| 摘要 |
PURPOSE:To improve the drivability especially at medium and low load regions by connecting to a distributor a sub advance mechanism for advancing an ignition timing when a vacuum not greater than an atmospheric pressure is applied thereto, and also connecting to the sub advance mechanism a main advance mechanism for further advancing the ignition timing. CONSTITUTION:Vacuum operated type sub and main advance mechanisms 7 and 8 for advancing an ignition timing are connected through a connecting rod 9 to a breaker plate 6 with a breaker arm 5 in a distributor 4. At medium and low load regions where a pressure at an advance port 23 is a substantially atmospheric pressure and a pressure at a position downstream of a throttle valve 3 is under the atmospheric pressure, a sub diaphragm 12 in the sub advance mechanism 7 is drawn toward a sub pressure chamber 18 against a sub spring 20 to rotate the breaker plate 6 in a direction of arrow A through the connecting rod 9 until a flange 19 formed at one end of the connecting rod 9 abuts against an inner end of a connecting member 17, thus advancing the ignition timing.
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