| 摘要 |
PROBLEM TO BE SOLVED: To satisfactorily maintain fuel consumption and exhaust emission control performance, while securing engine stability by discriminating the engine stability when an ignition coil temperature exceeds a prescribed value, and changing the air-fuel ratio of the fuel and the gas to a rich side or delaying the ignition time, when stability is low so as to secure engine stability. SOLUTION: During the operation of an engine 1, a control unit 19 discriminates whether or not engine operating condition is lean combustion, and when it is 'YES', a discrimination whether or not temperature of an ignition coil 12 detected by a temperature sensor 14 exceeds the predetermined value is made. When it is 'YES', a heat resistance requiring time tA of the ignition coil 12 is computed, and this value is set as a current-carrying time required value, and current-carrying time of the ignition coil 12 is shortened from tO to tA for correction. In order to discriminate the engine stability, fluctuations in the engine speed based on the signal from a crank angle sensor 17 is compared with the rotary fluctuation reference value. When discrimination that the fluctuation is larger than the reference value and that the stability is low is made, air-fuel ratio of the fuel and the gas and ignition time are corrected in a direction of increasing the engine stability.
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