Abstract:
The present invention provides an electromagnet device which can obtain a desirable attraction force (retention force) between an iron core and a movable iron piece, a method of assembling the electromagnet device and an electromagnetic relay using the electromagnet device, the electromagnet device including an electromagnet block having the iron core being wound by a coil and an auxiliary yoke fixed to one end portion of the iron core, a yoke connected to the one end portion of the iron core via a permanent magnet, the movable iron piece pivotably supported on a pivoting shaft center (serving as a fulcrum) located in an end face edge portion of the yoke so that the movable iron piece pivots on a basis of magnetization and demagnetization of the electromagnet block, where the permanent magnet is located on an extension line of an axial center of the iron core and is interposed between the auxiliary yoke and the yoke.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims benefit of priority to Japanese Patent Application No. 2012-185883, filed on Aug. 24, 2012 of which the full contents are herein incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to an electromagnet device. 
     C Japanese Utility Model Publication No. 1983-157947 discloses one of the conventional electromagnetic device to be used in an electromagnetic relay. The electromagnetic relay disclosed in the said document attracts and retains a movable iron piece and uses residual magnetism of a magnetic circuit, wherein the magnetic circuit consists of an iron core with a coil wound around, an iron core frame made of a semi-hard magnetic material, and the movable iron piece. In this electromagnetic relay, since the iron core frame is made of a semi-hard magnetic material, the iron core frame itself is magnetized to become a magnet. 
     However, in this electromagnetic relay, it is difficult to obtain a desirable attraction force between the iron core and the movable iron piece. Hence, for example, when a large switching load is needed, it is difficult to drive a movable touch piece having a large spring force. Particularly while maintaining a moved state, a strong retention force is needed. Accordingly, it is difficult to put this electromagnetic relay into practical use. 
     SUMMARY OF THE INVENTION 
     The present invention provides a desirable attraction force (retention force) between an iron core and a movable iron piece of an electromagnet device. 
     In accordance with one aspect of an electromagnet device including: an electromagnet block that includes an iron core being wound by a coil and an auxiliary yoke fixed to one end portion of the iron core; a yoke connected to the one end portion of the iron core via a permanent magnet; a movable iron piece pivotably supported on a pivoting shaft center, located in an end face edge portion of the yoke so that the movable iron piece is adapted to pivot on a basis of magnetization and demagnetization of the electromagnet block, wherein the permanent magnet is located on an extension line of an axial center of the iron core and is interposed between the auxiliary yoke and the yoke. 
     According to one embodiment of the electromagnet device, wherein the auxiliary yoke further comprises a caulking hole having an annular step portion on an upper surface of the caulking whole, and one end portion of the iron core is fitted into the caulking hole. 
     According to another embodiment of the electromagnet device, one end portion of the iron core is fitted into the caulking hole of the auxiliary yoke by spin caulking.—The term “spin caulking” means a method of pressing down the one end portion of the iron core while rotating a jig, thereby caulking the one end portion of the iron core into the caulking hole of the auxiliary yoke. 
     According to still another embodiment of the electromagnet device, the yoke and the auxiliary yoke are connected to each other via narrow-width portions, the narrow-width portions extends from adjacent corner portions of the auxiliary yoke. 
     The invention also provides a method of assembling an electromagnet device that includes an electromagnet block, the method includes winding a coil around a spool, inserting an iron core into a central hole of the spool, caulkin-fixing an auxiliary yoke to one end of the iron core which protrudes from the spool, pivotably supporting a movable iron piece through a yoke, the movable iron piece is adapted to pivot on a basis of magnetization and demagnetization of the electromagnet block, unifying the yoke and the permanent magnet by joining the yoke to the permanent magnet and connecting and fixing the auxiliary yoke and the yoke to each other so that the permanent magnet is interposed between the auxiliary yoke and the yoke. 
     A method of assembling an electromagnet device comprising an electromagnet block, the method further comprising winding a coil around a spool, inserting an iron core into a central hole of the spool, caulking-fixing an auxiliary yoke to one end of the iron core which protrudes from the spool, pivotably supporting a movable iron piece through a yoke, the movable iron piece is adapted to pivot on a basis of magnetization and demagnetization of the electromagnet block, unifying the permanent magnet and the auxiliary yoke by joining the permanent magnet to an outer surface of the auxiliary yoke, and connecting and fixing the auxiliary yoke and the yoke to each other so that the permanent magnet is interposed between the auxiliary yoke and the yoke. 
     The invention also provides a method of assembling an electromagnet device that includes an electromagnet block, the method further includes winding a coil around a spool, inserting an iron core in a central hole of the spool, and caulking-fixing an auxiliary yoke to one end of the iron core which protrudes from the spool, pivotably supporting a movable iron piece through a yoke, the movable iron piece is adapted to pivot on a basis of magnetization and demagnetization of the electromagnet block, unifying the yoke and the permanent magnet by joining the yoke to the permanent magnet, and joining opposing surfaces of the auxiliary yoke and the yoke to each other so that the permanent magnet is interposed between the auxiliary yoke and the yoke. 
     The invention further provides an electromagnetic relay comprising the electromagnet device as discussed above. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A and 1B  are perspective views of an electromagnetic relay incorporating an electromagnet device according to a first embodiment of the invention; 
         FIG. 2  is an exploded perspective view of the electromagnetic relay as illustrated in  FIG. 1 , which is obliquely viewed from the top; 
         FIG. 3  is an exploded perspective view of the electromagnetic relay as illustrated in  FIG. 1 , which is obliquely viewed from the bottom; 
         FIGS. 4A and 4B  are perspective views showing the electromagnet device; 
         FIG. 5  is an exploded perspective view of the electromagnet device as illustrated in  FIG. 4A , which is obliquely viewed from the top; 
         FIG. 6  is an exploded perspective view of the electromagnet device as illustrated in  FIG. 4B , which is obliquely viewed from the bottom; 
         FIG. 7A  is an exploded perspective view of a yoke, an auxiliary yoke, and a plate-like permanent magnet as illustrated in  FIG. 6 ; 
         FIG. 7B  is a perspective view showing a state in which the yoke, the auxiliary yoke, and the plate-like permanent magnet are assembled; 
         FIGS. 8A and 8B  are cross-sectional views showing states before and after an operation of the electromagnetic relay illustrated in  FIG. 1 ; 
         FIGS. 9A and 9B  are schematic cross-sectional views for describing an operation process of the electromagnet device according to the invention; 
         FIGS. 10A and 10B  are schematic cross-sectional views for describing an operation process of the electromagnet device which is subsequent to the operation process illustrated in  FIGS. 9A and 9B ; and 
         FIG. 11  is a schematic cross-sectional view showing a state in which an auxiliary yoke and a yoke are connected to each other by an adhesive. 
     
    
    
     DETAILED DESCRIPTION 
     An electromagnet device according to the present invention is described with reference to the  FIGS. 1A to 10B . The electromagnet device is incorporated into a latching type electromagnetic relay as illustrated in  FIGS. 1A to 8B . In this case, the electromagnetic relay includes a base  10 , an electromagnet device  20 , a contact mechanism  70 , a card  80  and a box-shaped cover  90 . Further, the card  80  is connected to the electromagnet device  20  and drives the contact mechanism  70 . 
     As illustrated in  FIGS. 2 and 3 , in the base  10  has an approximately C-shaped insulation wall  11  which protrudes from an upper surface of the base  10  and is located at a center portion on the upper surface. In addition, the electromagnet device  20  described below is arranged on one side on the upper surface, and the contact mechanism  70  is arranged on the other side on the upper surface. The insulation wall  11  includes fitting grooves  12  formed in both inside surfaces, respectively which face each other. In the fitting grooves  12 , both side edge portions of a yoke  50  are press-fitted. In addition, a center portion of an upper end of the insulation wall  11  is provided with a pair of guide ribs  13  that are in parallel with each other and protrude from an upper surface thereof. 
     As illustrated in  FIGS. 4A ,  4 B, and  5 , the electromagnet device  20  includes an electromagnet block  30  in which an iron core  40  having an almost T-shaped cross section passes through a central hole  33  of a spool  32  around which a coil  31  is wound, and an auxiliary yoke  45  is caulking-fixed to an upper end portion  41  end (one end portion) of the iron core  40  which is passed through the central hole  33 . The electromagnet device  20  further includes the yoke  50  having an L-shaped cross section which is assembled so that a plate-like permanent magnet  21  is interposed between the yoke  50  and an upper end face of the iron core  40 , a support spring  55  attached to a rear surface of the yoke  50 , and a movable iron piece  60  which is pivotably supported on a lower end face edge portion of the yoke  50  via the support spring  55 . The lower end face edge portion of the yoke  50  serves as a fulcrum for pivoting the movable iron piece  60 . 
     In the spool  32 , extended wires of the coil  31  are connected and soldered to coil terminals  35 , wherein the coil terminals  35  are press-fitted in corner portions of a lower guard portion  34 . In the spool  32 , an alignment protrusion  37  protrudes from an upper surface of an upper guard portion  36 . The alignment protrusion  37  aligns a position of the auxiliary yoke  45 . 
     The iron core  40  includes a cylindrical iron core body  40   a , a cylindrical upper end portion (one end portion)  41  which is formed via a step portion  40   c  in an upper end of the iron core body  40   a  and has a smaller diameter than the iron core body  40   a , and a disk-like magnetic pole portion  42  which is formed in a lower end of the iron core body  40   a  and has a larger diameter than the iron core body  40   a . A curving portion  40   b  is formed along a circumferential direction in the boundary of the iron core body  40   a  and the magnetic pole portion  42 . 
     The auxiliary yoke  45  has a caulking hole  46  in the center. In the auxiliary yoke  45 , connection narrow-width portions (also referred to as narrow-width portion)  47  extend in parallel with each other from adjacent corner portions of the auxiliary yoke  45  respectively. The connection narrow-width portions  47  are magnetic resistance portions with a small cross-sectional area compared with a side surface of the auxiliary yoke  45 . In an upper surface edge portion of the caulking hole  46 , an annular step portion  46   a , one step lower than the upper surface, is formed. 
     The plate-like permanent magnet  21  has a width dimension substantially the same as a width dimension of the auxiliary yoke  45 . 
     The yoke  50  having an almost L-shaped cross section includes a vertical portion  51  provided with notch portions  52  which are formed at both sides of the vertical portion  51  respectively. The notch portions  52  function to elastically engage the support spring  55 . The yoke  50  further includes a horizontal portion  53  which laterally extends from an upper end of the vertical portion  51 . 
     As illustrated in  FIG. 5  and  FIG. 6 , in the support spring  55 , a pair of elastic arm portions  56  extend in parallel with each other from both side edges of the support spring  55  respectively and an elastic support portion  59  extends from a lower edge portion of the support spring  55 . An engaging pawl  57  is protrudes from a leading end of either of the elastic arm portions  56  and a latching pawl  58  stands up from a leading end of the other elastic arm portion  56 . 
     The movable iron piece  60  includes an attracted surface  66  and a step portion  62 . The attracted surface  66  has an approximately rectangular shape and is formed in a rear half portion on an upper surface of the horizontal portion  61 . The step portion  62  is lower by one step than the attracted surface  66  and is formed in a front half portion. A contact protrusion  63  of a rectangular shape having a smaller area than the attracted surface  66  protrudes from the step portion  62  through a protruding process. The movable iron piece  60  has notch portions  65  for engaging the card  80  at both side edges of a leading end portion of the vertical portion  64  of the movable iron piece respectively. The boundary between the horizontal portion  61  and the vertical portion  64  serves as a pivoting shaft center  67 . The pivoting shaft center  67  is latched to a lower end edge portion of the yoke  50 . 
     As illustrated in  FIG. 2 , the contact mechanism  70  includes first and second fixed touch pieces  71 ,  72  arranged to face each other at a predetermined distance, and a movable touch piece  73  arranged between the first and second fixed touch pieces  71 ,  72 . A movable contact  73   a  is provided in the movable touch piece  73 . The first and the second touch pieces  71 ,  72  include a first and a second fixed contact respectively. The movable contact  73   a  is alternately attached to and detached from the first fixed contact  71   a  and the second fixed contact  72   a . Two sets of latching pawls  74 ,  75  are provided in an upper end portion of the movable touch piece  73 . The latching pawls  74 ,  75  vertically latch a remaining end edge portion  83  of the card  80 . 
     As illustrated in  FIGS. 2 and 3 , in the card  80 , the contact protrusion  81  protrudes from one end of edge portion  83 , a pair of elastic arm portions  82  extend from both sides of the contact protrusion  81  respectively, and a pair of latching arm portions  84  extend from both ends of the remaining end of the edge portion  83  respectively. 
     The box-shaped cover  90  has a box shape which can fit in the base  10 . The box-shaped cover  90  is provided with a position-regulating projecting portion  91  that bulges downward from a ceiling surface (refer to  FIG. 8 ) thereof, and a degassing hole  92  provided in the bottom of the position-regulating projecting portion  91 . The position-regulating projecting portion  91  prevents the card  80  aligned under the position-regulating projecting portion  91  from lifting. The box-shaped cover  90  has a marking recess  93  in an end portion of an upper surface thereof. 
     Accordingly, when assembling the electromagnetic relay, first, the permanent magnet  21  is integrally joined to the horizontal portion  53  of the yoke  50  (refer to  FIGS. 7A and 7B ). In this case, since the side surface of the horizontal portion  53  and the side surface of the permanent magnet  21  are flush with each other, alignment accuracy of the yoke  50  with respect to the permanent magnet  21  is increased. Next, the iron core  40  is inserted in the central hole  33  of the spool  32  around which the coil  31  is wound, and the upper end portion  41  which is passed through the central hole  33  is fixed to the auxiliary yoke  45  by spin caulking. In this way, the electromagnet block  30  is assembled. In this case, since the upper end portion  41  is subjected to spin caulking in a state in which the upper end portion  41  is fitted in the caulking hole  46 , the iron core  40  can be fixed to the auxiliary yoke  45  with high alignment accuracy. Moreover, since the upper end portion  41  is fixed to the annular step portion  46   a  of the auxiliary yoke  45  by spin caulking, the caulked and crushed upper end portion  41  can be received within the annular step portion  46   a . Accordingly, the permanent magnet  21  can be kept in area contact with the auxiliary yoke  45  in a state in which the crushed upper end portion  41  does not protrude from an upper surface of the auxiliary yoke  45 . The term “spin caulking” means a method of pressing down the end portion of the upper end portion  41  while rotating a jig, thereby caulking the end portion into the caulking hole  46  of the auxiliary yoke  45 . 
     The movable iron piece  60  is positioned in the lower end edge portion of the vertical portion  51  of the yoke  50 . The engaging pawl  57  and the latching pawl  58  of the support spring  55  are engaged with and latched to the notch portions  52  of the yoke  50  respectively. In this way, the movable iron piece  60  is pivotably supported. Then, the connection narrow-width portion  47  of the electromagnet block  30  is joined to the vertical portion  51  of the yoke  50  by laser bonding. Thus, the electromagnet device  20  in which the plate-like permanent magnet  21  is interposed between the auxiliary yoke  45  and the horizontal portion  53  is completed. Since the connection narrow-width portions  47  that extend as two strips are laser-welded to the yoke  50 , they can be easily welded in a simple manner, and the auxiliary yoke  45  and the yoke  50  can be stably fixed without wobbling. Then, both side edge portions of the yoke  50  are press-fitted in the fitting grooves  12  provided in the inside surfaces of the insulation wall  11  of the base  10 . In the present embodiment, the connection narrow-width portions  47  are fixed to the yoke  50  by laser welding. However, the fixing method is not limited to laser wielding and any fixing method can be used which connects and fixes the connection narrow-width portions  47  to the yoke  50 . 
     On the other hand, assembling is performed so that the second fixed touch piece  72 , the movable touch piece  73 , and the first fixed touch piece  71  of the contact mechanism  70  are press-fitted on the other side in the upper surface of the base  10  which is partitioned by the insulation wall  11 . Subsequently, the contact protrusion  81  of the card  80  is brought into contact with an upper end portion of the movable iron piece  60 , and the pair of elastic arm portions  82  are engaged with the pair of engaging notch portions  65  provided in the vertical portion  64  of the movable iron piece  60  respectively. The latching pawls  74  and  75  of the movable touch piece  73  are latched to the remaining end edge portion  83  of the card  80 . Finally, the following process is performed and assembling work is completed. That is, the box-shaped cover  90  is fitted into the base  10 , and sealing is performed by injecting a sealing material (not illustrated) into the bottom of the base  10 . After that, inner gas is degassed through the degassing hole  92  of the box-shaped cover  90 , and then the degassing hole  92  is subjected to heat caulking. 
     Next, an operation of the magnetic relay having the above-described structure will be described. As illustrated in  FIG. 8A , when a voltage is not applied to the coil  31 , while the contact protrusion  63  of the movable iron piece  60  is separated from the magnetic pole portion  42  of the iron core  40 , the movable contact  73   a  is in contact with the first fixed contact  71   a . In addition, the permanent magnet  21  is located on an extended line of the axial center of the iron core  40  and is interposed between the auxiliary yoke  45  and the yoke  50 . As a result, in regard to the magnetic flux of the permanent magnet  21 , as illustrated in  FIG. 9A , the magnetic flux from out of the permanent magnet  21  flows through a magnetic circuit (an auxiliary magnetic circuit) M1 which is constructed of the auxiliary yoke  45 , and leakage flux from out of the permanent magnet  21  forms a magnetic circuit (a main magnetic circuit) M2 via the yoke  50 . The movable iron piece  60  is maintained by balance between a spring force of the movable touch piece  73  and the magnetism generated by the magnetic flux which flows through the magnetic circuit M1 and the magnetic flux that flows through the magnetic circuit M2. Although the magnetic circuit M1 is magnetically saturated, since the yoke  50  and the auxiliary yoke  45  are connected to each other via the connection narrow-width portions  47  having a cross section smaller than that of a contacted surface of the yoke  50 , the magnetically saturated state more easily forms. 
     When the voltage is applied so that magnetic flux of the same direction as the magnetic flux of the permanent magnet  21  is generated in the coil  31 , the magnetic flux generated by the voltage applied to the coil  31  flows to the magnetic circuit M2 (refer to  FIG. 9B ), and an attraction force which attracts the movable iron piece  60  increases. For this reason, the movable iron piece  60  pivots on the pivoting shaft center  67 , resisting against the spring force of the movable touch piece  73 . Thus the movable iron piece  60  is attracted to the magnetic pole portion  42  of the iron core  40 , and the contact protrusion  63  is attached to the magnetic pole portion  42 . 
     When the contact protrusion  63  is attracted to the magnetic pole portion  42 , the vertical portion  64  of the movable iron piece  60  presses the movable touch piece  73  via the card  80 , and the movable contact  73   a  separates from the first fixed contact  71   a , and comes into contact with the second fixed contact  72   a  ( FIG. 8B ). 
     Subsequently, even though the application of the voltage to the coil  31  is stopped, as illustrated in  FIG. 10A , a combined magnetic force of the magnetic flux which flows to the magnetic circuit M1 which includes the auxiliary yoke  45  from the permanent magnet  21 , and the magnetic flux which flows to the magnetic circuit M2 which includes the yoke  50 , the movable iron piece  60 , and the iron core  40  is larger than the spring force of the movable touch piece  73 . For this reason, the movable iron piece  60  maintains this current state, without pivoting. 
     When a return voltage of a direction reversed to the previously described application voltage is applied to the coil  31  (refer to  FIG. 10B ) so that the magnetism of the permanent magnet  21  acting on the movable iron piece  60  will be canceled, the movable contact  73   a  separates from the second fixed contact  72   a , comes into contact with the first fixed contact  71   a , and returns to the original state. 
     Even though the return voltage is applied in the present embodiment, since the magnetic circuit M1 is in a magnetically saturated state, the magnetic flux does not flow through the magnetic circuit M1. Whole magnetic flux of the coil is generated by the applied return voltage and flows to the magnetic circuit M2 which includes the yoke, the movable iron piece, and the iron core, and a return operation is carried out. It results in a latching type electromagnetic relay having high magnetic efficiency and consuming less power. 
     The present invention is not limited to the above-described embodiment, but various modifications thereof are possible. In the above embodiment, at the time of assembling the electromagnet device  20 , the connection narrow-width portions  47  are fixed to the yoke  50  by laser welding. However, the assembling method is not limited to laser wielding. For example, as illustrated in  FIG. 11 , in regard to the auxiliary yoke  45  and the yoke  50 , the auxiliary yoke  45  and the yoke  50  may be joined to each other by applying an epoxy-based adhesive  95  to an inside surface of the plate-like permanent magnet  21 . Since the auxiliary yoke  45  and the yoke  50  can be connected to each other only by a simple measure of applying an adhesive  95 , assembling performance of the electromagnet device  20  improves. In addition, the method of applying the adhesive  95  and the method of laser-welding the connection narrow-width portions  47  to the yoke  50  both may be simultaneously employed. 
     In this embodiment, the electromagnet block  30  is assembled after the permanent magnet  21  is integrally joined to the horizontal portion  53  of the yoke  50 . Alternatively, for example, the permanent magnet  21  may be integrally joined to an outer surface of the auxiliary yoke  45  after the electromagnet block  30  is assembled. With this method, alignment accuracy of the permanent magnet  21  with respect to the iron core  40  is improved. 
     It is needless to say that the electromagnet device according to the present invention is applied not only to an electromagnetic relay but also to other electronic equipment. 
     There has thus been shown and described an electromagnetic device and an electromagnetic relay which fulfills all the advantages sought therefore. Many changes, modifications, variations and other uses and applications of the subject invention will, however, become apparent to those skilled in the art after considering this specification and the accompanying drawings which disclose the preferred embodiments thereof. All such changes, modifications, variations and other uses and applications which do not depart from the spirit and scope of the invention are deemed to be covered by the invention, which is to be limited only by the claims which follow. 
     Although the invention has been described in detail for the purpose of illustration based on what is currently considered to be the most practical and preferred embodiments, it is to be understood that such detail is solely for that purpose and that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover modifications and equivalent arrangements that are within the spirit and scope of the appended claims. For example, it is to be understood that the present invention contemplates that, to the extent possible, one or more features of any embodiment can be combined with one or more features of any other embodiment