Transformer with tapered core

Abstract

In a transformer including a low-voltage input coil, a high-voltage output coil disposed coaxially of the low-voltage input coil, and a core for magnetically connecting both of the coils together; the improvement comprising a first bobbin around which the low-voltage input coil is wound which first bobbin has an inner-diameter hole, wherein the core comprises a rod portion to be inserted into the inner-diameter hole of the first bobbin and a flange portion provided at one axial end of the rod portion. In another aspect of the invention, the transformer further comprises a second bobbin around which the high-voltage output coil is wound, and a connector adapted to be connected to an ignition plug which connector is mounted on an end surface of the second bobbin on the opposite side of the flange portion of the core in such a manner that a mounting direction of the connector substantially coincides with an axial direction of the second bobbin. In a further aspect of the invention, the transformer further comprises a shield case formed of a magnetic conductive material surrounding an outer periphery of the connector or entirely surrounding the transformer. The rod portion of the core may have a tapering cross section such that it is gradually tapered from a low voltage side of the high-voltage output coil to a high voltage side thereof. With this arrangement, the transformer may be easily assembled and made compact. Further, a magnetic efficiency may be improved, and an insulating distance between the low-voltage input coil and the high-voltage output coil may be ensured.