  Connecting terminal 
           125  Fixed contact 
           200  Contact structure 
           202   a ,  202   b  Rivet-type contact 
           300  Contact structure 
           302   a  Doughnut-type contact 
           302   b  Crossbar-type contact