| 摘要 |
PROBLEM TO BE SOLVED: To facilitate ignition even under an operational condition where combustion is easy to be unstable while suppressing abrasion of an electrode.SOLUTION: By supplying primary current to a primary coil 15a of an ignition coil 15 and cutting off the primary current, discharge voltage is generated between electrodes of an ignition plug 9 connected to a secondary coil 15b. An ignition device includes a changeover circuit 18 that switches the polarity of the second coil 15b between positive polarity and negative polarity by switching the flow direction of current through the primary coil 15a. Under a predetermined operational condition with low combustion stability, the polarity of the secondary coil 15b is set to positive polarity, and under operational conditions other than the above operational condition, it is set to negative polarity.SELECTED DRAWING: Figure 2 |
