Patent Publication Number: US-10770252-B2

Title: Magnetic system of electromagnetic relay

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of PCT International Application No. PCT/IB2016/053739, filed on Jun. 23, 2016, which claims priority under 35 U.S.C. § 119 to Chinese Patent Application No. 201510371849.4, filed on Jun. 30, 2015. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to an electromagnetic relay and, more particularly, to a magnetic system of an electromagnetic relay. 
     BACKGROUND 
     A magnetic system of an electromagnetic relay generally known in the art comprises an iron core, a coil, a yoke, and an armature. The iron core passes through the coil. A first end of the iron core is connected to the yoke. The armature is disposed at a second end of the iron core opposite the first end and faces an end surface of the second end of the iron core. A surface of the armature faces an end surface of the yoke and contacts an edge of the yoke. 
     In a magnetic circuit of the existing electromagnetic relay, a cross sectional area of a magnetic gap between the yoke and the armature is defined by an area of the end surface of the yoke. Since the area of the end surface of the yoke is limited by a thickness of the yoke, the cross sectional area of the magnetic gap between the yoke and the armature is limited by the thickness of the yoke. In order to increase the cross sectional area of the magnetic gap between the yoke and the armature, in a yoke design of some manufacturers, the edge of the yoke abutting against the armature is stamped to increase the thickness of the end portion of the yoke and the cross sectional area of the magnetic gap. However, this solution complicates the manufacturing process and reduces manufacturing efficiency. 
     SUMMARY 
     A magnetic system of an electromagnetic relay according to the invention comprises a coil, an iron core, a yoke, and an armature. The iron core extends through the coil and has a first end and a second end opposite to the first end. A second part of the yoke is connected to the first end of the iron core and a first part of the yoke extends in a length direction of the iron core and is separated from the coil. The armature is disposed at the second end of the iron core and has a main body and a bending portion bent from the main body by a predetermined angle. The main body faces an end surface of the second end of the iron core. The bending portion is disposed at an inner side of an end portion of the first part of the yoke and faces the iron core. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will now be described by way of example with reference to the accompanying Figures, of which: 
         FIG. 1  is a perspective view of an electromagnetic relay according to an embodiment; 
         FIG. 2  is an exploded perspective view of the electromagnetic relay of  FIG. 1 ; and 
         FIG. 3  is a perspective view of an electromagnetic relay according to another embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENT(S) 
     Exemplary embodiments of the present invention will be described hereinafter in detail with reference to the attached drawings, wherein like reference numerals refer to like elements. The present invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that the present disclosure will be thorough and complete and will fully convey the concept of the disclosure to those skilled in the art. 
     A magnetic system of an electromagnetic relay according to an embodiment is shown in  FIGS. 1 and 2 . The electromagnetic relay comprises an iron core  100 , a coil  200 , a yoke  300 , and an armature  400 . 
     The iron core  100 , as shown in  FIGS. 1 and 2 , passes through the coil  200  and has a first end  101  and a second end  102  opposite to the first end  101 . The yoke  300  is connected to the first end  101  of the iron core  100 . The armature  400  is disposed at the second end  102  of the iron core  100  and faces an end surface of the second end  102  of the iron core  100 . 
     In the shown embodiment, the iron core  100  has a rectangular cross section. In other embodiments, the iron core  100  may have a round cross section, an oval cross section, or any other suitable shaped cross section. 
     The yoke  300 , as shown in  FIGS. 1 and 2 , comprises a first part  301  and a second part  302  substantially perpendicular to the first part  301 . The first part  301  is integrally connected to the second part  302 . The yoke  300  substantially exhibits an L-shape as a whole. An installation hole  320 , as shown in  FIG. 2 , is formed in the second part  302  of the yoke  300 . The first part  301  of the yoke  300  has a length substantially equal to a length of the iron core  100  and is formed in a flat-plate shape. 
     As shown in  FIGS. 1 and 2 , the second part  302  of the yoke  300  is connected to the first end  101  of the iron core  100 . The first end  101  of the iron core  100  is fitted into the installation hole  320  so as to assemble the yoke  300  and the iron core  100  together. The first part  301  of the yoke  300  extends in a length direction of the iron core  100  and is separated from the coil  200 . The first part  301  of the yoke  300  is substantially parallel to an axis of the coil  200 . The second part  302  of the yoke  300  is substantially perpendicular to the axis of the coil  200 . The iron core  100  and the coil  200  have a same axis. 
     The armature  400 , as shown in  FIGS. 1 and 2 , comprises a main body  402  facing an end surface of the second end  102  of the iron core  100  and a bending portion  401  bent from the main body  402  by a predetermined angle, for example, by 90 degrees. In other embodiments, the bending portion  401  may be bent from the main body  402  by an angle between 70 and 110 degrees, between 80 and 100 degrees, or between 85 and 95 degrees. 
     The bending portion  401  of the armature  400  is disposed at an inner side, facing the iron core  100 , of an end portion  310  of the first part  301  of the yoke  300  as shown in  FIGS. 1 and 2 , so that the bending portion  401  of the armature  400  is interposed between the iron core  100  and the end portion  310  of the first part  301  of the yoke  300 ; the bending portion  401  of the armature  400  faces the inner side of the end portion  310  of the first part  301  of the yoke  300 . The bending portion  401  of the armature  400  contacts an inner side edge  312  of an end surface  311  of the end portion  310  of the first part  301  of the yoke  300 , so that the inner side edge  312  serves as a pivot fulcrum of the armature  400 . The armature  400  may be rotated about the inner side edge  312  of the end surface  311 . The end portion  310  of the first part  301  of the yoke  300 , in an embodiment, has a width substantially equal to a width of the bending portion  401  of the armature  400 . 
     A cross sectional area of a magnetic gap between the yoke  300  and the armature  400  is defined by a surface area of the bending portion  401  of the armature  400  facing the end portion  310  of the yoke  300 . Thereby, it is possible to increase the cross-sectional area of the magnetic gap between the armature  400  and the yoke  300  by increasing the surface area of the bending portion  401  of the armature facing the yoke  300 . In this way, it is easy to increase the electromagnetic attraction force exerted on the armature  400  by the yoke  300 . 
     As shown in  FIG. 1 , the iron core  100  exerts a first electromagnetic attraction force F 1  on the main body  402  of the armature  400  in a substantially horizontal direction. The first electromagnetic attraction force F 1  produces a first torque on the armature  400  with respect to the pivot fulcrum (the inner side edge  312 ). The yoke  300  exerts a second electromagnetic attraction force F 2  on the bending portion  401  of the armature  400  in a substantially perpendicular direction. The second electromagnetic attraction force F 2  produces a second torque on the armature  400  with respect to the pivot fulcrum (the inner side edge  312 ). As shown in  FIG. 1 , the first torque produced by the first electromagnetic attraction force F 1  and the second torque produced by the second electromagnetic attraction force F 2  have the same direction (for example, counter-clockwise direction in  FIG. 1 ) with respect to the pivot fulcrum (the inner side edge  312 ). A total torque exerted on the armature  400  is equal to the sum of the first torque and the second torque. 
     An electromagnetic relay according to another embodiment of the invention is shown in  FIG. 3 . The electromagnetic relay comprises an iron core  100 ′, a coil  200 ′, a yoke  300 ′, and an armature  400 ′. The electromagnetic relay of the embodiment of  FIG. 3  is similar to the embodiment of  FIGS. 1 and 2 ; like reference numbers refer to like elements and only the differences from the embodiment shown in  FIGS. 1 and 2  will be described in detail herein. 
     As shown in  FIG. 3 , an end portion  310 ′ of a first part  301 ′ of the yoke  300 ′ is bent away from the iron core  100 ′ with respect to a main body portion (the other portion except the end portion  310 ′) of the first part  301 ′, so as to increase a distance between the end portion  310 ′ of the first part  301 ′ of the yoke  300 ′ and the coil  200 ′. In this way, a distance between an bending portion  401 ′ of the armature  400 ′ and the coil  200 ′ as well as a distance between the bending portion  401 ′ of the armature  400 ′ and the iron core  100 ′ are increased, which effectively prevents the bending portion  401 ′ of the armature  400 ′ from touching or hitting the coil  200 ′ and the iron core  100 ′ during rotation of the bending portion  401 ′ of the armature  400 ′ about the inner side edge (pivot fulcrum)  312 ′. 
     A positioning step  412 ′, as shown in  FIG. 3 , is formed on an outer side of the bending portion  401 ′ of the armature  400 ′ opposite to the iron core  100 ′. The inner side edge  312 ′ of the end portion  310 ′ of the first part  301 ′ is positioned in a corner of the positioning step  412 ′ of the armature  400 ′. In this way, the yoke  300 ′ does not slide while the armature  400 ′ is rotated about the inner side edge (pivot fulcrum)  312 ′.