| 摘要 |
To provide a pulse for engine ignition timing, a magnetic circuit is provided which includes a permanent magnet and magnetically conducting bodies with a gap provided between one pole face of the magnet and the remainder of the magnetic structure for passage of another magnetic body in its path of revolution in which it is driven by a shaft of the engine. A Hall generator is also provided at a suitable location in the magnetic circuit for responding to a sudden reduction of the magnetic flux when the revolving body exits from the air gap. A portion of the magnetic circuit including the permanent magnet is arranged to be shifted so as to increase the air gap in response to engine intake vacuum, which weakens the effect of the magnet on the Hall generator and advances the timing. An additional magnet provides a branch magnetic circuit which likewise weakens the effect on the Hall generator, but in this case upon approaching the main magnetic circuit, which is caused to happen when the engine speed increases.
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