Ignition coil core isolation

An ignition coil module having an imaginary longitudinal centerline and comprising:

• a primary coil for conducting primary electric current;
• a secondary coil that is electromagnetically coupled with the primary coil for delivering a spark plug firing voltage when primary current conducted by the primary coil abruptly changes;
• a bobbin comprising an imaginary centerline disposed coincident with the module centerline and comprising a sidewall having an inner surface that laterally bounds a hollow interior space and an outer surface on which the secondary coil is disposed;
• a ferromagnetic core that is disposed within the interior space of the bobbin, that has a longitudinal centerline coincident with the centerlines of both the module and the bobbin, and that comprises an outer surface having a confronting area which confronts and is spaced from a confronted area of the inner surface of the bobbin sidewall;
• and
• encapsulant disposed in the interior space of the bobbin between the confronting area of the outer surface of the core and the confronted area of the inner surface of the bobbin sidewall.

A ferromagnetic core having an imaginary longitudinal centerline and comprising:

• a stack of individual flat laminations arranged parallel to the centerline, wherein
• two of the laminations bound the stack,
• each lamination comprises opposite longitudinal edges that are non-parallel to the centerline to endow zones at opposite sides of the core with a substantially frustoconical profile, and
• the zones are separated by flat outer faces of the two laminations bounding the stack.

A ferromagnetic core having an imaginary longitudinal centerline running from a proximal end to a distal end and comprising:

• a stack of individual flat laminations arranged parallel to the centerline, wherein
• two of the laminations bound the stack,
• each lamination comprises opposite longitudinal edges that endow opposite sides of the core with zones that have a defined longitudinal profile and that are separated by flat outer faces of the two laminations bounding the stack, and
• some of the laminations comprise tabs projecting outward from their longitudinal edges beyond the defined longitudinal profile.

An ignition coil module having an imaginary longitudinal centerline and comprising:

• a primary coil for conducting primary electric current;
• a secondary coil that is electromagnetically coupled with the primary coil for delivering a spark plug firing voltage when primary current conducted by the primary coil abruptly changes;
• a bobbin comprising an imaginary centerline disposed coincident with the module centerline and comprising a sidewall having an inner surface that laterally bounds a hollow interior space and an outer surface on which one of the coils is disposed;
• a ferromagnetic core that is disposed within the interior space of the bobbin, that has a longitudinal centerline coincident with the centerlines of both the module and the bobbin, and that comprises an outer surface having a confronting area which confronts and is spaced from a confronted area of the inner surface of the bobbin sidewall;
• a retainer that fits to the proximal end of the bobbin to capture the core within the bobbin;
• and
• wherein the retainer comprises a ring that is disposed within the interior space and comprises formations that provide clearance to the bobbin sidewall to allow encapsulant that is introduced into the interior space via the proximal end of the bobbin to flow past the retainer and fill the interior space between the confronting and confronted areas.

A method of encapsulating a ferromagnetic core within a bobbin of an ignition coil module, the method comprising:

• providing a bobbin comprising a sidewall having an exterior surface on which one of a primary and a secondary coil is disposed and an interior surface bounding a hollow interior space that is open at a longitudinal end;
• disposing a ferromagnetic core within the hollow interior of the bobbin via the open longitudinal end of the bobbin, including circumferentially locating the core to the bobbin and placing an imaginary longitudinal centerline of the core coincident with an imaginary longitudinal centerline of the bobbin;
• and
• capturing the core within the bobbin by disposing on the bobbin at the open longitudinal end, a retainer that has a cooperation with the bobbin allowing encapsulant to flow past the retainer;
• and
• flowing encapsulant into the interior space of the bobbin to encapsulate the core by introducing encapsulant through the open longitudinal end of the bobbin and flowing encapsulant past the retainer.