Abstract:
An electromagnetic coil assembly for an electromagnetic apparatus has a bobbin, a coil formed of an electrical wire wound a spool of the bobbin, a thermal protection device including a pair of lead wires, a first and a second lead wires, extending from thereof. The first lead wire is connected to one end of the electrical wire through a first connecting member. The second lead wire is connected to one end of a lead wire of an electric circuit through a second connecting member. At least one securing member having a groove-shaped cross-section is secured, e.g., welded securely or fittied pressedly, on a first end surface of the bobbin. The thermal protection device, the first connecting member, and the second connecting member are disposed on the first end surface of the bobbin and are covered by the securing member.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to an electromagnetic coil 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 the mounting structure for a thermal protection device, electrical wires, and caulking terminals in the electromagnetic coil assembly.  
           [0003]    2. Description of Related Art  
           [0004]    Referring to FIGS. 1 and 2, an electromagnetic coil assembly  4 , which comprises a bobbin  1  and a coil  3 , is known in the art. Bobbin  1  has a toroidal shape having a spool portion, which has an exterior open edge. Coil  3  is formed of electrical wire  2 , which is wound around the spool portion. An electromagnetic coil assembly  4 , for example, is used in an electromagnetic clutch  6  of a compressor  5  in an automobile air conditioning system, as shown in FIG. 3. Electromagnetic coil assembly  4  may be provided with a thermal protection device  7 , e.g., a thermal fuse or a thermal switch, which is sensitive to high temperatures in electromagnetic clutch  6 . Thermal protection device  7  isolates a power source, such as an automobile engine, to protect electromagnetic clutch  6  and compressor  5  when high temperatures due to friction are generated between the parts in electromagnetic clutch  6 .  
           [0005]    Referring again to FIGS. 1 and 2, thermal protection device  7  has a pair of leads, a first lead  7   a  and a second lead  7   b , extending from either end of thermal protection device  7 . An end of first lead  7   a  of thermal protection device  7  is connected to a wire end portion  2   a  of electrical wire  2  through a first caulking terminal  8 . An end of second lead  7   b  of thermal protection device  7  is connected to a third lead  9 , which is connected to the external power source (not shown), through a second caulking terminal  10 . Thermal protection device  7 , first lead  7   a  and second lead  7   b , wire end portion  2   a , and third lead  9  are disposed on a first end surface  1   a  of bobbin  1 . A securing member  11  having a groove-shaped cross-section is fixed securely on first end surface  1   a  by adhesives. Thermal protection device  7  is fitted into the groove-shaped portion of securing member  11 . A pair of projection portions  12   a  and  12   b  are formed on first end surface  1   a . First lead  7   a  and second lead  7   b  are fixeded to projection portions  12   a  and  12   b , respectively. Consequently, thermal protection device  7 , as well as first caulking terminal  8  and second caulking terminal  10 , is fixed to first end surface  1   a  of bobbin  1 .  
           [0006]    As shown in FIG. 1, electromagnetic coil assembly  4  is inserted into a core  5  ring  13  having a groove-shaped cross-section and a toroidal shape in plan view, such that thermal protection device  7  on first end surface  1   a  is positioned in an open end of core ring  13 . Thereafter, a resin  14  is poured into the open end of core ring  13 , and electromagnetic coil assembly  4  is fixed within core ring  13 .  
           [0007]    In electromagnetic coil assembly  4 , the retention strength of thermal  40  protection device  7 , first caulking terminal  8 , and second caulking terminal  10  within core ring  13  is relatively low. Therefore, resin  14  may enter into the spaces between thermal protection device  7 , first caulking terminal  8 , and second caulking terminal  10  and first end surface  1  a of bobbin  1 . Consequently, thermal protection device  7 , first caulking terminal  8 , and second caulking terminal  10  may be pushed upward by resin  14  entering into the spaces between these elements, and as a result, these elements may not be covered by resin  14  and may be exposed outside core ring  13 . Thus, when electromagnetic coil assembly  4  disposed in core ring  13  is equipped with the parts, which comprise, for example, electromagnetic clutch  6 , defects or damage may occur at thermal protection device  7 , first caulking terminal  8 , and second caulking terminal  10 .  
         SUMMARY OF THE INVENTION  
         [0008]    An object of the present invention is to reduce or eliminate the above-mentioned defects or damage, which may be encountered in known electromagnetic coil assemblies with thermal protection devices and caulking terminals.  
           [0009]    In an embodiment of the present invention, an electromagnetic coil assembly for an electromagnetic apparatus comprises a bobbin, a coil, and a thermal protection device. The bobbin comprises a cylindrical tubular spool, and a pair of annular flanges projecting radially from the spool to form an exterior open edge. The coil is formed of an electrical wire. The electrical wire is wound around the spool between the flanges. The thermal protection device has a first and a second lead wires, each extending from one side thereof. The first lead wire is connected to one end of the electrical wire through a first connecting member. The second lead wire is connected to one end of a third lead wire of an electrical circuit through a second connecting member. The thermal protection device, the first lead wire, the second lead wire, the first connecting member, the second connecting member, and one end of the electrical wire, one end of the third lead wire are disposed and fixed on a first end surface of the bobbin. At least one securing member having a groove-shaped cross-section is fixed, e.g., welded securely or fitted pressedly, on the first end surface of the bobbin. The thermal protection device, the first connecting member, and the second connecting member are covered by the securing member.  
           [0010]    Other objects, features, and advantages will be apparent to persons of ordinary skill in the art from the following description of the invention with reference to the accompanying drawings.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    The present invention may be more readily understood with reference to the following drawings, in which:  
         [0012]    [0012]FIG. 1 is a perspective and exploded view of a known electromagnetic coil assembly and core ring;  
         [0013]    [0013]FIG. 2 is a plan view of a first end surface of a bobbin of the known electromagnetic coil assembly;  
         [0014]    [0014]FIG. 3 is a longitudinal, cross-sectional view of a known compressor for use in an automotive air-conditioning system, which includes an electromagnetic clutch having an electromagnetic coil assembly;  
         [0015]    [0015]FIG. 4 is a plan view of a first end surface of a bobbin of an electromagnetic coil assembly, according to a first embodiment of the present invention;  
         [0016]    [0016]FIGS. 5 a - 5   b  are cross-sectional views of securing members depicted in FIG. 4;  
         [0017]    [0017]FIG. 6 is a cross-sectional view of projection portions depicted in FIG. 4;  
         [0018]    [0018]FIG. 7 is a plan view of a first end surface of a bobbin of an electromagnetic coil assembly, according to a second embodiment of the present invention;  
         [0019]    [0019]FIG. 8 is a plan view of a first end surface of a bobbin of an electromagnetic coil assembly, according to a third embodiment of the present invention;  
         [0020]    [0020]FIGS. 9 a - 9   c  are a cross-sectional view of securing members depicted in FIG. 8;  
         [0021]    [0021]FIG. 10 is a plan view of a first end surface of a bobbin of an electromagnetic coil assembly, according to a fourth embodiment of the present invention;  
         [0022]    [0022]FIG. 11 is a plan view of a first end surface of a bobbin of an electromagnetic coil assembly, according to a fifth embodiment of the present invention;  
         [0023]    [0023]FIG. 12 is a cross-sectional view of one deformation embodiment of projection portions depicted in FIG. 4; and  
         [0024]    [0024]FIG. 13 is a cross-sectional view of one deformation embodiment of projection portions depicted in FIG. 11.  
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0025]    Referring to FIGS.  4 - 6 , an electromagnetic coil assembly of a first embodiment of the present invention is shown. An electromagnetic coil assembly  15  comprises a bobbin  16 , a coil  18 , a thermal protection device  19  (e.g., a thermal fuse or a thermal switch), a first caulking terminal  20 , and a second caulking terminal  22 . Bobbin  16  has a spool portion, which has an exterior open edge formed by two annular flange on the spool portion. Coil  18  is formed of an electrical wire  17 , which is wound around the spool portion of bobbin  16 . Thermal protection device  19  has a pair of leads, a first lead  19   a  and a second lead  19   b , each extending from one end of thermal protection device  19 . An end of first lead  19   a  of thermal protection device  19  is connected to a wire end portion  17   a  of electrical wire  17  through first caulking terminal  20 . An end of second lead  19   b  of thermal protection device  19  is connected to one end portion of a third lead  21 , which is connected to the external power source (not shown), through second caulking terminal  22 . Thermal protection device  19 , first caulking terminal  20 , second caulking terminal  22 , first lead  19   a , second lead  19   b , wire end portion  17   a , and third lead  21  are disposed on a first end surface  16   a  of bobbin  16 . Another end portion of third lead  21  is wound around the spool portion of bobbin  16 .  
         [0026]    Securing members  23   a ,  23   b , and  23   c  having a groove-shaped cross-section are welded securely on first end surface  16   a  of bobbin  16 , as shown in FIG. 5 a , or are fitted pressedly on first end surface  16   a  of bobbin  16 , as shown in FIG. 5 b . Securing members  23   a ,  23   b , and  23   c  are fixed on first end surface  16   a  of bobbin  16 , which made of resin. For example, securing members  23   a ,  23   b , and  23   c  may be fixed to bobbin  16  by high frequency welding. Thermal protection device  19 , first caulking terminal  20 , and second caulking terminal  22  are covered by securing members  23   a ,  23   b , and  23   c , respectively.  
         [0027]    Referring again to FIG. 4, projection portions  24   a  and  24   b  are disposed on first end surface  16   a  of bobbin  16 . First lead  19   a  and second lead  19   b  are secured to projection portions  24   a  and  24   b , respectively. As shown in FIG. 6, projection portions  24   a  and  24   b , each has a hook shape and are molded (e.g., integrally molded) with first end surface  16   a  of bobbin  16 . The thickness of each of projection portions  24   a  and  24   b  gradually increases towards its base.  
         [0028]    Electromagnetic coil assembly  15  is inserted into a core ring (not shown) having a groove-shaped cross-section and a toroidal shape in plan view, such that thermal protection device  19  on first end surface  16   a  is positioned in an open end of the core ring. Thereafter, a resin is poured into the open end of the core ring, and electromagnetic coil assembly  15  is fixed within the core ring.  
         [0029]    In the electromagnetic coil assembly according to the first embodiment of present invention, thermal protection device  19 , first caulking terminal  20 , and second caulking terminal  22  are covered by securing members  23   a ,  23   b , and  23   c , respectively. Therefore, after electromagnetic coil assembly  15  is fixed within the core ring by using resin, the exposure of thermal protection device  19 , first caulking terminal  20 , and second caulking terminal  22  from the resin bath may be reduced or effectively eliminated. Tensile force is added to first lead  19   a , second lead  19   b , wire end portion  17   a  of electrical wire  17 , and third lead  21 . Therefore, the reaction force F is transferred from first lead  19   a  and second lead  19   b  to projection portions  24   a  and  24   b , which retain first lead  19   a  and second lead  19   b , as shown in FIG. 6. Consequently, projection portions  24   a  and  24   b  may be reinforced to have thicknesses gradually increasing towards their bases, so that the deformations of projection portions  24   a  and  24   b  by the reaction force F are reduced or eliminated.  
         [0030]    Referring to FIG. 7, an electromagnetic coil assembly of a second embodiment of the present invention is shown. In an electromagnetic coil assembly  15 ′, a thermal protection device  19 ′, a first caulking terminal  20 ′, a second caulking terminal  22 ′, a first lead  19   a ′ and a second lead  19   b ′ of thermal protection device  19 ′, a wire end portion  17   a ′ of an electrical wire  17 ′ adjacent to first caulking terminal  20 ′, and a third lead  21 ′, which is connected to the external power source (not shown) and is adjacent to second caulking terminal  22 ′, are covered by securing members  23   a ′,  23   b ′, and  23   c ′, each having groove-shaped cross-sections. The remaining structure of electromagnetic coil assembly  15 ′ is substantially the same as electromagnetic coil assembly  15 . In the electromagnetic coil assembly according to the second embodiment of present invention, thermal protection device  19 ′, first caulking terminat  20 ′, second caulking terminal  22 ′, first lead  19   a ′ and second lead  19   b ′ of thermal protection device  19 ′, wire end portion  17   a ′ of electrical wire  17 ′, and third lead  21 ′ are substantially covered by securing members  23   a ′,  23   b ′, and  23   c ′. Therefore, after electromagnetic coil assembly  15 ′ is fixed within the core ring by using resin, the exposure of thermal protection device  19 ′, first caulking terminal  20 ′, and second caulking terminal  22 ′ from the resin bath may be reduced or effectively eliminated.  
         [0031]    Referring to FIGS. 8, 9 a  to  9   c , an electromagnetic coil assembly of a third embodiment of the present invention is shown. In an electromagnetic coil assembly  15 ″, each of securing members  23   a ″,  23   b ″, and  23   c ″ has a hook-shaped cross-section and is welded securely on a first end surface  16   a ″ of a bobbin  16 ″, as shown in FIG. 9 a ; is integrally molded with first end surface  16   a ″ of bobbin  16 ″, as shown in FIG. 9 b ; or is fitted pressedly on first end surface  16   a ″ of bobbin  16 ″, as shown in FIG. 9 c . A thermal protection device  19 ″, a first caulking terminal  20 ″, a second caulking terminal  22 ″, a first lead  19   a ″ and a second lead  19   b ″ of thermal protection device  19 ″, a wire end portion  17   a ″ of an electrical wire  17 ″ adjacent to first caulking terminal  20 ″, and a third lead  21 ″, which is connected to the external power source (not shown) and is adjacent to second caulking terminal  22 ″, are substantially covered by securing members  23   a ″,  23   b ″, and  23   c″.    
         [0032]    The structure of electromagnetic coil assembly  15 ″ is substantially the same as electromagnetic coil assembly  15 ′ except that securing members  23   a ″,  23   b ″, and  23   c ″ are used instead of securing members  23   a ′,  23   b ′, and  23   c ′, and are molded, e.g., integrally molded, with first end surface  16   a ″ of bobbin  16 ″. In the electromagnetic coil assembly according to the third embodiment of present invention, thermal protection device  19 ″, first caulking terminal  20 ″, second caulking terminal  22 ″, first lead  19   a ″ and second lead  19   b ″ of thermal protection device  19 ″, wire end portion  17   a ″ of electrical wire  17 ″, and third lead  21 ″ are substantially covered by securing members  23   a ″,  23   b ″, and  23   c ″. Therefore, after electromagnetic coil assembly  15 ″ is fixed within the core ring by using resin, the exposure of thermal protection device  19 ″, first caulking terminal  20 ″, and second caulking terminal  22 ″ from the resin bath may be reduced or effectively eliminated.  
         [0033]    Referring to FIG. 10, an electromagnetic coil assembly of a fourth embodiment of the present invention is shown. In an electromagnetic coil assembly  25 , a groove  27  is formed on a first end surface  26   a  of a bobbin  26 . A thermal protection device  28 ; a first lead  28   a  and a second lead  28   b  of thermal protection device  28 ; a first caulking terminal  29 ; a wire end portion  30   a  of an electrical wire  30  adjacent to first caulking terminal  29 ; a second caulking terminal  31 ; and a third lead  32 , which is connected to the external power source (not shown) and is adjacent to second caulking terminal  31 ; are disposed in groove  27 . The structure of electromagnetic coil assembly  25  is substantially the same as electromagnetic coil assembly  15 ″ except that groove  27  is formed instead of securing  23   a ″,  23   b ″, and  23   c″.    
         [0034]    In the electromagnetic coil assembly according to the fourth embodiment of present invention, thermal protection device  28 , first lead  28   a , second lead  28   b , first caulking terminal  29 , wire end portion  30   a  of electrical wire  30 , second caulking terminal  31 , and third lead  32  are disposed in groove  27 . Therefore, after electromagnetic coil assembly  25  is fixed within the core ring by using resin, the wear resistance between thermal protection device  28 , first caulking terminal  29 , second caulking terminal  31  and both side walls of groove  27  may prevent thermal protection device  28 , first caulking terminal  29 , and second caulking terminal  31  from exposuring from the resin bath.  
         [0035]    Referring to FIG. 11, an electromagnetic coil assembly of a fifth embodiment of the present invention is shown. In an electromagnetic coil assembly  35 , each of projection portions  38   a  and  38   b  has a hook shape and is molded, e.g. integrally molded, with a first end surface  36   a  of a bobbin  36 . Projection portion  38   a  is adjacent to a starting end portion of a first lead  37   a  of a thermal protection device  37 . Projection portion  38   b  is adjacent to a starting end portion of a second lead  37   b  of thermal protection device  37 . Each of projection portions  41   a  and  41   b  has a hook shape and is molded, e.g., integrally molded, with first end surface  36   a  of bobbin  36 . Projection portion  41   a  retains wire end portion  40   a  of electrical wire  40  adjacent to first caulking terminal  39 . Projection portion  41   b  retains a third lead  43 , which is connected to the external power source (not shown), adjacent to second caulking terminal  42 . Wire end portion  40   a  of electrical wire  40  adjacent to first caulking terminal  39  and first lead  37   a  of thermal protection device  37  overlap and are secured to projection portions  41  a and  38   a , which are adjacent to each other, respectively. Third lead  43  adjacent to second caulking terminal  42  and second lead  37   b  of thermal protection device  37  overlap and are secured to projection portions  41   b  and  38   b , which are adjacent to each other, respectively. The structure of projection portions  38   a ,  38   b ,  41   a , and  41   b  is substantially the same as projection portions  24   a  and  24   b  in FIG. 6. The structure of electromagnetic coil assembly  35  is substantially the same as the known electromagnetic coil assembly except as described above.  
         [0036]    In this embodiment of electromagnetic coil assembly  35 , adjacent portions of starting end portions of first lead  37   a  and second lead  37   b  of thermal protection device  37  are secured to projection portions  38   a  and  38   b , respectively. The distance between projection portion  38   a  and projection portion  38   b  is reduced or minimized. Therefore, the upward force on thermal protection device  37  created by the resin, which is poured into the spaces between projection portions  38   a  and  38   b  and first end surface  36   a , may be reduced or eliminated. As a result, after electromagnetic coil assembly  35  is fixed within the core ring by using resin, the exposure of thermal protection device  37  from the resin bath may be reduced or eliminated. Further, projection portion  41   a , which retains wire end portion  40   a  of electrical wire  40  adjacent to first caulking terminal  39 , and projection portion  41   b , which retains lead  43  adjacent to second caulking terminal  42 , are disposed on first end surface  36   a  in addition to projection portions  38   a  and  38   b . Therefore, after electromagnetic coil assembly  35  is fixed within the core ring by using resin, the exposure of thermal protection device  37 , first caulking terminal  39 , and second caulking terminal  42  from the resin bath may be reduced or effectively eliminated. Further, wire end portion  40   a  of electrical wire  40  adjacent to first caulking terminal  39  and first lead  37   a  of thermal protection device  37  overlap and are secured to projection portions  41   a  and  38   a , respectively. Lead  43  adjacent to second caulking terminal  42  and second lead  37   b  of thermal protection device  37  overlap and are secured to projection portions  41   b  and  38   b , respectively. Consequently, after electromagnetic coil assembly  35  is fixed within the core ring by using resin, the exposure of thermal protection device  37 , first caulking terminal  39 , and second caulking terminal  42  from the resin bath may be reduced or effectively eliminated.  
         [0037]    In the above-described embodiments, the unification of securing members  23   a ′,  23   b ′, and  23   c ′ of FIG. 7 is within the contemplation of the present invention. Referring to FIG. 12, one deformation embodiment of the first embodiment of the present invention, an engagement portion of projection portions  24   a  and  24   b , first lead  19   a , and second lead  19   b , is shown. It is desirable to gradually reduce the height of the engagement portion above first end surface  16   a  towards the inner part of the engagement portion. In this embodiment, when first lead  19   a  and second lead  19   b  are engaged in projection portions  24   a  and  24   b , first lead  19   a  and second lead  19   b  are guided to the inner part of the engagement portion and are pressed on first end surface  16   a . As a result, after electromagnetic coil assembly  15  is fixed within the core ring by using resin, the exposure of thermal protection devices  19 , first caulking terminal  20 , and second caulking terminal  22  from the resin bath may be reduced or effectively eliminated.  
         [0038]    Further, the unification of securing members  23   a ″,  23   b ″, and  23   c ″ of FIG. 8 is also within the contemplation of the present invention. Referring to FIG. 13, one deformation embodiment of the fifth embodiment of the present invention, an engagement portion of projection portions  38   a ,  38   b ,  41   a , and  41   b , and first lead  37   a  and second lead  37   b , wire end portion  40   a  of electrical wire  40 , and third lead  43 , is shown. It is desirable to gradually reduce the height of the engagement portion above first end surface  36   a  towards the inner part of the engagement portion. In this embodiment, when first lead  37   a  and second lead  37   b , wire end portion  40   a  of electrical wire  40 , and third lead  43  are engaged in projection portions  38   a ,  38   b ,  41   a , and  41   b ; and first lead  37   a , and second lead  37   b ; and wire end portion  40   a  of electrical wire  40 ; and third lead  43  are guided to the inner part of the engagement portion and are pressed on first end surface  36   a . As a result, after electromagnetic coil assembly  35  is fixed within the core ring by using resin, the exposure of thermal protection devices  37 , first caulking terminal  39 , and second caulking terminal  42  from the resin bath may be reduced or effectively eliminated.  
         [0039]    As described above, in the embodiments of the present invention of an electromagnetic coil assembly, securing members having groove-shaped cross-sections, which are welded securely on a first end surface of a bobbin, or which are fitted pressedly on the first end surface of the bobbin, cover a thermal protection device, a first caulking terminal, and a second caulking terminal. Therefore, after the electromagnetic coil assembly is fixed within the core ring by using resin, the exposure of the thermal protection device, the first caulking terminal, and the second caulking terminal from resin bath may be reduced or effectively eliminated.  
         [0040]    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.