Abstract:
A silent electromagnetic relay in which a predetermined degree of silencing effect can be maintained regardless of a change to the specification, a higher silencing effect can be obtained at the time of return, the parts control is easy, and the cost of manufacturing is low. A first silent spring is mounted in a position of an inward face of a moving iron to be attracted to an iron core of an electromagnet portion, and an L-shaped moving iron turning based on excitation and demagnetization of the electromagnet portion is housed in a housing that is a resin molded product. Furthermore, a second silent spring for coming in contact with an inner face of the housing is mounted to an outward face of the moving iron and on an opposite side to the first silent spring.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a silent electromagnetic relay and particularly to a silent electromagnetic relay which generates no offensive collision noise at times of operation and return. 
     2. Description of the Related Art 
     As a conventional silent electromagnetic relay, there is a silencing device of a small relay as shown in FIG. 1 of Japanese Patent Application Laid-open No. 8-69737, for example, in which an elastic member 31 bent substantially in a V shape is mounted in a position of an L-shaped armature 27 and facing a magnetic pole portion of a core 29 and an elastic member 32 is mounted in a position of the armature 27 and facing an outward face of the yoke 23, the armature 27 supported for turning on an upper end portion of a yoke 23. The elastic member 31 comes in contact with the core 29 at the time of operation and the elastic member 32 comes in contact with the yoke 23 at the time of return and, as a result, the elastic members 31, 32 absorb the collision noise. 
     However, in the above-described small relay, it is necessary to change a bending angle of the armature according to a change to the specification made by a customer, e.g., a change to an operating voltage, a return voltage, or the like in the above-described small relay, though the basic structure is the same. In this case, in general, in order to eliminate the necessity to start over designing related to operations of the core and the armature, the bending angle of the armature is changed while keeping a distance between the magnetic pole portion of the core and a contact face of the armature constant and therefore a distance between the outward face of the yoke and the contact face of the armature changes. Consequently, in order to maintain a predetermined degree of silencing effect at the time of return, it is necessary to change a shape of the elastic member that comes in contact with the outward face of the yoke. As a result, a silent spring adapted to a customer specification need be prepared, which complicates parts control and increases cost of manufacturing. 
     Moreover, in the above-described small relay, a metal armature comes in contact with a metal core or a metal yoke both at the time of operation and at the time of return and therefore it is not easy to obtain high silencing effect. 
     In view of the above problems, it is an object of the present invention to provide a silent electromagnetic relay in which a predetermined degree of silencing effect can be maintained irrespective of a change to the specification, a higher silencing effect can be obtained at the time of return, the parts control is easy, and the cost of manufacturing is low. 
     SUMMARY OF THE INVENTION 
     To achieve the above object, according to the present invention, there is provided a silent electromagnetic relay including an L-shaped moving iron for turning based on excitation and demagnetization of an electromagnet portion housed in a housing that is a resin molded product, a first silent spring being mounted in a position of an inward face of a moving iron to be attracted to an iron core of the electromagnet portion and a second silent spring for coming in contact with an inner face of the housing being mounted to an outward face of the moving iron and on an opposite side to the first silent spring. 
     According to the invention, the first and second silent springs are mounted in such positions that a distance between the moving iron and a magnetic pole portion of the iron core need not be changed even if the specification is changed. Therefore, shapes of the first and second silent springs need not be changed. As a result, a predetermined degree of silencing effect can be maintained and parts control becomes easy to thereby reduce cost of manufacturing. 
     Moreover, because the second silent spring mounted to the moving iron comes in contact with an inner face of the housing that is the resin molded product in return, it is possible to obtain an electromagnetic relay having a higher silencing effect than a conventional one. 
     As an embodiment of the invention, the first silent spring and the second silent spring may have the same shapes. 
     According to the embodiment, because the silent springs having the same shapes can be used, the silent springs can be produced by using one kind of stamping die. Therefore, the parts control becomes easy to thereby further reduce the cost of manufacturing. 
     As other embodiments of the invention, the second silent spring may come in contact with a bottom face of the housing or the second silent spring may come in contact with a ceiling face of the housing. 
     According to the embodiments, because the second silent spring made of metal comes in contact with the housing that is the resin molded product, it is possible to obtain the electromagnetic relay having the higher silencing effect than in a conventional art in which the spring comes in contact with a metal yoke. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a general perspective view of a silent electromagnetic relay according to a first embodiment of the present invention; 
         FIG. 2  shows a perspective view of the silent electromagnetic relay which is shown in  FIG. 1  and from which a cover is detached; 
         FIG. 3  shows a sectional view of a silent electromagnetic relay shown in  FIG. 1 ; 
         FIGS. 4A and 4B  show perspective views of an electromagnet block of the silent electromagnetic relay shown in  FIG. 2  from different angles; 
         FIGS. 5A and 5B  show perspective views of a moving iron shown in  FIGS. 4A and 4B ; 
         FIGS. 6A and 6B  show perspective views of a silent spring shown in  FIGS. 5A and 5B ;  FIGS. 6C and 6D  show perspective views of a silent spring according to a second embodiment;  FIGS. 6E and 6F  show perspective views of a silent spring according to a third embodiment; 
         FIGS. 7A and 7B  show perspective views showing a silent spring according to a fourth embodiment;  FIGS. 7C and 7D  show perspective views showing a silent spring according to a fifth embodiment;  FIGS. 7E and 7F  show perspective views showing a silent spring according to a sixth embodiment; 
         FIGS. 8A and 8B  show perspective views of a silent spring according to a seventh embodiment; and 
         FIG. 9  shows a partial sectional view of a silent electromagnetic relay and showing an eighth embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Embodiments according to the present invention will be described with reference to  FIGS. 1 to 9 . 
     In an electromagnetic relay according to a first embodiment, as shown in  FIGS. 1 to 5B , an electromagnet portion  20 , a moving iron  30 , a contact mechanism portion  40 , and a card  50  are housed in a housing  10  formed by fitting a case cover  13  with a base  11 . 
     The base  11  is formed by providing an insulating wall  12  having a substantially II planar shape and protruding from a substantially central portion of an upper face of the base  11 . The electromagnet portion  20  which will be described later is disposed while surrounded with the insulating wall  12  on a half of the upper face of the base  11  and the contact mechanism portion  40  which will be described later is disposed on the other half of the upper face. From a lower face of the base  11 , a plurality of leg portions  14  protrude. This is advantageous in that collision noise is less likely to be directly propagated from the base  11  to a substrate or the like (not shown) and that a high silencing effect can be obtained. 
     The electromagnet portion  20  is formed by winding a coil  22  around a spool  21  having flange portions  21   a ,  21   b  at opposite end portions and inserting an iron core  23  having a T-shaped section through a central hole of the spool  21  to use protruding one end portion of the iron core  23  as a magnetic pole portion  23   a  and to swage protruding the other end portion  23   b  onto a horizontal portion  24   a  of a yoke  24  having a substantially L-shaped section. A pair of coil terminals  25 ,  25  are press fitted into a lower flange portion  21   b  of the spool  21  and lead wires of the coil  22  are entwined around and soldered to the coil terminals  25 ,  25 , respectively. 
     The moving iron  30  is made of a magnetic member bent to have a substantially L-shaped section as shown in  FIG. 5  and formed at opposite side edge portions of a wide horizontal portion  31  with positioning notch portions  31   a ,  31   b . The moving iron  30  is formed at an upper end portion of a narrow vertical portion  32  with engaging notch portions  33  to be engaged with a card  50  which will be described later. Furthermore, first and second silent springs  35 ,  36  having the same shapes are respectively secured to and integrated with upper and lower faces of the horizontal portion  31  by electric welding. The first and second silent springs  35 ,  36  have substantially T planar shapes in which narrow elastic portions  35   b ,  36   b  extend from the centers of wide mounting portions  35   a ,  36   a , respectively, as shown in  FIGS. 6A and 6B . It is needless to say that the first and second silent springs  35 ,  36  do not necessarily have to be fixed by electric welding but may be fixed by swaging. 
     According to the embodiment, because silent springs  35 ,  36  can be simultaneously integrated with the upper and lower faces of the horizontal portion  31  of the moving iron  30  by electric welding, there is an advantage that man-hours required for assembly can be reduced to thereby reduce production cost. 
     The moving iron  30  is positioned at a lower end edge portion of a vertical portion  24   b  of the yoke  24  and supported for turning through a hinge spring  26 . As a result, the horizontal portion  31  of the moving iron  30  faces the magnetic pole portion  23   a  of the iron core  23  to be able to come in contact with the magnetic pole portion  23   a . In a non-excited state, the silent spring  35  is not in contact with the magnetic pole portion  23   a  of the iron core  23 . By mounting the electromagnet portion  20  from above along the insulating wall  12  of the base  11 , the electromagnet portion  20  is fixed to the base  11 . 
     The contact mechanism portion  40  is formed of a fixed contact piece  43  provided with a fixed contact  44  and a moving contact piece  41  provided with a moving contact  42 . The fixed contact piece  43  and the moving contact piece  41  are respectively press fitted in the base  11  to stand to thereby oppose the moving contact  42  to the fixed contact  44  so that the moving contact  42  can come in contact with and move away from the fixed contact  44 . 
     The card  50  is a resin molded product for coupling the electromagnet portion  20  and the contact mechanism portion  40  by engaging one end of it to the notch portions  33  of the moving iron  30  and engaging the other end portion of it to an upper end portion of the moving contact piece  41  of the contact mechanism portion  40 . 
     Consequently, by fitting the case cover  13  with the base  11  after mounting the electromagnet portion  20  mounted with the moving iron  30  and mounting the contact mechanism portion  40  to the base  11 , respectively, and coupling them with the card  50 , the electromagnet portion  20  and the like are housed in the housing  10 . 
     Next, operation of the electromagnetic relay formed of the above-described component parts will be described. 
     When the electromagnet portion  20  is not excited, the moving iron  30  is biased by spring force of the moving contact piece  41  through the card  50  and the moving contact  42  is separated from the fixed contact  44 . On the other hand, the horizontal portion  31  of the moving iron  30  is separated from the magnetic pole portion  23   a  of the iron core  23  and the second silent spring  36  is in pressure contact with a bottom face of the base  11 . 
     Then, if a voltage is applied to excite the coil  22 , the horizontal portion  31  of the moving iron  30  is attracted to the magnetic pole portion  23   a  of the iron core  23  and turns. As a result, the vertical portion  32  of the moving iron  30  presses the moving contact piece  41  through the card  50  and therefore the moving contact piece  41  turns and the moving contact  42  comes in contact with the fixed contact  44 . Furthermore, the first silent spring  35  comes in contact with the magnetic pole portion  23   a  of the iron core  23  and then the horizontal portion  31  of the moving iron  30  is attracted to the magnetic pole portion  23   a  of the iron core  23  through the first silent spring  35 . 
     Then, if application of the voltage to the coil  22  is stopped, the moving iron  30  is pushed back by the spring force of the moving contact piece  41  through the card  50 . As a result, the moving iron  30  turns in an opposite direction, the first silent spring  35  and the horizontal portion  31  of the moving iron  30  move away from the magnetic pole portion  23   a  of the iron core  23 , and the moving contact  42  moves away from the fixed contact  44 . Then, the second silent spring  36  provided to the horizontal portion  31  of the moving iron  30  comes in contact with the bottom face of the base  11 . 
     According to the embodiment, even if the first silent spring  35  comes in contact with the magnetic pole portion  23   a  of the iron core  23  as the moving iron  30  turns or even if the second silent spring  36  comes in contact with the bottom face of the base  11 , the first and second silent springs  35 ,  36  absorb and reduce the collision noise to thereby provide a quiet electromagnetic relay. Especially, because the second silent spring  36  comes in contact with the base  11  that is the resin molded product, an extremely quiet electromagnetic relay can be obtained. 
     Although the silent spring having the substantially T planar shape has been described in the above embodiment, the spring is not necessarily limited to it. For example, the spring may be a silent spring  35  (the second embodiment) having a substantially H planar shape in which an elastic portion  35   b  having a tapered face is provided between mounting portions  35   a ,  35   a  of a pair as shown in  FIGS. 6C and 6D , for example. The present embodiment is advantageous in that a mounted orientation is not specified and that positioning is easy. Moreover, the spring may be a silent spring  35  (a third embodiment) in which a wide elastic portion  35   b  having a tapered face is provided to a wide mounting portion  35   a  as shown in  FIGS. 6E and 6F . 
     Furthermore, the spring may be a silent spring  35  (a fourth embodiment) in which a wide elastic portion  35   b  having a curved face extends from a wide mounting portion  35   a  as shown in  FIGS. 7A and 7B , a silent spring  35  (a fifth embodiment) in which a dome-shaped elastic portion  35   b  extends from a wide mounting portion  35   a  as shown in  FIGS. 7C and 7D , and a silent spring  35  (a sixth embodiment) in which a wide elastic portion  35   b  having a curved face extends from a wide mounting portion  35   a  as shown in  FIGS. 7E and 7F . 
     Moreover, the spring may be a silent spring  35  (a seventh embodiment) having a substantially II planar shape in which two elastic portions  35   b ,  35   c  having tapered faces extend parallel from a wide mounting portion  35   a  as shown in  FIGS. 8A and 8B . Especially, the elastic portions  35   b ,  35   c  of the silent spring  35  according to the seventh embodiment have different bending angles and different mountain heights. Therefore, after first bringing the higher-mountain elastic portion  35   b  in contact to thereby reduce speed and acceleration of the moving iron  30 , the lower-mountain elastic portion  35   c  may be brought in contact to bring a spring load in contact. According to the present embodiment, there is an advantage that the most suitable adjustment to an operation stroke of the moving iron  30  becomes possible to thereby obtain a high silencing effect. 
     An eighth embodiment is a case where a second silent spring  36  fixed to a moving iron  30  is brought in contact with a ceiling face of a case cover  13  fitted with a base  11  as shown in  FIG. 9 . Because other portions are similar to those in the above-described embodiments, the same portions are provided with the same reference numerals to omit description of them. 
     EXAMPLE 
     In the electromagnetic relay according to the first embodiment, amounts of change in an operation sound and a return sound before and after mounting of the first and second silent springs were measured. The result showed a reduction of the operation sound by about 10 dB and a reduction of the return sound by about 20 dB due to mounting of the first and second silent springs. 
     INDUSTRIAL APPLICABILITY 
     It is needless to say that the silent electromagnetic relay according to the invention is not limited to the above-described embodiments but may be applied to other electromagnetic relays.