Patent Publication Number: US-11043347-B2

Title: Electromagnetic relay

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based on and claims priority to Japanese Patent Application No. 2017-224556, filed on Nov. 22, 2017, the entire contents of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to an electromagnetic relay. 
     2. Description of the Related Art 
     A fixed contact is swaged so as to be attached to a fixed spring of an electromagnetic relay. When the contact is swaged to the fixed spring, the pressed end of the contact protrudes from the surface of the fixed spring. 
     In the conventional method of swaging a contact, although coupling strength is high, there is a possibility that a portion protruding from the fixed spring may be brought into contact with a molded part such as a bobbin. If the protruding portion contacts with the bobbin, the bobbin may be chipped and the chipped pieces may be interposed between contacts, which may cause conduction failure. Further, if the protruding portion contacts with the bobbin, the bobbin or the fixed spring may be deformed. As a result, assembly dimensions may deviate from design values, resulting in a decrease in a non-adjustment rate and an increase in a failure rate. If a structure for avoiding contact between the protruding portion of the contact and the bobbin is provided, it may decrease the strength of the bobbin or may hinder downsizing of the bobbin*. 
     RELATED-ART DOCUMENTS 
     Patent Documents 
     [Patent Document 1] Japanese Unexamined Patent Application Publication No. 9-97550 
     SUMMARY OF THE INVENTION 
     It is a general object of an embodiment of the present invention to provide an electromagnetic relay that can prevent a fixed contact from interfering with other parts. 
     According to at least one embodiment, an electromagnetic relay includes a fixed spring, a fixed contact configured to be swaged so as to be attached to the fixed spring, a movable spring, and a movable contact provided on the movable spring so as to be capable of making contact with the fixed contact, wherein a swaged portion of the fixed contact is formed so as not to protrude from a surface of the fixed spring. 
     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. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded perspective view of an electromagnetic relay according to an embodiment; 
         FIGS. 2A and 2B  are diagrams illustrating the electromagnetic relay in an assembled state; 
         FIG. 3  is a perspective view of a break spring according to the present embodiment; 
         FIG. 4  is a cross-sectional view of the break spring having break contacts being attached; 
         FIG. 5  is a perspective view of a make spring according to the present embodiment; 
         FIG. 6  is a cross-sectional view of the make spring having make contacts being attached; 
         FIG. 7  is a front view of a contact fitted to an electromagnet; 
         FIG. 8  is a front view of a spool; 
         FIG. 9  is a perspective view of a break spring according to a comparative example; 
         FIG. 10  is a cross-sectional view of the break spring having break contacts being attached; 
         FIG. 11  is a front view of a contact fitted to an electromagnet according to the comparative example; 
         FIG. 12  is a front view of a spool according to the comparative example; and 
         FIG. 13  is a schematic diagram of a recess according to a variation of the embodiment. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     According to at least one embodiment, an electromagnetic relay that can prevent a fixed contact from interfering with other parts can be provided. 
     In the following, embodiments of the present invention will be described with reference to the accompanying drawings. In the drawings, the same elements are denoted by the same reference numerals, and a duplicate description thereof will be omitted. 
       FIG. 1  is an exploded perspective view of an electromagnetic relay  50  according to an embodiment.  FIGS. 2A and 2B  are diagrams illustrating the electromagnetic relay  50  in an assembled state. 
     In the following, three axes (x-axis, y-axis, and z-axis) that are perpendicular to each other are used as references to describe shapes and positional relationships of components of the electromagnetic relay  50 . As illustrated in  FIG. 1 , the x-axis is a direction in which components of a contact  3  are fitted to an electromagnet  2 . The y-axis is a width direction of the electromagnetic relay  50  and is also a direction in which pairs of terminals  31   b  and terminals  32   c  are arranged. The z-axis is a direction in which the electromagnet  2  and the contact  3  are fitted to a base  1  and a cover  4 . A +z direction is taken as upwards and a −z direction is taken as downwards. Also, the x-axis and the y-axis are horizontal directions. A +x side is a side at which a make spring  32  and a break spring  33  are fitted to the electromagnet  2 . A −x side is a side at which a movable spring  26  is fitted to the electromagnet  2 . A +y side is a side at which a terminal  33   b  of the break spring  33  is disposed. In the following, the +x side may be represented as a front side, the −x side may be represented as a back side, the +y side may be represented as a right side, and the −y side may be represented as a left side. 
     For example, the electromagnetic relay  50  according to the present embodiment is used for a vehicle in which a 12V DC battery or a 24V DC battery is installed, or is used for a mild hybrid vehicle in which a 48V DC battery is installed. To be more specific, the electromagnetic relay  50  is used for switching control of a control circuit of a 12V DC battery, a 24V DC battery, or a 48V DC battery. 
     The electromagnetic relay  50  illustrated in  FIG. 1  and  FIGS. 2A and 2B  is a sealed and hinge type relay. The electromagnetic relay  50  includes the electromagnet  2  that is fitted to the base  1 , the contact  3  that opens and closes in response to the operation of the electromagnet  2 , and the cover  4  that covers the electromagnet  2  and the contact  3 . The contact  3  is what is known as a transfer contact, and movable contacts  30  are disposed between fixed contacts  34  and fixed contacts  35 . In a state in which an electric current does not flow through the electromagnet  2 , the movable contacts  30  contacts with the fixed contacts  35  on the break side (break contacts). In a state in which an electric current flows through the electromagnet  2 , the movable contacts  30  contacts with the make fixed contacts  34  on the make side (make contacts). 
     The base  1  is made of an electrically-insulating resin, and includes a rectangular frame  10  and a bottom  11  that closes the bottom side of the frame  10 . The base  1  has a recessed portion  12  that is defined by the frame  10  and the bottom  11  and opens upward. The electromagnet  2  and the contact  3  are fixedly supported by the recessed portion  12 . The cover  4  is adhesively fixed to the frame  10 . 
     The electromagnet  2  includes a hollow body  20   g  extending along the z-axis, a spool  20  including an upper flange  20   a  located at the top of the spool  20  and a lower flange  20   b  located at the bottom of the spool  20 , an iron core  21  housed in the body  20   g , and a coil  22  provided on the outer surface of the spool  20 . The lower flange  20   b  is fixedly supported by the recessed portion  12 . 
     A stepped portion  20   c  is formed at the center of the upper flange  20   a . A narrow portion  20   h  having a width narrower than that of the upper flange  20   a  along the y-axis is provided on the front side of the stepped portion  20   c . Right and left side walls  20   d  is raised upward from the narrow portion  20   h . Above the front end of the upper flange  20   a , an upper wall  20   e  parallel to the upper flange  20   a  is provided between two side walls  20   d . A box-shaped space SP with the front and back sides being open is formed by the upper flange  20   a , side walls  20   d , and upper wall  20   e . At the upper end of the right side wall  20   d , a slit  20   f  is formed from the front towards the back to be parallel to the upper wall  20   e . The slit  20   f  is used to mount the break spring  33 , which will be described later. 
     The iron core  21  is a columnar member formed of magnetic steel, for example. An upper end surface  21   a  of the iron core  21  is exposed to the outside from the upper flange  20   a  while the iron core  21  is housed in the spool. The part of the iron core  21  other than the end surface  21   a  is fixedly supported inside the body  20   g . The wire of the coil  22  is wound around the outer surface of the body  20   g  between the upper flange  20   a  and the lower flange  20   b . Each end of the coil  22  is connected to corresponding one of coil terminals  23  fixed to the base  1 . A yoke  24  is fixedly connected to the lower end of the iron core  21  by, for example, swaging. 
     The yoke  24  is a plate-shaped member formed by die-cutting and bending a magnetic steel sheet into an L-shape in cross section, for example. In a state in which the electromagnetic relay  50  is assembled, the yoke  24  extends below the lower flange  20   b  along the x-axis and extends behind the body  20   g  along the z-axis. An upper end  24   a  of the yoke  24  is located at approximately the same height as the end surface  21   a.    
     An armature  25  is a flat plate-shaped member formed by die-cutting a magnetic steel sheet, for example. In an assembled state as illustrated in  FIG. 2B , the armature  25  is disposed above the upper flange  20   a  so as to be approximately parallel to the upper flange  20   a . At this time, the rear end of the armature  25  contacts with the upper end  24   a  and is supported in a swingable manner. The front bottom surface of the armature  25  is disposed facing the end surface  21   a . This configuration allows a magnetic circuit to be formed among the iron core  21 , the yoke  24 , and the armature  25  upon the electromagnet  2  being operated. 
     The armature  25  is attached to the movable spring  26 , and is resiliently and relatively-movably coupled to the yoke  24  via the movable spring  26 . The movable spring  26  is formed by die-cutting and bending a thin sheet formed of phosphor bronze for springs into an approximately L-shape. As illustrated in  FIG. 1 , the movable spring  26  integrally includes a vertical portion  26   a  fixed to the back surface of the yoke  24  by, for example, swaging, a horizontal portion  26   b  fixed to the upper surface of the armature  25  by, for example, swaging, right and left hinge springs  26   c  formed so as to be bent and connecting the vertical portion  26   a  and the horizontal portion  26   b , and right and left arms  26   d  bifurcated from the horizontal portion  26   b  in the right-left direction and extending frontward. 
     The movable spring  26  functions as a hinge that elastically connects the yoke  24  and the armature  25 , and biases the armature  25  in a direction away from the end surface  21   a  by means of the spring force of the hinge springs  26   c . The movable contacts  30  are attached to the respective tips of the arms  26   d  by, for example, swaging. The arms  26   d  are inserted into the space SP between the upper wall  20   e  and the upper flange  20   a  from the back side. The movable contacts  30  are disposed in the space SP so as to be capable of making contact with the make contacts  34  and the break contacts  35 , which will be described later. 
     The right and left ends of the vertical portion  26   a  form terminals  31   b  that are bent frontward at approximately a right angle and extend downward. The terminals  31   b  are disposed at the right and left rear corners of the recessed portion  12 , and penetrate the bottom  11  of the base  1 . 
     The make spring  32  is formed by die-cutting and bending a copper sheet, for example. As illustrated in  FIG. 1 , the make spring  32  integrally includes a front plate  32   a  extending in front of the spool  20  in the vertical direction, horizontal portions  32   b  formed by bending the top of the front plate  32   a  backward at approximately a right angle and bifurcated from the top of the front plate  32   a  along the y-axis and extending backward, and right and left terminals  32   c  formed by bending the right and left ends of the front plate  32   a  backward at approximately a right angle and extending below the front plate  32   a.    
     The horizontal portions  32   b  are inserted into the space SP from the front side of the spool  20 . As illustrated in  FIG. 2B , in a state in which the electromagnetic relay  50  is assembled, the horizontal portions  32   b  are positioned below the arms  26   d . The make contacts  34 , disposed facing the respective movable contacts  30 , are attached to the horizontal portions  32   b  by, for example, swaging. As illustrated in  FIG. 2B , the terminals  32   c  are disposed at the right and left front ends of the recessed portion  12 , and penetrate the bottom  11  of the base  1 . 
     The break spring  33  is formed by die-cutting and bending a copper sheet, for example. The break spring  33  integrally includes a horizontal portion  33   a  that extends along the y-axis and the terminal  33   b  that is bent downward from the right end of the horizontal portion  33   a  at approximately a right angle. 
     In the assembled state as illustrated in  FIG. 2B , the horizontal portion  33   a  is inserted into the slit  20   f  from the front side, and is positioned above the arms  26   d . The two break contacts  35 , disposed facing the respective movable contacts  30 , are attached to the horizontal portion  33   a  by, for example, swaging. 
     In the assembled state as illustrated in  FIG. 2B , the terminals  32   c , the coil terminals  23 , and the terminals  31   b  are aligned along the x-axis and protrude downward from the base  1 . The lower ends of the terminals  32   c , the coil terminals  23 , and the terminals  31   b  are approximately on the same level. Any or all of the terminals  32   c , the coil terminals  23 , and the terminals  31   b  may be integrally formed with the base  1  by, for example, insert molding. The terminals  32   c , the coil terminals  23 , and the terminals  31   b  are dispersed in the front-back and right-left directions of the electromagnetic relay  50 . Thus, it is possible to provide a sufficient distance between the terminals while also downsizing the electromagnetic relay  50 , making it easy to form a pattern of a circuit on which the electromagnetic relay  50  is mounted. 
     For example, the electromagnetic relay  50  is operated as follows. When voltage is not applied to the coil  22 , the movable spring  26  biases the armature  25  in a direction away from the movable spring  26 . Accordingly, the movable contacts  30  are held at a non-operating position away from the make contacts  34  while making contact with the break contacts  35  (see  FIG. 7 ). At this time, contact pairs of the movable contacts  30  and the break contacts  35  are closed, allowing an electric current to flow between the terminals  31   b  and the terminal  33   b  through the contact pairs. 
     Conversely, when voltage is applied to the coil  22 , magnetic attractive force of the electromagnet  2  attracts the armature  25  toward the upper surface  21   a  against the spring force of the movable spring  26 , and the movable contacts  30  move downward. Accordingly, the movable contacts  30  make contact with the make contacts  34 . Also, the movable contacts  30  are stationarily held at an operating position. 
     Because contact pairs of the movable contacts  30  and make contacts  34  are provided at the right and left, a parallel circuit is formed between the two contact pairs when the electromagnet  2  is operated. Accordingly, an electric current is branched and flows through each of the two contact pairs. 
     Next referring to  FIG. 3  through  FIG. 8 , configurations in which the fixed contacts including the make contacts  34  and the break contacts  35  are attached to the fixed springs including the make spring  32  and the break spring  33 , respectively, will be described.  FIG. 3  is a perspective view of the break spring  33  according to the present embodiment.  FIG. 4  is a cross-sectional view of the break spring  33  having the break contacts  35  being attached.  FIG. 5  is a perspective view of the make spring  32  according to the present embodiment.  FIG. 6  is a cross-sectional view of the make spring  32  having the make contacts  34  being attached.  FIG. 7  is a front view of the contact  3  fitted to the electromagnet  2 .  FIG. 8  is a front view of the spool  20 . 
     As illustrated in  FIG. 3  and  FIG. 4 , the horizontal portion  33   a  has approximately circular shaped holes  33   c  for attaching the break contacts  35 . The break contacts  35  are inserted from below into the holes  33   c  and portions of the break contacts  35  protruding from the horizontal portion  33   a  are swaged. In this way, the break contacts  35  are attached to the break spring  33 . 
     The upper surface of the horizontal portion  33   a , namely the surface on which the break contacts  35  are swaged, has recesses  33   d  in the holes  33   c . The recesses  33   d  are each formed in a stepped shape around the entire outer edge of the upper side of the corresponding hole  33   c . The recesses  33   d  are concentric with the holes  33   c , and a diameter of the recesses  33   d  is larger than a diameter of the holes  33   c.    
     When the break contacts  35  are swaged to the holes  33   c  having the above-described shape, swaged portions  35   a  are each formed so as to extend into the corresponding recess  33   d  as illustrated in  FIG. 4 . Thus, the swaged portions  35   a  do not protrude from the horizontal portion  33   a . Accordingly, the upper surface of the horizontal portion  33   a  can be made flat, and also the break contacts  35  can be securely attached to the break spring  33 . 
     As illustrated in  FIG. 5  and  FIG. 6 , the horizontal portions  32   b  have approximately circular shaped holes  32   d  for attaching the make contacts  34 . The make contacts  34  are inserted from above into the holes  32   d  and portions of the make contacts  34  protruding from the horizontal portions  32   b  are swaged. In this way, the make contacts  34  are attached to the make spring  32 . 
     The lower surfaces of the horizontal portions  32   b , namely the surfaces on which the make contacts  34  are swaged, have recesses  32   e  in the holes  32   d . The recesses  32   e  are each formed in a stepped shape around the entire outer edge of the lower side of the horizontal portions  32   b . The recesses  32   e  are concentric with the holes  32   d , and a diameter of the recesses  32   e  is larger than a diameter of the holes  32   d.    
     When the make contacts  34  are swaged to the holes  32   d  having the above-described shape, swaged portions  34   a  are each formed so as to extend into the corresponding recess  32   e  as illustrated in  FIG. 6 . Thus, the swaged portions  34   a  do not protrude from the horizontal portions  32   b . Accordingly, the lower surfaces of the horizontal portions  32   b  can be made flat, and also the make contacts  34  can be securely attached to the make spring  32 . 
     As described, the swaged portions  35   a  are formed so as not to protrude from the upper surface of the horizontal portion  33   a . Accordingly, when the contact  3  is fitted to the electromagnet  2 , the swaged portions  35   a  do not readily make contact with the lower surface of the upper wall  20   e . Therefore, as illustrated in  FIG. 7  and  FIG. 8 , the lower surface of the upper wall  20   e  can be made flat, eliminating the need to provide the lower surface of the upper wall  20   e  with a structure for avoiding contact with the swaged portions  35   a  (see  FIG. 12 ). 
     Similarly, the swaged portions  34   a  are formed so as not to protrude from the lower surfaces of the horizontal portions  32   b . Accordingly, when the contact  3  is fitted to the electromagnet  2 , the swaged portions  34   a  do not readily make contact with the upper surface of the narrow portion  20   h . Therefore, as illustrated in  FIG. 7  and  FIG. 8 , the upper surface of the narrow portion  20   h  can be made flat, eliminating the need to provide the narrow portion  20   h  with a structure for avoiding contact with the swaged portions  34   a  (see  FIG. 12 ). 
     By making the upper wall  20   e  and the narrow portion  20   h  flat, the thickness of the upper wall  20   e  and the thickness of the narrow portion  20   h  can be made uniform when the upper wall  20   e  and the narrow portion  20   h  are molded. Accordingly, moldability and strength of the spool  20  can be expected to improve. 
     Further, the swaged portions  34   a  and  35   a  are formed so as not to protrude from the break spring  33  and the make spring  32 , allowing the surfaces of the break spring  33  and the make spring  32  to be made flat. Accordingly, when the fixed springs including the make spring  32  and the break spring  33 , whose fixed contacts including the make contacts  34  and the break contacts  35  have been swaged, are press-fitted to the spool  20 , the make contacts  34  and the break contacts  35  can be prevented from interfering with the spool  20 , and thus, wear and chipping of parts can be reduced. Accordingly, it is possible to prevent a foreign material due to wear and chipping from entering the electromagnetic relay  50 , and thus reduce malfunction caused by the foreign material. Also, by preventing the parts from interfering with each other, it is possible to reduce malfunction due to assembly failure. Such malfunction occurs, for example, when the fixed springs are forcibly press-fitted to the spool  20 , causing the spool  20  or the fixed springs to be deformed. 
     It should be noted that, even when the electromagnetic relay  50  has a different internal configuration from that of the present embodiment, namely even when the swaged portions of the make contacts  34  and the break contacts  35  are positioned so as to face parts other than the spool  20 , the make contacts  34  and the break contacts  35  can be prevented from interfering with the parts by attaching the make contacts  34  and the break contacts  35  in the same way as the present embodiment. Accordingly, a similar effect to that of the present embodiment can be exhibited. 
     Also, according to the present embodiment, a stepped recess is formed in a hole such that a portion of a fixed contact extends into the stepped recess and becomes parallel to the surface of a horizontal portion. Thus, coupling strength does not decrease as compared to a method of swaging a fixed contact to a hole without a recess. 
     Shortening the fixed contact can result in material savings. Also, providing the stepped recess can increase the area of the fixed contact making contact with the fixed spring. Accordingly, it is possible to reduce heat generation and improve strength. 
     As a comparative example, a hole without a recess will be described below.  FIG. 9  is a perspective view of a break spring  133  according to a comparative example.  FIG. 10  is a cross-sectional view of the break spring  133  having break contacts  135  being attached.  FIG. 11  is a front view of a contact  3  fitted to an electromagnet  2  according to the comparative example.  FIG. 12  is a front view of a spool  20  according to the comparative example. 
     As illustrated in  FIG. 9 , the break spring  133  does not have recesses in holes  133   c  for attaching the break contacts  135 . Thus, when break contacts  135  are swaged and attached, swaged portions  135   a  protrude from the surface of a horizontal portion  33   a  because there are no spaces that allow the swaged portions  135   a  to enter, as illustrated in  FIG. 10 . Although not illustrated, swaged portions  34   a  also protrude from the surfaces of the horizontal portions  32   b  when recesses are not provided in holes  32   d.    
     In this case, when the contact  3  is fitted to the electromagnet  2 , the swaged portions  135   a  tend to make contact with the bottom surface of the upper wall  20   e . Therefore, the break contacts  135  tend to interfere with the spool  20 . As illustrated in  FIG. 12  and  FIG. 13 , the lower surface of the upper wall  20   e  has thus grooves  120  through which the swaged portions  135   a  pass when the break spring  133  is press-fitted to the spool  20 . 
     Similarly, when the contact  3  is fitted to the electromagnet  2 , the swaged portions  34   a  tend to make contact with the upper surface of a narrow portion  20 . Therefore, the make contacts  34  tend to interfere with the spool  20 . As illustrated in  FIG. 12 , the upper surface of the narrow portion  20   h  has thus grooves  121  through which the swaged portions  34   a  pass when the make spring  32  is press-fitted to the spool  20 . 
     When the spool  20  has the grooves  120  and  121 , the thickness of the upper wall  20   e  and the thickness of the narrow portion  20   h  do not become uniform. Thus, moldability and strength of the spool may decrease. Conversely, in the present embodiment, as described with reference to  FIG. 8 , the surface of the upper wall  20   e  and the surface of the narrow portion  20   h  can be made flat. Accordingly, moldability and strength of the spool  20  can improve. 
     Referring to  FIG. 13 , a variation will be described.  FIG. 13  is a schematic diagram of a recess according to a variation of the embodiment. Recesses are not limited to those illustrated in  FIG. 3  and  FIG. 5  and are not necessarily formed around the entire outer edges of the holes  32   d  and  33   c . The recesses may have any shape as long as the swaged portions  34   a  and  35   a  do not protrude from the surfaces of the fixed springs. For example, as with the case of recesses  133   d  formed in a cross shape illustrated in  FIG. 13 , the outer edge of the hole  33   c  may be recessed in part. 
     Further, the recesses may have a tapered shape in cross section. The recesses are not required to be formed in a stepped shape as in the case of the recesses  32   e  and  33   d  illustrated in  FIG. 3  and  FIG. 5 . 
     Although the embodiments have been specifically described above, the present disclosure is not limited to the above-described embodiments. These specific embodiments may be modified by a person skilled in the art as long as the features of the present disclosure are included. Elements and their arrangement, conditions, and shapes are not limited to the above-described embodiments and may be modified as necessary. It should be noted that combination of the elements of the above-described embodiments may be changed as long as no technical contradiction occurs. 
     Further, the electromagnetic relay  50  may have internal configurations other than those of the above-described embodiments. 
     In the above-described embodiments, the number of the movable contacts and of the fixed contacts is 2. However, the number of movable contacts and of the fixed contacts may be 1 or may be 3 or more. 
     In the above-described embodiments, both the make spring  32  and the break spring  33  have the recesses, such that both the swaged portions  34   a  and  35   a  do not protrude. Alternatively, either one of the make contacts  34  and the break contacts  35  may have recesses. In the electromagnetic relay  50  according to the embodiment illustrated in  FIG. 1  and  FIG. 2 , it is preferable for the break spring  33  to have recesses.