1. Field of the Invention
The present invention relates to an ignition coil apparatus for an internal combustion engine that is provided with a low-tension side connector whose terminal is electrically connected to an end of a primary winding through fusing.
2. Description of the Related Art
As an ignition coil apparatus for an internal combustion engine, there has been known one in which a primary winding is electrically connected at its one end to a terminal of a low-tension side connector through a fusing method.
In the case of this ignition coil apparatus for an internal combustion engine, as shown in a first patent document (Japanese patent application laid-open No. 2000-348785) for example, the terminal of the low-tension side connector connected to the one end of the primary winding has a fusing portion turned or bent into a U shape that is formed of a planar portion and a turned portion with its base end portion having a radius of curvature R.
An electric connection between the terminal of the low-tension side connector and the one end of the primary winding is carried out as follows. That is, the fusing portion with the one end of the primary winding being clamped between the planar portion and the turned portion is placed on a first fusing electrode, and a second fusing electrode arranged in opposition to the first fusing electrode is pushed to the first fusing electrode through the fusing portion, whereby an enamel film on the one end of the primary winding is burnt out by supplying an electric current to the first and second fusing electrodes.
In the ignition coil apparatus for an internal combustion engine as constructed above, the planar portion of the fusing portion and a main portion of the turned portion except the base end portion are parallel with respect to each other and are of planar shapes, thus posing the following problems.
(1) Since the radius of curvature R of the base end portion is set according to the cross-sectional shape of the one end of the primary winding, the terminal is required to have a radius of curvature of R matched to a wire diameter (i.e., the diameter of a winding wire or conductor) at the one end of the primary winding, and hence, a special press die is needed for that purpose and the manufacturing cost increases accordingly.
(2) Since the fusing portion is opened at a side opposite to the base end portion, there is a fear that the one end of the primary winding might be moved toward the side opposite to the base end portion when the secondary electrode is pushed to the primary electrode before fusing, so a current path formed at the time of fusing might vary in each fusing, thus making it impossible to obtain a stable fusing state.