Abstract:
An electromagnetic relay includes an electromagnet unit, a contact unit including a movable contact spring with a movable contact provided thereon and a fixed contact spring with a fixed contact provided thereon, and a base block configured to support the electromagnet unit and the contact unit, wherein the electromagnet unit is supported at a first face of the base block, and the contact unit is supported at a second face of the base block facing in an opposite direction from the first face, and wherein the base block includes a first insulating wall extending from the first face alongside the electromagnet unit and a second insulating wall extending from the second face alongside the contact unit, the second insulating wall being situated on an opposite side from the first insulating wall across the second face.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The disclosures herein relate to an electromagnetic relay. 
         [0003]    2. Description of the Related Art 
         [0004]    An electromagnetic relay is known as a device that utilizes an electromagnet to control the open and closed state of contacts. The electromagnetic relay may simply be referred to as a relay. Electric current flowing through the coil of the electromagnet generates a magnetic field, based on which the iron core attracts the armature to cause the fixed contact and the movable contact to come in contact with each other. The resulting “on” state of the electromagnetic relay allows electric current to be supplied. Upon the stoppage of the current supply to the coil, the magnetic field disappears, resulting in the armature being released from the iron core due to the restoring force of a spring. As a result, the movable contact is separated from the fixed contact to cause the “off” state, thereby blocking the electric current supplied through the electromagnetic relay. In recent years, the demand has been increasing for an electromagnetic relay operable at high voltages. 
         [0005]    For such an electromagnetic relay, size compactness is required, and so are a sufficiently strong attracting force working against the load of the spring and a sufficiently large insulating distance between the electromagnet and the contacts.
   [Patent Document 1] Japanese Patent Application Publication No. 11-339623   [Patent Document 2] Japanese Patent Application Publication No. 2011-100618   [Patent Document 3] Japanese Patent Application Publication No. 9-245602   
 
       SUMMARY OF THE INVENTION 
       [0009]    It is a general object of the present invention to provide an electromagnetic relay that substantially obviates one or more problems caused by the limitations and disadvantages of the related art. 
         [0010]    According to an embodiment, an electromagnetic relay includes a base block, an electromagnet unit supported on a first side of the base block and including an iron core, a coil winded around the iron core, and an armature configured to be pivotably supported on the iron core, a contact unit supported on the base block and including a movable contact spring with a movable contact provided thereon and a fixed contact spring with a fixed contact provided thereon, and a first insulating wall extending from the first face alongside the electromagnet unit. 
         [0011]    An electromagnetic relay according to at least one embodiment has small size, and also has a sufficiently strong attracting force working against the load of the spring and a sufficiently large insulating distance between the electromagnet and the contacts. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    Other objects and further features of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings, in which: 
           [0013]      FIG. 1  is an axonometric view of an electromagnetic relay; 
           [0014]      FIG. 2  is a side elevation view of the electromagnetic relay; 
           [0015]      FIGS. 3A and 3B  are cross-sectional views of the electromagnetic relay; 
           [0016]      FIG. 4  is a drawing for illustrating the electromagnetic relay; 
           [0017]      FIG. 5  is a side elevation view of the electromagnetic relay of a first embodiment; 
           [0018]      FIGS. 6A and 6B  are cross-sectional views of the electromagnetic relay of the first embodiment; 
           [0019]      FIG. 7  is a side elevation view of the electromagnetic relay of the first embodiment; 
           [0020]      FIG. 8  is a front view of the electromagnetic relay of the first embodiment; 
           [0021]      FIG. 9  is a drawing for illustrating the electromagnetic relay of the first embodiment; 
           [0022]      FIG. 10  is a drawing for illustrating the electromagnetic relay of the first embodiment; 
           [0023]      FIG. 11  is an axonometric view of an iron core of the first embodiment; 
           [0024]      FIG. 12  is an axonometric view of the iron core and coil of the first embodiment; 
           [0025]      FIG. 13  is a drawing illustrating the attracting force characteristics of the electromagnetic relay; and 
           [0026]      FIG. 14  is a drawing for explaining the electromagnetic relay of a second embodiment. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0027]    In the following, embodiments for implementing the invention will be described. The same members or the like are referred to by the same numerals, and a description thereof will be omitted 
       First Embodiment 
       [0028]    An electromagnetic relay will be described by referring to  FIG. 1  through  FIG. 4 .  FIG. 1  is an axonometric view of the electromagnetic relay.  FIG. 2  is a side elevation view of the electromagnetic relay.  FIG. 3A  is a cross-sectional view taken along a dotted and dashed line  2 A- 2 B in  FIG. 2 .  FIG. 3B  is an enlarged view of an area enclosed by a dotted and dashed line  3 A in  FIG. 3A .  FIG. 4  is an axonometric view of the electromagnetic relay after removing an armature  40  and a hinge spring  60 . 
         [0029]    The electromagnetic relay illustrated in  FIG. 1  through  FIG. 4  includes a fixed contact  10 , a movable contact  20 , a coil  30 , the armature  40 , a card  50 , the hinge spring  60 , and a base block  70 . The fixed contact  10  is disposed at an end of a fixed-contact spring  11 . The movable contact  20  is disposed at an end of a movable-contact spring  21 . The coil  30  is winded around an iron core  31 . The iron core  31  has a first end  31   a  that is in contact with a first end  40   a  of the armature  40  connected to the hinge spring  60 . The gap between a second end  31   b  of the iron core  31  and a second end  40   b  of the armature  40  is open when no electric current is flowing through the coil  30 . 
         [0030]    In the electromagnetic relay having such a structure, electric current flowing through the coil generates a magnetic field. The magnetic force created by the magnetic field causes the armature  40  to pivot around the contact point between its first end  40   a  and the first end  31   a  of the iron core  31  such that the second end  40   b  of the armature  40  moves toward the second end  31   b  of the iron core  31 . As a result, the second end  31   b  of the iron core  31  and the second end  40   b  of the armature  40  are placed in contact with each other. When this happens, the card  50  connected to the second end  40   b  of the armature  40  moves, so that the movable-contact spring  21  placed in contact with the tip end of the card  50  is pressed toward the fixed-contact spring  11 . Consequently, the movable contact  20  comes in contact with the fixed contact  10 , resulting in electric current being supplied through the movable contact  20  and the fixed contact  10 . 
         [0031]    Upon the stoppage of the supply of electric current to the coil  30 , the magnetic field generated by the coil  30  disappears, and so does the magnetic force that serves to attract the second end  40   b  of the armature  40  toward the second end  31   b  of the iron core  31 . As a result, the armature  40  returns to its original position due to the restoring force of the hinge spring  60 . Namely, the second end  40   b  is separated from the second end  31   b , and, in conjunction therewith, the card  50  moves to disconnect the fixed contact  10  and the movable contact  20  from each other, thereby stopping the supply of electric current. 
         [0032]    In the following, a description will be given of the relationship between the load of the spring and the attracting force by referring to  FIG. 13 . In  FIG. 13 , the load of the spring is shown by a dotted and dashed line, and the attracting force of the electromagnetic relay illustrated in  FIG. 1  through  FIG. 4  is shown by a dashed line. The electromagnetic relay can operate properly if the attracting force is larger (i.e., situated higher in  FIG. 13 ) than the load of the spring. 
         [0033]    A displacement A indicates a point from which the movable-contact spring  21  starts moving toward the fixed-contact spring  11  upon the application of electric current to the coil  30 . A displacement B indicates a point at which the movable contact  20  disposed on the movable-contact spring  21  comes in contact with the fixed contact  10  disposed on the fixed-contact spring  11 . In a range from the displacement A to the displacement B, the movable-contact spring  21  moves toward the fixed-contact spring  11 . A displacement C indicates a point at which the second end  31   b  of the iron core and the second end  40   b  of the armature  40  are placed in close contact with each other. In a range from the displacement B to the displacement C, the movable contact  20  is pressed further onto the fixed contact  10  by the attracting force that pulls the armature  40  toward the iron core  31  even after the movable contact  20  comes in contact with the fixed contact  10 . 
         [0034]    In the range from the displacement B to the displacement C, a sufficiently stronger attracting force than the load of the spring is needed in order to prevent contact bounce caused by the collision between the movable contact and the fixed contact during the operation of the electromagnetic relay, and is also needed in order to clean the contacts through sliding movements between the movable contact and the fixed contact. 
         [0035]    Further, an electromagnetic relay operable at high voltage is required to have a sufficiently large distance between elements of the electromagnet such as the coil  30  or the iron core  31  and elements of a contact structure such as the movable contact  20 , the fixed contact  10 , the movable-contact spring  21 , and the fixed-contact spring  11 . This distance is referred to as an insulating distance. An insulating distance includes a spatial distance which is a distance of a space between two elements and a creepage distance which is a distance between two elements along the surface of the base block  70  and the like. In general, a creepage distance is required to be larger than a spatial distance. Therefore, the electromagnetic relay is required to have a large creepage distance along the surface of the base block  70  between the coil  30  or the iron core  31  and the elements including the movable contact  20 , the fixed contact  10 , the movable-contact spring  21 , the fixed-contact spring  11 . 
         [0036]    In the electromagnetic relay illustrated in  FIG. 1  through  FIG. 4 , however, the first end  31   a  and second end  31   b  of the iron core  31  project toward a first insulating wall  70   a  as illustrated in  FIGS. 3A and 3B  and  FIG. 4 . Because of this, a distance L 1 , which is the creepage distance on the base block  70 , cannot be made large. It may be noted that a width W 1  of the first end  31   a  and the second end  31   b  of the iron core  31  is 3.8 mm. 
       &lt;Electromagnetic Relay&gt; 
       [0037]    In the following, the electromagnetic relay of the first embodiment will be described by referring to  FIG. 5  through  FIG. 10 .  FIG. 5  is a side elevation view of the electromagnetic relay.  FIG. 6A  is a cross-sectional view of the electromagnetic relay taken along the dotted and dashed line  5 A- 5 B in  FIG. 5 .  FIG. 6B  is an enlarged view of an area enclosed by the dotted and dashed line  6 A in  FIG. 6A .  FIG. 7  is a side elevation view of the electromagnetic relay of the opposite side from the side illustrated in  FIG. 5 .  FIG. 8  is a front view of the electromagnetic relay.  FIG. 9  is a side elevation view of the electromagnetic relay in which the base block is removed.  FIG. 10  is an axonometric view of the electromagnetic relay in which the armature  40  and the hinge spring  60  are removed. 
         [0038]    The electromagnetic relay of the present embodiment includes the fixed contact  10 , the movable contact  20 , the coil  30 , the armature  40 , the card  50 , the hinge spring  60 , and a base block  170 . The card  50  is made of an insulating material. The base block  170  is made of an insulating material such as a resin material. The fixed contact  10  is disposed at an end of a fixed-contact spring  11 . The movable contact  20  is disposed at an end of a movable-contact spring  21 . 
         [0039]    As illustrated in  FIG. 6A , the base block  170  has a first insulating wall  170   a  projecting from one edge of a first face of the base block  170  substantially perpendicularly to such the first face, and a second insulating wall  170   b  projecting from the opposite edge, to the first insulating wall  170   a , of a second face of the base block  170  substantially perpendicularly to such a face. An electromagnet unit including an iron core  131  and the armature  40  is disposed on the first face of the base block  170 . A contact unit including the movable contact  20  and the fixed contact  10  is disposed on the second face of the base block  170 . 
         [0040]    As illustrated in  FIG. 11 , the iron core  131  has wider portions at a first end  131   a  and a second end  131   b  that are wider than the center portion of the iron core  131 . As illustrated in  FIG. 12 , the coil  30  is formed by winding a fine metal wire around the iron core  131 . The center portion of the iron core  131  is covered with the winded metal wire, with the first end  131   a  and the second end  131   b  being exposed as magnetic pole faces. The first end  131   a  is in contact with the first end  40   a  of the armature  40  connected to the hinge spring  60 . A gap between the second end  131   b  and the second end  40   b  of the armature  40  is open when no electric current is flowing through the coil  30 . 
         [0041]    In the electromagnetic relay of the present embodiment, electric current flowing through the coil  30  generates a magnetic field. The magnetic force created by the magnetic field causes the armature  40  to pivot around the contact point between the armature  40  connected to the hinge spring  60  and the iron core  131  such that the second end  40   b  of the armature  40  moves toward the second end  131   b  of the iron core  131 . As a result, the second end  131   b  and the second end  40   b  are placed in contact with each other. In conjunction with this, the card  50  connected to the armature  40  moves. As a result, the movable-contact spring  21  placed in contact with the tip end of the card  50  is pressed toward the fixed-contact spring  11  so as to cause the movable contact  20  and the fixed contact  10  to come in contact with each other. Electric current is thus supplied through the fixed contact  10  and the movable contact  20 . 
         [0042]    Upon the stoppage of the supply of electric current to the coil  30 , the magnetic field generated by the coil  30  disappears, and so does the magnetic force, that serves to attract the armature  40  toward the iron core  131 . As a result, the armature  40  returns to its original position due to the restoring force of the hinge spring  60 . Namely, the second end  40   b  is separated from the second end  131   b , which causes the card  50  to move. The fixed contact  10  and the movable contact  20  are thus separated from each other to stop the supply of electric current. 
         [0043]    In the electromagnetic relay of the present embodiment, each side of the first end  131   a  and second end  131   b  of the iron core  131  facing the first insulating wall  170   a  is retracted as illustrated in  FIG. 6B , so that a width W 2  of the first end  131   a  and the second end  131   b  is narrower than the width W 1  as illustrated in  FIG. 4 . The width W 1  of the first end  31   a  and second end  31   b  in the electromagnetic relay illustrated in  FIG. 1  is 3.8 mm. In comparison, the width W 2  of the present embodiment is 3.55 mm, which is 0.25 mm narrower. With this arrangement, the magnetic pole face of the second end  131   b  that faces the second end  40   b  of the armature  40  has a total area size smaller than that of the structure illustrated in  FIG. 1 . Further, since the sides of the first end  131   a  and second end  131   b  facing the first insulating wall  170   a  are retracted, the first insulating wall  170   a  may be formed to extend further upward as illustrated in  FIG. 5 ,  FIG. 6  or  FIG. 10 . Namely, the first insulating wall  170   a  may have a length L 2  that is longer than the insulating wall  70   a.    
         [0044]    In the present embodiment, the length L 2  of the first insulating wall  170   a  may be set approximately to 5.6 mm, which is 1-mm longer than the length L 1  of the first insulating wall  70   a  that is 4.6 mm. With this arrangement, an area of the magnetic pole face of the present embodiment can be reduced to increase an attracting force in the range from the displacement B to the displacement C in  FIG. 13 . Also, the creepage distance of the base block  170  is increased. In this arrangement, the first end  131   a  and the second end  131   b  of the iron core  131  can be situated on the inner side of the first insulating wall  170   a . It may be noted that the first insulating wall  170   a  has a thickness t of approximately 0.3 mm. 
         [0045]    Inspection of the electromagnetic relay may involve the use of a work tool having a sharp tip. Since the coil  30  is a winding of an extremely fine metal wire, accidently sticking a work tool having a sharp tip in the coil  30  may cause a wire disconnection. In the present embodiment, an area of the coil  30  covered by the first insulating wall  170   a  can be increased as the length L 2  of the first insulating wall  170   a  is increased. This serves to prevent, to an extent possible, a work tool from accidentally sticking in the coil  30 , thereby suppressing the generation of a defective product and improving the production yield. 
         [0046]    Moreover, by further increasing length L 2  of the first insulating wall  170   a  upward, a gap between the armature  40  and the first insulating wall  170   a  can be decreased. This serves to prevent foreign substances from entering the gap between the armature  40  and the first insulating wall  170   a  to cause a defective operation. 
         [0047]    The reason why the length L 2  of the first insulating wall  170   a  is set to 5.6 mm is to ensure compliance with the UL61010-2-201 standard. This standard requires a creepage distance of 6 mm or longer with a voltage of 300 V, and when the electromagnetic relay being used with a maximum rated voltage of 277 V, a creepage distance of 5.54 mm or longer is needed. The present embodiment is designed to satisfy this requirement. 
         [0048]      FIG. 13  illustrates comparisons between the electromagnetic relay of the first embodiment and the electromagnetic relay illustrated in  FIG. 1  through  FIG. 4 .  FIG. 13  illustrates the relationship between the displacement of the armature  40  and the load of the spring in the electromagnetic relays. The electromagnetic relay of the present embodiment exhibits an attracting force stronger than that of the electromagnetic relay illustrated in  FIG. 1  through  FIG. 4  in the range from the displacement B to the displacement C in which the displacement is smaller than approximately 0.21 mm. As is illustrated, the electromagnetic relay of the present embodiment utilizes the decreased width W 2  of the first end  131   a  and second end  131   b  of the iron core  131  so as to provide an increased attracting force in the range of small displacements. 
       Second Embodiment 
       [0049]    In the following, an electromagnetic relay according to a second embodiment will be described. The electromagnetic relay of the present embodiment has a recess in a side of the first insulating wall as illustrated in  FIG. 14 , thereby increasing a creepage distance despite a limited length L 3  of the base block. 
         [0050]    A creepage distance is defined as a distance along the surface of a first insulating wall  270   a . The presence of a recess thus increases the creepage distance accordingly. The provision of a recess  271  having a depth p of 0.15 mm in the first insulating wall  270   a  serves to increase the creepage distance by 2×p, i.e., by 0.3 mm. Namely, the length L 3  of the first insulating wall  270   a  may properly be set 0.3-mm shorter than the length L 2  of the first insulating wall of the first embodiment. In the first embodiment, the length L 2  is 5.6 mm. In the second embodiment, the provision of the recess  271  allows the length L 3  to be shortened to 5.3 mm at the shortest. The first insulating wall  270   a  may have a plurality of recesses  271  formed therein. 
         [0051]    Configurations other than those described above are the same as or similar to those of the first embodiment. 
         [0052]    Further, although a description has been given with respect to one or more embodiments of the present invention, the contents of such a description do not limit the scope of the invention. 
         [0053]    The present application is based on and claims the benefit of priority of Japanese priority application No. 2016-015515 filed on Jan. 29, 2016, with the Japanese Patent Office, the entire contents of which are hereby incorporated by reference.