| 摘要 |
To reduce spurious sparks, and then misfire of an ICE having a magneto with an E armature, upon approach of a magnet (23) in a pole wheel (13) to the leading leg (26) of the E core at high speed ranges of the ICE, the magnetic reluctance of the magnetic path which includes the leading legs (26, 26a) of the E core (14, 14a) is increased with respect to that of the magnetic path which includes the trailing core (25), so that the inductivity of the magnetic circuit including the leading leg is decreased. This can be achieved by providing a wider air gap (X) at the leading leg (26) than at the center leg (15) and the trailing leg (25) of the E core; or reducing the cross-sectional area, or effective magnetic cross-sectional area, e.g. by reducing the number of laminations of the core, at the leading leg or reducing the size of the pole shoe surface (27) facing an air gap which is the same for all legs. A uniform air gap facilitates assembly of the E core. An additional air gap (28) can be introduced in the magnetic circuit which includes the leading leg (26a).
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