Abstract:
An electromagnet assembly for an electromagnetic apparatus has a ring member, a coil bobbin having an electrical wire wound a spool of the ring member, and a ring case. The ring member is disposed in an annular groove of the ring case. An opening is formed through the ring case adjacent to its closed end surface. A connector is disposed on the ring case adjacent to its closed end surface and covers the opening. A first and a second ends of the electrical wire and a first and a second ends of a lead wire are joined in, respectively the connector. A projection portion formed on the connector is inserted into the opening, and is fixed adhesively to an end surface of the ring member of the coil bobbin.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an electromagnet assembly for use in an electromagnetic apparatus, such as an electromagnetic clutch for use in controlling the transmission of power from an automobile engine to a refrigerant compressor in an automobile air conditioning system. More particularly, it relates to a connecting structure between a connector and a ring case in the electromagnet assembly. 
     2. Description of Related Art 
     Referring to  FIG. 1 , an electromagnet assembly  7 , which comprises a ring member  1 , a coil bobbin  3 , and a ring case  4 , is known in the art. Ring member  1  has a toroidal shape having a spool portion, which has an exterior open edge. Coil bobbin  3  has ring member  1  and an electrical wire  2 , which is wound around the spool portion of ring member  1 . Ring case  4  has an annular groove, an open edge of which is in a direction parallel to its axis. Coil bobbin  3  is inserted into the annular groove of ring case  4 . An opening  4   a  is formed through ring case  4  adjacent to its closed end surface. A connector  5  is disposed on ring case  4  adjacent to its closed end surface and covers opening  4   a . A first end  2   a  and a second end  2   b  of electrical wire  2  and a first lead  6   a  and a second lead  6   b , which extend to the external electric circuit, are joined, respectively in connector  5 . Electromagnet assembly  7 , for example, is used in an electromagnetic clutch  9  of a compressor  8  in an automobile air conditioning system, as shown in FIG.  2 . Electromagnet assembly  7  engages compressor  8  through a ring-shaped plate  10 , which is affixed to the closed end surface of ring case  4 . 
     Referring to  FIGS. 3-6 , the connecting structure between connector  5  and ring case  4  and the wiring connecting structure in connector  5  are shown. As shown in  FIGS. 3 and 4 , connector  5  has a case  5   a  having a box shape including a bottom, and cap  5   b , which closes an open end of case  5   a . Case  5   a  is fixed to ring case  4  by a pair of first hooks  10   a  formed on ring shaped plate  10  which engage a pair of first receiving portions  5   a   1  formed on case  5   a . In an engaging process, first hooks  10   a  are formed by bending straight portions to engage first receiving portions  5   a   1 . Cap  5   b  is fixed to case  5   a  by engaging a plurality of second receiving portions  5   a   2  formed at case  5   a  with a plurality of hooks  5   b   1  formed at cap  5   b . A projection portion  5   a   3 , which is formed on case  5   a , is inserted into opening  4   a . An O-ring  11 , which is disposed in an annular groove formed on case  5   a , surrounds opening  4   a  and abuts the closed end surface of ring case  4 . 
     As shown in  FIGS. 4-6 , first end  2   a  and second end  2   b  of electrical wire  2  are introduced into opening  4   a  through holes  1   a  and  1   b  formed on an end surface of ring member  1  and are extended into connector  5  through a pair of penetrating holes  5   a   4 , which are formed through projection portion  5   a   3 . A contact  12  having a first electric connection is connected to an end of second lead  6   b , which is inserted into connector  5 . In addition, contact  12  having a second electric connection is connected to an end of first lead  6   a , which is inserted into connector  5 . First end  2   a  of electrical wire  2  is disposed between a first receiving portion formed at case  5   a  of connector  5  and a second receiving portion formed at contact  12 , which is connected to first lead  6   a . Second end  2   b  of electrical wire  2  is disposed between a third receiving portion formed at case  5   a  of connector  5  and a fourth receiving portion formed at contact  12 , which is connected to second lead  6   b . Thus, first end  2   a  and second end  2   b  of electrical wire  2  are connected to first lead  6   a  and second lead  6   b , respectively. 
     Coil bobbin  3  is fixed to ring case  4  by a resin  13  (e.g., epoxy resin) which is poured into ring case  4  from an open end of the annular groove of ring case  4 . O-ring  11 , which is disposed between case  5   a  and the closed end of ring case  4 , prevents resin  13  from leaking to the outside of the closed end surface of ring case  4  through the gap between projection portion  5   a   3  of case  5   a  and a surrounding wall of opening  4   a , when resin  13  is poured into ring case  4 . 
     In the known electromagnet assembly  7  for use in an electromagnetic apparatus, it is necessary to secure first hooks  10   a  to ring-shaped plate  10  and to equip O-ring  11  when connector  5  is fixed to ring case  4 . As a result, the efficiency during manufacturing of fixing connector  5  to ring case  4  may be reduced. 
     SUMMARY OF THE INVENTION 
     A need has arisen to provide an electromagnet assembly for use in an electromagnetic apparatus which has a greater manufacturing efficiency in fixing a connector to a ring case, when compared with a known electromagnet assembly. 
     In an embodiment of the present invention, an electromagnet assembly for an electromagnetic apparatus comprises a ring member, a coil bobbin, a ring case, and a connector. The ring member comprises a tubular spool, e.g., a cylindrical spool, with a pair of annular flanges projecting radially from the spool. The coil bobbin comprises the ring member and an electrical wire. The electrical wire is wound around the spool between the flanges. The ring case comprises an annular groove, which has an open edge. The coil bobbin is disposed in the ring case&#39;s annular groove. An opening is formed through the ring case adjacent to its closed end surface. A connector is disposed on the ring case adjacent to its closed end surface, such that the connector covers the opening. A first end and a second end of the electrical wire and a first lead wire and a second lead wire of an electric circuit are connected, respectively in the connector. A projection portion formed on the connector is inserted into the opening and is fixed adhesively to an end surface of the ring member. 
     In another embodiment of the present invention, an electromagnet assembly for an electromagnetic apparatus comprises a ring member, a coil bobbin, a ring case, and a connector. The ring member comprises a tubular spool, e.g., a cylindrical spool, with a pair of annular flanges projecting radially from the spool. The coil bobbin comprises the ring member and an electrical wire. The electrical wire is wound around the spool between the flanges. The ring case comprises an annular groove, which has an open edge. The coil bobbin is disposed in the ring case&#39;s annular groove. An opening is formed through the ring case adjacent to its closed end surface. A connector is disposed on the ring case adjacent to its closed end surface, such that the connector covers the opening. A first end and a second end of the electrical wire and a first and a second lead wire of an electric circuit are connected, respectively in the connector. A projection portion formed on an end surface of the ring member of the coil bobbin is inserted into the opening and is fixed adhesively to the connector. 
     Objects, features, and advantages will be apparent to persons of ordinary skill in the art from the following detailed description of the invention and the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention may be more readily understood with reference to the following drawings. 
         FIG. 1  is a perspective and exploded view of a known electromagnet assembly for use in an electromagnetic apparatus. 
         FIG. 2  is a longtitudial, cross-sectional view of a known compressor for use in an automotive air-conditioning system which includes an electromagnetic clutch having the known electromagnet assembly. 
         FIG. 3  is a plan view of a closed end side of a ring case of the known electromagnet assembly. 
         FIG. 4  is a cross-sectional view taken along the line IV—IV of FIG.  3 . 
         FIG. 5  is a cross-sectional view taken along the line V—V of FIG.  4 . 
         FIG. 6  is a cross-sectional view taken along the line VI—VI of FIG.  4 . 
         FIG. 7  is a plan view of a closed end side of a ring case of an electromagnet assembly for use in an electromagnetic apparatus, according to a first embodiment of the present invention. 
         FIG. 8  is a cross-sectional view taken along the line VIII—VIII of FIG.  7 . 
         FIG. 9  is a cross-sectional view taken along the line IX—IX of FIG.  8 . 
         FIG. 10  is a cross-sectional view taken along the line X—X of FIG.  8 . 
         FIG. 11  is a cross-sectional view, which corresponds to  FIG. 8 , of an electromagnet assembly for use in an electromagnetic apparatus, according to a first alternative of the first embodiment of the present invention. 
         FIGS. 12 and 13  are cross-sectional views, which correspond to  FIG. 8 , of an electromagnet assembly for use in an electromagnetic apparatus, according to a second alternative of the first embodiment of the present invention. 
         FIG. 14  is a cross-sectional view, which corresponds to  FIG. 8 , of an electromagnet assembly for use in an electromagnetic apparatus, according to a third alternative of the first embodiment of the present invention. 
         FIG. 15  is a cross-sectional view, which corresponds to  FIG. 8 , of an electromagnet assembly for use in an electromagnetic apparatus, according to a fourth alternative of the first embodiment of the present invention. 
         FIG. 16  is a cross-sectional view, which corresponds to  FIG. 8 , of an electromagnet assembly for use in an electromagnetic apparatus, according to a second embodiment of the present invention; 
         FIG. 17  is a cross-sectional view taken along the line XVII—XVII of FIG.  16 . 
         FIG. 18  is a cross-sectional view taken along the line XVIII—XVIII of FIG.  16 . 
         FIG. 19  is a cross-sectional view, which corresponds to  FIG. 16 , of an electromagnet assembly for use in an electromagnetic apparatus, according to a first alternative of the second embodiment of the present invention. 
         FIG. 20  is a cross-sectional view taken along the line XX—XX of FIG.  19 . 
         FIG. 21  is a cross-sectional view, which corresponds to  FIG. 16 , of an electromagnet assembly for use in an electromagnetic apparatus, according to a second alternative of the second embodiment of the present invention. 
         FIG. 22  is a cross-sectional view, which corresponds to  FIG. 16 , of an electromagnet assembly for use in an electromagnetic apparatus, according to a third alternative of the second embodiment of the present invention. 
         FIGS. 23 and 24  are cross-sectional views, which correspond to  FIG. 16 , of an electromagnet assembly for use in an electromagnetic apparatus, according to a fourth alternative of the second embodiment of the present invention. 
         FIG. 25  is a cross-sectional view, which corresponds to  FIG. 16 , of an electromagnet assembly for use in an electromagnetic apparatus, according to a fifth alternative of the second embodiment of the present invention. 
         FIG. 26  is a cross-sectional view, which corresponds to  FIG. 16 , of an electromagnet assembly for use in an electromagnetic apparatus, according to a sixth alternative of the second embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring to  FIGS. 7-10 , a first embodiment of the present invention of an electromagnet assembly for use in an electromagnetic apparatus is shown. In the following explanation and  FIGS. 7-10 , the same reference numbers are used to represent the same parts of an electromagnet assembly for use in an electromagnetic apparatus as shown in  FIGS. 1-6 . Therefore, further explanation of similar parts is here omitted. 
     In an electromagnet assembly  17 , according to this embodiment, a projection portion  15   a   3  is formed on a case  15   a  of a connector  15 , is pressedly fitted into an opening  4   a  formed through a ring case  4  adjacent to its closed end surface, and is fixed to an end surface of ring member  1  of a coil bobbin  3 , e.g., by high frequency adhesion or ultrasonic adhesion or the like. Connector  15  is fixed to ring case  4  by which projection portion  15   a   3  of case  15   a  of connector  15  is fixed adhesively to the end surface of ring member  1  of coil bobbin  3 . Coil bobbin  3  is fixed within ring case  4  by resin, e.g., epoxy resin. A bottom surface of case  15   a  of connector  15  surrounds opening  4   a  and abuts ring case  4  adjacent to its closed end surface. Hooks  10   a  and an O-ring  11  of the known electromagnet assembly  7 , which are shown in  FIGS. 3 and 4 , are not part of electromagnet assembly  17 . The structure of electromagnet assembly  17  is substantially the same as the known electromagnet assembly  7 , except as described above. 
     In electromagnet assembly  17  for use in the electromagnetic apparatus, the engaging process for fixing a connector to a ring case is no longer necessary. Therefore, the manufacturing efficiency of fixing the connector to the ring case in the present invention may be increased compared with that of known electromagnet assemblies. Further, in electromagnet assembly  17 , there is no gap between a side surface of projection portion  15   a   3  of case  15   a  of connector  15  and an annular wall of opening  4   a  formed through ring case  4  adjacent to its closed end surface because projection portion  15   a   3  of connector  15  is pressedly fitted into opening  4   a  of ring case  4 . Consequently, this structure prevents the leakage of resin  13  to the outside of the closed end surface of ring case  4  through opening  4   a  when resin  13  is poured into ring case  4 . As a result, in electromagnet assembly  17 , the manufacturing process for placing of O-ring  11  of known electromagnet assembly  7  is no longer necessary, and the manufacturing efficiency of fixing a connector to a ring case in the present invention may be increased compared with that of known electromagnet assemblies. Further, because the number of parts of electromagnet assembly  17  is reduced compared with the known electromagnet assembly, the manufacturing cost of electromagnet assembly  17  may be reduced compared with that of known electromagnet assemblies. 
     Referring to  FIG. 11 , in a first alternative to the first embodiment of the present invention, hook portion  15   a   4  may be formed around a tip portion of projection portion  15   a   3 , and hook portion  15   a   4  may be pressedly fitted into opening  4   a  formed through ring case  4  adjacent to its closed end surface and may engage a rim of opening  4   a . As a result, hook portion  15   a   4  closes the entrance of the gap between the side surface of projection portion  15   a   3  of connector  15  and an annular wall of opening  4   a , and when resin  13  is poured into ring case  4 , the leakage of resin  13  to the outside of the closed end surface of ring case  4  through opening  4   a  may be prevented. Further, in the first embodiment of the present invention, a bond may be coated to the side surface of projection portion  15   a   3 , and the side surface of projection portion  15   a   3  may be fixed adhesively to the annular wall of opening  4   a . As a result, the gap between the side surface of projection portion  15   a   3  and the annular wall of opening  4   a  is closed by the bond, and when resin  13  is poured into ring case  4 , the leakage of resin  13  to the outside of the closed end surface of ring case  4  through opening  4   a  may be prevented. 
     Referring to  FIGS. 12 and 13 , in a second alternative to the first embodiment of the present invention, a second projection portion  15   a   5  may be formed around a first projection portion  15   a   3  of case  15   a  of connector  15 , and second projection portion  15   a   5  may engage a concave portion  4   a   1  formed around the annular wall of opening  4   a  of ring case  4 . Second projection portion  15   a   5  of case  15   a  may be fixed to concave portion  4   a   1  formed around the annular wall of opening  4   a  of ring case  4 , e.g., by high frequency adhesion or ultrasonic adhesion or the like. An annular projection portion  15   a   6  may be formed on the first end surface of case  15   a , and annular projection portion  15   a   6  may engage an annular concave portion  4   a   2  formed on the closed end surface of ring case  4 . Annular projection portion  15   a   6  of case  15   a  is fixed to annular concave portion  4   a   2  formed on the closed end surface of ring case  4 , e.g., by high frequency adhesion or ultrasonic adhesion or the like. A plurality of third projection portions  15   a   7  may be formed on the tip portion of first projection portion  15   a   3  of case  15   a , and the plurality of third projection portions  15   a   7  may abut the end surface of ring member  1 . The plurality of third projection portions  15   a   7  of the tip portion of first projection portion  15   a   3  of case  15   a  may be fixed to the end surface of ring member  1 , e.g., by high frequency adhesion or ultrasonic adhesion or the like. As shown in  FIGS. 12 and 13 , second projection portion  15   a   5 , concave portion  4   a   1 , annular projection portion  15   a   6 , annular concave portion  4   a   2 , and third projection portions  15   a   7  may have a variety of cross-sectional shapes. As a result, in electromagnet assembly  17 , the manufacturing process for placing of O-ring  11  of known electromagnet assembly  7 , and the engaging process for fixing connector  15  to ring case  4  are no longer necessary, and the manufacturing efficiency of fixing a connector to a ring case in the present invention may be increased compared with that of known electromagnet assemblies. Further, in this alternative to the first embodiment, second projection portion  15   a   5  may be formed by a concave portion, and concave portion  4   a   1  may be formed by a projection portion, which engages second portion  15   a   5 . Annular projection portion  15   a   6  may be formed by a annular concave portion, and annular concave portion  4   a   2  may be formed by an annular projection portion, which engages annular portion  15   a   6 . 
     Referring to  FIG. 14 , in a third alternative to the first embodiment of the present invention, a notched portion  15   a   8  may be formed at first projection portion  15   a   3  of case  15   a  of connector  15 , and first projection portion  15   a   3  may be pressedly fitted into opening  4   a  formed through ring case  4  adjacent to its closed end surface. Hook portion  15   a   4  may be formed around a tip portion of first projection portion  15   a   3 , and may engage a rim of opening  4   a  of ring case  4 . A plurality of third projection portions  15   a   7  may be formed on the tip portion of first projection portion  15   a   3  of case  15   a , and the plurality of third projection portions  15   a   7  may abut the end surface of ring member  1 . First projection portion  15   a   3  of case  15   a  of connector  15  may be fixed to the end surface of ring member  1 , e.g., by high frequency adhesion or ultrasonic adhesion or the like. Moreover, a plurality of concave portion may be formed on the end surface of ring member  1 , and may engage the plurality of third projection portions  15   a   7 . As a result, in electromagnet assembly  17 , the manufacturing process for placing of O-ring  11  of known electromagnet assembly  7 , and the engaging process for fixing connector  15  to ring case  4  are no longer necessary, and the manufacturing efficiency of fixing a connector to a ring case in the present invention may be increased compared with that of known electromagnet assemblies. 
     Referring to  FIG. 15 , in a fourth alternative to the first embodiment of the present invention, a second projection portion  15   a   5  may be formed around first projection portion  15   a   3  of case  15   a  of connector  15 . A concave portion  4   a   1  may be formed around the annular wall of opening  4   a  formed through ring case  4  adjacent to its closed end surface. First projection portion  15   a   3  of case  15   a  is pressedly fitted into opening  4   a , and second projection portion  15   a   5  may engage concave portion  4   a   1  of ring case  4 . A plurality of third projection portions  15   a   7  may be formed on the tip portion of first projection portion  15   a   3  of case  15   a , and may abut the end surface of ring member  1 . First projection portion  15   a   3  of case  15   a  may be fixed to the end surface of ring member  1 , e.g., by high frequency adhesion or ultrasonic adhesion or the like. Moreover, a plurality of concave portion may be formed on the end surface of ring member  1 , and may engage the plurality of third projection portions  15   a   7 . As a result, in electromagnet assembly  17 , the manufacturing process for placing of O-ring  11  of known electromagnet assembly  7 , and the engaging process for fixing connector  15  to ring case  4  are no longer necessary, and the manufacturing efficiency of fixing a connector to a ring case in the present invention may be increased compared with that of known electromagnet assemblies. Further, in this alternative to the first embodiment, second projection portion  15   a   5  may be formed by a concave portion, and concave portion  4   a   1  may be formed by a projection portion, which engages second projection portion  15   a   5 . 
     Referring to  FIGS. 16-18 , a second embodiment of the present invention of an electromagnet assembly for use in an electromagnetic apparatus is shown. In the following explanation and  FIGS. 16-18 , the same reference numbers are used to represent the same parts of electromagnet assembly  7  as shown in  FIGS. 1-6 . Therefore, further explanation of similar parts here is omitted. 
     In electromagnet assembly  27 , according to this embodiment, a projection portion  21   b , is formed on an end surface of a ring member  21  of a coil bobbin  23 , is pressedly fitted into an opening  4   a  formed through a ring case  4  adjacent to its closed end surface, and is fixed to a case  25   a  of a connector  25 , e.g., by high frequency adhesion or ultrasonic adhesion or the like. Connector  25  is fixed to ring case  4  by which case  25   a  is fixed adhesively to projection portion  21   b  formed on the end surface of a ring member  21  of a coil bobbin  23 . Coil bobbin  23  is fixed within ring case  4  by resin, e.g., epoxy resin. A bottom surface of case  25   a  of connector  25  surrounds opening  4   a  and abuts ring case  4  adjacent to its closed end surface. Hooks  10   a  and an O-ring  11  of the known electromagnet assembly, which are shown in  FIGS. 3 and 4 , are not part of electromagnet assembly  27 . The structure of electromagnet assembly  27  is substantially the same as the known electromagnet assembly  7 , except as described above. 
     In electromagnet assembly  27 , the engaging process for fixing connector  25  to ring case  4  is no longer necessary. Therefore, the manufacturing efficiency of fixing a connector to a ring case in the present invention may be increased compared with that of known electromagnet assemblies. Further, in electromagnet assembly  27 , projection portion  21   b , which is formed on an end surface of a ring member  21  of a coil bobbin  23 , is pressedly fitted into an opening  4   a  formed through a ring case  4  adjacent to its closed end surface, and is fixed to a case  25   a  of a connector  25 . Consequently, this structure prevents the leakage of resin  13  to the outside of the closed end surface of ring case  4  through opening  4   a  when resin  13  is poured into ring case  4 , because there is no gap between the side surface of projection portion  21   b  and the annular wall of opening  4   a . As a result, in electromagnet assembly  27 , the manufacturing process for placing of O-ring  11  of known electromagnet assembly  7  is no longer necessary, and the manufacturing efficiency of fixing a connector to a ring case in the present invention may be increased compared with that of known electromagnet assemblies. Further, because the number of parts of electromagnet assembly  27  is reduced compared with known electromagnet assemblies, the manufacturing cost of electromagnet assembly  27  may be reduced compared with that of known electromagnet assemblies. Moreover, in the second embodiment of the present invention, a bond may be coated to the side surface of projection portion  21   b , and the side surface of projection portion  21   b  may be fixed adhesively to the annular wall of opening  4   a . As a result, the gap between the side surface of projection portion  21   b  and the annular wall of opening  4   a  is closed by the bond, and when resin  13  is poured into ring case  4 , the leakage of resin  13  to the outside of the closed end surface of ring case  4  through opening  4   a  may be prevented. 
     Referring to  FIGS. 19 and 20 , in a first alternative to the second embodiment of the present invention, a projection portion  25   a   4  is formed on case  25   a  of connector  25  and may be fitted into a concave portion  21   b   1 , which is formed on a first projection portion  21   b  of coil bobbin  23 . As a result, adhesion surfaces between projection portion  21   b  and case  25   a  are increased, and the strength with which connector  25  is fixed to ring case  4 , may be increased. Projection portion  25   a   4  may have a variety of cross-sectional shapes. Moreover, projection portion  25   a   4  may be a single projection or a plurality of projections. 
     Referring to  FIG. 21 , in a second alternative to the second embodiment of the present invention, a second projection portion  21   b   2  is formed on a tip portion of a first projection portion  21   b  and may be fitted into a concave portion  25   a   5 , which is formed on case  25   a  of connector  25 . As a result, adhesion surfaces of between projection portion  21   b  and case  25   a  are increased, and the strength with which connector  25  is fixed to ring case  4 , may be increased. Second projection portion  21   b   2  may have a variety of cross-sectional shapes. Moreover, second projection portion  21   b   2  may be a single projection or a plurality of projections. 
     Referring to  FIG. 22 , in a third alternative to the second embodiment of the present invention, a tip portion of first projection portion  21   b  of coil bobbin  23  may be fitted into a concave portion  25   a   6  formed on case  25   a  of connector  25 . As a result, adhesion surfaces between projection portion  21   b  and case  25   a  are increased, and the strength with which connector  25  is fixed to ring case  4 , may be increased. 
     Referring to  FIGS. 23 and 24 , in a fourth alternative to the second embodiment of the present invention, a second projection portion  21   b   3  may be formed around a first projection portion  21   b  of ring member  21  of coil bobbin  23 , and a concave portion  4   a   1  may be formed around the annular wall of opening  4   a  of ring case  4 . Second projection portion  21   b   3  of ring member  21  of coil bobbin  23  may engage a concave portion  4   a   1  of opening  4   a  of ring case  4 , and ring member  21  of coil bobbin  23  may be fixed to ring case  4 , e.g., by high frequency adhesion or ultrasonic adhesion or the like. A plurality of third projection portions  21   b   2  may be formed on a tip portion of first projection portion  21   b  of ring member  21  of coil bobbin  23 , and a plurality of concave portions  25   a   5  may be formed on the first end surface of case  25   a  of connector  25 . The plurality of third projection portions  21   b   2  may engage the plurality of concave portions  25   a   5  of the first end surface of case  25   a  of connector  25 , and coil bobbin  23  may be fixed to case  25   a  of connector  25 , e.g., by high frequency adhesion or an ultrasonic adhesion or the like. As a result, in electromagnet assembly  27 , the manufacturing process for placing of O-ring  11  of known electromagnet assembly  7 , and the engaging process for fixing connector  25  to ring case  4  are no longer necessary, and the manufacturing efficiency of fixing a connector to a ring case in the present invention may be increased compared with that of known electromagnet assemblies. As shown in  FIGS. 23 and 24 , second projection portion  21   b   3 , concave portion  4   a   1 , third projection portions  21   b   2 , and concave portions  25   a   5  may have a variety of cross-sectional shapes. Further, in this alternative to the second embodiment, second projection portion  21   b   3  may be formed by a concave portion, and concave portion  4   a   1  may be formed by a projection portion, which engages projection portion  21   b   3 . Third projection portions  21   b   2  may be formed by concave portions, and concave portions  25   a   5  may be formed by projection portions, which engage third projection portions  21   b   2 . 
     Referring to  FIG. 25 , in a fifth alternative to the second embodiment of the present invention, a notched portion  21   b   4  may be formed at first projection portion  21   b  of ring member  21  of coil bobbin  23 , and first projection portion  21   b  may be pressedly fitted into opening  4   a  formed through ring case  4  adjacent to its closed end surface. A hook portion  21   b   5  may be formed around a tip portion of first projection portion  21   b , and may engage a rim of opening  4   a  of ring case  4 . A plurality of second projection portions  21   b   2  may be formed on the tip portion of first projection portion  21   b  of ring member  21  of coil bobbin  23 , and the plurality of second projection portions  21   b   2  may engage a plurality of concave portions  25   a   5 , which may be formed on the first end surface of case  25   a  of connector  25 . Case  25   a  of connector  25  may be fixed to ring member  21  of coil bobbin  23 , e.g., by high frequency adhesion or ultrasonic adhesion or the like. As a result, in electromagnet assembly  27 , the manufacturing process for placing of O-ring  11  of known electromagnet assembly  7 , and the engaging process for fixing connector  25  to ring case  4  are no longer necessary, and the manufacturing efficiency of fixing a connector to a ring case in the present invention may be increased compared with that of known electromagnet assemblies. Second projection portions  21   b   2  and concave portions  25   a   5  may have a variety of cross-sectional shapes. 
     Referring to  FIG. 26 , in a sixth alternative to the second embodiment of the present invention, a second projection portion  21   b   3  may be formed around first projection portion  21   b  of ring member  21  of coil bobbin  23 . A concave portion  4   a   1  may be formed around the annular wall of opening  4   a  formed through ring case  4  adjacent to its closed end surface. First projection portion  21   b  is pressedly fitted into opening  4   a , and second projection portion  21   b   3  may engage concave portion  4   a   1  of ring case  4 . A plurality of third projection portions  21   b   2  may be formed on the tip portion of first projection portion  21   b  of ring member  21  of coil bobbin  23 , and may engage a plurality of concave portions  25   a   5 , which may be formed on the first end surface of case  25   a  of connector  25 . Case  25   a  of connector  25  may be fixed to first projection portion  21   b  of ring member  21  of coil bobbin  23 , e.g., by high frequency adhesion or ultrasonic adhesion or the like. As a result, in electromagnet assembly  27 , the manufacturing process for placing of O-ring  11  of known electromagnet assembly  7 , and the engaging process for fixing connector  25  to ring case  4  are no longer necessary, and the manufacturing efficiency of fixing a connector to a ring case in the present invention may be increased compared with that of known electromagnet assemblies. Further, in this alternative to the second embodiment, second projection portion  21   b   3  may be formed by a concave portion, and concave portion  4   a   1  may be formed by a projection portion, which engages second projection portion  21   b   3 . Similarly, third projection portions  21   b   2  may be formed by convex portions, and concave portions  25   a   5  may be formed by projection portions, which engage third projection portions  21   b   2 . Moreover, second projection portion  21   b   3 , concave portion  4   a   1 , third projection portions  21   b   2 , and concave portions  25   a   5  may have a variety of cross-sectional shapes. 
     As described above, with respect to embodiments of the present invention of an electromagnet assembly for use in an electromagnetic apparatus, a projection portion formed on a connector is inserted into an opening formed through a ring case adjacent to its closed end surface. The connector is fixed adhesively to an end surface of a ring member of a coil bobbin, or a projection portion formed on an end surface of a ring member of a coil bobbin is inserted into an opening formed through a ring case adjacent to its closed end surface. If the ring member is inserted into an opening, it may be fixed adhesively to a case of a connector. As a result, the connector is fixed to the coil bobbin, which is fixed to the ring case, without an engaging process, and the connector is fixed to the ring case. Therefore, the engaging process is no longer necessary, and the manufacturing efficiency of fixing the connector to the ring case may be increased as compared with that of a known electromagnet assemblies. 
     Although the present invention has been described in connection with preferred embodiments, the invention is not limited thereto. It will be understood by those skilled in the art that variations and modifications may be made within the scope and spirit of this invention, as defined by the following claims.